Finished up ChatComponent

Bump ProtocolLib from 4.6.0-SNAPSHOT to 4.7.1-SNAPSHOT

.github/dependabot.yml

@@ -0,0 +1,11 @@
+# To get started with Dependabot version updates, you'll need to specify which
+# package ecosystems to update and where the package manifests are located.
+# Please see the documentation for all configuration options:
+# https://help.github.com/github/administering-a-repository/configuration-options-for-dependency-updates
+
+version: 2
+updates:
+  - package-ecosystem: "gradle" # See documentation for possible values
+    directory: "/" # Location of package manifests
+    schedule:
+      interval: "daily"

README.md

@@ -16,7 +16,7 @@
 # Information for development
 
 ## Javadoc
-The 6.0.0 Javadoc can be found [here](https://javadoc.jitpack.io/com/willfp/eco/6.0.0/javadoc/)
+The 6.8.0 Javadoc can be found [here](https://javadoc.jitpack.io/com/willfp/eco/6.8.0/javadoc/)
 
 ## Plugin Information
 
@@ -31,7 +31,6 @@ depend:
 eco is available from any of these places:
 
 - [GitHub](https://github.com/Auxilor/eco/releases)
-- [Spigot](https://www.spigotmc.org/resources/eco.87955/)
 - [Polymart](https://polymart.org/resource/eco.773)
 - [Build it locally](https://github.com/Auxilor/eco#build-locally).
 
@@ -72,7 +71,7 @@ Maven:
 </dependency>
 ```
 
-Replace `Tag` with a release tag for eco, eg `6.0.0`.
+Replace `Tag` with a release tag for eco, eg `6.8.0`.
 
 ## Build locally:
 
@@ -158,8 +157,12 @@ Here's a list of some (not all) of the features of eco:
 
 <h1 align="center">
   <br>
+    <a href="http://gamersupps.gg/discount/Auxilor?afmc=Auxilor" target="_blank">
+      <img src="https://i.imgur.com/uFDpBAC.png" alt="supps banner">
+    </a>
     <a href="https://dedimc.promo/Auxilor" target="_blank">
       <img src="https://i.imgur.com/zdDLhFA.png" alt="dedimc banner">
     </a>
   <br>
 </h1>
+

build.gradle

@@ -57,14 +57,14 @@ allprojects {
         compileOnly 'org.jetbrains:annotations:19.0.0'
 
         // Lombok
-        compileOnly 'org.projectlombok:lombok:1.18.20'
+        compileOnly 'org.projectlombok:lombok:1.18.22'
         annotationProcessor 'org.projectlombok:lombok:1.18.20'
         testCompileOnly 'org.projectlombok:lombok:1.18.20'
         testAnnotationProcessor 'org.projectlombok:lombok:1.18.20'
 
         // Test
         testImplementation 'org.junit.jupiter:junit-jupiter-api:5.3.1'
-        testRuntimeOnly 'org.junit.jupiter:junit-jupiter-engine:5.3.1'
+        testRuntimeOnly 'org.junit.jupiter:junit-jupiter-engine:5.8.1'
     }
 
     tasks.withType(JavaCompile) {
@@ -84,6 +84,7 @@ allprojects {
 
     shadowJar {
         relocate('org.bstats', 'com.willfp.eco.shaded.bstats')
+        relocate('net.kyori.adventure.text.minimessage', 'com.willfp.eco.shaded.minimessage')
     }
 
     jar {

eco-api/build.gradle

@@ -6,12 +6,18 @@ group 'com.willfp'
 version rootProject.version
 
 dependencies {
-    compileOnly 'org.spigotmc:spigot-api:1.17-R0.1-SNAPSHOT'
-    compileOnly 'org.apache.maven:maven-artifact:3.0.3'
-    compileOnly 'com.comphenix.protocol:ProtocolLib:4.6.0-SNAPSHOT'
-    compileOnly 'com.google.code.gson:gson:2.8.7'
-    compileOnly 'net.kyori:adventure-text-serializer-gson:4.8.1'
+    // Adventure
+    compileOnly 'net.kyori:adventure-platform-bukkit:4.0.0'
+    compileOnly 'net.kyori:adventure-text-minimessage:4.1.0-SNAPSHOT'
+    compileOnly 'net.kyori:adventure-api:4.9.1'
+    compileOnly 'net.kyori:adventure-text-serializer-gson:4.9.2'
     compileOnly 'net.kyori:adventure-text-serializer-legacy:4.8.1'
+
+    // Other
+    compileOnly 'org.spigotmc:spigot-api:1.17.1-R0.1-SNAPSHOT'
+    compileOnly 'org.apache.maven:maven-artifact:3.0.3'
+    compileOnly 'com.comphenix.protocol:ProtocolLib:4.7.1-SNAPSHOT'
+    compileOnly 'com.google.code.gson:gson:2.8.7'
 }
 
 java {

eco-api/src/main/java/com/willfp/eco/core/EcoPlugin.java

@@ -54,7 +54,7 @@ import java.util.stream.Collectors;
 @SuppressWarnings("unused")
 public abstract class EcoPlugin extends JavaPlugin {
     /**
-     * The spigot resource ID of the plugin.
+     * The polymart resource ID of the plugin.
      */
     @Getter
     private final int resourceId;
@@ -169,14 +169,14 @@ public abstract class EcoPlugin extends JavaPlugin {
     private final ProxyFactory proxyFactory;
 
     /**
-     * Create a new plugin without a specified color, proxy support, spigot, or bStats.
+     * Create a new plugin without a specified color, proxy support, polymart, or bStats.
      */
     protected EcoPlugin() {
         this("&f");
     }
 
     /**
-     * Create a new plugin without proxy support, spigot, or bStats.
+     * Create a new plugin without proxy support, polymart, or bStats.
      *
      * @param color The color.
      */
@@ -186,7 +186,7 @@ public abstract class EcoPlugin extends JavaPlugin {
 
 
     /**
-     * Create a new plugin unlinked to spigot and bStats.
+     * Create a new plugin unlinked to polymart and bStats.
      *
      * @param proxyPackage The package where proxy implementations are stored.
      * @param color        The color of the plugin (used in messages, using standard formatting)
@@ -199,7 +199,7 @@ public abstract class EcoPlugin extends JavaPlugin {
     /**
      * Create a new plugin without proxy or extension support.
      *
-     * @param resourceId The spigot resource ID for the plugin.
+     * @param resourceId The polymart resource ID for the plugin.
      * @param bStatsId   The bStats resource ID for the plugin.
      * @param color      The color of the plugin (used in messages, using standard formatting)
      */
@@ -212,7 +212,7 @@ public abstract class EcoPlugin extends JavaPlugin {
     /**
      * Create a new plugin without proxy support.
      *
-     * @param resourceId           The spigot resource ID for the plugin.
+     * @param resourceId           The polymart resource ID for the plugin.
      * @param bStatsId             The bStats resource ID for the plugin.
      * @param color                The color of the plugin (used in messages, using standard formatting)
      * @param supportingExtensions If the plugin supports extensions.
@@ -227,7 +227,7 @@ public abstract class EcoPlugin extends JavaPlugin {
     /**
      * Create a new plugin without extension support.
      *
-     * @param resourceId   The spigot resource ID for the plugin.
+     * @param resourceId   The polymart resource ID for the plugin.
      * @param bStatsId     The bStats resource ID for the plugin.
      * @param proxyPackage The package where proxy implementations are stored.
      * @param color        The color of the plugin (used in messages, using standard formatting)
@@ -242,7 +242,7 @@ public abstract class EcoPlugin extends JavaPlugin {
     /**
      * Create a new plugin.
      *
-     * @param resourceId           The spigot resource ID for the plugin.
+     * @param resourceId           The polymart resource ID for the plugin.
      * @param bStatsId             The bStats resource ID for the plugin.
      * @param proxyPackage         The package where proxy implementations are stored.
      * @param color                The color of the plugin (used in messages, using standard formatting)
@@ -305,10 +305,27 @@ public abstract class EcoPlugin extends JavaPlugin {
         this.logger = Eco.getHandler().createLogger(this);
         this.proxyFactory = this.proxyPackage.equalsIgnoreCase("") ? null : Eco.getHandler().createProxyFactory(this);
 
-        this.langYml = new LangYml(this);
-        this.configYml = new ConfigYml(this);
+        this.langYml = this.createLangYml();
+        this.configYml = this.createConfigYml();
 
         Eco.getHandler().addNewPlugin(this);
+
+        /*
+        The minimum eco version check was moved here because it's very common
+        to add a lot of code in the constructor of plugins; meaning that the plugin
+        can throw errors without it being obvious to the user that the reason is
+        because they have an outdated version of eco installed.
+         */
+
+        DefaultArtifactVersion runningVersion = new DefaultArtifactVersion(Eco.getHandler().getEcoPlugin().getDescription().getVersion());
+        DefaultArtifactVersion requiredVersion = new DefaultArtifactVersion(this.getMinimumEcoVersion());
+        if (!(runningVersion.compareTo(requiredVersion) > 0 || runningVersion.equals(requiredVersion))) {
+            this.getLogger().severe("You are running an outdated version of eco!");
+            this.getLogger().severe("You must be on at least" + this.getMinimumEcoVersion());
+            this.getLogger().severe("Download the newest version here:");
+            this.getLogger().severe("https://polymart.org/download/773/recent/JSpprMspkuyecf5y1wQ2Jn8OoLQSQ_IW");
+            Bukkit.getPluginManager().disablePlugin(this);
+        }
     }
 
     /**
@@ -336,29 +353,22 @@ public abstract class EcoPlugin extends JavaPlugin {
             });
         }
 
-        DefaultArtifactVersion runningVersion = new DefaultArtifactVersion(Eco.getHandler().getEcoPlugin().getDescription().getVersion());
-        DefaultArtifactVersion requiredVersion = new DefaultArtifactVersion(this.getMinimumEcoVersion());
-        if (!(runningVersion.compareTo(requiredVersion) > 0 || runningVersion.equals(requiredVersion))) {
-            this.getLogger().severe("You are running an outdated version of eco!");
-            this.getLogger().severe("You must be on at least" + this.getMinimumEcoVersion());
-            this.getLogger().severe("Download the newest version here:");
-            this.getLogger().severe("https://polymart.org/download/773/recent/JSpprMspkuyecf5y1wQ2Jn8OoLQSQ_IW");
-            Bukkit.getPluginManager().disablePlugin(this);
-        }
-
         if (this.getBStatsId() != 0) {
             Eco.getHandler().registerBStats(this);
         }
 
-        Set<String> enabledPlugins = Arrays.stream(Bukkit.getPluginManager().getPlugins()).map(Plugin::getName).collect(Collectors.toSet());
+        Set<String> enabledPlugins = Arrays.stream(Bukkit.getPluginManager().getPlugins())
+                .map(Plugin::getName)
+                .map(String::toLowerCase)
+                .collect(Collectors.toSet());
 
-        if (enabledPlugins.contains("PlaceholderAPI")) {
+        if (enabledPlugins.contains("PlaceholderAPI".toLowerCase())) {
             this.loadedIntegrations.add("PlaceholderAPI");
             PlaceholderManager.addIntegration(Eco.getHandler().createPAPIIntegration(this));
         }
 
         this.loadIntegrationLoaders().forEach((integrationLoader -> {
-            if (enabledPlugins.contains(integrationLoader.getPluginName())) {
+            if (enabledPlugins.contains(integrationLoader.getPluginName().toLowerCase())) {
                 this.loadedIntegrations.add(integrationLoader.getPluginName());
                 integrationLoader.load();
             }
@@ -571,6 +581,28 @@ public abstract class EcoPlugin extends JavaPlugin {
      */
     protected abstract List<Listener> loadListeners();
 
+    /**
+     * Useful for custom LangYml implementations.
+     * <p>
+     * Override if needed.
+     *
+     * @return lang.yml.
+     */
+    protected LangYml createLangYml() {
+        return new LangYml(this);
+    }
+
+    /**
+     * Useful for custom ConfigYml implementations.
+     * <p>
+     * Override if needed.
+     *
+     * @return config.yml.
+     */
+    protected ConfigYml createConfigYml() {
+        return new ConfigYml(this);
+    }
+
     /**
      * Create the display module for the plugin.
      *

eco-api/src/main/java/com/willfp/eco/core/Handler.java

@@ -13,9 +13,12 @@ import com.willfp.eco.core.gui.GUIFactory;
 import com.willfp.eco.core.integrations.placeholder.PlaceholderIntegration;
 import com.willfp.eco.core.proxy.Cleaner;
 import com.willfp.eco.core.proxy.ProxyFactory;
+import com.willfp.eco.core.requirement.RequirementFactory;
 import com.willfp.eco.core.scheduling.Scheduler;
+import net.kyori.adventure.platform.bukkit.BukkitAudiences;
 import org.bukkit.inventory.ItemStack;
 import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
 
 import java.util.List;
 import java.util.logging.Logger;
@@ -30,6 +33,7 @@ public interface Handler {
      * @param plugin The plugin.
      * @return The scheduler.
      */
+    @NotNull
     Scheduler createScheduler(@NotNull EcoPlugin plugin);
 
     /**
@@ -38,6 +42,7 @@ public interface Handler {
      * @param plugin The plugin.
      * @return The event manager.
      */
+    @NotNull
     EventManager createEventManager(@NotNull EcoPlugin plugin);
 
     /**
@@ -46,6 +51,7 @@ public interface Handler {
      * @param plugin The plugin.
      * @return The factory.
      */
+    @NotNull
     NamespacedKeyFactory createNamespacedKeyFactory(@NotNull EcoPlugin plugin);
 
     /**
@@ -54,6 +60,7 @@ public interface Handler {
      * @param plugin The plugin.
      * @return The factory.
      */
+    @NotNull
     MetadataValueFactory createMetadataValueFactory(@NotNull EcoPlugin plugin);
 
     /**
@@ -62,6 +69,7 @@ public interface Handler {
      * @param plugin The plugin.
      * @return The factory.
      */
+    @NotNull
     RunnableFactory createRunnableFactory(@NotNull EcoPlugin plugin);
 
     /**
@@ -70,6 +78,7 @@ public interface Handler {
      * @param plugin The plugin.
      * @return The factory.
      */
+    @NotNull
     ExtensionLoader createExtensionLoader(@NotNull EcoPlugin plugin);
 
     /**
@@ -78,6 +87,7 @@ public interface Handler {
      * @param plugin The plugin.
      * @return The handler.
      */
+    @NotNull
     ConfigHandler createConfigHandler(@NotNull EcoPlugin plugin);
 
     /**
@@ -86,6 +96,7 @@ public interface Handler {
      * @param plugin The plugin.
      * @return The logger.
      */
+    @NotNull
     Logger createLogger(@NotNull EcoPlugin plugin);
 
     /**
@@ -94,6 +105,7 @@ public interface Handler {
      * @param plugin The plugin.
      * @return The integration.
      */
+    @NotNull
     PlaceholderIntegration createPAPIIntegration(@NotNull EcoPlugin plugin);
 
     /**
@@ -102,6 +114,7 @@ public interface Handler {
      * @param plugin The plugin.
      * @return The factory.
      */
+    @NotNull
     ProxyFactory createProxyFactory(@NotNull EcoPlugin plugin);
 
     /**
@@ -109,6 +122,7 @@ public interface Handler {
      *
      * @return The plugin.
      */
+    @NotNull
     EcoPlugin getEcoPlugin();
 
     /**
@@ -116,6 +130,7 @@ public interface Handler {
      *
      * @return The factory.
      */
+    @NotNull
     ConfigFactory getConfigFactory();
 
     /**
@@ -123,6 +138,7 @@ public interface Handler {
      *
      * @return The factory.
      */
+    @NotNull
     DropQueueFactory getDropQueueFactory();
 
     /**
@@ -130,6 +146,7 @@ public interface Handler {
      *
      * @return The factory.
      */
+    @NotNull
     GUIFactory getGUIFactory();
 
     /**
@@ -137,6 +154,7 @@ public interface Handler {
      *
      * @return The cleaner.
      */
+    @NotNull
     Cleaner getCleaner();
 
     /**
@@ -152,6 +170,7 @@ public interface Handler {
      * @param name The name.
      * @return The plugin.
      */
+    @Nullable
     EcoPlugin getPluginByName(@NotNull String name);
 
     /**
@@ -159,6 +178,7 @@ public interface Handler {
      *
      * @return A list of plugin names in lowercase.
      */
+    @NotNull
     List<String> getLoadedPlugins();
 
     /**
@@ -167,6 +187,7 @@ public interface Handler {
      * @param itemStack The base ItemStack.
      * @return The FastItemStack.
      */
+    @NotNull
     FastItemStack createFastItemStack(@NotNull ItemStack itemStack);
 
     /**
@@ -175,4 +196,20 @@ public interface Handler {
      * @param plugin The plugin.
      */
     void registerBStats(@NotNull EcoPlugin plugin);
+
+    /**
+     * Get the requirement factory.
+     *
+     * @return The factory.
+     */
+    @NotNull
+    RequirementFactory getRequirementFactory();
+
+    /**
+     * Get Adventure audiences.
+     *
+     * @return The audiences.
+     */
+    @Nullable
+    BukkitAudiences getAdventure();
 }

eco-api/src/main/java/com/willfp/eco/core/PluginDependent.java

@@ -9,11 +9,12 @@ import org.jetbrains.annotations.NotNull;
  *
  * @param <T> The eco plugin type.
  */
-public abstract class PluginDependent<T extends EcoPlugin> {
+public abstract class PluginDependent<@NotNull T extends EcoPlugin> {
     /**
      * The {@link EcoPlugin} that is stored.
      */
     @Getter(AccessLevel.PROTECTED)
+    @NotNull
     private final T plugin;
 
     /**

eco-api/src/main/java/com/willfp/eco/core/config/base/LangYml.java

@@ -2,6 +2,7 @@ package com.willfp.eco.core.config.base;
 
 import com.willfp.eco.core.EcoPlugin;
 import com.willfp.eco.core.config.yaml.YamlBaseConfig;
+import com.willfp.eco.util.StringUtils;
 import org.jetbrains.annotations.NotNull;
 
 /**
@@ -42,6 +43,18 @@ public class LangYml extends YamlBaseConfig {
      * @return The message with a prefix appended.
      */
     public String getMessage(@NotNull final String message) {
-        return getPrefix() + this.getString("messages." + message);
+        return getMessage(message, StringUtils.FormatOption.WITH_PLACEHOLDERS);
+    }
+
+    /**
+     * Get a chat message.
+     *
+     * @param message The key of the message.
+     * @param option  The format options.
+     * @return The message with a prefix appended.
+     */
+    public String getMessage(@NotNull final String message,
+                             @NotNull final StringUtils.FormatOption option) {
+        return getPrefix() + this.getString("messages." + message, option);
     }
 }

eco-api/src/main/java/com/willfp/eco/core/config/interfaces/Config.java

@@ -1,5 +1,6 @@
 package com.willfp.eco.core.config.interfaces;
 
+import com.willfp.eco.util.StringUtils;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 
@@ -165,7 +166,9 @@ public interface Config extends Cloneable {
      * @return The found value, or an empty string if not found.
      */
     @NotNull
-    String getString(@NotNull String path);
+    default String getString(@NotNull String path) {
+        return getString(path, true);
+    }
 
     /**
      * Get a string from config.
@@ -175,8 +178,36 @@ public interface Config extends Cloneable {
      * @return The found value, or an empty string if not found.
      */
     @NotNull
+    default String getString(@NotNull String path,
+                             boolean format) {
+        return this.getString(path, format, StringUtils.FormatOption.WITH_PLACEHOLDERS);
+    }
+
+    /**
+     * Get a string from config.
+     *
+     * @param path   The key to fetch the value from.
+     * @param option The format option.
+     * @return The found value, or an empty string if not found.
+     */
+    @NotNull
+    default String getString(@NotNull String path,
+                             @NotNull final StringUtils.FormatOption option) {
+        return this.getString(path, true, option);
+    }
+
+    /**
+     * Get a string from config.
+     *
+     * @param path   The key to fetch the value from.
+     * @param format If the string should be formatted.
+     * @param option The format option.
+     * @return The found value, or an empty string if not found.
+     */
+    @NotNull
     String getString(@NotNull String path,
-                     boolean format);
+                     boolean format,
+                     @NotNull StringUtils.FormatOption option);
 
     /**
      * Get a string from config.
@@ -185,7 +216,9 @@ public interface Config extends Cloneable {
      * @return The found value, or null if not found.
      */
     @Nullable
-    String getStringOrNull(@NotNull String path);
+    default String getStringOrNull(@NotNull String path) {
+        return getStringOrNull(path, true);
+    }
 
     /**
      * Get a string from config.
@@ -195,8 +228,36 @@ public interface Config extends Cloneable {
      * @return The found value, or null if not found.
      */
     @Nullable
+    default String getStringOrNull(@NotNull String path,
+                                   boolean format) {
+        return this.getStringOrNull(path, format, StringUtils.FormatOption.WITH_PLACEHOLDERS);
+    }
+
+    /**
+     * Get a string from config.
+     *
+     * @param path   The key to fetch the value from.
+     * @param option The format option.
+     * @return The found value, or null if not found.
+     */
+    @Nullable
+    default String getStringOrNull(@NotNull String path,
+                                   @NotNull StringUtils.FormatOption option) {
+        return this.getStringOrNull(path, true, option);
+    }
+
+    /**
+     * Get a string from config.
+     *
+     * @param path   The key to fetch the value from.
+     * @param format If the string should be formatted.
+     * @param option The format option.
+     * @return The found value, or null if not found.
+     */
+    @Nullable
     String getStringOrNull(@NotNull String path,
-                           boolean format);
+                           boolean format,
+                           @NotNull StringUtils.FormatOption option);
 
     /**
      * Get a list of strings from config.
@@ -207,7 +268,9 @@ public interface Config extends Cloneable {
      * @return The found value, or a blank {@link java.util.ArrayList} if not found.
      */
     @NotNull
-    List<String> getStrings(@NotNull String path);
+    default List<String> getStrings(@NotNull String path) {
+        return getStrings(path, true);
+    }
 
     /**
      * Get a list of strings from config.
@@ -217,8 +280,36 @@ public interface Config extends Cloneable {
      * @return The found value, or a blank {@link java.util.ArrayList} if not found.
      */
     @NotNull
+    default List<String> getStrings(@NotNull String path,
+                                    boolean format) {
+        return this.getStrings(path, format, StringUtils.FormatOption.WITH_PLACEHOLDERS);
+    }
+
+    /**
+     * Get a list of strings from config.
+     *
+     * @param path   The key to fetch the value from.
+     * @param option The format option.
+     * @return The found value, or a blank {@link java.util.ArrayList} if not found.
+     */
+    @Nullable
+    default List<String> getStrings(@NotNull String path,
+                                    @NotNull StringUtils.FormatOption option) {
+        return getStrings(path, true, option);
+    }
+
+    /**
+     * Get a list of strings from config.
+     *
+     * @param path   The key to fetch the value from.
+     * @param format If the strings should be formatted.
+     * @param option The option.
+     * @return The found value, or a blank {@link java.util.ArrayList} if not found.
+     */
+    @NotNull
     List<String> getStrings(@NotNull String path,
-                            boolean format);
+                            boolean format,
+                            @NotNull StringUtils.FormatOption option);
 
     /**
      * Get a list of strings from config.
@@ -227,7 +318,9 @@ public interface Config extends Cloneable {
      * @return The found value, or null if not found.
      */
     @Nullable
-    List<String> getStringsOrNull(@NotNull String path);
+    default List<String> getStringsOrNull(@NotNull String path) {
+        return getStringsOrNull(path, true);
+    }
 
     /**
      * Get a list of strings from config.
@@ -237,8 +330,36 @@ public interface Config extends Cloneable {
      * @return The found value, or null if not found.
      */
     @Nullable
+    default List<String> getStringsOrNull(@NotNull String path,
+                                          boolean format) {
+        return getStringsOrNull(path, format, StringUtils.FormatOption.WITH_PLACEHOLDERS);
+    }
+
+    /**
+     * Get a list of strings from config.
+     *
+     * @param path   The key to fetch the value from.
+     * @param option The format option.
+     * @return The found value, or null if not found.
+     */
+    @Nullable
+    default List<String> getStringsOrNull(@NotNull String path,
+                                          @NotNull StringUtils.FormatOption option) {
+        return getStringsOrNull(path, true, option);
+    }
+
+    /**
+     * Get a list of strings from config.
+     *
+     * @param path   The key to fetch the value from.
+     * @param format If the strings should be formatted.
+     * @param option The format option.
+     * @return The found value, or null if not found.
+     */
+    @Nullable
     List<String> getStringsOrNull(@NotNull String path,
-                                  boolean format);
+                                  boolean format,
+                                  @NotNull StringUtils.FormatOption option);
 
     /**
      * Get a decimal from config.

eco-api/src/main/java/com/willfp/eco/core/config/json/JSONBaseConfig.java

@@ -0,0 +1,54 @@
+package com.willfp.eco.core.config.json;
+
+import com.willfp.eco.core.Eco;
+import com.willfp.eco.core.EcoPlugin;
+import com.willfp.eco.core.config.json.wrapper.LoadableJSONConfigWrapper;
+import com.willfp.eco.core.config.yaml.wrapper.LoadableYamlConfigWrapper;
+import org.jetbrains.annotations.NotNull;
+
+/**
+ * Config implementation for configs present in the plugin's base directory (eg config.json).
+ * <p>
+ * Automatically updates.
+ */
+public abstract class JSONBaseConfig extends LoadableJSONConfigWrapper {
+    /**
+     * @param configName      The name of the config
+     * @param removeUnused    Whether keys not present in the default config should be removed on update.
+     * @param plugin          The plugin.
+     * @param updateBlacklist Substring of keys to not add/remove keys for.
+     */
+    protected JSONBaseConfig(@NotNull final String configName,
+                             final boolean removeUnused,
+                             @NotNull final EcoPlugin plugin,
+                             @NotNull final String... updateBlacklist) {
+        super(
+                Eco.getHandler().getConfigFactory().createUpdatableJSONConfig(
+                        configName,
+                        plugin,
+                        "",
+                        plugin.getClass(),
+                        removeUnused, updateBlacklist
+                )
+        );
+    }
+
+    /**
+     * @param configName   The name of the config
+     * @param removeUnused Whether keys not present in the default config should be removed on update.
+     * @param plugin       The plugin.
+     */
+    protected JSONBaseConfig(@NotNull final String configName,
+                             final boolean removeUnused,
+                             @NotNull final EcoPlugin plugin) {
+        super(
+                Eco.getHandler().getConfigFactory().createUpdatableJSONConfig(
+                        configName,
+                        plugin,
+                        "",
+                        plugin.getClass(),
+                        removeUnused
+                )
+        );
+    }
+}

eco-api/src/main/java/com/willfp/eco/core/config/json/JSONExtendableConfig.java

@@ -0,0 +1,44 @@
+package com.willfp.eco.core.config.json;
+
+import com.willfp.eco.core.Eco;
+import com.willfp.eco.core.EcoPlugin;
+import com.willfp.eco.core.config.json.wrapper.LoadableJSONConfigWrapper;
+import com.willfp.eco.core.config.yaml.wrapper.LoadableYamlConfigWrapper;
+import org.jetbrains.annotations.NotNull;
+
+/**
+ * Config implementation for configs present in one of two places:
+ * <ul>
+ *     <li>Plugin base directory (eg config.yml, lang.yml)</li>
+ *     <li>Other extension's configs</li>
+ * </ul>
+ * <p>
+ * Automatically updates.
+ */
+public abstract class JSONExtendableConfig extends LoadableJSONConfigWrapper {
+    /**
+     * @param configName       The name of the config
+     * @param removeUnused     Whether keys not present in the default config should be removed on update.
+     * @param plugin           The plugin.
+     * @param updateBlacklist  Substring of keys to not add/remove keys for.
+     * @param subDirectoryPath The subdirectory path.
+     * @param source           The class that owns the resource.
+     */
+    protected JSONExtendableConfig(@NotNull final String configName,
+                                   final boolean removeUnused,
+                                   @NotNull final EcoPlugin plugin,
+                                   @NotNull final Class<?> source,
+                                   @NotNull final String subDirectoryPath,
+                                   @NotNull final String... updateBlacklist) {
+        super(
+                Eco.getHandler().getConfigFactory().createUpdatableJSONConfig(
+                        configName,
+                        plugin,
+                        subDirectoryPath,
+                        source,
+                        removeUnused,
+                        updateBlacklist
+                )
+        );
+    }
+}

eco-api/src/main/java/com/willfp/eco/core/config/wrapper/ConfigFactory.java

@@ -30,6 +30,24 @@ public interface ConfigFactory {
                                      boolean removeUnused,
                                      @NotNull String... updateBlacklist);
 
+    /**
+     * Updatable config.
+     *
+     * @param configName       The name of the config
+     * @param plugin           The plugin.
+     * @param subDirectoryPath The subdirectory path.
+     * @param source           The class that owns the resource.
+     * @param removeUnused     Whether keys not present in the default config should be removed on update.
+     * @param updateBlacklist  Substring of keys to not add/remove keys for.
+     * @return The config implementation.
+     */
+    JSONConfig createUpdatableJSONConfig(@NotNull String configName,
+                                         @NotNull EcoPlugin plugin,
+                                         @NotNull String subDirectoryPath,
+                                         @NotNull Class<?> source,
+                                         boolean removeUnused,
+                                         @NotNull String... updateBlacklist);
+
     /**
      * JSON loadable config.
      *

eco-api/src/main/java/com/willfp/eco/core/config/wrapper/ConfigWrapper.java

@@ -1,6 +1,7 @@
 package com.willfp.eco.core.config.wrapper;
 
 import com.willfp.eco.core.config.interfaces.Config;
+import com.willfp.eco.util.StringUtils;
 import lombok.Getter;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
@@ -125,48 +126,33 @@ public abstract class ConfigWrapper<T extends Config> implements Config {
         return handle.getBoolsOrNull(path);
     }
 
-    @Override
-    public @NotNull String getString(@NotNull final String path) {
-        return handle.getString(path);
-    }
 
     @Override
     public @NotNull String getString(@NotNull final String path,
-                                     final boolean format) {
-        return handle.getString(path, format);
-    }
-
-    @Override
-    public @Nullable String getStringOrNull(@NotNull final String path) {
-        return handle.getStringOrNull(path);
+                                     final boolean format,
+                                     @NotNull final StringUtils.FormatOption option) {
+        return handle.getString(path, format, option);
     }
 
     @Override
     public @Nullable String getStringOrNull(@NotNull final String path,
-                                            final boolean format) {
-        return handle.getStringOrNull(path, format);
-    }
-
-    @Override
-    public @NotNull List<String> getStrings(@NotNull final String path) {
-        return handle.getStrings(path);
+                                            final boolean format,
+                                            @NotNull final StringUtils.FormatOption option) {
+        return handle.getStringOrNull(path, format, option);
     }
 
     @Override
     public @NotNull List<String> getStrings(@NotNull final String path,
-                                            final boolean format) {
-        return handle.getStrings(path, format);
-    }
-
-    @Override
-    public @Nullable List<String> getStringsOrNull(@NotNull final String path) {
-        return handle.getStringsOrNull(path);
+                                            final boolean format,
+                                            @NotNull final StringUtils.FormatOption option) {
+        return handle.getStrings(path, format, option);
     }
 
     @Override
     public @Nullable List<String> getStringsOrNull(@NotNull final String path,
-                                                   final boolean format) {
-        return handle.getStringsOrNull(path, format);
+                                                   final boolean format,
+                                                   @NotNull final StringUtils.FormatOption option) {
+        return handle.getStringsOrNull(path, format, option);
     }
 
     @Override

eco-api/src/main/java/com/willfp/eco/core/display/Display.java

@@ -1,22 +1,12 @@
 package com.willfp.eco.core.display;
 
 import lombok.experimental.UtilityClass;
-import org.apache.commons.lang.Validate;
-import org.bukkit.NamespacedKey;
 import org.bukkit.entity.Player;
 import org.bukkit.inventory.ItemStack;
-import org.bukkit.inventory.meta.ItemMeta;
-import org.bukkit.persistence.PersistentDataContainer;
-import org.bukkit.persistence.PersistentDataType;
 import org.jetbrains.annotations.ApiStatus;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 
-import java.util.ArrayList;
-import java.util.HashMap;
-import java.util.List;
-import java.util.Map;
-
 /**
  * Utility class to manage client-side item display.
  */
@@ -28,29 +18,9 @@ public class Display {
     public static final String PREFIX = "§z";
 
     /**
-     * All registered display modules.
+     * The display handler.
      */
-    private static final Map<DisplayPriority, List<DisplayModule>> MODULES = new HashMap<>();
-
-    /**
-     * NamespacedKey for finalizing.
-     */
-    private static NamespacedKey finalizeKey = null;
-
-    /**
-     * Register display module.
-     *
-     * @param module The module.
-     */
-    public void registerDisplayModule(@NotNull final DisplayModule module) {
-        List<DisplayModule> modules = MODULES.get(module.getPriority());
-
-        modules.removeIf(module1 -> module1.getPluginName().equalsIgnoreCase(module.getPluginName()));
-
-        modules.add(module);
-
-        MODULES.put(module.getPriority(), modules);
-    }
+    public static DisplayHandler handler = null;
 
     /**
      * Display on ItemStacks.
@@ -71,39 +41,7 @@ public class Display {
      */
     public ItemStack display(@NotNull final ItemStack itemStack,
                              @Nullable final Player player) {
-        if (!itemStack.hasItemMeta()) {
-            return itemStack; // return early if there's no customization of the item
-        }
-
-        Map<String, Object[]> pluginVarArgs = new HashMap<>();
-
-        for (DisplayPriority priority : DisplayPriority.values()) {
-            List<DisplayModule> modules = MODULES.get(priority);
-            for (DisplayModule module : modules) {
-                pluginVarArgs.put(module.getPluginName(), module.generateVarArgs(itemStack));
-            }
-        }
-
-        revert(itemStack);
-
-        ItemMeta meta = itemStack.getItemMeta();
-
-        if (meta == null) {
-            return itemStack;
-        }
-
-        for (DisplayPriority priority : DisplayPriority.values()) {
-            List<DisplayModule> modules = MODULES.get(priority);
-            for (DisplayModule module : modules) {
-                Object[] varargs = pluginVarArgs.get(module.getPluginName());
-                module.display(itemStack, varargs);
-                if (player != null) {
-                    module.display(itemStack, player, varargs);
-                }
-            }
-        }
-
-        return itemStack;
+        return handler.display(itemStack, player);
     }
 
     /**
@@ -135,35 +73,7 @@ public class Display {
      * @return The ItemStack.
      */
     public ItemStack revert(@NotNull final ItemStack itemStack) {
-        if (Display.isFinalized(itemStack)) {
-            unfinalize(itemStack);
-        }
-
-        if (!itemStack.hasItemMeta()) {
-            return itemStack;
-        }
-
-        ItemMeta meta = itemStack.getItemMeta();
-
-        if (meta == null) {
-            return itemStack;
-        }
-
-        List<String> lore = meta.getLore();
-
-        if (lore != null && lore.removeIf(line -> line.startsWith(Display.PREFIX))) { // only apply lore modification if needed
-            meta.setLore(lore);
-            itemStack.setItemMeta(meta);
-        }
-
-        for (DisplayPriority priority : DisplayPriority.values()) {
-            List<DisplayModule> modules = MODULES.get(priority);
-            for (DisplayModule module : modules) {
-                module.revert(itemStack);
-            }
-        }
-
-        return itemStack;
+        return handler.revert(itemStack);
     }
 
     /**
@@ -173,21 +83,7 @@ public class Display {
      * @return The ItemStack.
      */
     public ItemStack finalize(@NotNull final ItemStack itemStack) {
-        Validate.notNull(finalizeKey, "Key cannot be null!");
-
-        if (itemStack.getType().getMaxStackSize() > 1) {
-            return itemStack;
-        }
-
-        ItemMeta meta = itemStack.getItemMeta();
-        if (meta == null) {
-            return itemStack;
-        }
-
-        PersistentDataContainer container = meta.getPersistentDataContainer();
-        container.set(finalizeKey, PersistentDataType.INTEGER, 1);
-        itemStack.setItemMeta(meta);
-        return itemStack;
+        return handler.finalize(itemStack);
     }
 
     /**
@@ -197,18 +93,7 @@ public class Display {
      * @return The ItemStack.
      */
     public ItemStack unfinalize(@NotNull final ItemStack itemStack) {
-        Validate.notNull(finalizeKey, "Key cannot be null!");
-
-        ItemMeta meta = itemStack.getItemMeta();
-
-        if (meta == null) {
-            return itemStack;
-        }
-
-        PersistentDataContainer container = meta.getPersistentDataContainer();
-        container.remove(finalizeKey);
-        itemStack.setItemMeta(meta);
-        return itemStack;
+        return handler.unfinalize(itemStack);
     }
 
     /**
@@ -218,31 +103,61 @@ public class Display {
      * @return If finalized.
      */
     public boolean isFinalized(@NotNull final ItemStack itemStack) {
-        Validate.notNull(finalizeKey, "Key cannot be null!");
-
-        ItemMeta meta = itemStack.getItemMeta();
-
-        if (meta == null) {
-            return false;
-        }
-
-        PersistentDataContainer container = meta.getPersistentDataContainer();
-        return container.has(finalizeKey, PersistentDataType.INTEGER);
+        return handler.isFinalized(itemStack);
     }
 
     /**
-     * Set key to be used for finalization.
+     * Register a new display module.
      *
-     * @param finalizeKey The key.
+     * @param module The module.
      */
-    @ApiStatus.Internal
-    public static void setFinalizeKey(@NotNull final NamespacedKey finalizeKey) {
-        Display.finalizeKey = finalizeKey;
+    public void registerDisplayModule(@NotNull final DisplayModule module) {
+        handler.registerDisplayModule(module);
     }
 
-    static {
-        for (DisplayPriority priority : DisplayPriority.values()) {
-            MODULES.put(priority, new ArrayList<>());
+    /**
+     * Initialize the display system.
+     *
+     * @param handler The handler.
+     */
+    @ApiStatus.Internal
+    public static void init(@NotNull final DisplayHandler handler) {
+        if (Display.handler != null) {
+            throw new IllegalArgumentException("Already Initialized!");
+        }
+        Display.handler = handler;
+    }
+
+    /**
+     * Extremely janky method - also internal, so don't use it. <b>This method is
+     * NOT part of the API and may be removed at any time!</b>
+     * <p>
+     * This calls a display module with the specified parameters, now
+     * you might ask why I need a static java method when the DisplayHandler
+     * implementation could just call it itself? Well, kotlin doesn't really
+     * like dealing with vararg ambiguity, and so while kotlin can't figure out
+     * what is and isn't a vararg when I call display with a player, java can.
+     * <p>
+     * Because of this, I need to have this part of the code in java.
+     *
+     * <b>Don't call this method as part of your plugins!</b>
+     * <p>
+     * No, seriously - don't. This skips a bunch of checks and you'll almost
+     * definitely break something.
+     *
+     * @param module    The display module.
+     * @param itemStack The ItemStack.
+     * @param player    The player.
+     * @param args      The args.
+     */
+    @ApiStatus.Internal
+    public static void callDisplayModule(@NotNull final DisplayModule module,
+                                         @NotNull final ItemStack itemStack,
+                                         @Nullable final Player player,
+                                         @NotNull final Object... args) {
+        module.display(itemStack, args);
+        if (player != null) {
+            module.display(itemStack, player, args);
         }
     }
 }

eco-api/src/main/java/com/willfp/eco/core/display/DisplayHandler.java

@@ -0,0 +1,60 @@
+package com.willfp.eco.core.display;
+
+import org.bukkit.entity.Player;
+import org.bukkit.inventory.ItemStack;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+
+/**
+ * Interface for display implementations.
+ */
+public interface DisplayHandler {
+    /**
+     * Register display module.
+     *
+     * @param module The module.
+     */
+    void registerDisplayModule(@NotNull DisplayModule module);
+
+    /**
+     * Display on ItemStacks.
+     *
+     * @param itemStack The item.
+     * @param player    The player.
+     * @return The ItemStack.
+     */
+    ItemStack display(@NotNull final ItemStack itemStack,
+                      @Nullable final Player player);
+
+    /**
+     * Revert on ItemStacks.
+     *
+     * @param itemStack The item.
+     * @return The ItemStack.
+     */
+    ItemStack revert(@NotNull final ItemStack itemStack);
+
+    /**
+     * Finalize an ItemStacks.
+     *
+     * @param itemStack The item.
+     * @return The ItemStack.
+     */
+    ItemStack finalize(@NotNull final ItemStack itemStack);
+
+    /**
+     * Unfinalize an ItemStacks.
+     *
+     * @param itemStack The item.
+     * @return The ItemStack.
+     */
+    ItemStack unfinalize(@NotNull final ItemStack itemStack);
+
+    /**
+     * If an item is finalized.
+     *
+     * @param itemStack The item.
+     * @return If finalized.
+     */
+    boolean isFinalized(@NotNull final ItemStack itemStack);
+}

eco-api/src/main/java/com/willfp/eco/core/display/DisplayModule.java

@@ -36,8 +36,8 @@ public abstract class DisplayModule extends PluginDependent<EcoPlugin> {
      * @param itemStack The item.
      * @param args      Optional args for display.
      */
-    protected void display(@NotNull final ItemStack itemStack,
-                           @NotNull final Object... args) {
+    public void display(@NotNull final ItemStack itemStack,
+                        @NotNull final Object... args) {
         // Technically optional.
     }
 
@@ -48,9 +48,9 @@ public abstract class DisplayModule extends PluginDependent<EcoPlugin> {
      * @param player    The player.
      * @param args      Optional args for display.
      */
-    protected void display(@NotNull final ItemStack itemStack,
-                           @Nullable final Player player,
-                           @NotNull final Object... args) {
+    public void display(@NotNull final ItemStack itemStack,
+                        @Nullable final Player player,
+                        @NotNull final Object... args) {
         // Technically optional.
     }
 
@@ -59,7 +59,7 @@ public abstract class DisplayModule extends PluginDependent<EcoPlugin> {
      *
      * @param itemStack The item.
      */
-    protected void revert(@NotNull final ItemStack itemStack) {
+    public void revert(@NotNull final ItemStack itemStack) {
         // Technically optional.
     }
 
@@ -69,7 +69,7 @@ public abstract class DisplayModule extends PluginDependent<EcoPlugin> {
      * @param itemStack The itemStack.
      * @return The plugin-specific varargs.
      */
-    protected Object[] generateVarArgs(@NotNull final ItemStack itemStack) {
+    public Object[] generateVarArgs(@NotNull final ItemStack itemStack) {
         return new Object[0];
     }
 

eco-api/src/main/java/com/willfp/eco/core/events/ArmorEquipEvent.java

@@ -16,7 +16,6 @@ import org.jetbrains.annotations.NotNull;
  *
  * @see ArmorChangeEvent
  */
-@Deprecated
 public class ArmorEquipEvent extends PlayerEvent {
     /**
      * Bukkit parity.

eco-api/src/main/java/com/willfp/eco/core/fast/FastItemStack.java

@@ -3,6 +3,7 @@ package com.willfp.eco.core.fast;
 import com.willfp.eco.core.Eco;
 import org.bukkit.Material;
 import org.bukkit.enchantments.Enchantment;
+import org.bukkit.inventory.ItemFlag;
 import org.bukkit.inventory.ItemStack;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
@@ -10,6 +11,7 @@ import org.jetbrains.annotations.Nullable;
 import java.util.List;
 import java.util.Map;
 import java.util.Objects;
+import java.util.Set;
 
 /**
  * FastItemStack contains methods to modify and read items faster than in default bukkit.
@@ -47,6 +49,51 @@ public interface FastItemStack {
      */
     List<String> getLore();
 
+
+    /**
+     * Set the rework penalty.
+     *
+     * @param cost The rework penalty to set.
+     */
+    void setRepairCost(int cost);
+
+    /**
+     * Get the rework penalty.
+     * .
+     *
+     * @return The rework penalty found on the item.
+     */
+    int getRepairCost();
+
+    /**
+     * Add ItemFlags.
+     *
+     * @param hideFlags The flags.
+     */
+    void addItemFlags(ItemFlag... hideFlags);
+
+    /**
+     * Remove ItemFlags.
+     *
+     * @param hideFlags The flags.
+     */
+    void removeItemFlags(ItemFlag... hideFlags);
+
+    /**
+     * Get the ItemFlags.
+     *
+     * @return The flags.
+     */
+    Set<ItemFlag> getItemFlags();
+
+    /**
+     * Test the item for a flag.
+     *
+     * @param flag The flag.
+     * @return If the flag is present.
+     */
+    boolean hasItemFlag(ItemFlag flag);
+
     /**
      * Get the Bukkit ItemStack again.
      *

eco-api/src/main/java/com/willfp/eco/core/gui/GUIFactory.java

@@ -2,12 +2,10 @@ package com.willfp.eco.core.gui;
 
 import com.willfp.eco.core.gui.menu.MenuBuilder;
 import com.willfp.eco.core.gui.slot.SlotBuilder;
-import org.bukkit.entity.Player;
+import com.willfp.eco.core.gui.slot.functional.SlotProvider;
 import org.bukkit.inventory.ItemStack;
 import org.jetbrains.annotations.NotNull;
 
-import java.util.function.Function;
-
 /**
  * Internal component used by {@link com.willfp.eco.core.gui.menu.Menu#builder(int)}
  * and {@link com.willfp.eco.core.gui.slot.Slot#builder(ItemStack)}.
@@ -19,7 +17,7 @@ public interface GUIFactory {
      * @param provider The provider.
      * @return The builder.
      */
-    SlotBuilder createSlotBuilder(@NotNull Function<Player, ItemStack> provider);
+    SlotBuilder createSlotBuilder(@NotNull SlotProvider provider);
 
     /**
      * Create menu builder.

eco-api/src/main/java/com/willfp/eco/core/gui/menu/CloseHandler.java

@@ -0,0 +1,19 @@
+package com.willfp.eco.core.gui.menu;
+
+import org.bukkit.event.inventory.InventoryCloseEvent;
+import org.jetbrains.annotations.NotNull;
+
+/**
+ * Interface to run on menu close.
+ */
+@FunctionalInterface
+public interface CloseHandler {
+    /**
+     * Performs this operation on the given arguments.
+     *
+     * @param event The close event.
+     * @param menu  The menu.
+     */
+    void handle(@NotNull InventoryCloseEvent event,
+                @NotNull Menu menu);
+}

eco-api/src/main/java/com/willfp/eco/core/gui/menu/Menu.java

@@ -2,9 +2,16 @@ package com.willfp.eco.core.gui.menu;
 
 import com.willfp.eco.core.Eco;
 import com.willfp.eco.core.gui.slot.Slot;
+import org.bukkit.NamespacedKey;
 import org.bukkit.entity.Player;
 import org.bukkit.inventory.Inventory;
+import org.bukkit.inventory.ItemStack;
+import org.bukkit.persistence.PersistentDataType;
 import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+
+import java.util.List;
+import java.util.Set;
 
 /**
  * GUI version of {@link Inventory}.
@@ -44,6 +51,51 @@ public interface Menu {
      */
     Inventory open(@NotNull Player player);
 
+    /**
+     * Get captive items.
+     *
+     * @param player The player.
+     * @return The items.
+     */
+    List<ItemStack> getCaptiveItems(@NotNull Player player);
+
+    /**
+     * Write data.
+     *
+     * @param player The player.
+     * @param key    The key.
+     * @param type   The type.
+     * @param value  The value.
+     * @param <T>    The type.
+     * @param <Z>    The type.
+     */
+    <T, Z> void writeData(@NotNull Player player,
+                          @NotNull NamespacedKey key,
+                          @NotNull PersistentDataType<T, Z> type,
+                          @NotNull Z value);
+
+    /**
+     * Read data.
+     *
+     * @param player The player.
+     * @param key    The key.
+     * @param type   The type.
+     * @param <T>    The type.
+     * @param <Z>    The type.
+     * @return The data.
+     */
+    @Nullable <T, Z> T readData(@NotNull Player player,
+                                @NotNull NamespacedKey key,
+                                @NotNull PersistentDataType<T, Z> type);
+
+    /**
+     * Get all data keys for a player.
+     *
+     * @param player The player.
+     * @return The keys.
+     */
+    Set<NamespacedKey> getKeys(@NotNull Player player);
+
     /**
      * Create a builder with a given amount of rows.
      *

eco-api/src/main/java/com/willfp/eco/core/gui/menu/MenuBuilder.java

@@ -31,6 +31,14 @@ public interface MenuBuilder {
                         int column,
                         @NotNull Slot slot);
 
+    /**
+     * Run function to modify the builder.
+     *
+     * @param modifier The modifier.
+     * @return The builder.
+     */
+    MenuBuilder modfiy(@NotNull Consumer<MenuBuilder> modifier);
+
     /**
      * Set the menu mask.
      *
@@ -45,7 +53,18 @@ public interface MenuBuilder {
      * @param action The handler.
      * @return The builder.
      */
-    MenuBuilder onClose(@NotNull Consumer<InventoryCloseEvent> action);
+    default MenuBuilder onClose(@NotNull Consumer<InventoryCloseEvent> action) {
+        onClose((event, menu) -> action.accept(event));
+        return this;
+    }
+
+    /**
+     * Set the menu close handler.
+     *
+     * @param action The handler.
+     * @return The builder.
+     */
+    MenuBuilder onClose(@NotNull CloseHandler action);
 
     /**
      * Build the menu.

eco-api/src/main/java/com/willfp/eco/core/gui/slot/FillerMask.java

@@ -7,6 +7,7 @@ import org.bukkit.Material;
 import org.bukkit.inventory.ItemStack;
 import org.jetbrains.annotations.NotNull;
 
+import java.util.Arrays;
 import java.util.List;
 
 /**
@@ -39,35 +40,46 @@ public class FillerMask {
      */
     public FillerMask(@NotNull final Material material,
                       @NotNull final String... pattern) {
-        if (material == Material.AIR) {
-            throw new IllegalArgumentException("Material cannot be air!");
+        this(new MaskMaterials(material), pattern);
+    }
+
+    /**
+     * Create a new filler mask.
+     *
+     * @param materials The mask materials.
+     * @param pattern  The pattern.
+     */
+    public FillerMask(@NotNull final MaskMaterials materials,
+                      @NotNull final String... pattern) {
+        if (Arrays.stream(materials.materials()).anyMatch(material -> material == Material.AIR)) {
+            throw new IllegalArgumentException("Materials cannot be air!");
         }
 
         mask = ListUtils.create2DList(6, 9);
 
-        ItemStack itemStack = new ItemStackBuilder(material)
-                .setDisplayName("&r")
-                .build();
+        for (int i = 0; i < materials.materials().length; i++) {
+            ItemStack itemStack = new ItemStackBuilder(materials.materials()[i])
+                    .setDisplayName("&r")
+                    .build();
 
-        int row = 0;
+            int row = 0;
 
-        for (String patternRow : pattern) {
-            int column = 0;
-            if (patternRow.length() != 9) {
-                throw new IllegalArgumentException("Invalid amount of columns in pattern!");
-            }
-            for (char c : patternRow.toCharArray()) {
-                if (c == '0') {
-                    mask.get(row).set(column, null);
-                } else if (c == '1') {
-                    mask.get(row).set(column, new FillerSlot(itemStack));
-                } else {
-                    throw new IllegalArgumentException("Invalid character in pattern! (Must only be 0 and 1)");
+            for (String patternRow : pattern) {
+                int column = 0;
+                if (patternRow.length() != 9) {
+                    throw new IllegalArgumentException("Invalid amount of columns in pattern!");
                 }
+                for (char c : patternRow.toCharArray()) {
+                    if (c == '0') {
+                        mask.get(row).set(column, null);
+                    } else if (c == Character.forDigit(i + 1, 10)) {
+                        mask.get(row).set(column, new FillerSlot(itemStack));
+                    }
 
-                column++;
+                    column++;
+                }
+                row++;
             }
-            row++;
         }
     }
 }

eco-api/src/main/java/com/willfp/eco/core/gui/slot/FillerSlot.java

@@ -30,4 +30,9 @@ public class FillerSlot implements Slot {
     public ItemStack getItemStack(@NotNull final Player player) {
         return itemStack;
     }
+
+    @Override
+    public boolean isCaptive() {
+        return false;
+    }
 }

eco-api/src/main/java/com/willfp/eco/core/gui/slot/MaskMaterials.java

@@ -0,0 +1,14 @@
+package com.willfp.eco.core.gui.slot;
+
+import org.bukkit.Material;
+import org.jetbrains.annotations.NotNull;
+
+/**
+ * Mask materials store a set of materials which can be accessed by
+ * a filler mask.
+ *
+ * @param materials The materials.
+ */
+public record MaskMaterials(@NotNull Material... materials) {
+
+}

eco-api/src/main/java/com/willfp/eco/core/gui/slot/Slot.java

@@ -1,6 +1,8 @@
 package com.willfp.eco.core.gui.slot;
 
 import com.willfp.eco.core.Eco;
+import com.willfp.eco.core.gui.slot.functional.SlotProvider;
+import org.bukkit.Material;
 import org.bukkit.entity.Player;
 import org.bukkit.inventory.ItemStack;
 import org.jetbrains.annotations.NotNull;
@@ -19,6 +21,22 @@ public interface Slot {
      */
     ItemStack getItemStack(@NotNull Player player);
 
+    /**
+     * If the slot is captive. (Can items be placed in it).
+     *
+     * @return If captive.
+     */
+    boolean isCaptive();
+
+    /**
+     * Create a builder for an ItemStack.
+     *
+     * @return The builder.
+     */
+    static SlotBuilder builder() {
+        return Eco.getHandler().getGUIFactory().createSlotBuilder((player, menu) -> new ItemStack(Material.AIR));
+    }
+
     /**
      * Create a builder for an ItemStack.
      *
@@ -26,7 +44,7 @@ public interface Slot {
      * @return The builder.
      */
     static SlotBuilder builder(@NotNull final ItemStack itemStack) {
-        return Eco.getHandler().getGUIFactory().createSlotBuilder(player -> itemStack);
+        return Eco.getHandler().getGUIFactory().createSlotBuilder((player, menu) -> itemStack);
     }
 
     /**
@@ -36,6 +54,16 @@ public interface Slot {
      * @return The builder.
      */
     static SlotBuilder builder(@NotNull final Function<Player, ItemStack> provider) {
+        return Eco.getHandler().getGUIFactory().createSlotBuilder((player, menu) -> provider.apply(player));
+    }
+
+    /**
+     * Create a builder for a player-specific ItemStack.
+     *
+     * @param provider The provider.
+     * @return The builder.
+     */
+    static SlotBuilder builder(@NotNull final SlotProvider provider) {
         return Eco.getHandler().getGUIFactory().createSlotBuilder(provider);
     }
 }

eco-api/src/main/java/com/willfp/eco/core/gui/slot/SlotBuilder.java

@@ -1,5 +1,7 @@
 package com.willfp.eco.core.gui.slot;
 
+import com.willfp.eco.core.gui.slot.functional.SlotHandler;
+import com.willfp.eco.core.gui.slot.functional.SlotModifier;
 import org.bukkit.event.inventory.InventoryClickEvent;
 import org.jetbrains.annotations.NotNull;
 
@@ -15,7 +17,17 @@ public interface SlotBuilder {
      * @param action The handler.
      * @return The builder.
      */
-    SlotBuilder onLeftClick(@NotNull BiConsumer<InventoryClickEvent, Slot> action);
+    default SlotBuilder onLeftClick(@NotNull BiConsumer<InventoryClickEvent, Slot> action) {
+        return onLeftClick((event, slot, menu) -> action.accept(event, slot));
+    }
+
+    /**
+     * Set click handler.
+     *
+     * @param handler The handler.
+     * @return The builder.
+     */
+    SlotBuilder onLeftClick(@NotNull SlotHandler handler);
 
     /**
      * Set click handler.
@@ -23,7 +35,17 @@ public interface SlotBuilder {
      * @param action The handler.
      * @return The builder.
      */
-    SlotBuilder onRightClick(@NotNull BiConsumer<InventoryClickEvent, Slot> action);
+    default SlotBuilder onRightClick(@NotNull BiConsumer<InventoryClickEvent, Slot> action) {
+        return onRightClick((event, slot, menu) -> action.accept(event, slot));
+    }
+
+    /**
+     * Set click handler.
+     *
+     * @param handler The handler.
+     * @return The builder.
+     */
+    SlotBuilder onRightClick(@NotNull SlotHandler handler);
 
     /**
      * Set click handler.
@@ -31,7 +53,17 @@ public interface SlotBuilder {
      * @param action The handler.
      * @return The builder.
      */
-    SlotBuilder onShiftLeftClick(@NotNull BiConsumer<InventoryClickEvent, Slot> action);
+    default SlotBuilder onShiftLeftClick(@NotNull BiConsumer<InventoryClickEvent, Slot> action) {
+        return onShiftLeftClick((event, slot, menu) -> action.accept(event, slot));
+    }
+
+    /**
+     * Set click handler.
+     *
+     * @param handler The handler.
+     * @return The builder.
+     */
+    SlotBuilder onShiftLeftClick(@NotNull SlotHandler handler);
 
     /**
      * Set click handler.
@@ -39,7 +71,17 @@ public interface SlotBuilder {
      * @param action The handler.
      * @return The builder.
      */
-    SlotBuilder onShiftRightClick(@NotNull BiConsumer<InventoryClickEvent, Slot> action);
+    default SlotBuilder onShiftRightClick(@NotNull BiConsumer<InventoryClickEvent, Slot> action) {
+        return onShiftRightClick((event, slot, menu) -> action.accept(event, slot));
+    }
+
+    /**
+     * Set click handler.
+     *
+     * @param handler The handler.
+     * @return The builder.
+     */
+    SlotBuilder onShiftRightClick(@NotNull SlotHandler handler);
 
     /**
      * Set click handler.
@@ -47,7 +89,32 @@ public interface SlotBuilder {
      * @param action The handler.
      * @return The builder.
      */
-    SlotBuilder onMiddleClick(@NotNull BiConsumer<InventoryClickEvent, Slot> action);
+    default SlotBuilder onMiddleClick(@NotNull BiConsumer<InventoryClickEvent, Slot> action) {
+        return onMiddleClick((event, slot, menu) -> action.accept(event, slot));
+    }
+
+    /**
+     * Set click handler.
+     *
+     * @param handler The handler.
+     * @return The builder.
+     */
+    SlotBuilder onMiddleClick(@NotNull SlotHandler handler);
+
+    /**
+     * Modify the ItemStack.
+     *
+     * @param modifier The modifier.
+     * @return The builder.
+     */
+    SlotBuilder setModifier(@NotNull SlotModifier modifier);
+
+    /**
+     * Set slot to be a captive slot.
+     *
+     * @return The builder.
+     */
+    SlotBuilder setCaptive();
 
     /**
      * Build the slot.

eco-api/src/main/java/com/willfp/eco/core/gui/slot/functional/SlotHandler.java

@@ -0,0 +1,23 @@
+package com.willfp.eco.core.gui.slot.functional;
+
+import com.willfp.eco.core.gui.menu.Menu;
+import com.willfp.eco.core.gui.slot.Slot;
+import org.bukkit.event.inventory.InventoryClickEvent;
+import org.jetbrains.annotations.NotNull;
+
+/**
+ * Interface to run on slot click.
+ */
+@FunctionalInterface
+public interface SlotHandler {
+    /**
+     * Performs this operation on the given arguments.
+     *
+     * @param event The click event.
+     * @param slot  The slot
+     * @param menu  The menu.
+     */
+    void handle(@NotNull InventoryClickEvent event,
+                @NotNull Slot slot,
+                @NotNull Menu menu);
+}

eco-api/src/main/java/com/willfp/eco/core/gui/slot/functional/SlotModifier.java

@@ -0,0 +1,23 @@
+package com.willfp.eco.core.gui.slot.functional;
+
+import com.willfp.eco.core.gui.menu.Menu;
+import org.bukkit.entity.Player;
+import org.bukkit.inventory.ItemStack;
+import org.jetbrains.annotations.NotNull;
+
+/**
+ * Interface to run on slot modify.
+ */
+@FunctionalInterface
+public interface SlotModifier {
+    /**
+     * Performs this operation on the given arguments.
+     *
+     * @param player   The player.
+     * @param menu     The menu.
+     * @param previous The previous ItemStack.
+     */
+    void modify(@NotNull Player player,
+                @NotNull Menu menu,
+                @NotNull ItemStack previous);
+}

eco-api/src/main/java/com/willfp/eco/core/gui/slot/functional/SlotProvider.java

@@ -0,0 +1,22 @@
+package com.willfp.eco.core.gui.slot.functional;
+
+import com.willfp.eco.core.gui.menu.Menu;
+import org.bukkit.entity.Player;
+import org.bukkit.inventory.ItemStack;
+import org.jetbrains.annotations.NotNull;
+
+/**
+ * Interface to run on slot display.
+ */
+@FunctionalInterface
+public interface SlotProvider {
+    /**
+     * Performs this operation on the given arguments.
+     *
+     * @param player The player.
+     * @param menu   The menu.
+     * @return The ItemStack.
+     */
+    ItemStack provide(@NotNull Player player,
+                      @NotNull Menu menu);
+}

eco-api/src/main/java/com/willfp/eco/core/integrations/antigrief/AntigriefManager.java

@@ -29,6 +29,16 @@ public class AntigriefManager {
         registered.add(antigrief);
     }
 
+    /**
+     * Unregister an AntiGrief/Land Management integration.
+     *
+     * @param antigrief The integration to unregister.
+     */
+    public void unregister(@NotNull final AntigriefWrapper antigrief) {
+        registered.removeIf(it -> it.getPluginName().equalsIgnoreCase(antigrief.getPluginName()));
+        registered.remove(antigrief);
+    }
+
     /**
      * Can player break block.
      *

eco-api/src/main/java/com/willfp/eco/core/integrations/customitems/CustomItemsWrapper.java

@@ -1,9 +1,11 @@
 package com.willfp.eco.core.integrations.customitems;
 
+import com.willfp.eco.core.integrations.Integration;
+
 /**
  * Wrapper class for custom item integrations.
  */
-public interface CustomItemsWrapper {
+public interface CustomItemsWrapper extends Integration {
     /**
      * Register all the custom items for a specific plugin into eco.
      *

eco-api/src/main/java/com/willfp/eco/core/integrations/mcmmo/McmmoManager.java

@@ -16,7 +16,7 @@ public class McmmoManager {
     /**
      * A set of all registered integrations.
      */
-    private final Set<McmmoWrapper> regsistered = new HashSet<>();
+    private final Set<McmmoWrapper> registered = new HashSet<>();
 
     /**
      * Register a new integration.
@@ -24,7 +24,7 @@ public class McmmoManager {
      * @param integration The integration to register.
      */
     public void register(@NotNull final McmmoWrapper integration) {
-        regsistered.add(integration);
+        registered.add(integration);
     }
 
     /**
@@ -34,7 +34,7 @@ public class McmmoManager {
      * @return The bonus drop count.
      */
     public int getBonusDropCount(@NotNull final Block block) {
-        for (McmmoWrapper mcmmoWrapper : regsistered) {
+        for (McmmoWrapper mcmmoWrapper : registered) {
             return mcmmoWrapper.getBonusDropCount(block);
         }
         return 0;
@@ -47,7 +47,7 @@ public class McmmoManager {
      * @return If the event is fake.
      */
     public boolean isFake(@NotNull final Event event) {
-        for (McmmoWrapper mcmmoWrapper : regsistered) {
+        for (McmmoWrapper mcmmoWrapper : registered) {
             return mcmmoWrapper.isFake(event);
         }
         return false;

eco-api/src/main/java/com/willfp/eco/core/integrations/placeholder/PlaceholderManager.java

@@ -5,7 +5,9 @@ import org.bukkit.entity.Player;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 
+import java.util.HashMap;
 import java.util.HashSet;
+import java.util.Map;
 import java.util.Optional;
 import java.util.Set;
 import java.util.concurrent.atomic.AtomicReference;
@@ -18,7 +20,7 @@ public class PlaceholderManager {
     /**
      * All registered placeholders.
      */
-    private static final Set<PlaceholderEntry> REGISTERED_PLACEHOLDERS = new HashSet<>();
+    private static final Map<String, PlaceholderEntry> REGISTERED_PLACEHOLDERS = new HashMap<>();
 
     /**
      * All registered placeholder integrations.
@@ -41,8 +43,8 @@ public class PlaceholderManager {
      * @param expansion The {@link PlaceholderEntry} to register.
      */
     public static void registerPlaceholder(@NotNull final PlaceholderEntry expansion) {
-        REGISTERED_PLACEHOLDERS.removeIf(placeholderEntry -> placeholderEntry.getIdentifier().equalsIgnoreCase(expansion.getIdentifier()));
-        REGISTERED_PLACEHOLDERS.add(expansion);
+        REGISTERED_PLACEHOLDERS.remove(expansion.getIdentifier());
+        REGISTERED_PLACEHOLDERS.put(expansion.getIdentifier(), expansion);
     }
 
     /**
@@ -54,14 +56,15 @@ public class PlaceholderManager {
      */
     public static String getResult(@Nullable final Player player,
                                    @NotNull final String identifier) {
-        Optional<PlaceholderEntry> matching = REGISTERED_PLACEHOLDERS.stream().filter(expansion -> expansion.getIdentifier().equalsIgnoreCase(identifier)).findFirst();
-        if (matching.isEmpty()) {
-            return null;
+        PlaceholderEntry entry = REGISTERED_PLACEHOLDERS.get(identifier.toLowerCase());
+        if (entry == null) {
+            return "";
         }
-        PlaceholderEntry entry = matching.get();
+
         if (player == null && entry.requiresPlayer()) {
             return "";
         }
+
         return entry.getResult(player);
     }
 
@@ -74,8 +77,10 @@ public class PlaceholderManager {
      */
     public static String translatePlaceholders(@NotNull final String text,
                                                @Nullable final Player player) {
-        AtomicReference<String> translatedReference = new AtomicReference<>(text);
-        REGISTERED_INTEGRATIONS.forEach(placeholderIntegration -> translatedReference.set(placeholderIntegration.translate(translatedReference.get(), player)));
-        return translatedReference.get();
+        String processed = text;
+        for (PlaceholderIntegration integration : REGISTERED_INTEGRATIONS) {
+            processed = integration.translate(processed, player);
+        }
+        return processed;
     }
 }

eco-api/src/main/java/com/willfp/eco/core/integrations/shop/ShopManager.java

@@ -0,0 +1,36 @@
+package com.willfp.eco.core.integrations.shop;
+
+import lombok.experimental.UtilityClass;
+import org.jetbrains.annotations.NotNull;
+
+import java.util.HashSet;
+import java.util.Set;
+
+/**
+ * Class to handle shop integrations.
+ */
+@UtilityClass
+public class ShopManager {
+    /**
+     * A set of all registered integrations.
+     */
+    private final Set<ShopWrapper> registered = new HashSet<>();
+
+    /**
+     * Register a new integration.
+     *
+     * @param integration The integration to register.
+     */
+    public void register(@NotNull final ShopWrapper integration) {
+        registered.add(integration);
+    }
+
+    /**
+     * Register eco item provider for shop plugins.
+     */
+    public void registerEcoProvider() {
+        for (ShopWrapper shopWrapper : registered) {
+            shopWrapper.registerEcoProvider();
+        }
+    }
+}

eco-api/src/main/java/com/willfp/eco/core/integrations/shop/ShopWrapper.java

@@ -0,0 +1,13 @@
+package com.willfp.eco.core.integrations.shop;
+
+import com.willfp.eco.core.integrations.Integration;
+
+/**
+ * Wrapper class for shop integrations.
+ */
+public interface ShopWrapper extends Integration {
+    /**
+     * Register eco item provider for shop plugins.
+     */
+    void registerEcoProvider();
+}

eco-api/src/main/java/com/willfp/eco/core/items/CustomItem.java

@@ -1,6 +1,9 @@
 package com.willfp.eco.core.items;
 
+import com.willfp.eco.core.Eco;
 import lombok.Getter;
+import org.apache.commons.lang.Validate;
+import org.bukkit.Bukkit;
 import org.bukkit.NamespacedKey;
 import org.bukkit.inventory.ItemStack;
 import org.jetbrains.annotations.NotNull;
@@ -47,6 +50,12 @@ public class CustomItem implements TestableItem {
         this.key = key;
         this.test = test;
         this.item = item;
+
+        Eco.getHandler().getEcoPlugin().getScheduler().runLater(() -> {
+            if (!matches(getItem())) {
+                Bukkit.getLogger().severe("Item with key " + key + " is invalid!");
+            }
+        }, 1);
     }
 
     @Override

eco-api/src/main/java/com/willfp/eco/core/items/Items.java

@@ -1,25 +1,29 @@
 package com.willfp.eco.core.items;
 
-import com.willfp.eco.core.items.builder.ItemBuilder;
-import com.willfp.eco.core.items.builder.ItemStackBuilder;
+import com.willfp.eco.core.items.args.LookupArgParser;
+import com.willfp.eco.core.items.provider.ItemProvider;
 import com.willfp.eco.core.recipe.parts.EmptyTestableItem;
 import com.willfp.eco.core.recipe.parts.MaterialTestableItem;
 import com.willfp.eco.core.recipe.parts.ModifiedTestableItem;
 import com.willfp.eco.core.recipe.parts.TestableStack;
 import com.willfp.eco.util.NamespacedKeyUtils;
+import com.willfp.eco.util.NumberUtils;
 import lombok.experimental.UtilityClass;
 import org.bukkit.Material;
 import org.bukkit.NamespacedKey;
-import org.bukkit.enchantments.Enchantment;
 import org.bukkit.inventory.ItemStack;
 import org.bukkit.inventory.meta.ItemMeta;
 import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
 
+import java.util.ArrayList;
 import java.util.Arrays;
-import java.util.HashMap;
-import java.util.HashSet;
+import java.util.List;
 import java.util.Map;
 import java.util.Set;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.function.Predicate;
+import java.util.stream.Collectors;
 
 /**
  * Class to manage all custom and vanilla items.
@@ -29,17 +33,45 @@ public final class Items {
     /**
      * All recipe parts.
      */
-    private static final Map<NamespacedKey, CustomItem> REGISTRY = new HashMap<>();
+    private static final Map<NamespacedKey, TestableItem> REGISTRY = new ConcurrentHashMap<>();
 
     /**
-     * Register a new recipe part.
+     * All item providers.
+     */
+    private static final Map<String, ItemProvider> PROVIDERS = new ConcurrentHashMap<>();
+
+    /**
+     * All recipe parts.
+     */
+    private static final List<LookupArgParser> ARG_PARSERS = new ArrayList<>();
+
+    /**
+     * Register a new custom item.
      *
-     * @param key  The key of the recipe part.
-     * @param part The recipe part.
+     * @param key  The key of the item.
+     * @param item The item.
      */
     public void registerCustomItem(@NotNull final NamespacedKey key,
-                                   @NotNull final CustomItem part) {
-        REGISTRY.put(key, part);
+                                   @NotNull final TestableItem item) {
+        REGISTRY.put(key, item);
+    }
+
+    /**
+     * Register a new item provider.
+     *
+     * @param provider The provider.
+     */
+    public void registerItemProvider(@NotNull final ItemProvider provider) {
+        PROVIDERS.put(provider.getNamespace(), provider);
+    }
+
+    /**
+     * Register a new arg parser.
+     *
+     * @param parser The parser.
+     */
+    public void registerArgParser(@NotNull final LookupArgParser parser) {
+        ARG_PARSERS.add(parser);
     }
 
     /**
@@ -52,14 +84,41 @@ public final class Items {
     }
 
     /**
-     * Lookup item from string.
+     * This is the backbone of the entire eco item system.
      * <p>
-     * Used for recipes.
+     * You can lookup a TestableItem for any material, custom item,
+     * or item in general, and it will return it with any modifiers
+     * passed as parameters. This includes stack size (item amount)
+     * and enchantments that should be present on the item.
+     * <p>
+     * If you want to get an ItemStack instance from this, then just call
+     * {@link TestableItem#getItem()}.
+     * <p>
+     * The advantages of the testable item system are that there is the inbuilt
+     * {@link TestableItem#matches(ItemStack)} - this allows to check if any item
+     * is that testable item; which may sound negligible but actually it allows for
+     * much more power an flexibility. For example, you can have an item with an
+     * extra metadata tag, extra lore lines, different display name - and it
+     * will still work as long as the test passes. This is very important
+     * for custom crafting recipes where other plugins may add metadata
+     * values or the play may rename the item.
      *
-     * @param key The string to test.
-     * @return The found testable item, or an empty item if not found.
+     * @param key The lookup string.
+     * @return The testable item, or an {@link EmptyTestableItem}.
      */
     public TestableItem lookup(@NotNull final String key) {
+        if (key.contains("?")) {
+            String[] options = key.split("\\?");
+            for (String option : options) {
+                TestableItem lookup = lookup(option);
+                if (!(lookup instanceof EmptyTestableItem)) {
+                    return lookup;
+                }
+            }
+
+            return new EmptyTestableItem();
+        }
+
         String[] args = key.split(" ");
         if (args.length == 0) {
             return new EmptyTestableItem();
@@ -67,6 +126,8 @@ public final class Items {
 
         TestableItem item = null;
 
+        int stackAmount = 1;
+
         String[] split = args[0].toLowerCase().split(":");
 
         if (split.length == 1) {
@@ -78,73 +139,102 @@ public final class Items {
         }
 
         if (split.length == 2) {
-            CustomItem part = REGISTRY.get(NamespacedKeyUtils.create(split[0], split[1]));
+            String namespace = split[0];
+            String keyID = split[1];
+            NamespacedKey namespacedKey = NamespacedKeyUtils.create(namespace, keyID);
 
+            TestableItem part = REGISTRY.get(namespacedKey);
+
+            if (part == null && PROVIDERS.containsKey(namespace)) {
+                ItemProvider provider = PROVIDERS.get(namespace);
+                item = provider.provideForKey(keyID);
+                if (item instanceof EmptyTestableItem || item == null) {
+                    return new EmptyTestableItem();
+                }
+                registerCustomItem(namespacedKey, item);
+            }
+
+            /*
+            Legacy id:amount format
+            This has been superseded by id amount
+             */
             if (part == null) {
                 Material material = Material.getMaterial(split[0].toUpperCase());
                 if (material == null || material == Material.AIR) {
                     return new EmptyTestableItem();
                 }
-                item = new TestableStack(new MaterialTestableItem(material), Integer.parseInt(split[1]));
+                item = new MaterialTestableItem(material);
+                stackAmount = Integer.parseInt(split[1]);
             } else {
                 item = part;
             }
         }
 
+        /*
+        Legacy namespace:id:amount format
+        This has been superseded by namespace:id amount
+         */
         if (split.length == 3) {
-            CustomItem part = REGISTRY.get(NamespacedKeyUtils.create(split[0], split[1]));
-            item = part == null ? new EmptyTestableItem() : new TestableStack(part, Integer.parseInt(split[2]));
+            TestableItem part = REGISTRY.get(NamespacedKeyUtils.create(split[0], split[1]));
+            if (part == null) {
+                return new EmptyTestableItem();
+            }
+            item = part;
+            stackAmount = Integer.parseInt(split[2]);
         }
 
+        boolean usingNewStackFormat = false;
+
+        if (args.length >= 2) {
+            try {
+                stackAmount = Integer.parseInt(args[1]);
+                usingNewStackFormat = true;
+            } catch (NumberFormatException ignored) {
+            }
+        }
+
+        // Marked as redundant but i am covering all bases here
         if (item == null || item instanceof EmptyTestableItem) {
             return new EmptyTestableItem();
         }
 
-        String[] enchantArgs = Arrays.copyOfRange(args, 1, args.length);
+        ItemStack example = item.getItem();
+        ItemMeta meta = example.getItemMeta();
+        assert meta != null;
 
-        Map<Enchantment, Integer> requiredEnchantments = new HashMap<>();
+        String[] modifierArgs = Arrays.copyOfRange(args, usingNewStackFormat ? 2 : 1, args.length);
 
-        for (String enchantArg : enchantArgs) {
-            String[] enchantArgSplit = enchantArg.split(":");
+        List<Predicate<ItemStack>> predicates = new ArrayList<>();
 
-            Enchantment enchantment = Enchantment.getByKey(NamespacedKey.minecraft(enchantArgSplit[0].toLowerCase()));
-            int level = Integer.parseInt(enchantArgSplit[1]);
-
-            requiredEnchantments.put(enchantment, level);
+        for (LookupArgParser argParser : ARG_PARSERS) {
+            Predicate<ItemStack> predicate = argParser.parseArguments(modifierArgs, meta);
+            if (predicate != null) {
+                predicates.add(argParser.parseArguments(modifierArgs, meta));
+            }
         }
 
-        if (requiredEnchantments.isEmpty()) {
+        example.setItemMeta(meta);
+        if (!predicates.isEmpty()) {
+            item = new ModifiedTestableItem(
+                    item,
+                    test -> {
+                        for (Predicate<ItemStack> predicate : predicates) {
+                            if (!predicate.test(test)) {
+                                return false;
+                            }
+                        }
+
+                        return true;
+                    },
+                    example
+            );
+        }
+
+        if (stackAmount <= 1) {
             return item;
+        } else {
+            return new TestableStack(item, stackAmount);
         }
-
-        ItemBuilder builder = new ItemStackBuilder(item.getItem());
-        requiredEnchantments.forEach(builder::addEnchantment);
-        ItemStack example = builder.build();
-
-        return new ModifiedTestableItem(
-                item,
-                itemStack -> {
-                    if (!itemStack.hasItemMeta()) {
-                        return false;
-                    }
-
-                    ItemMeta meta = itemStack.getItemMeta();
-
-                    assert meta != null;
-
-                    for (Map.Entry<Enchantment, Integer> entry : requiredEnchantments.entrySet()) {
-                        if (!meta.hasEnchant(entry.getKey())) {
-                            return false;
-                        }
-                        if (meta.getEnchantLevel(entry.getKey()) < entry.getValue()) {
-                            return false;
-                        }
-                    }
-
-                    return true;
-                },
-                example
-        );
     }
 
     /**
@@ -154,7 +244,7 @@ public final class Items {
      * @return If is recipe.
      */
     public boolean isCustomItem(@NotNull final ItemStack itemStack) {
-        for (CustomItem item : REGISTRY.values()) {
+        for (TestableItem item : REGISTRY.values()) {
             if (item.matches(itemStack)) {
                 return true;
             }
@@ -162,12 +252,49 @@ public final class Items {
         return false;
     }
 
+    /**
+     * Get custom item from item.
+     *
+     * @param itemStack The item.
+     * @return The custom item, or null if not exists.
+     */
+    @Nullable
+    public CustomItem getCustomItem(@NotNull final ItemStack itemStack) {
+        for (TestableItem item : REGISTRY.values()) {
+            if (item.matches(itemStack)) {
+                return getOrWrap(item);
+            }
+        }
+        return null;
+    }
+
     /**
      * Get all registered custom items.
      *
      * @return A set of all items.
      */
     public Set<CustomItem> getCustomItems() {
-        return new HashSet<>(REGISTRY.values());
+        return REGISTRY.values().stream().map(Items::getOrWrap).collect(Collectors.toSet());
+    }
+
+    /**
+     * Return a CustomItem instance for a given TestableItem.
+     * <p>
+     * Used internally since 6.10.0 when the registration moved from {@link CustomItem}
+     * to {@link TestableItem} for added flexibility.
+     *
+     * @param item The item.
+     * @return The CustomItem.
+     */
+    public CustomItem getOrWrap(@NotNull final TestableItem item) {
+        if (item instanceof CustomItem) {
+            return (CustomItem) item;
+        } else {
+            return new CustomItem(
+                    NamespacedKeyUtils.createEcoKey("wrapped_" + NumberUtils.randInt(0, 100000)),
+                    item::matches,
+                    item.getItem()
+            );
+        }
     }
 }

eco-api/src/main/java/com/willfp/eco/core/items/args/EnchantmentArgParser.java

@@ -0,0 +1,83 @@
+package com.willfp.eco.core.items.args;
+
+import org.bukkit.NamespacedKey;
+import org.bukkit.enchantments.Enchantment;
+import org.bukkit.inventory.ItemStack;
+import org.bukkit.inventory.meta.EnchantmentStorageMeta;
+import org.bukkit.inventory.meta.ItemMeta;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.function.Predicate;
+
+/**
+ * Parses enchantment arguments.
+ */
+public class EnchantmentArgParser implements LookupArgParser {
+    @Override
+    public @Nullable Predicate<ItemStack> parseArguments(@NotNull final String[] args,
+                                                         @NotNull final ItemMeta meta) {
+        Map<Enchantment, Integer> requiredEnchantments = new HashMap<>();
+
+        for (String enchantArg : args) {
+            String[] enchantArgSplit = enchantArg.split(":");
+
+            Enchantment enchantment = Enchantment.getByKey(NamespacedKey.minecraft(enchantArgSplit[0].toLowerCase()));
+            if (enchantment == null) {
+                continue;
+            }
+
+            if (enchantArgSplit.length < 2) {
+                continue;
+            }
+
+            int level = Integer.parseInt(enchantArgSplit[1]);
+
+            requiredEnchantments.put(enchantment, level);
+        }
+
+        if (requiredEnchantments.isEmpty()) {
+            return null;
+        }
+
+        if (meta instanceof EnchantmentStorageMeta storageMeta) {
+            requiredEnchantments.forEach((enchantment, integer) -> storageMeta.addStoredEnchant(enchantment, integer, true));
+        } else {
+            requiredEnchantments.forEach((enchantment, integer) -> meta.addEnchant(enchantment, integer, true));
+        }
+
+        return test -> {
+            if (!test.hasItemMeta()) {
+                return false;
+            }
+
+            ItemMeta testMeta = test.getItemMeta();
+
+            assert testMeta != null;
+
+            if (testMeta instanceof EnchantmentStorageMeta storageMeta) {
+                for (Map.Entry<Enchantment, Integer> entry : requiredEnchantments.entrySet()) {
+                    if (!storageMeta.hasStoredEnchant(entry.getKey())) {
+                        return false;
+                    }
+                    if (storageMeta.getStoredEnchantLevel(entry.getKey()) < entry.getValue()) {
+                        return false;
+                    }
+                }
+            } else {
+                for (Map.Entry<Enchantment, Integer> entry : requiredEnchantments.entrySet()) {
+                    if (!testMeta.hasEnchant(entry.getKey())) {
+                        return false;
+                    }
+                    if (testMeta.getEnchantLevel(entry.getKey()) < entry.getValue()) {
+                        return false;
+                    }
+                }
+            }
+
+            return true;
+        };
+    }
+}

eco-api/src/main/java/com/willfp/eco/core/items/args/LookupArgParser.java

@@ -0,0 +1,25 @@
+package com.willfp.eco.core.items.args;
+
+import com.willfp.eco.core.items.TestableItem;
+import org.bukkit.inventory.ItemStack;
+import org.bukkit.inventory.meta.ItemMeta;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+
+import java.util.function.Predicate;
+
+/**
+ * An argument parser should generate the predicate as well
+ * as modify the ItemMeta for {@link TestableItem#getItem()}.
+ */
+public interface LookupArgParser {
+    /**
+     * Parse the arguments.
+     *
+     * @param args The arguments.
+     * @param meta The ItemMeta to modify.
+     * @return The predicate test to apply to the modified item.
+     */
+    @Nullable Predicate<ItemStack> parseArguments(@NotNull String[] args,
+                                                  @NotNull ItemMeta meta);
+}

eco-api/src/main/java/com/willfp/eco/core/items/args/TextureArgParser.java

@@ -0,0 +1,59 @@
+package com.willfp.eco.core.items.args;
+
+import com.willfp.eco.util.SkullUtils;
+import org.bukkit.inventory.ItemStack;
+import org.bukkit.inventory.meta.ItemMeta;
+import org.bukkit.inventory.meta.SkullMeta;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+
+import java.util.function.Predicate;
+
+/**
+ * Parse skull textures.
+ */
+public class TextureArgParser implements LookupArgParser {
+    @Override
+    public @Nullable Predicate<ItemStack> parseArguments(@NotNull final String[] args,
+                                                         @NotNull final ItemMeta meta) {
+        String skullTexture = null;
+
+        for (String arg : args) {
+            String[] argSplit = arg.split(":");
+            if (!argSplit[0].equalsIgnoreCase("texture")) {
+                continue;
+            }
+
+            if (argSplit.length < 2) {
+                continue;
+            }
+
+            skullTexture = argSplit[1];
+        }
+
+        if (meta instanceof SkullMeta skullMeta && skullTexture != null) {
+            SkullUtils.setSkullTexture(skullMeta, skullTexture);
+        }
+
+        if (skullTexture == null) {
+            return null;
+        }
+
+        String finalSkullTexture = skullTexture;
+        return test -> {
+            if (!test.hasItemMeta()) {
+                return false;
+            }
+
+            ItemMeta testMeta = test.getItemMeta();
+
+            assert testMeta != null;
+
+            if (testMeta instanceof SkullMeta skullMeta && finalSkullTexture != null) {
+                return finalSkullTexture.equalsIgnoreCase(SkullUtils.getSkullTexture(skullMeta));
+            }
+
+            return true;
+        };
+    }
+}

eco-api/src/main/java/com/willfp/eco/core/items/provider/ItemProvider.java

@@ -0,0 +1,40 @@
+package com.willfp.eco.core.items.provider;
+
+import com.willfp.eco.core.items.TestableItem;
+import lombok.Getter;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+
+/**
+ * Item providers are call-site registrations for items. In other words,
+ * they only register their items when a request is made. This is marginally
+ * slower, however it is required for certain plugins, and fixes bugs related to
+ * loading orders.
+ *
+ * @see TestableItem
+ */
+public abstract class ItemProvider {
+    /**
+     * The namespace.
+     */
+    @Getter
+    private final String namespace;
+
+    /**
+     * Create a new ItemProvider for a specific namespace.
+     *
+     * @param namespace The namespace.
+     */
+    protected ItemProvider(@NotNull final String namespace) {
+        this.namespace = namespace;
+    }
+
+    /**
+     * Provide a TestableItem for a given key.
+     *
+     * @param key The item ID.
+     * @return The TestableItem, or null if not found.
+     */
+    @Nullable
+    public abstract TestableItem provideForKey(@NotNull final String key);
+}

eco-api/src/main/java/com/willfp/eco/core/recipe/parts/MaterialTestableItem.java

@@ -2,6 +2,7 @@ package com.willfp.eco.core.recipe.parts;
 
 import com.willfp.eco.core.items.TestableItem;
 import lombok.Getter;
+import org.apache.commons.lang.Validate;
 import org.bukkit.Material;
 import org.bukkit.inventory.ItemStack;
 import org.jetbrains.annotations.NotNull;
@@ -23,6 +24,8 @@ public class MaterialTestableItem implements TestableItem {
      * @param material The material.
      */
     public MaterialTestableItem(@NotNull final Material material) {
+        Validate.isTrue(material != Material.AIR, "You can't have air as the type!");
+
         this.material = material;
     }
 

eco-api/src/main/java/com/willfp/eco/core/recipe/parts/ModifiedTestableItem.java

@@ -2,6 +2,7 @@ package com.willfp.eco.core.recipe.parts;
 
 import com.willfp.eco.core.items.TestableItem;
 import lombok.Getter;
+import org.apache.commons.lang.Validate;
 import org.bukkit.inventory.ItemStack;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
@@ -17,6 +18,7 @@ public class ModifiedTestableItem implements TestableItem {
     /**
      * The item.
      */
+    @Getter
     private final TestableItem handle;
 
     /**

eco-api/src/main/java/com/willfp/eco/core/recipe/parts/TestableStack.java

@@ -1,17 +1,12 @@
 package com.willfp.eco.core.recipe.parts;
 
-import com.willfp.eco.core.Eco;
 import com.willfp.eco.core.items.TestableItem;
 import lombok.Getter;
 import org.apache.commons.lang.Validate;
 import org.bukkit.inventory.ItemStack;
-import org.bukkit.inventory.meta.ItemMeta;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 
-import java.util.ArrayList;
-import java.util.List;
-
 /**
  * Stacks of items.
  */
@@ -19,6 +14,7 @@ public class TestableStack implements TestableItem {
     /**
      * The item.
      */
+    @Getter
     private final TestableItem handle;
 
     /**
@@ -35,7 +31,8 @@ public class TestableStack implements TestableItem {
      */
     public TestableStack(@NotNull final TestableItem item,
                          final int amount) {
-        Validate.isTrue(!(item instanceof TestableStack));
+        Validate.isTrue(!(item instanceof TestableStack), "You can't stack a stack!");
+        Validate.isTrue(!(item instanceof EmptyTestableItem), "You can't stack air!");
 
         this.handle = item;
         this.amount = amount;
@@ -55,19 +52,7 @@ public class TestableStack implements TestableItem {
     @Override
     public ItemStack getItem() {
         ItemStack temp = handle.getItem().clone();
-        ItemMeta meta = temp.getItemMeta();
-        assert meta != null;
-
-        List<String> lore = meta.hasLore() ? meta.getLore() : new ArrayList<>();
-        assert lore != null;
-        lore.add("");
-        String add = Eco.getHandler().getEcoPlugin().getLangYml().getString("multiple-in-craft");
-        add = add.replace("%amount%", String.valueOf(amount));
-        lore.add(add);
-        meta.setLore(lore);
-        temp.setItemMeta(meta);
         temp.setAmount(amount);
-
         return temp;
     }
 }

eco-api/src/main/java/com/willfp/eco/core/recipe/recipes/ShapedCraftingRecipe.java

@@ -1,16 +1,19 @@
 package com.willfp.eco.core.recipe.recipes;
 
+import com.willfp.eco.core.Eco;
 import com.willfp.eco.core.EcoPlugin;
 import com.willfp.eco.core.PluginDependent;
 import com.willfp.eco.core.items.TestableItem;
 import com.willfp.eco.core.recipe.Recipes;
 import com.willfp.eco.core.recipe.parts.EmptyTestableItem;
+import com.willfp.eco.core.recipe.parts.TestableStack;
 import lombok.Getter;
 import org.bukkit.Bukkit;
 import org.bukkit.NamespacedKey;
 import org.bukkit.inventory.ItemStack;
 import org.bukkit.inventory.RecipeChoice;
 import org.bukkit.inventory.ShapedRecipe;
+import org.bukkit.inventory.meta.ItemMeta;
 import org.jetbrains.annotations.NotNull;
 
 import java.util.ArrayList;
@@ -79,6 +82,10 @@ public final class ShapedCraftingRecipe extends PluginDependent<EcoPlugin> imple
         ShapedRecipe shapedRecipe = new ShapedRecipe(this.getKey(), this.getOutput());
         shapedRecipe.shape("012", "345", "678");
         for (int i = 0; i < 9; i++) {
+            if (parts.get(i) instanceof EmptyTestableItem) {
+                continue;
+            }
+
             char character = String.valueOf(i).toCharArray()[0];
             shapedRecipe.setIngredient(character, parts.get(i).getItem().getType());
         }
@@ -86,8 +93,28 @@ public final class ShapedCraftingRecipe extends PluginDependent<EcoPlugin> imple
         ShapedRecipe displayedRecipe = new ShapedRecipe(this.getDisplayedKey(), this.getOutput());
         displayedRecipe.shape("012", "345", "678");
         for (int i = 0; i < 9; i++) {
+            if (parts.get(i) instanceof EmptyTestableItem) {
+                continue;
+            }
+
             char character = String.valueOf(i).toCharArray()[0];
-            displayedRecipe.setIngredient(character, new RecipeChoice.ExactChoice(parts.get(i).getItem()));
+            ItemStack item = parts.get(i).getItem();
+
+            if (parts.get(i) instanceof TestableStack) {
+                ItemMeta meta = item.getItemMeta();
+                assert meta != null;
+
+                List<String> lore = meta.hasLore() ? meta.getLore() : new ArrayList<>();
+                assert lore != null;
+                lore.add("");
+                String add = Eco.getHandler().getEcoPlugin().getLangYml().getString("multiple-in-craft");
+                add = add.replace("%amount%", String.valueOf(item.getAmount()));
+                lore.add(add);
+                meta.setLore(lore);
+                item.setItemMeta(meta);
+            }
+
+            displayedRecipe.setIngredient(character, new RecipeChoice.ExactChoice(item));
         }
 
         Bukkit.getServer().addRecipe(shapedRecipe);

eco-api/src/main/java/com/willfp/eco/core/requirement/Requirement.java

@@ -0,0 +1,28 @@
+package com.willfp.eco.core.requirement;
+
+import org.bukkit.entity.Player;
+import org.jetbrains.annotations.NotNull;
+
+import java.util.List;
+
+/**
+ * A requirement is a defined goal that a player must meet.
+ */
+public abstract class Requirement {
+    /**
+     * Create a new requirement.
+     */
+    protected Requirement() {
+
+    }
+
+    /**
+     * Test if the player meets the requirement.
+     *
+     * @param player The player.
+     * @param args   The arguments.
+     * @return The requirement.
+     */
+    public abstract boolean doesPlayerMeet(@NotNull Player player,
+                                           @NotNull List<String> args);
+}

eco-api/src/main/java/com/willfp/eco/core/requirement/RequirementFactory.java

@@ -0,0 +1,17 @@
+package com.willfp.eco.core.requirement;
+
+import org.jetbrains.annotations.NotNull;
+
+/**
+ * Interface for internal requirement factory implementations.
+ */
+public interface RequirementFactory {
+    /**
+     * Create a requirement.
+     *
+     * @param name The name.
+     * @return The requirement returned for the name.
+     * Will return a requirement that is always true if not found.
+     */
+    Requirement create(@NotNull String name);
+}

eco-api/src/main/java/com/willfp/eco/core/requirement/Requirements.java

@@ -0,0 +1,41 @@
+package com.willfp.eco.core.requirement;
+
+import com.willfp.eco.core.Eco;
+import lombok.experimental.UtilityClass;
+import org.jetbrains.annotations.NotNull;
+
+/**
+ * Contains methods and fields pertaining to requirements.
+ */
+@UtilityClass
+public class Requirements {
+    /**
+     * Requires a player to have a permission.
+     */
+    public static final Requirement HAS_PERMISSION = Eco.getHandler().getRequirementFactory().create("has-permission");
+
+    /**
+     * Placeholder equals value.
+     */
+    public static final Requirement PLACEHOLDER_EQUALS = Eco.getHandler().getRequirementFactory().create("placeholder-equals");
+
+    /**
+     * Numeric placeholder greater than value.
+     */
+    public static final Requirement PLACEHOLDER_GREATER_THAN = Eco.getHandler().getRequirementFactory().create("placeholder-greater-than");
+
+    /**
+     * Numeric placeholder less than value.
+     */
+    public static final Requirement PLACEHOLDER_LESS_THAN = Eco.getHandler().getRequirementFactory().create("placeholder-less-than");
+
+    /**
+     * Get Requirements matching ID.
+     *
+     * @param name The ID to search for.
+     * @return The matching Requirements.
+     */
+    public static Requirement getByID(@NotNull final String name) {
+        return Eco.getHandler().getRequirementFactory().create(name);
+    }
+}

eco-api/src/main/java/com/willfp/eco/core/tuples/Pair.java

@@ -38,4 +38,26 @@ public class Pair<A, B> {
         this.first = first;
         this.second = second;
     }
+
+    /**
+     * component1 exists to allow a pair to be destructured by kotlin.
+     * The default kotlin pair already has this, however there is no default
+     * pair in java so this exists for parity.
+     *
+     * @return First.
+     */
+    public A component1() {
+        return first;
+    }
+
+    /**
+     * component2 exists to allow a pair to be destructured by kotlin.
+     * The default kotlin pair already has this, however there is no default
+     * pair in java so this exists for parity.
+     *
+     * @return First.
+     */
+    public B component2() {
+        return second;
+    }
 }

eco-api/src/main/java/com/willfp/eco/core/tuples/Triplet.java

@@ -34,4 +34,15 @@ public class Triplet<A, B, C> extends Pair<A, B> {
 
         this.third = third;
     }
+
+    /**
+     * component3 exists to allow a pair to be destructured by kotlin.
+     * The default kotlin pair already has this, however there is no default
+     * pair in java so this exists for parity.
+     *
+     * @return First.
+     */
+    public C component3() {
+        return third;
+    }
 }

eco-api/src/main/java/com/willfp/eco/core/web/UpdateChecker.java

@@ -31,7 +31,9 @@ public class UpdateChecker extends PluginDependent<EcoPlugin> {
     public void getVersion(@NotNull final Consumer<? super String> consumer) {
         this.getPlugin().getScheduler().runAsync(() -> {
             try {
-                InputStream inputStream = new URL("https://api.spigotmc.org/legacy/update.php?resource=" + this.getPlugin().getResourceId()).openStream();
+                InputStream inputStream = new URL(
+                        "https://api.polymart.org/v1/getResourceInfoSimple?key=version&resource_id=" + this.getPlugin().getResourceId()
+                ).openStream();
                 Scanner scanner = new Scanner(inputStream);
 
                 if (scanner.hasNext()) {

eco-api/src/main/java/com/willfp/eco/util/ArrowUtils.java

@@ -19,7 +19,7 @@ public class ArrowUtils {
      * Get the bow from an arrow.
      *
      * @param arrow The arrow.
-     * @return The bow.
+     * @return The bow, or null if no bow.
      */
     @Nullable
     public ItemStack getBow(@NotNull final Arrow arrow) {

eco-api/src/main/java/com/willfp/eco/util/BlockUtils.java

@@ -63,6 +63,7 @@ public class BlockUtils {
      * @param limit            The maximum size of vein to return.
      * @return A set of all {@link Block}s.
      */
+    @NotNull
     public Set<Block> getVein(@NotNull final Block start,
                               @NotNull final List<Material> allowedMaterials,
                               final int limit) {

eco-api/src/main/java/com/willfp/eco/util/LightningUtils.java

@@ -2,6 +2,7 @@ package com.willfp.eco.util;
 
 import lombok.experimental.UtilityClass;
 import org.bukkit.Location;
+import org.bukkit.Sound;
 import org.bukkit.entity.LivingEntity;
 import org.jetbrains.annotations.NotNull;
 
@@ -10,18 +11,37 @@ import org.jetbrains.annotations.NotNull;
  */
 @UtilityClass
 public class LightningUtils {
+
     /**
      * Strike lightning on player without fire.
      *
      * @param victim The entity to smite.
      * @param damage The damage to deal.
+     * @param silent If the lightning sound should be played locally
+     */
+    public void strike(@NotNull final LivingEntity victim,
+                       final double damage,
+                       final boolean silent) {
+        Location loc = victim.getLocation();
+
+        if (silent) {
+            victim.getWorld().spigot().strikeLightningEffect(loc, true);
+            victim.getWorld().playSound(loc, Sound.ENTITY_LIGHTNING_BOLT_IMPACT, 1, 1);
+        } else {
+            victim.getWorld().strikeLightningEffect(loc);
+        }
+
+        victim.damage(damage);
+    }
+
+    /**
+     * Strike lightning on a victim without fire.
+     *
+     * @param victim The entity to smite.
+     * @param damage The damage to deal.
      */
     public void strike(@NotNull final LivingEntity victim,
                        final double damage) {
-        Location loc = victim.getLocation();
-
-        victim.getWorld().strikeLightningEffect(loc);
-
-        victim.damage(damage);
+        strike(victim, damage, false);
     }
 }

eco-api/src/main/java/com/willfp/eco/util/ListUtils.java

@@ -1,6 +1,8 @@
 package com.willfp.eco.util;
 
 import lombok.experimental.UtilityClass;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
 
 import java.util.ArrayList;
 import java.util.List;
@@ -18,8 +20,9 @@ public class ListUtils {
      * @param <T>     The type of the object stored in the list.
      * @return The list, filled will null objects.
      */
-    public <T> List<List<T>> create2DList(final int rows,
-                                          final int columns) {
+    @NotNull
+    public <@Nullable T> List<List<T>> create2DList(final int rows,
+                                                    final int columns) {
         List<List<T>> list = new ArrayList<>(rows);
         while (list.size() < rows) {
             List<T> row = new ArrayList<>(columns);

eco-api/src/main/java/com/willfp/eco/util/MenuUtils.java

@@ -0,0 +1,24 @@
+package com.willfp.eco.util;
+
+import com.willfp.eco.core.tuples.Pair;
+import lombok.experimental.UtilityClass;
+import org.jetbrains.annotations.NotNull;
+
+/**
+ * Utilities / API methods for menus.
+ */
+@UtilityClass
+public class MenuUtils {
+    /**
+     * Convert 0-53 slot to row and column pair.
+     *
+     * @param slot The slot.
+     * @return The pair of row and columns.
+     */
+    @NotNull
+    public Pair<Integer, Integer> convertSlotToRowColumn(final int slot) {
+        int row = Math.floorDiv(slot, 9);
+        int column = slot - row * 9;
+        return new Pair<>(row + 1, column + 1);
+    }
+}

eco-api/src/main/java/com/willfp/eco/util/NamespacedKeyUtils.java

@@ -17,6 +17,7 @@ public class NamespacedKeyUtils {
      * @param string The string.
      * @return The key.
      */
+    @NotNull
     public NamespacedKey createEcoKey(@NotNull final String string) {
         return Objects.requireNonNull(NamespacedKey.fromString("eco:" + string));
     }
@@ -28,6 +29,7 @@ public class NamespacedKeyUtils {
      * @param key       The key.
      * @return The key.
      */
+    @NotNull
     public NamespacedKey create(@NotNull final String namespace,
                                 @NotNull final String key) {
         return Objects.requireNonNull(NamespacedKey.fromString(namespace + ":" + key));

eco-api/src/main/java/com/willfp/eco/util/NumberUtils.java

@@ -1,5 +1,6 @@
 package com.willfp.eco.util;
 
+import lombok.experimental.NonFinal;
 import lombok.experimental.UtilityClass;
 import org.jetbrains.annotations.NotNull;
 
@@ -109,6 +110,7 @@ public class NumberUtils {
      * @param number The number to convert.
      * @return The number, converted to a roman numeral.
      */
+    @NotNull
     public String toNumeral(final int number) {
         if (number >= 1 && number <= 4096) {
             int l = NUMERALS.floorKey(number);
@@ -199,6 +201,7 @@ public class NumberUtils {
      * @param toFormat The number to format.
      * @return Formatted.
      */
+    @NotNull
     public String format(final double toFormat) {
         DecimalFormat df = new DecimalFormat("0.00");
         String formatted = df.format(toFormat);

eco-api/src/main/java/com/willfp/eco/util/PlayerUtils.java

@@ -0,0 +1,66 @@
+package com.willfp.eco.util;
+
+import com.willfp.eco.core.Eco;
+import com.willfp.eco.core.Prerequisite;
+import lombok.experimental.UtilityClass;
+import net.kyori.adventure.audience.Audience;
+import net.kyori.adventure.platform.bukkit.BukkitAudiences;
+import org.bukkit.command.CommandSender;
+import org.bukkit.entity.Player;
+import org.jetbrains.annotations.NotNull;
+
+/**
+ * Utilities / API methods for players.
+ */
+@UtilityClass
+public class PlayerUtils {
+    /**
+     * Get the audience from a player.
+     *
+     * @param player The player.
+     * @return The audience.
+     */
+    @NotNull
+    public Audience getAudience(@NotNull final Player player) {
+        BukkitAudiences adventure = Eco.getHandler().getAdventure();
+
+        if (Prerequisite.HAS_PAPER.isMet()) {
+            if (player instanceof Audience) {
+                return (Audience) player;
+            } else {
+                return Audience.empty();
+            }
+        } else {
+            if (adventure == null) {
+                return Audience.empty();
+            } else {
+                return adventure.player(player);
+            }
+        }
+    }
+
+    /**
+     * Get the audience from a command sender.
+     *
+     * @param sender The command sender.
+     * @return The audience.
+     */
+    @NotNull
+    public Audience getAudience(@NotNull final CommandSender sender) {
+        BukkitAudiences adventure = Eco.getHandler().getAdventure();
+
+        if (Prerequisite.HAS_PAPER.isMet()) {
+            if (sender instanceof Audience) {
+                return (Audience) sender;
+            } else {
+                return Audience.empty();
+            }
+        } else {
+            if (adventure == null) {
+                return Audience.empty();
+            } else {
+                return adventure.sender(sender);
+            }
+        }
+    }
+}

eco-api/src/main/java/com/willfp/eco/util/SkullUtils.java

@@ -5,8 +5,10 @@ import org.apache.commons.lang.Validate;
 import org.bukkit.inventory.meta.SkullMeta;
 import org.jetbrains.annotations.ApiStatus;
 import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
 
 import java.util.function.BiConsumer;
+import java.util.function.Function;
 
 /**
  * Utilities / API methods for player heads.
@@ -23,6 +25,11 @@ public class SkullUtils {
      */
     private BiConsumer<SkullMeta, String> metaSetConsumer = null;
 
+    /**
+     * The meta get function.
+     */
+    private Function<SkullMeta, String> metaGetConsumer = null;
+
     /**
      * Set the texture of a skull from base64.
      *
@@ -37,16 +44,33 @@ public class SkullUtils {
         metaSetConsumer.accept(meta, base64);
     }
 
+    /**
+     * Get the texture of a skull - in base64.
+     *
+     * @param meta The meta to modify.
+     * @return The texture, potentially null.
+     */
+    @Nullable
+    public String getSkullTexture(@NotNull final SkullMeta meta) {
+        Validate.isTrue(initialized, "Must be initialized!");
+        Validate.notNull(metaGetConsumer, "Must be initialized!");
+
+        return metaGetConsumer.apply(meta);
+    }
+
     /**
      * Initialize the skull texture function.
      *
-     * @param function The function.
+     * @param function  The function.
+     * @param function2 Get function.
      */
     @ApiStatus.Internal
-    public void initialize(@NotNull final BiConsumer<SkullMeta, String> function) {
+    public void initialize(@NotNull final BiConsumer<SkullMeta, String> function,
+                           @NotNull final Function<SkullMeta, String> function2) {
         Validate.isTrue(!initialized, "Already initialized!");
 
         metaSetConsumer = function;
+        metaGetConsumer = function2;
         initialized = true;
     }
 }

eco-api/src/main/java/com/willfp/eco/util/StringUtils.java

@@ -1,10 +1,13 @@
 package com.willfp.eco.util;
 
 import com.google.common.collect.ImmutableList;
+import com.willfp.eco.core.Prerequisite;
 import com.willfp.eco.core.integrations.placeholder.PlaceholderManager;
 import lombok.experimental.UtilityClass;
 import net.kyori.adventure.text.Component;
 import net.kyori.adventure.text.format.TextDecoration;
+import net.kyori.adventure.text.minimessage.MiniMessage;
+import net.kyori.adventure.text.minimessage.markdown.DiscordFlavor;
 import net.kyori.adventure.text.serializer.gson.GsonComponentSerializer;
 import net.kyori.adventure.text.serializer.legacy.LegacyComponentSerializer;
 import net.md_5.bungee.api.ChatColor;
@@ -34,6 +37,8 @@ public class StringUtils {
             .add(Pattern.compile("<GRADIENT:([0-9A-Fa-f]{6})>(.*?)</GRADIENT:([0-9A-Fa-f]{6})>", Pattern.CASE_INSENSITIVE))
             .add(Pattern.compile("<GRADIENT:#([0-9A-Fa-f]{6})>(.*?)</GRADIENT:#([0-9A-Fa-f]{6})>", Pattern.CASE_INSENSITIVE))
             .add(Pattern.compile("<G:([0-9A-Fa-f]{6})>(.*?)</G:([0-9A-Fa-f]{6})>", Pattern.CASE_INSENSITIVE))
+            .add(Pattern.compile("<G:#([0-9A-Fa-f]{6})>(.*?)</G:#([0-9A-Fa-f]{6})>", Pattern.CASE_INSENSITIVE))
+            .add(Pattern.compile("<G#([0-9A-Fa-f]{6})>(.*?)</G#([0-9A-Fa-f]{6})>", Pattern.CASE_INSENSITIVE))
             .add(Pattern.compile("<#:([0-9A-Fa-f]{6})>(.*?)</#:([0-9A-Fa-f]{6})>"))
             .add(Pattern.compile("\\{#:([0-9A-Fa-f]{6})}(.*?)\\{/#:([0-9A-Fa-f]{6})}"))
             .build();
@@ -48,58 +53,215 @@ public class StringUtils {
             .build();
 
     /**
-     * Format a list of strings - converts Placeholders and Color codes.
+     * Legacy serializer.
+     */
+    private static final LegacyComponentSerializer LEGACY_COMPONENT_SERIALIZER = LegacyComponentSerializer.builder()
+            .character('\u00a7')
+            .useUnusualXRepeatedCharacterHexFormat()
+            .hexColors()
+            .build();
+
+    /**
+     * Format a list of strings.
+     * <p>
+     * Converts color codes and placeholders.
+     *
+     * @param list The messages to format.
+     * @return The message, formatted.
+     */
+    @NotNull
+    public List<String> formatList(@NotNull final List<String> list) {
+        return formatList(list, (Player) null);
+    }
+
+    /**
+     * Format a list of strings.
+     * <p>
+     * Coverts color codes and placeholders for a player.
      *
      * @param list   The messages to format.
      * @param player The player to translate placeholders with respect to.
      * @return The message, format.
      */
+    @NotNull
     public List<String> formatList(@NotNull final List<String> list,
                                    @Nullable final Player player) {
+        return formatList(list, player, FormatOption.WITH_PLACEHOLDERS);
+    }
+
+    /**
+     * Format a list of strings.
+     * <p>
+     * Converts color codes and placeholders if specified.
+     *
+     * @param list   The messages to format.
+     * @param option The format option.
+     * @return The message, formatted.
+     */
+    @NotNull
+    public List<String> formatList(@NotNull final List<String> list,
+                                   @NotNull final FormatOption option) {
+        return formatList(list, null, option);
+    }
+
+    /**
+     * Format a list of strings.
+     * <p>
+     * Coverts color codes and placeholders for a player if specified.
+     *
+     * @param list   The messages to format.
+     * @param player The player to translate placeholders with respect to.
+     * @param option The options.
+     * @return The message, format.
+     */
+    @NotNull
+    public List<String> formatList(@NotNull final List<String> list,
+                                   @Nullable final Player player,
+                                   @NotNull final FormatOption option) {
         List<String> translated = new ArrayList<>();
         for (String string : list) {
-            translated.add(format(string, player));
+            translated.add(format(string, player, option));
         }
 
         return translated;
     }
 
     /**
-     * Format a list of strings - converts Placeholders and Color codes.
-     *
-     * @param list The messages to format.
-     * @return The message, formatted.
-     */
-    public List<String> formatList(@NotNull final List<String> list) {
-        return formatList(list, null);
-    }
-
-    /**
-     * Format a string - converts Placeholders and Color codes.
-     *
-     * @param message The message to format.
-     * @param player  The player to translate placeholders with respect to.
-     * @return The message, formatted.
-     */
-    public String format(@NotNull final String message,
-                         @Nullable final Player player) {
-        String processedMessage = message;
-        processedMessage = translateGradients(processedMessage);
-        processedMessage = PlaceholderManager.translatePlaceholders(processedMessage, player);
-        processedMessage = translateHexColorCodes(processedMessage);
-        processedMessage = ChatColor.translateAlternateColorCodes('&', processedMessage);
-        return processedMessage;
-    }
-
-    /**
-     * Format a string without respect to a player.
+     * Format a string.
+     * <p>
+     * Converts color codes and placeholders.
      *
      * @param message The message to translate.
      * @return The message, formatted.
      * @see StringUtils#format(String, Player)
      */
+    @NotNull
     public String format(@NotNull final String message) {
-        return format(message, null);
+        return format(message, (Player) null);
+    }
+
+    /**
+     * Format a string.
+     * <p>
+     * Converts color codes and placeholders for a player.
+     *
+     * @param message The message to format.
+     * @param player  The player to translate placeholders with respect to.
+     * @return The message, formatted.
+     */
+    @NotNull
+    public String format(@NotNull final String message,
+                         @Nullable final Player player) {
+        return format(message, player, FormatOption.WITH_PLACEHOLDERS);
+    }
+
+    /**
+     * Format a string.
+     * <p>
+     * Converts color codes and placeholders if specified.
+     *
+     * @param message The message to translate.
+     * @param option  The format option.
+     * @return The message, formatted.
+     * @see StringUtils#format(String, Player)
+     */
+    @NotNull
+    public String format(@NotNull final String message,
+                         @NotNull final FormatOption option) {
+        return format(message, null, option);
+    }
+
+    /**
+     * Format a string to a component.
+     * <p>
+     * Converts color codes and placeholders.
+     *
+     * @param message The message to translate.
+     * @return The message, formatted, as a component.
+     * @see StringUtils#format(String, Player)
+     */
+    @NotNull
+    public Component formatToComponent(@NotNull final String message) {
+        return formatToComponent(message, (Player) null);
+    }
+
+    /**
+     * Format a string.
+     * <p>
+     * Converts color codes and placeholders for a player.
+     *
+     * @param message The message to format.
+     * @param player  The player to translate placeholders with respect to.
+     * @return The message, formatted.
+     */
+    @NotNull
+    public Component formatToComponent(@NotNull final String message,
+                                       @Nullable final Player player) {
+        return formatToComponent(message, player, FormatOption.WITH_PLACEHOLDERS);
+    }
+
+    /**
+     * Format a string to a component.
+     * <p>
+     * Converts color codes and placeholders if specified.
+     *
+     * @param message The message to translate.
+     * @param option  The format option.
+     * @return The message, formatted, as a component.
+     * @see StringUtils#format(String, Player)
+     */
+    @NotNull
+    public Component formatToComponent(@NotNull final String message,
+                                       @NotNull final FormatOption option) {
+        return formatToComponent(message, null, option);
+    }
+
+    /**
+     * Format a string to a component.
+     * <p>
+     * Coverts color codes and placeholders for a player if specified.
+     *
+     * @param message The message to format.
+     * @param player  The player to translate placeholders with respect to.
+     * @param option  The format options.
+     * @return The message, formatted, as a component.
+     */
+    @NotNull
+    public Component formatToComponent(@NotNull final String message,
+                                       @Nullable final Player player,
+                                       @NotNull final FormatOption option) {
+        return toComponent(format(message, player, option));
+    }
+
+    /**
+     * Format a string.
+     * <p>
+     * Coverts color codes and placeholders for a player if specified.
+     *
+     * @param message The message to format.
+     * @param player  The player to translate placeholders with respect to.
+     * @param option  The format options.
+     * @return The message, formatted.
+     */
+    @NotNull
+    public String format(@NotNull final String message,
+                         @Nullable final Player player,
+                         @NotNull final FormatOption option) {
+        String processedMessage = message;
+        if (option == FormatOption.WITH_PLACEHOLDERS) {
+            processedMessage = PlaceholderManager.translatePlaceholders(processedMessage, player);
+        }
+        processedMessage = translateGradients(processedMessage);
+        processedMessage = translateHexColorCodes(processedMessage);
+        processedMessage = ChatColor.translateAlternateColorCodes('&', processedMessage);
+        if (Prerequisite.HAS_PAPER.isMet()) {
+            processedMessage = translateMiniMessage(processedMessage);
+        }
+        return processedMessage;
+    }
+
+    private static String translateMiniMessage(@NotNull final String message) {
+        return LEGACY_COMPONENT_SERIALIZER.serialize(MiniMessage.withMarkdownFlavor(DiscordFlavor.get()).parse(message));
     }
 
     private static String translateHexColorCodes(@NotNull final String message) {
@@ -167,6 +329,9 @@ public class StringUtils {
                                                  @NotNull final Color end,
                                                  final int step) {
         ChatColor[] colors = new ChatColor[step];
+        if (step <= 1) {
+            return colors;
+        }
         int stepR = Math.abs(start.getRed() - end.getRed()) / (step - 1);
         int stepG = Math.abs(start.getGreen() - end.getGreen()) / (step - 1);
         int stepB = Math.abs(start.getBlue() - end.getBlue()) / (step - 1);
@@ -204,6 +369,7 @@ public class StringUtils {
      * @param object The object to convert to string.
      * @return The object stringified.
      */
+    @NotNull
     public String internalToString(@Nullable final Object object) {
         if (object == null) {
             return "null";
@@ -229,6 +395,7 @@ public class StringUtils {
      * @param prefix The substring to remove.
      * @return The string with the prefix removed.
      */
+    @NotNull
     public String removePrefix(@NotNull final String string,
                                @NotNull final String prefix) {
         if (string.startsWith(prefix)) {
@@ -243,10 +410,15 @@ public class StringUtils {
      * @param legacy The legacy string.
      * @return The JSON String.
      */
-    public String legacyToJson(@NotNull final String legacy) {
+    @NotNull
+    public String legacyToJson(@Nullable final String legacy) {
+        String processed = legacy;
+        if (legacy == null) {
+            processed = "";
+        }
         return GsonComponentSerializer.gson().serialize(
                 Component.empty().decoration(TextDecoration.ITALIC, false).append(
-                        LegacyComponentSerializer.legacySection().deserialize(legacy)
+                        LEGACY_COMPONENT_SERIALIZER.deserialize(processed)
                 )
         );
     }
@@ -257,9 +429,52 @@ public class StringUtils {
      * @param json The JSON string.
      * @return The legacy string.
      */
+    @NotNull
     public String jsonToLegacy(@NotNull final String json) {
-        return LegacyComponentSerializer.legacySection().serialize(
+        return LEGACY_COMPONENT_SERIALIZER.serialize(
                 GsonComponentSerializer.gson().deserialize(json)
         );
     }
+
+    /**
+     * Convert legacy (bukkit) text to Component.
+     *
+     * @param legacy The legacy text.
+     * @return The component.
+     */
+    @NotNull
+    public Component toComponent(@Nullable final String legacy) {
+        String processed = legacy;
+        if (legacy == null) {
+            processed = "";
+        }
+
+        return LEGACY_COMPONENT_SERIALIZER.deserialize(processed);
+    }
+
+    /**
+     * Convert Component to legacy (bukkit) text.
+     *
+     * @param component The component.
+     * @return The legacy text.
+     */
+    @NotNull
+    public String toLegacy(@NotNull final Component component) {
+        return LEGACY_COMPONENT_SERIALIZER.serialize(component);
+    }
+
+    /**
+     * Options for formatting.
+     */
+    public enum FormatOption {
+        /**
+         * Completely formatted.
+         */
+        WITH_PLACEHOLDERS,
+
+        /**
+         * Completely formatted without placeholders.
+         */
+        WITHOUT_PLACEHOLDERS
+    }
 }

eco-api/src/main/java/com/willfp/eco/util/TeamUtils.java

@@ -43,6 +43,7 @@ public class TeamUtils {
      * @param color The color to find the team for.
      * @return The team.
      */
+    @NotNull
     public Team fromChatColor(@NotNull final ChatColor color) {
         if (CHAT_COLOR_TEAMS.containsKey(color)) {
             return CHAT_COLOR_TEAMS.get(color);
@@ -70,6 +71,7 @@ public class TeamUtils {
      * @param material The material to find the team from.
      * @return The team.
      */
+    @NotNull
     public Team getMaterialColorTeam(@NotNull final Material material) {
         return fromChatColor(MATERIAL_COLORS.getOrDefault(material, ChatColor.WHITE));
     }

eco-api/src/main/java/com/willfp/eco/util/VectorUtils.java

@@ -44,6 +44,7 @@ public class VectorUtils {
      * @param vec The vector to simplify.
      * @return The vector, simplified.
      */
+    @NotNull
     public Vector simplifyVector(@NotNull final Vector vec) {
         double x = Math.abs(vec.getX());
         double y = Math.abs(vec.getY());
@@ -76,6 +77,7 @@ public class VectorUtils {
      * @param radius The radius.
      * @return An array of {@link Vector}s.
      */
+    @NotNull
     public Vector[] getCircle(final int radius) {
         Vector[] cached = CIRCLE_CACHE.get(radius);
         if (cached != null) {
@@ -112,6 +114,7 @@ public class VectorUtils {
      * @param radius The radius of the square.
      * @return An array of {@link Vector}s.
      */
+    @NotNull
     public Vector[] getSquare(final int radius) {
         List<Vector> vectors = new ArrayList<>();
 
@@ -136,6 +139,7 @@ public class VectorUtils {
      * @param radius The radius of the cube.
      * @return An array of {@link Vector}s.
      */
+    @NotNull
     public Vector[] getCube(final int radius) {
         List<Vector> vectors = new ArrayList<>();
 

eco-core/build.gradle

@@ -4,7 +4,7 @@ buildscript {
     }
 
     dependencies {
-        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:1.5.21"
+        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:1.5.31"
     }
 }
 
@@ -16,6 +16,14 @@ subprojects {
 
     dependencies {
         compileOnly project(":eco-api")
-        compileOnly 'org.jetbrains.kotlin:kotlin-stdlib:1.5.21'
+        compileOnly 'org.jetbrains.kotlin:kotlin-stdlib:1.5.31'
+    }
+
+    compileKotlin {
+        kotlinOptions {
+            jvmTarget = "16"
+        }
+        targetCompatibility = JavaVersion.VERSION_16
+        sourceCompatibility = JavaVersion.VERSION_16
     }
 }

eco-core/core-backend/build.gradle

@@ -2,7 +2,9 @@ group 'com.willfp'
 version rootProject.version
 
 dependencies {
-    compileOnly 'org.spigotmc:spigot-api:1.17-R0.1-SNAPSHOT'
-    compileOnly 'me.clip:placeholderapi:2.10.9'
+    compileOnly 'org.spigotmc:spigot-api:1.17.1-R0.1-SNAPSHOT'
+    compileOnly 'me.clip:placeholderapi:2.10.10'
     compileOnly 'org.reflections:reflections:0.9.12'
+    compileOnly 'net.kyori:adventure-text-minimessage:4.1.0-SNAPSHOT'
+    compileOnly 'net.kyori:adventure-platform-bukkit:4.0.0'
 }

eco-core/core-backend/src/main/kotlin/com/willfp/eco/internal/config/EcoConfigFactory.kt

@@ -6,6 +6,7 @@ import com.willfp.eco.core.config.interfaces.JSONConfig
 import com.willfp.eco.core.config.wrapper.ConfigFactory
 import com.willfp.eco.internal.config.json.EcoJSONConfigSection
 import com.willfp.eco.internal.config.json.EcoLoadableJSONConfig
+import com.willfp.eco.internal.config.json.EcoUpdatableJSONConfig
 import com.willfp.eco.internal.config.yaml.EcoLoadableYamlConfig
 import com.willfp.eco.internal.config.yaml.EcoUpdatableYamlConfig
 import com.willfp.eco.internal.config.yaml.EcoYamlConfigSection
@@ -30,6 +31,24 @@ class EcoConfigFactory : ConfigFactory {
         )
     }
 
+    override fun createUpdatableJSONConfig(
+        configName: String,
+        plugin: EcoPlugin,
+        subDirectoryPath: String,
+        source: Class<*>,
+        removeUnused: Boolean,
+        vararg updateBlacklist: String
+    ): JSONConfig {
+        return EcoUpdatableJSONConfig(
+            configName,
+            plugin,
+            subDirectoryPath,
+            source,
+            removeUnused,
+            *updateBlacklist
+        )
+    }
+
     override fun createLoadableJSONConfig(
         configName: String,
         plugin: EcoPlugin,

eco-core/core-backend/src/main/kotlin/com/willfp/eco/internal/config/json/EcoJSONConfigWrapper.kt

@@ -6,14 +6,15 @@ import com.willfp.eco.core.config.interfaces.JSONConfig
 import com.willfp.eco.util.StringUtils
 import org.apache.commons.lang.Validate
 import java.util.*
+import java.util.concurrent.ConcurrentHashMap
 
 @Suppress("UNCHECKED_CAST")
 open class EcoJSONConfigWrapper : JSONConfig {
     val handle: Gson = GsonBuilder().setPrettyPrinting().create()
 
-    val values: MutableMap<String, Any?> = HashMap()
+    val values = ConcurrentHashMap<String, Any?>()
 
-    private val cache: MutableMap<String, Any> = HashMap()
+    private val cache = ConcurrentHashMap<String, Any>()
 
     fun init(values: Map<String, Any?>) {
         this.values.clear()
@@ -138,17 +139,17 @@ open class EcoJSONConfigWrapper : JSONConfig {
 
     override fun getSubsections(path: String): List<JSONConfig> {
         val subsections = getSubsectionsOrNull(path)
-        return subsections ?: ArrayList()
+        return subsections ?: mutableListOf()
     }
 
     override fun getSubsectionsOrNull(path: String): List<JSONConfig>? {
         val maps = getOfKnownType(path, Any::class.java) as List<Map<String, Any>>?
             ?: return null
-        val configs: MutableList<JSONConfig> = ArrayList()
+        val configs = mutableListOf<JSONConfig>()
         for (map in maps) {
             configs.add(EcoJSONConfigSection(map))
         }
-        return configs
+        return configs.toMutableList()
     }
 
     override fun getInt(path: String): Int {
@@ -170,11 +171,11 @@ open class EcoJSONConfigWrapper : JSONConfig {
         return Objects.requireNonNullElse(getOfKnownType(path, Int::class.java), def)
     }
 
-    override fun getInts(path: String): List<Int> {
-        return Objects.requireNonNullElse(getOfKnownType(path, Any::class.java), ArrayList<Any>()) as List<Int>
+    override fun getInts(path: String): MutableList<Int> {
+        return (Objects.requireNonNullElse(getOfKnownType(path, Any::class.java), emptyList<Int>()) as List<Int>).toMutableList()
     }
 
-    override fun getIntsOrNull(path: String): List<Int>? {
+    override fun getIntsOrNull(path: String): MutableList<Int>? {
         return if (has(path)) {
             getInts(path)
         } else {
@@ -194,11 +195,11 @@ open class EcoJSONConfigWrapper : JSONConfig {
         }
     }
 
-    override fun getBools(path: String): List<Boolean> {
-        return Objects.requireNonNullElse(getOfKnownType(path, Any::class.java), ArrayList<Any>()) as List<Boolean>
+    override fun getBools(path: String): MutableList<Boolean> {
+        return (Objects.requireNonNullElse(getOfKnownType(path, Any::class.java), emptyList<Boolean>()) as List<Boolean>).toMutableList()
     }
 
-    override fun getBoolsOrNull(path: String): List<Boolean>? {
+    override fun getBoolsOrNull(path: String): MutableList<Boolean>? {
         return if (has(path)) {
             getBools(path)
         } else {
@@ -206,64 +207,44 @@ open class EcoJSONConfigWrapper : JSONConfig {
         }
     }
 
-    override fun getString(path: String): String {
-        return getString(path, true)
-    }
-
     override fun getString(
         path: String,
-        format: Boolean
+        format: Boolean,
+        option: StringUtils.FormatOption
     ): String {
         val string = getOfKnownType(path, String::class.java) ?: ""
-        return if (format) StringUtils.format(string) else string
-    }
-
-    override fun getStringOrNull(path: String): String? {
-        return if (has(path)) {
-            getString(path)
-        } else {
-            null
-        }
+        return if (format) StringUtils.format(string, option) else string
     }
 
     override fun getStringOrNull(
         path: String,
-        format: Boolean
+        format: Boolean,
+        option: StringUtils.FormatOption
     ): String? {
         return if (has(path)) {
-            getString(path, format)
+            getString(path, format, option)
         } else {
             null
         }
     }
 
-    override fun getStrings(path: String): List<String> {
-        return getStrings(path, true)
-    }
-
     override fun getStrings(
         path: String,
-        format: Boolean
-    ): List<String> {
+        format: Boolean,
+        option: StringUtils.FormatOption
+    ): MutableList<String> {
         val strings =
-            Objects.requireNonNullElse(getOfKnownType(path, Any::class.java), ArrayList<Any>()) as List<String>
-        return if (format) StringUtils.formatList(strings) else strings
-    }
-
-    override fun getStringsOrNull(path: String): List<String>? {
-        return if (has(path)) {
-            getStrings(path)
-        } else {
-            null
-        }
+            (Objects.requireNonNullElse(getOfKnownType(path, Any::class.java), emptyList<String>()) as List<String>).toMutableList()
+        return if (format) StringUtils.formatList(strings, option) else strings
     }
 
     override fun getStringsOrNull(
         path: String,
-        format: Boolean
-    ): List<String>? {
+        format: Boolean,
+        option: StringUtils.FormatOption
+    ): MutableList<String>? {
         return if (has(path)) {
-            getStrings(path, format)
+            getStrings(path, format, option)
         } else {
             null
         }
@@ -281,11 +262,11 @@ open class EcoJSONConfigWrapper : JSONConfig {
         }
     }
 
-    override fun getDoubles(path: String): List<Double> {
-        return Objects.requireNonNullElse(getOfKnownType(path, Any::class.java), ArrayList<Any>()) as List<Double>
+    override fun getDoubles(path: String): MutableList<Double> {
+        return (Objects.requireNonNullElse(getOfKnownType(path, Any::class.java), emptyList<Double>()) as List<Double>).toMutableList()
     }
 
-    override fun getDoublesOrNull(path: String): List<Double>? {
+    override fun getDoublesOrNull(path: String): MutableList<Double>? {
         return if (has(path)) {
             getDoubles(path)
         } else {

eco-core/core-backend/src/main/kotlin/com/willfp/eco/internal/config/json/EcoLoadableJSONConfig.kt

@@ -8,11 +8,11 @@ import java.nio.file.Files
 import java.nio.file.StandardOpenOption
 
 @Suppress("UNCHECKED_CAST")
-class EcoLoadableJSONConfig(
+open class EcoLoadableJSONConfig(
     configName: String,
     private val plugin: EcoPlugin,
     private val subDirectoryPath: String,
-    private val source: Class<*>
+    val source: Class<*>
 ) : EcoJSONConfigWrapper(), LoadableConfig {
 
     private val configFile: File
@@ -27,7 +27,6 @@ class EcoLoadableJSONConfig(
     }
 
     override fun createFile() {
-        val resourcePath = resourcePath
         val inputStream = source.getResourceAsStream(resourcePath)!!
         val outFile = File(this.plugin.dataFolder, resourcePath)
         val lastIndex = resourcePath.lastIndexOf('/')
@@ -37,11 +36,7 @@ class EcoLoadableJSONConfig(
         }
         if (!outFile.exists()) {
             val out: OutputStream = FileOutputStream(outFile)
-            val buf = ByteArray(1024)
-            var len: Int
-            while (inputStream.read(buf).also { len = it } > 0) {
-                out.write(buf, 0, len)
-            }
+            inputStream.copyTo(out, 1024)
             out.close()
             inputStream.close()
         }
@@ -70,7 +65,7 @@ class EcoLoadableJSONConfig(
 
     @Throws(FileNotFoundException::class)
     fun init(file: File) {
-        super.init(handle.fromJson(FileReader(file), Map::class.java) as @NotNull MutableMap<String, Any>)
+        super.init(handle.fromJson(FileReader(file), Map::class.java) as MutableMap<String, Any>)
     }
 
     override fun getName(): String {

eco-core/core-backend/src/main/kotlin/com/willfp/eco/internal/config/json/EcoUpdatableJSONConfig.kt

@@ -0,0 +1,74 @@
+package com.willfp.eco.internal.config.json
+
+import com.willfp.eco.core.EcoPlugin
+import org.bukkit.configuration.InvalidConfigurationException
+import org.bukkit.configuration.file.YamlConfiguration
+import java.io.BufferedReader
+import java.io.IOException
+import java.io.InputStreamReader
+import java.nio.charset.StandardCharsets
+
+open class EcoUpdatableJSONConfig(
+    configName: String,
+    plugin: EcoPlugin,
+    subDirectoryPath: String,
+    source: Class<*>,
+    private val removeUnused: Boolean,
+    vararg updateBlacklist: String
+) : EcoLoadableJSONConfig(configName, plugin, subDirectoryPath, source) {
+
+    private val updateBlacklist: MutableList<String> = mutableListOf(*updateBlacklist)
+
+    fun update() {
+        super.clearCache()
+        try {
+            this.init(configFile)
+            val newConfig = configInJar
+            if (newConfig.getKeys(true) == this.getKeys(true)) {
+                return
+            }
+            newConfig.getKeys(true).forEach { key: String ->
+                if (!this.getKeys(true).contains(key)) {
+                    if (updateBlacklist.stream().noneMatch { s: String -> key.contains(s) }) {
+                        this.set(key, newConfig[key])
+                    }
+                }
+            }
+            if (removeUnused) {
+                this.getKeys(true).forEach { s ->
+                    if (!newConfig.getKeys(true).contains(s)) {
+                        if (updateBlacklist.stream().noneMatch(s::contains)) {
+                            this.set(s, null)
+                        }
+                    }
+                }
+            }
+            this.save()
+        } catch (e: IOException) {
+            e.printStackTrace()
+        } catch (e: InvalidConfigurationException) {
+            e.printStackTrace()
+        }
+    }
+
+    private val configInJar: YamlConfiguration
+        get() {
+            val newIn = this.source.getResourceAsStream(resourcePath) ?: throw NullPointerException("$name is null?")
+            val reader = BufferedReader(InputStreamReader(newIn, StandardCharsets.UTF_8))
+            val newConfig = YamlConfiguration()
+            try {
+                newConfig.load(reader)
+            } catch (e: IOException) {
+                e.printStackTrace()
+            } catch (e: InvalidConfigurationException) {
+                e.printStackTrace()
+            }
+            return newConfig
+        }
+
+    init {
+        this.updateBlacklist.removeIf { obj: String -> obj.isEmpty() }
+        plugin.configHandler.addConfig(this)
+        update()
+    }
+}

eco-core/core-backend/src/main/kotlin/com/willfp/eco/internal/config/updating/EcoConfigHandler.kt

@@ -1,34 +1,29 @@
 package com.willfp.eco.internal.config.updating
 
 import com.willfp.eco.core.EcoPlugin
-import com.willfp.eco.core.PluginDependent
 import com.willfp.eco.core.config.interfaces.LoadableConfig
 import com.willfp.eco.core.config.updating.ConfigHandler
 import com.willfp.eco.core.config.updating.ConfigUpdater
 import com.willfp.eco.internal.config.json.EcoLoadableJSONConfig
+import com.willfp.eco.internal.config.json.EcoUpdatableJSONConfig
 import com.willfp.eco.internal.config.updating.exceptions.InvalidUpdateMethodException
 import com.willfp.eco.internal.config.yaml.EcoLoadableYamlConfig
 import com.willfp.eco.internal.config.yaml.EcoUpdatableYamlConfig
 import org.reflections.Reflections
 import org.reflections.scanners.MethodAnnotationsScanner
-import java.lang.reflect.Modifier
 
 class EcoConfigHandler(
-    plugin: EcoPlugin
-) : PluginDependent<EcoPlugin>(plugin), ConfigHandler {
+    private val plugin: EcoPlugin
+) : ConfigHandler {
     private val reflections: Reflections = Reflections(
         this.plugin::class.java.classLoader,
         MethodAnnotationsScanner()
     )
 
-    private val configs: MutableList<LoadableConfig> = ArrayList()
+    private val configs = mutableListOf<LoadableConfig>()
 
     override fun callUpdate() {
         for (method in reflections.getMethodsAnnotatedWith(ConfigUpdater::class.java)) {
-            if (!Modifier.isStatic(method.modifiers)) {
-                throw InvalidUpdateMethodException("Update method in ${method.declaringClass.name} must be static.")
-            }
-
             try {
                 when (method.parameterCount) {
                     0 -> method.invoke(null)
@@ -56,6 +51,7 @@ class EcoConfigHandler(
         for (config in configs) {
             when (config) {
                 is EcoUpdatableYamlConfig -> config.update()
+                is EcoUpdatableJSONConfig -> config.update()
                 is EcoLoadableYamlConfig -> config.reloadFromFile()
                 is EcoLoadableJSONConfig -> config.reloadFromFile()
             }

eco-core/core-backend/src/main/kotlin/com/willfp/eco/internal/config/yaml/EcoLoadableYamlConfig.kt

@@ -31,7 +31,6 @@ open class EcoLoadableYamlConfig(
     }
 
     final override fun createFile() {
-        val resourcePath = resourcePath
         val inputStream = source.getResourceAsStream(resourcePath)!!
         val outFile = File(this.plugin.dataFolder, resourcePath)
         val lastIndex = resourcePath.lastIndexOf('/')
@@ -41,11 +40,7 @@ open class EcoLoadableYamlConfig(
         }
         if (!outFile.exists()) {
             val out: OutputStream = FileOutputStream(outFile)
-            val buf = ByteArray(1024)
-            var len: Int
-            while (inputStream.read(buf).also { len = it } > 0) {
-                out.write(buf, 0, len)
-            }
+            inputStream.copyTo(out, 1024)
             out.close()
             inputStream.close()
         }

eco-core/core-backend/src/main/kotlin/com/willfp/eco/internal/config/yaml/EcoYamlConfigWrapper.kt

@@ -6,11 +6,12 @@ import org.apache.commons.lang.Validate
 import org.bukkit.configuration.ConfigurationSection
 import org.bukkit.configuration.file.YamlConfiguration
 import java.io.StringReader
+import java.util.concurrent.ConcurrentHashMap
 
 @Suppress("UNCHECKED_CAST")
 open class EcoYamlConfigWrapper<T : ConfigurationSection> : Config {
     lateinit var handle: T
-    private val cache: MutableMap<String, Any?> = HashMap()
+    private val cache = ConcurrentHashMap<String, Any?>()
 
     protected fun init(config: T): Config {
         handle = config
@@ -98,16 +99,16 @@ open class EcoYamlConfigWrapper<T : ConfigurationSection> : Config {
         }
     }
 
-    override fun getInts(path: String): List<Int> {
+    override fun getInts(path: String): MutableList<Int> {
         return if (cache.containsKey(path)) {
-            cache[path] as List<Int>
+            (cache[path] as MutableList<Int>).toMutableList()
         } else {
-            cache[path] = if (has(path)) ArrayList(handle.getIntegerList(path)) else ArrayList<Any>()
+            cache[path] = if (has(path)) ArrayList(handle.getIntegerList(path)) else mutableListOf<Int>()
             getInts(path)
         }
     }
 
-    override fun getIntsOrNull(path: String): List<Int>? {
+    override fun getIntsOrNull(path: String): MutableList<Int>? {
         return if (has(path)) {
             getInts(path)
         } else {
@@ -132,17 +133,17 @@ open class EcoYamlConfigWrapper<T : ConfigurationSection> : Config {
         }
     }
 
-    override fun getBools(path: String): List<Boolean> {
+    override fun getBools(path: String): MutableList<Boolean> {
         return if (cache.containsKey(path)) {
-            cache[path] as List<Boolean>
+            (cache[path] as MutableList<Boolean>).toMutableList()
         } else {
             cache[path] =
-                if (has(path)) ArrayList(handle.getBooleanList(path)) else ArrayList<Any>()
+                if (has(path)) ArrayList(handle.getBooleanList(path)) else mutableListOf<Boolean>()
             getBools(path)
         }
     }
 
-    override fun getBoolsOrNull(path: String): List<Boolean>? {
+    override fun getBoolsOrNull(path: String): MutableList<Boolean>? {
         return if (has(path)) {
             getBools(path)
         } else {
@@ -150,91 +151,80 @@ open class EcoYamlConfigWrapper<T : ConfigurationSection> : Config {
         }
     }
 
-    override fun getString(path: String): String {
-        return getString(path, true)
-    }
-
     override fun getString(
         path: String,
-        format: Boolean
+        format: Boolean,
+        option: StringUtils.FormatOption
     ): String {
-        if (format) {
+        if (format && option == StringUtils.FormatOption.WITHOUT_PLACEHOLDERS) {
             return if (cache.containsKey("$path\$FMT")) {
                 cache["$path\$FMT"] as String
             } else {
                 val string: String = handle.getString(path, "")!!
-                cache["$path\$FMT"] = StringUtils.format(string)
-                getString(path, format)
+                cache["$path\$FMT"] = StringUtils.format(string, option)
+                getString(path, format, option)
             }
         } else {
-            return if (cache.containsKey(path)) {
+            val string = if (cache.containsKey(path)) {
                 cache[path] as String
             } else {
                 cache[path] = handle.getString(path, "")!!
-                getString(path)
+                getString(path, format, option)
             }
-        }
-    }
 
-    override fun getStringOrNull(path: String): String? {
-        return if (has(path)) {
-            getString(path)
-        } else {
-            null
+            return if (format) StringUtils.format(string) else string
         }
     }
 
     override fun getStringOrNull(
         path: String,
-        format: Boolean
+        format: Boolean,
+        option: StringUtils.FormatOption
     ): String? {
         return if (has(path)) {
-            getString(path, format)
+            getString(path, format, option)
         } else {
             null
         }
     }
 
-    override fun getStrings(path: String): List<String> {
-        return getStrings(path, true)
-    }
-
     override fun getStrings(
         path: String,
-        format: Boolean
-    ): List<String> {
-        if (format) {
+        format: Boolean,
+        option: StringUtils.FormatOption
+    ): MutableList<String> {
+        if (format && option == StringUtils.FormatOption.WITHOUT_PLACEHOLDERS) {
             return if (cache.containsKey("$path\$FMT")) {
-                cache["$path\$FMT"] as List<String>
+                (cache["$path\$FMT"] as MutableList<String>).toMutableList()
             } else {
-                cache["$path\$FMT"] = StringUtils.formatList(if (has(path)) ArrayList(handle.getStringList(path)) else ArrayList<String>())
-                getStrings(path, true)
+                val list = if (has(path)) handle.getStringList(path) else mutableListOf<String>()
+                cache["$path\$FMT"] = StringUtils.formatList(list, option)
+                getStrings(path, true, option)
             }
         } else {
-            return if (cache.containsKey(path)) {
-                cache[path] as List<String>
+            val strings = if (cache.containsKey(path)) {
+                (cache[path] as MutableList<String>).toMutableList()
             } else {
                 cache[path] =
-                    if (has(path)) ArrayList(handle.getStringList(path)) else ArrayList<Any>()
-                getStrings(path, false)
+                    if (has(path)) ArrayList(handle.getStringList(path)) else mutableListOf<String>()
+                getStrings(path, false, option)
             }
-        }
-    }
 
-    override fun getStringsOrNull(path: String): List<String>? {
-        return if (has(path)) {
-            getStrings(path)
-        } else {
-            null
+            return if (format) {
+                StringUtils.formatList(strings, StringUtils.FormatOption.WITH_PLACEHOLDERS)
+            } else {
+                strings
+            }
         }
     }
 
     override fun getStringsOrNull(
         path: String,
-        format: Boolean
-    ): List<String>? {
+        format: Boolean,
+        option: StringUtils.FormatOption
+    ): MutableList<String>? {
         return if (has(path)) {
-            getStrings(path, format)
+            getStrings(path, format, option)
         } else {
             null
         }
@@ -257,16 +247,16 @@ open class EcoYamlConfigWrapper<T : ConfigurationSection> : Config {
         }
     }
 
-    override fun getDoubles(path: String): List<Double> {
+    override fun getDoubles(path: String): MutableList<Double> {
         return if (cache.containsKey(path)) {
-            cache[path] as List<Double>
+            (cache[path] as MutableList<Double>).toMutableList()
         } else {
-            cache[path] = if (has(path)) ArrayList(handle.getDoubleList(path)) else ArrayList<Any>()
+            cache[path] = if (has(path)) ArrayList(handle.getDoubleList(path)) else emptyList<Double>()
             getDoubles(path)
         }
     }
 
-    override fun getDoublesOrNull(path: String): List<Double>? {
+    override fun getDoublesOrNull(path: String): MutableList<Double>? {
         return if (has(path)) {
             getDoubles(path)
         } else {

eco-core/core-backend/src/main/kotlin/com/willfp/eco/internal/display/EcoDisplayHandler.kt

@@ -0,0 +1,119 @@
+package com.willfp.eco.internal.display
+
+import com.willfp.eco.core.EcoPlugin
+import com.willfp.eco.core.display.Display
+import com.willfp.eco.core.display.DisplayHandler
+import com.willfp.eco.core.display.DisplayModule
+import com.willfp.eco.core.display.DisplayPriority
+import com.willfp.eco.core.fast.FastItemStack
+import org.bukkit.NamespacedKey
+import org.bukkit.entity.Player
+import org.bukkit.inventory.ItemStack
+import org.bukkit.persistence.PersistentDataType
+
+class EcoDisplayHandler(plugin: EcoPlugin) : DisplayHandler {
+    /**
+     * All registered display modules.
+     */
+    private val registeredModules = mutableMapOf<DisplayPriority, MutableList<DisplayModule>>()
+
+    /**
+     * NamespacedKey for finalizing.
+     */
+    private val finalizeKey: NamespacedKey = plugin.namespacedKeyFactory.create("finalized")
+
+    init {
+        for (priority in DisplayPriority.values()) {
+            registeredModules[priority] = mutableListOf()
+        }
+    }
+
+    override fun registerDisplayModule(module: DisplayModule) {
+        val modules = registeredModules[module.priority] ?: return
+        modules.removeIf { module1: DisplayModule ->
+            module1.pluginName.equals(module.pluginName, ignoreCase = true)
+        }
+        modules.add(module)
+        registeredModules[module.priority] = modules
+    }
+
+    override fun display(itemStack: ItemStack, player: Player?): ItemStack {
+        val pluginVarArgs = mutableMapOf<String, Array<Any>>()
+
+        for (priority in DisplayPriority.values()) {
+            val modules = registeredModules[priority] ?: continue
+            for (module in modules) {
+                pluginVarArgs[module.pluginName] = module.generateVarArgs(itemStack)
+            }
+        }
+
+        Display.revert(itemStack)
+
+        itemStack.itemMeta ?: return itemStack
+
+        for (priority in DisplayPriority.values()) {
+            val modules = registeredModules[priority] ?: continue
+            for (module in modules) {
+                val varargs = pluginVarArgs[module.pluginName] ?: continue
+                Display.callDisplayModule(module, itemStack, player, *varargs)
+            }
+        }
+
+        return itemStack
+    }
+
+    override fun revert(itemStack: ItemStack): ItemStack {
+        if (Display.isFinalized(itemStack)) {
+            Display.unfinalize(itemStack)
+        }
+
+        val fast = FastItemStack.wrap(itemStack)
+        val lore = fast.lore
+
+        if (lore.isNotEmpty() && lore.removeIf { line: String ->
+                line.startsWith(
+                    Display.PREFIX
+                )
+            }) { // Only modify lore if needed.
+            fast.lore = lore
+        }
+
+        for (priority in DisplayPriority.values()) {
+            val modules = registeredModules[priority] ?: continue
+            for (module in modules) {
+                module.revert(itemStack)
+            }
+        }
+
+        return itemStack
+    }
+
+    override fun finalize(itemStack: ItemStack): ItemStack {
+        if (itemStack.type.maxStackSize > 1) {
+            return itemStack
+        }
+
+        val meta = itemStack.itemMeta ?: return itemStack
+
+        val container = meta.persistentDataContainer
+        container.set(finalizeKey, PersistentDataType.INTEGER, 1)
+        itemStack.itemMeta = meta
+        return itemStack
+    }
+
+    override fun unfinalize(itemStack: ItemStack): ItemStack {
+        val meta = itemStack.itemMeta ?: return itemStack
+
+        val container = meta.persistentDataContainer
+        container.remove(finalizeKey)
+        itemStack.itemMeta = meta
+        return itemStack
+    }
+
+    override fun isFinalized(itemStack: ItemStack): Boolean {
+        val meta = itemStack.itemMeta ?: return false
+
+        val container = meta.persistentDataContainer
+        return container.has(finalizeKey, PersistentDataType.INTEGER)
+    }
+}

eco-core/core-backend/src/main/kotlin/com/willfp/eco/internal/drops/impl/EcoDropQueue.kt

@@ -13,12 +13,12 @@ import org.bukkit.inventory.ItemStack
 import org.bukkit.util.Vector
 
 open class EcoDropQueue(player: Player) : InternalDropQueue {
-    val items: MutableList<ItemStack>
-    var xp: Int
+    val items = mutableListOf<ItemStack>()
+    var xp: Int = 0
     val player: Player
     var loc: Location
+    var hasTelekinesis = false
 
-    private var hasTelekinesis = false
     override fun addItem(item: ItemStack): InternalDropQueue {
         items.add(item)
         return this
@@ -79,8 +79,6 @@ open class EcoDropQueue(player: Player) : InternalDropQueue {
     }
 
     init {
-        items = ArrayList()
-        xp = 0
         this.player = player
         loc = player.location
     }

eco-core/core-backend/src/main/kotlin/com/willfp/eco/internal/drops/impl/EcoFastCollatedDropQueue.kt

@@ -10,11 +10,14 @@ class EcoFastCollatedDropQueue(player: Player) : EcoDropQueue(player) {
         val fetched = COLLATED_MAP[player]
 
         if (fetched == null) {
-            COLLATED_MAP[player] = CollatedDrops(items, loc, xp)
+            COLLATED_MAP[player] = CollatedDrops(items, loc, xp, hasTelekinesis)
         } else {
             fetched.addDrops(items)
             fetched.location = loc
             fetched.addXp(xp)
+            if (this.hasTelekinesis) {
+                fetched.forceTelekinesis()
+            }
 
             COLLATED_MAP[player] = fetched
         }
@@ -23,8 +26,10 @@ class EcoFastCollatedDropQueue(player: Player) : EcoDropQueue(player) {
     class CollatedDrops(
         val drops: MutableList<ItemStack>,
         var location: Location,
-        var xp: Int
+        var xp: Int,
+        var telekinetic: Boolean
     ) {
+
         fun addDrops(toAdd: List<ItemStack>): CollatedDrops {
             drops.addAll(toAdd)
             return this
@@ -34,6 +39,10 @@ class EcoFastCollatedDropQueue(player: Player) : EcoDropQueue(player) {
             this.xp += xp
             return this
         }
+
+        fun forceTelekinesis() {
+            telekinetic = true
+        }
     }
 
     companion object {

eco-core/core-backend/src/main/kotlin/com/willfp/eco/internal/events/EcoEventManager.kt

@@ -1,13 +1,12 @@
 package com.willfp.eco.internal.events
 
 import com.willfp.eco.core.EcoPlugin
-import com.willfp.eco.core.PluginDependent
 import com.willfp.eco.core.events.EventManager
 import org.bukkit.Bukkit
 import org.bukkit.event.HandlerList
 import org.bukkit.event.Listener
 
-class EcoEventManager constructor(plugin: EcoPlugin) : PluginDependent<EcoPlugin>(plugin), EventManager {
+class EcoEventManager (private val plugin: EcoPlugin) : EventManager {
     override fun registerListener(listener: Listener) {
         Bukkit.getPluginManager().registerEvents(listener, plugin)
     }

eco-core/core-backend/src/main/kotlin/com/willfp/eco/internal/extensions/EcoExtensionLoader.kt

@@ -2,7 +2,6 @@ package com.willfp.eco.internal.extensions
 
 import com.google.common.collect.ImmutableSet
 import com.willfp.eco.core.EcoPlugin
-import com.willfp.eco.core.PluginDependent
 import com.willfp.eco.core.config.yaml.YamlTransientConfig
 import com.willfp.eco.core.extensions.Extension
 import com.willfp.eco.core.extensions.ExtensionLoader
@@ -16,9 +15,9 @@ import java.net.URL
 import java.net.URLClassLoader
 
 class EcoExtensionLoader(
-    plugin: EcoPlugin
-) : PluginDependent<EcoPlugin>(plugin), ExtensionLoader {
-    private val extensions: MutableMap<Extension, URLClassLoader> = HashMap()
+    private val plugin: EcoPlugin
+) : ExtensionLoader {
+    private val extensions = mutableMapOf<Extension, URLClassLoader>()
 
     override fun loadExtensions() {
         val dir = File(this.plugin.dataFolder, "/extensions")
@@ -43,7 +42,7 @@ class EcoExtensionLoader(
 
     @Throws(MalformedExtensionException::class)
     private fun loadExtension(extensionJar: File) {
-        lateinit var url : URL
+        lateinit var url: URL
 
         try {
             url = extensionJar.toURI().toURL()
@@ -53,7 +52,7 @@ class EcoExtensionLoader(
 
         val classLoader = URLClassLoader(arrayOf(url), this.plugin::class.java.classLoader)
         val ymlIn = classLoader.getResourceAsStream("extension.yml")
-            ?: throw MalformedExtensionException ("No extension.yml found in " + extensionJar.name)
+            ?: throw MalformedExtensionException("No extension.yml found in " + extensionJar.name)
 
         val extensionYml = YamlTransientConfig(YamlConfiguration.loadConfiguration(InputStreamReader(ymlIn)))
 
@@ -64,7 +63,7 @@ class EcoExtensionLoader(
 
 
         if (mainClass == null) {
-            throw MalformedExtensionException ("Invalid extension.yml found in " + extensionJar.name)
+            throw MalformedExtensionException("Invalid extension.yml found in " + extensionJar.name)
         }
 
         if (name == null) {

eco-core/core-backend/src/main/kotlin/com/willfp/eco/internal/factory/EcoMetadataValueFactory.kt

@@ -1,11 +1,10 @@
 package com.willfp.eco.internal.factory
 
 import com.willfp.eco.core.EcoPlugin
-import com.willfp.eco.core.PluginDependent
 import com.willfp.eco.core.factory.MetadataValueFactory
 import org.bukkit.metadata.FixedMetadataValue
 
-class EcoMetadataValueFactory(plugin: EcoPlugin) : PluginDependent<EcoPlugin>(plugin), MetadataValueFactory {
+class EcoMetadataValueFactory(private val plugin: EcoPlugin) : MetadataValueFactory {
     override fun create(value: Any): FixedMetadataValue {
         return FixedMetadataValue(plugin, value)
     }

eco-core/core-backend/src/main/kotlin/com/willfp/eco/internal/factory/EcoNamespacedKeyFactory.kt

@@ -1,11 +1,10 @@
 package com.willfp.eco.internal.factory
 
 import com.willfp.eco.core.EcoPlugin
-import com.willfp.eco.core.PluginDependent
 import com.willfp.eco.core.factory.NamespacedKeyFactory
 import org.bukkit.NamespacedKey
 
-class EcoNamespacedKeyFactory(plugin: EcoPlugin) : PluginDependent<EcoPlugin>(plugin), NamespacedKeyFactory {
+class EcoNamespacedKeyFactory(private val plugin: EcoPlugin) : NamespacedKeyFactory {
     override fun create(key: String): NamespacedKey {
         return NamespacedKey(plugin, key)
     }

eco-core/core-backend/src/main/kotlin/com/willfp/eco/internal/factory/EcoRunnableFactory.kt

@@ -1,13 +1,12 @@
 package com.willfp.eco.internal.factory
 
 import com.willfp.eco.core.EcoPlugin
-import com.willfp.eco.core.PluginDependent
 import com.willfp.eco.core.factory.RunnableFactory
 import com.willfp.eco.core.scheduling.RunnableTask
 import com.willfp.eco.internal.scheduling.EcoRunnableTask
 import java.util.function.Consumer
 
-class EcoRunnableFactory(plugin: EcoPlugin) : PluginDependent<EcoPlugin>(plugin), RunnableFactory {
+class EcoRunnableFactory(private val plugin: EcoPlugin) : RunnableFactory {
     override fun create(consumer: Consumer<RunnableTask>): RunnableTask {
         return object : EcoRunnableTask(plugin) {
             override fun run() {

eco-core/core-backend/src/main/kotlin/com/willfp/eco/internal/fast/EcoFastItemStack.kt

@@ -1,6 +1,7 @@
 package com.willfp.eco.internal.fast
 
 import com.willfp.eco.core.fast.FastItemStack
+import org.bukkit.inventory.ItemFlag
 import org.bukkit.inventory.ItemStack
 
 abstract class EcoFastItemStack<T: Any>(
@@ -10,4 +11,8 @@ abstract class EcoFastItemStack<T: Any>(
     override fun unwrap(): ItemStack {
         return bukkit
     }
+
+    fun getBitModifier(hideFlag: ItemFlag): Int {
+        return 1 shl hideFlag.ordinal
+    }
 }

eco-core/core-backend/src/main/kotlin/com/willfp/eco/internal/gui/EcoGUIFactory.kt

@@ -3,14 +3,12 @@ package com.willfp.eco.internal.gui
 import com.willfp.eco.core.gui.GUIFactory
 import com.willfp.eco.core.gui.menu.MenuBuilder
 import com.willfp.eco.core.gui.slot.SlotBuilder
+import com.willfp.eco.core.gui.slot.functional.SlotProvider
 import com.willfp.eco.internal.gui.menu.EcoMenuBuilder
 import com.willfp.eco.internal.gui.slot.EcoSlotBuilder
-import org.bukkit.entity.Player
-import org.bukkit.inventory.ItemStack
-import java.util.function.Function
 
 class EcoGUIFactory : GUIFactory {
-    override fun createSlotBuilder(provider: Function<Player, ItemStack>): SlotBuilder {
+    override fun createSlotBuilder(provider: SlotProvider): SlotBuilder {
         return EcoSlotBuilder(provider)
     }
 

eco-core/core-backend/src/main/kotlin/com/willfp/eco/internal/gui/menu/EcoMenu.kt

@@ -1,40 +1,35 @@
 package com.willfp.eco.internal.gui.menu
 
+import com.willfp.eco.core.gui.menu.CloseHandler
 import com.willfp.eco.core.gui.menu.Menu
-import com.willfp.eco.core.gui.slot.FillerSlot
 import com.willfp.eco.core.gui.slot.Slot
-import com.willfp.eco.internal.gui.slot.EcoFillerSlot
+import com.willfp.eco.internal.gui.slot.EcoSlot
 import com.willfp.eco.util.StringUtils
 import org.bukkit.Bukkit
+import org.bukkit.NamespacedKey
 import org.bukkit.entity.Player
 import org.bukkit.event.inventory.InventoryCloseEvent
 import org.bukkit.inventory.Inventory
-import java.util.function.Consumer
+import org.bukkit.inventory.ItemStack
+import org.bukkit.persistence.PersistentDataType
 
+@Suppress("UNCHECKED_CAST")
 class EcoMenu(
     private val rows: Int,
-    private val slots: List<MutableList<Slot>>,
+    val slots: List<MutableList<EcoSlot>>,
     private val title: String,
-    private val onClose: Consumer<InventoryCloseEvent>
+    private val onClose: CloseHandler
 ): Menu {
-
     override fun getSlot(row: Int, column: Int): Slot {
         if (row < 1 || row > this.rows) {
-            throw IllegalArgumentException("Invalid row number!")
+            return slots[0][0]
         }
 
         if (column < 1 || column > 9) {
-            throw IllegalArgumentException("Invalid column number!")
+            return slots[0][0]
         }
 
-        val slot = slots[row - 1][column - 1]
-        if (slot is FillerSlot) {
-            slots[row - 1][column - 1] = EcoFillerSlot(slot.itemStack)
-
-            return getSlot(row, column)
-        }
-
-        return slot
+        return slots[row - 1][column - 1]
     }
 
     override fun open(player: Player): Inventory {
@@ -46,7 +41,7 @@ class EcoMenu(
                 if (i == rows * 9) {
                     break
                 }
-                val slotItem = item.getItemStack(player)
+                val slotItem = item.getItemStack(player, this)
                 val meta = slotItem.itemMeta
                 if (meta != null) {
                     val lore = meta.lore
@@ -67,7 +62,8 @@ class EcoMenu(
     }
 
     fun handleClose(event: InventoryCloseEvent) {
-        onClose.accept(event)
+        onClose.handle(event, this)
+        MenuHandler.unregisterMenu(event.inventory)
     }
 
     override fun getRows(): Int {
@@ -77,4 +73,34 @@ class EcoMenu(
     override fun getTitle(): String {
         return title
     }
+
+    override fun getCaptiveItems(player: Player): MutableList<ItemStack> {
+        val inventory = MenuHandler.getExtendedInventory(player.openInventory.topInventory)
+        inventory ?: return mutableListOf()
+        return inventory.captiveItems
+    }
+
+    override fun <T : Any, Z : Any> writeData(
+        player: Player,
+        key: NamespacedKey,
+        type: PersistentDataType<T, Z>,
+        value: Z
+    ) {
+        val inventory = MenuHandler.getExtendedInventory(player.openInventory.topInventory)
+        inventory ?: return
+        inventory.data[key] = value
+        inventory.refresh(player)
+    }
+
+    override fun <T : Any, Z : Any> readData(player: Player, key: NamespacedKey, type: PersistentDataType<T, Z>): T? {
+        val inventory = MenuHandler.getExtendedInventory(player.openInventory.topInventory)
+        inventory ?: return null
+        return inventory.data[key] as T?
+    }
+
+    override fun getKeys(player: Player): MutableSet<NamespacedKey> {
+        val inventory = MenuHandler.getExtendedInventory(player.openInventory.topInventory)
+        inventory ?: return HashSet()
+        return inventory.data.keys
+    }
 }

eco-core/core-backend/src/main/kotlin/com/willfp/eco/internal/gui/menu/EcoMenuBuilder.kt

@@ -1,22 +1,24 @@
 package com.willfp.eco.internal.gui.menu
 
+import com.willfp.eco.core.gui.menu.CloseHandler
 import com.willfp.eco.core.gui.menu.Menu
 import com.willfp.eco.core.gui.menu.MenuBuilder
 import com.willfp.eco.core.gui.slot.FillerMask
+import com.willfp.eco.core.gui.slot.FillerSlot
 import com.willfp.eco.core.gui.slot.Slot
 import com.willfp.eco.internal.gui.slot.EcoFillerSlot
+import com.willfp.eco.internal.gui.slot.EcoSlot
 import com.willfp.eco.util.ListUtils
 import com.willfp.eco.util.StringUtils
 import org.bukkit.Material
-import org.bukkit.event.inventory.InventoryCloseEvent
 import org.bukkit.inventory.ItemStack
 import java.util.function.Consumer
 
 class EcoMenuBuilder(private val rows: Int) : MenuBuilder {
     private var title = "Menu"
     private var maskSlots: List<MutableList<Slot?>>
-    private val slots: List<MutableList<Slot>> = ListUtils.create2DList(rows, 9)
-    private var onClose = Consumer { _: InventoryCloseEvent -> }
+    private val slots: List<MutableList<Slot?>> = ListUtils.create2DList(rows, 9)
+    private var onClose = CloseHandler { _, _ -> }
 
     override fun setTitle(title: String): MenuBuilder {
         this.title = StringUtils.format(title)
@@ -34,35 +36,45 @@ class EcoMenuBuilder(private val rows: Int) : MenuBuilder {
         return this
     }
 
+    override fun modfiy(modifier: Consumer<MenuBuilder>): MenuBuilder {
+        modifier.accept(this)
+        return this
+    }
+
     override fun setMask(mask: FillerMask): MenuBuilder {
         maskSlots = mask.mask
         return this
     }
 
-    override fun onClose(action: Consumer<InventoryCloseEvent>): MenuBuilder {
+    override fun onClose(action: CloseHandler): MenuBuilder {
         onClose = action
         return this
     }
 
     override fun build(): Menu {
-        val finalSlots: MutableList<MutableList<Slot>> = ArrayList()
-
-        for (maskRow in maskSlots) {
-            val row = ArrayList<Slot>()
-            for (slot in maskRow) {
-                row.add(slot ?: EcoFillerSlot(ItemStack(Material.AIR)))
-            }
-            finalSlots.add(ArrayList())
-            finalSlots.add(row)
-        }
+        val tempSlots: MutableList<MutableList<Slot?>> = ArrayList(maskSlots)
 
         for (i in slots.indices) {
             for (j in slots[i].indices) {
-                val slot = slots[i][j]
-                finalSlots[i][j] = slot
+                val slot = slots[i][j] ?: continue
+                tempSlots[i][j] = slot
             }
         }
 
+        val finalSlots = mutableListOf<MutableList<EcoSlot>>()
+
+        for (row in tempSlots) {
+            val tempRow = mutableListOf<EcoSlot>()
+            for (slot in row) {
+                var tempSlot = slot
+                if (tempSlot is FillerSlot) {
+                    tempSlot = EcoFillerSlot(tempSlot.itemStack)
+                }
+                tempRow.add((tempSlot ?: EcoFillerSlot(ItemStack(Material.AIR))) as EcoSlot)
+            }
+            finalSlots.add(tempRow)
+        }
+
         return EcoMenu(rows, finalSlots, title, onClose)
     }
 

eco-core/core-backend/src/main/kotlin/com/willfp/eco/internal/gui/menu/ExtendedInventory.kt

@@ -0,0 +1,55 @@
+package com.willfp.eco.internal.gui.menu
+
+import com.willfp.eco.internal.gui.slot.EcoCaptivatorSlot
+import com.willfp.eco.util.MenuUtils
+import com.willfp.eco.util.StringUtils
+import org.bukkit.NamespacedKey
+import org.bukkit.entity.Player
+import org.bukkit.inventory.Inventory
+import org.bukkit.inventory.ItemStack
+
+class ExtendedInventory(
+    val inventory: Inventory,
+    private val menu: EcoMenu
+) {
+    val captiveItems = mutableListOf<ItemStack>()
+    val data = mutableMapOf<NamespacedKey, Any>()
+
+    fun refresh(player: Player) {
+        captiveItems.clear()
+        for (i in 0 until inventory.size) {
+            val (row, column) = MenuUtils.convertSlotToRowColumn(i)
+            val slot = menu.getSlot(row, column)
+            if (slot is EcoCaptivatorSlot) {
+                val defaultItem = slot.getItemStack(player)
+                val item = inventory.getItem(i) ?: continue
+                if (item != defaultItem) {
+                    captiveItems.add(item)
+                }
+            }
+        }
+
+        var i = 0
+        for (row in menu.slots) {
+            for (slot in row) {
+                if (i == menu.rows * 9) {
+                    break
+                }
+                val slotItem = slot.getItemStack(player, menu)
+                val meta = slotItem.itemMeta
+                if (meta != null) {
+                    val lore = meta.lore
+                    if (lore != null) {
+                        lore.replaceAll{ s -> StringUtils.format(s, player) }
+                        meta.lore = lore
+                    }
+                    slotItem.itemMeta = meta
+                }
+                if (!slot.isCaptive) {
+                    inventory.setItem(i, slotItem)
+                }
+                i++
+            }
+        }
+    }
+}

eco-core/core-backend/src/main/kotlin/com/willfp/eco/internal/gui/menu/MenuHandler.kt

@@ -2,22 +2,31 @@ package com.willfp.eco.internal.gui.menu
 
 import com.willfp.eco.core.gui.menu.Menu
 import org.bukkit.inventory.Inventory
+import java.util.*
 
 object MenuHandler {
-    private val MENUS: MutableMap<Inventory, Menu> = HashMap()
+    private val menus = WeakHashMap<ExtendedInventory, EcoMenu>()
+    private val inventories = WeakHashMap<Inventory, ExtendedInventory>()
 
     fun registerMenu(
         inventory: Inventory,
-        menu: Menu
+        menu: EcoMenu
     ) {
-        MENUS[inventory] = menu
+        val extendedInventory = ExtendedInventory(inventory, menu)
+        inventories[inventory] = extendedInventory
+        menus[extendedInventory] = menu
     }
 
     fun unregisterMenu(inventory: Inventory) {
-        MENUS.remove(inventory)
+        menus.remove(inventories[inventory])
+        inventories.remove(inventory)
     }
 
     fun getMenu(inventory: Inventory): Menu? {
-        return MENUS[inventory]
+        return menus[inventories[inventory]]
+    }
+
+    fun getExtendedInventory(inventory: Inventory): ExtendedInventory? {
+        return inventories[inventory]
     }
 }

eco-core/core-backend/src/main/kotlin/com/willfp/eco/internal/gui/slot/EcoCaptivatorSlot.kt

@@ -0,0 +1,28 @@
+package com.willfp.eco.internal.gui.slot
+
+import com.willfp.eco.core.Eco
+import com.willfp.eco.core.gui.slot.functional.SlotHandler
+import org.bukkit.Material
+import org.bukkit.inventory.ItemStack
+
+class EcoCaptivatorSlot : EcoSlot(
+    { _, _ -> ItemStack(Material.AIR) },
+    allowMovingItem,
+    allowMovingItem,
+    allowMovingItem,
+    allowMovingItem,
+    allowMovingItem,
+    { _, _, _ -> }
+) {
+    companion object {
+        val plugin = Eco.getHandler().ecoPlugin
+
+        val allowMovingItem = SlotHandler { event, _, _ ->
+            event.isCancelled = false
+        }
+    }
+
+    override fun isCaptive(): Boolean {
+        return true
+    }
+}

eco-core/core-backend/src/main/kotlin/com/willfp/eco/internal/gui/slot/EcoFillerSlot.kt

@@ -1,13 +1,13 @@
 package com.willfp.eco.internal.gui.slot
 
 import org.bukkit.inventory.ItemStack
-import java.util.function.Function
 
 class EcoFillerSlot(itemStack: ItemStack) : EcoSlot(
-    Function { itemStack },
-    { _, _ -> },
-    { _, _ -> },
-    { _, _ -> },
-    { _, _ -> },
-    { _, _ -> }
+    { _, _ -> itemStack },
+    { _, _, _ -> },
+    { _, _, _ -> },
+    { _, _, _ -> },
+    { _, _, _ -> },
+    { _, _, _ -> },
+    { _, _, _ -> }
 )

eco-core/core-backend/src/main/kotlin/com/willfp/eco/internal/gui/slot/EcoSlot.kt

@@ -1,34 +1,58 @@
 package com.willfp.eco.internal.gui.slot
 
+import com.willfp.eco.core.gui.menu.Menu
 import com.willfp.eco.core.gui.slot.Slot
+import com.willfp.eco.core.gui.slot.functional.SlotHandler
+import com.willfp.eco.core.gui.slot.functional.SlotModifier
+import com.willfp.eco.core.gui.slot.functional.SlotProvider
+import com.willfp.eco.internal.gui.menu.MenuHandler
 import org.bukkit.entity.Player
 import org.bukkit.event.inventory.ClickType
 import org.bukkit.event.inventory.InventoryClickEvent
 import org.bukkit.inventory.ItemStack
-import java.util.function.BiConsumer
-import java.util.function.Function
 
 open class EcoSlot(
-    private val provider: Function<Player, ItemStack>,
-    private val onLeftClick: BiConsumer<InventoryClickEvent, Slot>,
-    private val onRightClick: BiConsumer<InventoryClickEvent, Slot>,
-    private val onShiftLeftClick: BiConsumer<InventoryClickEvent, Slot>,
-    private val onShiftRightClick: BiConsumer<InventoryClickEvent, Slot>,
-    private val onMiddleClick: BiConsumer<InventoryClickEvent, Slot>
+    private val provider: SlotProvider,
+    private val onLeftClick: SlotHandler,
+    private val onRightClick: SlotHandler,
+    private val onShiftLeftClick: SlotHandler,
+    private val onShiftRightClick: SlotHandler,
+    private val onMiddleClick: SlotHandler,
+    private val modifier: SlotModifier
 ) : Slot {
 
-    fun handleInventoryClick(event: InventoryClickEvent) {
+    fun handleInventoryClick(
+        event: InventoryClickEvent,
+        menu: Menu
+    ) {
         when (event.click) {
-            ClickType.LEFT -> this.onLeftClick.accept(event, this)
-            ClickType.RIGHT -> this.onRightClick.accept(event, this)
-            ClickType.SHIFT_LEFT -> this.onShiftLeftClick.accept(event, this)
-            ClickType.SHIFT_RIGHT -> this.onShiftRightClick.accept(event, this)
-            ClickType.MIDDLE -> this.onMiddleClick.accept(event, this)
-            else -> { }
+            ClickType.LEFT -> this.onLeftClick.handle(event, this, menu)
+            ClickType.RIGHT -> this.onRightClick.handle(event, this, menu)
+            ClickType.SHIFT_LEFT -> this.onShiftLeftClick.handle(event, this, menu)
+            ClickType.SHIFT_RIGHT -> this.onShiftRightClick.handle(event, this, menu)
+            ClickType.MIDDLE -> this.onMiddleClick.handle(event, this, menu)
+            else -> {
+            }
         }
     }
 
     override fun getItemStack(player: Player): ItemStack {
-        return provider.apply(player)
+        val menu = MenuHandler.getMenu(player.openInventory.topInventory)!!
+        val prev = provider.provide(player, menu)
+        modifier.modify(player, menu, prev)
+        return prev
+    }
+
+    fun getItemStack(
+        player: Player,
+        menu: Menu
+    ): ItemStack {
+        val prev = provider.provide(player, menu)
+        modifier.modify(player, menu, prev)
+        return prev
+    }
+
+    override fun isCaptive(): Boolean {
+        return false
     }
 }

eco-core/core-backend/src/main/kotlin/com/willfp/eco/internal/gui/slot/EcoSlotBuilder.kt

@@ -2,45 +2,65 @@ package com.willfp.eco.internal.gui.slot
 
 import com.willfp.eco.core.gui.slot.Slot
 import com.willfp.eco.core.gui.slot.SlotBuilder
-import org.bukkit.entity.Player
-import org.bukkit.event.inventory.InventoryClickEvent
-import org.bukkit.inventory.ItemStack
-import java.util.function.BiConsumer
-import java.util.function.Function
+import com.willfp.eco.core.gui.slot.functional.SlotHandler
+import com.willfp.eco.core.gui.slot.functional.SlotModifier
+import com.willfp.eco.core.gui.slot.functional.SlotProvider
 
-class EcoSlotBuilder(private val provider: Function<Player, ItemStack>) : SlotBuilder {
-    private var onLeftClick: BiConsumer<InventoryClickEvent, Slot> = BiConsumer { _, _ -> run { } }
-    private var onRightClick: BiConsumer<InventoryClickEvent, Slot> = BiConsumer { _, _ -> run { } }
-    private var onShiftLeftClick: BiConsumer<InventoryClickEvent, Slot> = BiConsumer { _, _ -> run { } }
-    private var onShiftRightClick: BiConsumer<InventoryClickEvent, Slot> = BiConsumer { _, _ -> run { } }
-    private var onMiddleClick: BiConsumer<InventoryClickEvent, Slot> = BiConsumer { _, _ -> run { } }
+class EcoSlotBuilder(private val provider: SlotProvider) : SlotBuilder {
+    private var captive = false
+    private var modifier: SlotModifier = SlotModifier{ player, menu, _ -> provider.provide(player, menu)}
 
-    override fun onLeftClick(action: BiConsumer<InventoryClickEvent, Slot>): SlotBuilder {
+    private var onLeftClick =
+        SlotHandler { _, _, _ -> run { } }
+    private var onRightClick =
+        SlotHandler { _, _, _ -> run { } }
+    private var onShiftLeftClick =
+        SlotHandler { _, _, _ -> run { } }
+    private var onShiftRightClick =
+        SlotHandler { _, _, _ -> run { } }
+    private var onMiddleClick =
+        SlotHandler { _, _, _ -> run { } }
+
+    override fun onLeftClick(action: SlotHandler): SlotBuilder {
         onLeftClick = action
         return this
     }
 
-    override fun onRightClick(action: BiConsumer<InventoryClickEvent, Slot>): SlotBuilder {
+    override fun onRightClick(action: SlotHandler): SlotBuilder {
         onRightClick = action
         return this
     }
 
-    override fun onShiftLeftClick(action: BiConsumer<InventoryClickEvent, Slot>): SlotBuilder {
+    override fun onShiftLeftClick(action: SlotHandler): SlotBuilder {
         onShiftLeftClick = action
         return this
     }
 
-    override fun onShiftRightClick(action: BiConsumer<InventoryClickEvent, Slot>): SlotBuilder {
+    override fun onShiftRightClick(action: SlotHandler): SlotBuilder {
         onShiftRightClick = action
         return this
     }
 
-    override fun onMiddleClick(action: BiConsumer<InventoryClickEvent, Slot>): SlotBuilder {
+    override fun onMiddleClick(action: SlotHandler): SlotBuilder {
         onMiddleClick = action
         return this
     }
 
+    override fun setCaptive(): SlotBuilder {
+        captive = true
+        return this
+    }
+
+    override fun setModifier(modifier: SlotModifier): SlotBuilder {
+        this.modifier = modifier
+        return this
+    }
+
     override fun build(): Slot {
-        return EcoSlot(provider, onLeftClick, onRightClick, onShiftLeftClick, onShiftRightClick, onMiddleClick)
+        return if (captive) {
+            EcoCaptivatorSlot()
+        } else {
+            EcoSlot(provider, onLeftClick, onRightClick, onShiftLeftClick, onShiftRightClick, onMiddleClick, modifier)
+        }
     }
 }

eco-core/core-backend/src/main/kotlin/com/willfp/eco/internal/proxy/EcoProxyFactory.kt

@@ -1,7 +1,6 @@
-package com.willfp.eco.internal.proxy;
+package com.willfp.eco.internal.proxy
 
 import com.willfp.eco.core.EcoPlugin
-import com.willfp.eco.core.PluginDependent
 import com.willfp.eco.core.proxy.AbstractProxy
 import com.willfp.eco.core.proxy.ProxyConstants
 import com.willfp.eco.core.proxy.ProxyFactory
@@ -11,8 +10,8 @@ import java.net.URLClassLoader
 import java.util.*
 
 class EcoProxyFactory(
-    plugin: EcoPlugin
-) : PluginDependent<EcoPlugin>(plugin), ProxyFactory {
+    private val plugin: EcoPlugin
+) : ProxyFactory {
     private val proxyClassLoader: ClassLoader = plugin::class.java.classLoader
     private val cache: MutableMap<Class<out AbstractProxy>, AbstractProxy> = IdentityHashMap()
 

eco-core/core-backend/src/main/kotlin/com/willfp/eco/internal/requirement/EcoRequirementFactory.kt

@@ -0,0 +1,17 @@
+package com.willfp.eco.internal.requirement
+
+import com.willfp.eco.core.requirement.Requirement
+import com.willfp.eco.core.requirement.RequirementFactory
+import com.willfp.eco.internal.requirement.requirements.*
+
+class EcoRequirementFactory: RequirementFactory {
+    override fun create(name: String): Requirement {
+        return when (name.lowercase()) {
+            "has-permission" -> RequirementHasPermission()
+            "placeholder-equals" -> RequirementPlaceholderEquals()
+            "placeholder-greater-than" -> RequirementPlaceholderGreaterThan()
+            "placeholder-less-than" -> RequirementPlaceholderLessThan()
+            else -> RequirementTrue()
+        }
+    }
+}

eco-core/core-backend/src/main/kotlin/com/willfp/eco/internal/requirement/requirements/RequirementHasPermission.kt

@@ -0,0 +1,18 @@
+package com.willfp.eco.internal.requirement.requirements
+
+import com.willfp.eco.core.requirement.Requirement
+import org.bukkit.entity.Player
+
+class RequirementHasPermission : Requirement() {
+    override fun doesPlayerMeet(
+        player: Player,
+        args: List<String>
+    ): Boolean {
+        if (args.isEmpty()) {
+            return false
+        }
+
+        val permission = args[0]
+        return player.hasPermission(permission)
+    }
+}

eco-core/core-backend/src/main/kotlin/com/willfp/eco/internal/requirement/requirements/RequirementPlaceholderEquals.kt

@@ -0,0 +1,20 @@
+package com.willfp.eco.internal.requirement.requirements
+
+import com.willfp.eco.core.integrations.placeholder.PlaceholderManager
+import com.willfp.eco.core.requirement.Requirement
+import org.bukkit.entity.Player
+
+class RequirementPlaceholderEquals : Requirement() {
+    override fun doesPlayerMeet(
+        player: Player,
+        args: List<String>
+    ): Boolean {
+        if (args.size < 2) {
+            return false
+        }
+
+        val placeholder = args[0]
+        val equals = args[1]
+        return PlaceholderManager.translatePlaceholders(placeholder, player).equals(equals, ignoreCase = true)
+    }
+}

eco-core/core-backend/src/main/kotlin/com/willfp/eco/internal/requirement/requirements/RequirementPlaceholderGreaterThan.kt

@@ -0,0 +1,20 @@
+package com.willfp.eco.internal.requirement.requirements
+
+import com.willfp.eco.core.integrations.placeholder.PlaceholderManager
+import com.willfp.eco.core.requirement.Requirement
+import org.bukkit.entity.Player
+
+class RequirementPlaceholderGreaterThan : Requirement() {
+    override fun doesPlayerMeet(
+        player: Player,
+        args: List<String>
+    ): Boolean {
+        if (args.size < 2) {
+            return false
+        }
+
+        val placeholder = args[0]
+        val equals = args[1].toDoubleOrNull() ?: return false
+        return PlaceholderManager.translatePlaceholders(placeholder, player).toDoubleOrNull() ?: 0.0 >= equals
+    }
+}

eco-core/core-backend/src/main/kotlin/com/willfp/eco/internal/requirement/requirements/RequirementPlaceholderLessThan.kt

@@ -0,0 +1,20 @@
+package com.willfp.eco.internal.requirement.requirements
+
+import com.willfp.eco.core.integrations.placeholder.PlaceholderManager
+import com.willfp.eco.core.requirement.Requirement
+import org.bukkit.entity.Player
+
+class RequirementPlaceholderLessThan : Requirement() {
+    override fun doesPlayerMeet(
+        player: Player,
+        args: List<String>
+    ): Boolean {
+        if (args.size < 2) {
+            return false
+        }
+
+        val placeholder = args[0]
+        val equals = args[1].toDoubleOrNull() ?: return false
+        return PlaceholderManager.translatePlaceholders(placeholder, player).toDoubleOrNull() ?: 0.0 < equals
+    }
+}

eco-core/core-backend/src/main/kotlin/com/willfp/eco/internal/requirement/requirements/RequirementTrue.kt

@@ -0,0 +1,13 @@
+package com.willfp.eco.internal.requirement.requirements
+
+import com.willfp.eco.core.requirement.Requirement
+import org.bukkit.entity.Player
+
+class RequirementTrue : Requirement() {
+    override fun doesPlayerMeet(
+        player: Player,
+        args: List<String>
+    ): Boolean {
+        return true
+    }
+}

eco-core/core-backend/src/main/kotlin/com/willfp/eco/internal/scheduling/EcoScheduler.kt

@@ -1,12 +1,11 @@
 package com.willfp.eco.internal.scheduling
 
 import com.willfp.eco.core.EcoPlugin
-import com.willfp.eco.core.PluginDependent
 import com.willfp.eco.core.scheduling.Scheduler
 import org.bukkit.Bukkit
 import org.bukkit.scheduler.BukkitTask
 
-class EcoScheduler(plugin: EcoPlugin) : PluginDependent<EcoPlugin>(plugin), Scheduler {
+class EcoScheduler(private val plugin: EcoPlugin) : Scheduler {
     override fun runLater(
         runnable: Runnable,
         ticksLater: Long

eco-core/core-nms/v1_16_R3/build.gradle

@@ -3,4 +3,6 @@ version rootProject.version
 
 dependencies {
     compileOnly 'org.spigotmc:spigot:1.16.5-R0.1-SNAPSHOT'
+    compileOnly 'net.kyori:adventure-api:4.9.1'
+    compileOnly 'net.kyori:adventure-text-serializer-gson:4.8.1'
 }