Added requirements into eco

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

@@ -13,6 +13,7 @@ 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 org.bukkit.inventory.ItemStack;
 import org.jetbrains.annotations.NotNull;
@@ -194,4 +195,11 @@ public interface Handler {
      * @param plugin The plugin.
      */
     void registerBStats(@NotNull EcoPlugin plugin);
+
+    /**
+     * Get the requirement factory.
+     *
+     * @return The factory.
+     */
+    RequirementFactory getRequirementFactory();
 }

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);
+    }
+}