Work on exposing custom entity definitions in the API

api/src/main/java/org/geysermc/geyser/api/entity/CustomEntityDefinition.java

@@ -0,0 +1,81 @@
+/*
+ * Copyright (c) 2025 GeyserMC. http://geysermc.org
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ *
+ * @author GeyserMC
+ * @link https://github.com/GeyserMC/Geyser
+ */
+
+package org.geysermc.geyser.api.entity;
+
+import org.checkerframework.checker.index.qual.Positive;
+import org.checkerframework.checker.nullness.qual.NonNull;
+import org.checkerframework.common.returnsreceiver.qual.This;
+import org.geysermc.geyser.api.GeyserApi;
+import org.geysermc.geyser.api.predicate.MinecraftPredicate;
+import org.geysermc.geyser.api.predicate.PredicateStrategy;
+import org.geysermc.geyser.api.predicate.context.entity.EntitySpawnContext;
+import org.geysermc.geyser.api.util.GenericBuilder;
+
+import java.util.List;
+
+public interface CustomEntityDefinition {
+
+    // TODO Identifier
+    String bedrockIdentifier();
+
+    float width();
+
+    float height();
+
+    float offset();
+
+    List<MinecraftPredicate<? super EntitySpawnContext>> predicates();
+
+    PredicateStrategy predicateStrategy();
+
+    static Builder builder(@NonNull String bedrockIdentifier, @NonNull JavaEntityType vanillaType) {
+        return GeyserApi.api().provider(Builder.class, bedrockIdentifier, vanillaType);
+    }
+
+    interface Builder extends GenericBuilder<CustomEntityDefinition> {
+
+        @This
+        Builder width(@Positive float width);
+
+        @This
+        Builder height(@Positive float height);
+
+        @This
+        Builder heightAndWidth(@Positive float value);
+
+        @This
+        Builder offset(@Positive float offset);
+
+        @This
+        Builder predicate(@NonNull MinecraftPredicate<? super EntitySpawnContext> predicate);
+
+        @This
+        Builder predicateStrategy(@NonNull PredicateStrategy strategy);
+
+        @Override
+        CustomEntityDefinition build();
+    }
+}

api/src/main/java/org/geysermc/geyser/api/entity/JavaEntityType.java

@@ -38,6 +38,8 @@ public interface JavaEntityType {
 
     boolean isUnregistered();
 
+    boolean vanilla();
+
     default boolean is(Identifier javaIdentifier) {
         return javaIdentifier().equals(javaIdentifier);
     }