Add support for modifying identifiers through the AvailableEntityIdentifiersPacket

This is the first of many commits that address adding support for custom entities through the Geyser API.

api/geyser/src/main/java/org/geysermc/geyser/api/GeyserApi.java

@@ -35,6 +35,7 @@ import org.geysermc.geyser.api.event.EventBus;
 import org.geysermc.geyser.api.extension.ExtensionManager;
 import org.geysermc.geyser.api.network.BedrockListener;
 import org.geysermc.geyser.api.network.RemoteServer;
+import org.geysermc.geyser.api.provider.ProviderManager;
 
 import java.util.List;
 import java.util.UUID;
@@ -99,6 +100,13 @@ public interface GeyserApi extends GeyserApiBase {
      */
     CommandManager commandManager();
 
+    /**
+     * Gets the {@link ProviderManager}.
+     *
+     * @return the provider manager
+     */
+    ProviderManager providerManager();
+
     /**
      * Gets the {@link EventBus} for handling
      * Geyser events.

api/geyser/src/main/java/org/geysermc/geyser/api/command/Command.java

@@ -98,27 +98,80 @@ public interface Command {
     }
 
     static <T extends CommandSource> Command.Builder<T> builder(Class<T> sourceType) {
-        return GeyserApi.api().commandManager().provideBuilder(sourceType);
+        return GeyserApi.api().providerManager().builderProvider().provideBuilder(Builder.class, sourceType);
     }
 
     interface Builder<T extends CommandSource> {
 
+        /**
+         * Sets the command name.
+         *
+         * @param name the command name
+         * @return the builder
+         */
         Builder<T> name(String name);
 
+        /**
+         * Sets the command description.
+         *
+         * @param description the command description
+         * @return the builder
+         */
         Builder<T> description(String description);
 
+        /**
+         * Sets the permission node.
+         *
+         * @param permission the permission node
+         * @return the builder
+         */
         Builder<T> permission(String permission);
 
+        /**
+         * Sets the aliases.
+         *
+         * @param aliases the aliases
+         * @return the builder
+         */
         Builder<T> aliases(List<String> aliases);
 
+        /**
+         * Sets if this command is executable on console.
+         *
+         * @param executableOnConsole if this command is executable on console
+         * @return the builder
+         */
         Builder<T> executableOnConsole(boolean executableOnConsole);
 
+        /**
+         * Sets the subcommands.
+         *
+         * @param subCommands the subcommands
+         * @return the builder
+         */
         Builder<T> subCommands(List<String> subCommands);
 
+        /**
+         * Sets if this command is bedrock only.
+         *
+         * @param bedrockOnly if this command is bedrock only
+         * @return the builder
+         */
         Builder<T> bedrockOnly(boolean bedrockOnly);
 
+        /**
+         * Sets the {@link CommandExecutor} for this command.
+         *
+         * @param executor the command executor
+         * @return the builder
+         */
         Builder<T> executor(CommandExecutor<T> executor);
 
+        /**
+         * Builds the command.
+         *
+         * @return the command
+         */
         Command build();
     }
 }

api/geyser/src/main/java/org/geysermc/geyser/api/command/CommandManager.java

@@ -34,15 +34,6 @@ import java.util.Map;
  */
 public abstract class CommandManager {
 
-    /**
-     * Provides a {@link Command.Builder}.
-     *
-     * @param sourceType the command source type
-     * @param <T> the type
-     * @return a command builder
-     */
-    protected abstract <T extends CommandSource> Command.Builder<T> provideBuilder(Class<T> sourceType);
-
     /**
      * Registers the given {@link Command}.
      *

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

@@ -0,0 +1,97 @@
+/*
+ * Copyright (c) 2019-2022 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.nullness.qual.NonNull;
+import org.geysermc.geyser.api.GeyserApi;
+
+/**
+ * Represents the data sent over to a client regarding
+ * an entity's identifier.
+ */
+public interface EntityIdentifier {
+
+    /**
+     * Gets whether this entity has a spawn egg or not.
+     *
+     * @return whether this entity has a spawn egg or not
+     */
+    boolean hasSpawnEgg();
+
+    /**
+     * Gets the entity's identifier that is sent to the client.
+     *
+     * @return the entity's identifier that is sent to the client.
+     */
+    @NonNull
+    String identifier();
+
+    /**
+     * Gets whether the entity is summonable or not.
+     *
+     * @return whether the entity is summonable or not
+     */
+    boolean isSummonable();
+
+    @NonNull
+    static Builder builder() {
+        return GeyserApi.api().providerManager().builderProvider().provideBuilder(Builder.class);
+    }
+
+    interface Builder {
+
+        /**
+         * Sets whether the entity has a spawn egg or not.
+         *
+         * @param spawnEgg whether the entity has a spawn egg or not
+         * @return the builder
+         */
+        Builder spawnEgg(boolean spawnEgg);
+
+        /**
+         * Sets the entity's identifier that is sent to the client.
+         *
+         * @param identifier the entity's identifier that is sent to the client
+         * @return the builder
+         */
+        Builder identifier(String identifier);
+
+        /**
+         * Sets whether the entity is summonable or not.
+         *
+         * @param summonable whether the entity is summonable or not
+         * @return the builder
+         */
+        Builder summonable(boolean summonable);
+
+        /**
+         * Builds the entity identifier.
+         *
+         * @return the entity identifier
+         */
+        EntityIdentifier build();
+    }
+}

api/geyser/src/main/java/org/geysermc/geyser/api/event/entity/DefineEntitiesEvent.java

@@ -0,0 +1,46 @@
+/*
+ * Copyright (c) 2019-2022 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.event.entity;
+
+import org.checkerframework.checker.nullness.qual.NonNull;
+import org.geysermc.geyser.api.connection.GeyserConnection;
+import org.geysermc.geyser.api.entity.EntityIdentifier;
+import org.geysermc.geyser.api.event.Event;
+
+import java.util.List;
+
+/**
+ * Called when Geyser sends a list of available entities to the
+ * Bedrock client. This will typically contain all the available
+ * entities within vanilla, but can be modified to include any custom
+ * entity defined through a resource pack.
+ *
+ * @param connection the {@link GeyserConnection} that is receiving the entities
+ * @param identifiers a mutable list of all the {@link EntityIdentifier}s
+ *                    sent to the client
+ */
+public record DefineEntitiesEvent(@NonNull GeyserConnection connection, @NonNull List<EntityIdentifier> identifiers) implements Event {
+}

api/geyser/src/main/java/org/geysermc/geyser/api/provider/BuilderProvider.java

@@ -0,0 +1,47 @@
+/*
+ * Copyright (c) 2019-2022 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.provider;
+
+import org.checkerframework.checker.nullness.qual.NonNull;
+import org.checkerframework.checker.nullness.qual.Nullable;
+
+/**
+ * Allows for obtaining instances of a builder that are
+ * used for constructing various data.
+ */
+public interface BuilderProvider extends Provider {
+
+    /**
+     * Provides a builder for the specified builder type.
+     *
+     * @param builderClass the builder class
+     * @param <B> the resulting type
+     * @param <T> the builder type
+     * @return the builder instance
+     */
+    @NonNull
+    <B extends T, T> B provideBuilder(@NonNull Class<T> builderClass, @Nullable Object... args);
+}

api/geyser/src/main/java/org/geysermc/geyser/api/provider/Provider.java

@@ -0,0 +1,29 @@
+/*
+ * Copyright (c) 2019-2022 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.provider;
+
+public interface Provider {
+}

api/geyser/src/main/java/org/geysermc/geyser/api/provider/ProviderManager.java

@@ -0,0 +1,41 @@
+/*
+ * Copyright (c) 2019-2022 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.provider;
+
+/**
+ * Holds a record of every {@link Provider} available
+ * that allows for accessing various information throughout
+ * the API.
+ */
+public interface ProviderManager {
+
+    /**
+     * Returns the {@link BuilderProvider}.
+     *
+     * @return the builder provider
+     */
+    BuilderProvider builderProvider();
+}

core/src/main/java/org/geysermc/geyser/GeyserImpl.java

@@ -70,6 +70,7 @@ import org.geysermc.geyser.network.RemoteServerImpl;
 import org.geysermc.geyser.pack.ResourcePack;
 import org.geysermc.geyser.registry.BlockRegistries;
 import org.geysermc.geyser.registry.Registries;
+import org.geysermc.geyser.registry.provider.GeyserProviderManager;
 import org.geysermc.geyser.scoreboard.ScoreboardUpdater;
 import org.geysermc.geyser.session.GeyserSession;
 import org.geysermc.geyser.session.PendingMicrosoftAuthentication;
@@ -145,6 +146,7 @@ public class GeyserImpl implements GeyserApi {
 
     private final EventBus eventBus;
     private final GeyserExtensionManager extensionManager;
+    private final GeyserProviderManager providerManager = new GeyserProviderManager();
 
     private final RemoteServer remoteServer;
     private final BedrockListener bedrockListener;
@@ -576,6 +578,11 @@ public class GeyserImpl implements GeyserApi {
         return this.bootstrap.getGeyserCommandManager();
     }
 
+    @Override
+    public GeyserProviderManager providerManager() {
+        return this.providerManager;
+    }
+
     @Override
     public EventBus eventBus() {
         return this.eventBus;

core/src/main/java/org/geysermc/geyser/command/GeyserCommandManager.java

@@ -148,11 +148,6 @@ public abstract class GeyserCommandManager extends CommandManager {
      */
     public abstract String description(String command);
 
-    @Override
-    protected <T extends CommandSource> Command.Builder<T> provideBuilder(Class<T> sourceType) {
-        return new CommandBuilder<>(sourceType);
-    }
-
     @RequiredArgsConstructor
     public static class CommandBuilder<T extends CommandSource> implements Command.Builder<T> {
         private final Class<T> sourceType;

core/src/main/java/org/geysermc/geyser/entity/GeyserEntityIdentifier.java

@@ -0,0 +1,85 @@
+/*
+ * Copyright (c) 2019-2022 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.entity;
+
+import com.nukkitx.nbt.NbtMap;
+import com.nukkitx.nbt.NbtMapBuilder;
+import org.checkerframework.checker.nullness.qual.NonNull;
+import org.geysermc.geyser.api.entity.EntityIdentifier;
+
+import java.util.concurrent.atomic.AtomicInteger;
+
+public record GeyserEntityIdentifier(NbtMap nbt) implements EntityIdentifier {
+    private static final AtomicInteger RUNTIME_ID_ALLOCATORS = new AtomicInteger(100000);
+
+    @Override
+    public boolean hasSpawnEgg() {
+        return this.nbt.getBoolean("hasspawnegg");
+    }
+
+    @NonNull
+    @Override
+    public String identifier() {
+        return this.nbt.getString("id");
+    }
+
+    @Override
+    public boolean isSummonable() {
+        return this.nbt.getBoolean("summonable");
+    }
+
+    public static class EntityIdentifierBuilder implements EntityIdentifier.Builder {
+        private final NbtMapBuilder nbt = NbtMap.builder();
+
+        @Override
+        public Builder spawnEgg(boolean spawnEgg) {
+            this.nbt.putBoolean("hasspawnegg", spawnEgg);
+            return this;
+        }
+
+        @Override
+        public Builder identifier(String identifier) {
+            this.nbt.putString("id", identifier);
+            return this;
+        }
+
+        @Override
+        public Builder summonable(boolean summonable) {
+            this.nbt.putBoolean("summonable", summonable);
+            return this;
+        }
+
+        @Override
+        public EntityIdentifier build() {
+            // Vanilla registry information
+            this.nbt.putString("bid", "");
+            this.nbt.putInt("rid", RUNTIME_ID_ALLOCATORS.getAndIncrement());
+            this.nbt.putBoolean("experimental", false);
+
+            return new GeyserEntityIdentifier(this.nbt.build());
+        }
+    }
+}

core/src/main/java/org/geysermc/geyser/registry/ProviderRegistries.java

@@ -0,0 +1,42 @@
+/*
+ * Copyright (c) 2019-2022 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.registry;
+
+import org.geysermc.geyser.api.provider.Provider;
+import org.geysermc.geyser.registry.loader.ProviderRegistryLoader;
+import org.geysermc.geyser.registry.provider.GeyserBuilderProvider;
+import org.geysermc.geyser.registry.provider.ProviderSupplier;
+
+/**
+ * Holds registries for the available {@link Provider}s
+ */
+public class ProviderRegistries {
+
+    /**
+     * A registry containing all the providers for builders.
+     */
+    public static final SimpleMappedRegistry<Class<?>, ProviderSupplier> BUILDERS = SimpleMappedRegistry.create(GeyserBuilderProvider.INSTANCE, ProviderRegistryLoader::new);
+}

core/src/main/java/org/geysermc/geyser/registry/loader/ProviderRegistryLoader.java

@@ -0,0 +1,45 @@
+/*
+ * Copyright (c) 2019-2022 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.registry.loader;
+
+import org.geysermc.geyser.registry.provider.AbstractProvider;
+import org.geysermc.geyser.registry.provider.ProviderSupplier;
+
+import java.util.IdentityHashMap;
+import java.util.Map;
+
+/**
+ * Registers the provider data from the provider.
+ */
+public class ProviderRegistryLoader implements RegistryLoader<AbstractProvider, Map<Class<?>, ProviderSupplier>> {
+
+    @Override
+    public Map<Class<?>, ProviderSupplier> load(AbstractProvider input) {
+        Map<Class<?>, ProviderSupplier> providers = new IdentityHashMap<>();
+        input.registerProviders(providers);
+        return providers;
+    }
+}

core/src/main/java/org/geysermc/geyser/registry/provider/AbstractProvider.java

@@ -0,0 +1,39 @@
+/*
+ * Copyright (c) 2019-2022 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.registry.provider;
+
+import lombok.RequiredArgsConstructor;
+import org.geysermc.geyser.api.provider.Provider;
+import org.geysermc.geyser.registry.SimpleMappedRegistry;
+
+import java.util.Map;
+
+@RequiredArgsConstructor
+public abstract class AbstractProvider implements Provider {
+    public abstract void registerProviders(Map<Class<?>, ProviderSupplier> providers);
+
+    public abstract SimpleMappedRegistry<Class<?>, ProviderSupplier> providerRegistry();
+}

core/src/main/java/org/geysermc/geyser/registry/provider/GeyserBuilderProvider.java

@@ -0,0 +1,64 @@
+/*
+ * Copyright (c) 2019-2022 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.registry.provider;
+
+import org.checkerframework.checker.nullness.qual.NonNull;
+import org.checkerframework.checker.nullness.qual.Nullable;
+import org.geysermc.geyser.api.command.Command;
+import org.geysermc.geyser.api.command.CommandSource;
+import org.geysermc.geyser.api.entity.EntityIdentifier;
+import org.geysermc.geyser.api.provider.BuilderProvider;
+import org.geysermc.geyser.command.GeyserCommandManager;
+import org.geysermc.geyser.entity.GeyserEntityIdentifier;
+import org.geysermc.geyser.registry.ProviderRegistries;
+import org.geysermc.geyser.registry.SimpleMappedRegistry;
+
+import java.util.Map;
+
+public class GeyserBuilderProvider extends AbstractProvider implements BuilderProvider {
+    public static GeyserBuilderProvider INSTANCE = new GeyserBuilderProvider();
+
+    private GeyserBuilderProvider() {
+    }
+
+    @SuppressWarnings("unchecked")
+    @Override
+    public void registerProviders(Map<Class<?>, ProviderSupplier> providers) {
+        providers.put(Command.Builder.class, args -> new GeyserCommandManager.CommandBuilder<>((Class<? extends CommandSource>) args[0]));
+        providers.put(EntityIdentifier.Builder.class, args -> new GeyserEntityIdentifier.EntityIdentifierBuilder());
+    }
+
+    @Override
+    public SimpleMappedRegistry<Class<?>, ProviderSupplier> providerRegistry() {
+        return ProviderRegistries.BUILDERS;
+    }
+
+    @SuppressWarnings("unchecked")
+    @Override
+    public <B extends T, T> @NonNull B provideBuilder(@NonNull Class<T> builderClass, @Nullable Object... args) {
+        return (B) this.providerRegistry().get(builderClass).create(args);
+    }
+}

core/src/main/java/org/geysermc/geyser/registry/provider/GeyserProviderManager.java

@@ -0,0 +1,36 @@
+/*
+ * Copyright (c) 2019-2022 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.registry.provider;
+
+import org.geysermc.geyser.api.provider.ProviderManager;
+
+public class GeyserProviderManager implements ProviderManager {
+
+    @Override
+    public GeyserBuilderProvider builderProvider() {
+        return GeyserBuilderProvider.INSTANCE;
+    }
+}

core/src/main/java/org/geysermc/geyser/registry/provider/ProviderSupplier.java

@@ -0,0 +1,31 @@
+/*
+ * Copyright (c) 2019-2022 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.registry.provider;
+
+public interface ProviderSupplier {
+
+    Object create(Object... args);
+}

core/src/main/java/org/geysermc/geyser/session/GeyserSession.java

@@ -61,6 +61,9 @@ import com.github.steveice10.packetlib.tcp.TcpClientSession;
 import com.github.steveice10.packetlib.tcp.TcpSession;
 import com.nukkitx.math.GenericMath;
 import com.nukkitx.math.vector.*;
+import com.nukkitx.nbt.NbtMap;
+import com.nukkitx.nbt.NbtMapBuilder;
+import com.nukkitx.nbt.NbtType;
 import com.nukkitx.protocol.bedrock.BedrockPacket;
 import com.nukkitx.protocol.bedrock.BedrockServerSession;
 import com.nukkitx.protocol.bedrock.data.*;
@@ -88,9 +91,12 @@ import org.geysermc.floodgate.util.BedrockData;
 import org.geysermc.geyser.Constants;
 import org.geysermc.geyser.GeyserImpl;
 import org.geysermc.geyser.api.connection.GeyserConnection;
+import org.geysermc.geyser.api.entity.EntityIdentifier;
+import org.geysermc.geyser.api.event.entity.DefineEntitiesEvent;
 import org.geysermc.geyser.api.network.RemoteServer;
 import org.geysermc.geyser.command.GeyserCommandSource;
 import org.geysermc.geyser.configuration.EmoteOffhandWorkaroundOption;
+import org.geysermc.geyser.entity.GeyserEntityIdentifier;
 import org.geysermc.geyser.entity.attribute.GeyserAttributeType;
 import org.geysermc.geyser.entity.type.Entity;
 import org.geysermc.geyser.entity.type.ItemFrameEntity;
@@ -129,6 +135,7 @@ import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.ScheduledFuture;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicInteger;
+import java.util.stream.Collectors;
 
 @Getter
 public class GeyserSession implements GeyserConnection, GeyserCommandSource {
@@ -595,9 +602,7 @@ public class GeyserSession implements GeyserConnection, GeyserCommandSource {
         biomeDefinitionListPacket.setDefinitions(Registries.BIOMES_NBT.get());
         upstream.sendPacket(biomeDefinitionListPacket);
 
-        AvailableEntityIdentifiersPacket entityPacket = new AvailableEntityIdentifiersPacket();
-        entityPacket.setIdentifiers(Registries.BEDROCK_ENTITY_IDENTIFIERS.get());
-        upstream.sendPacket(entityPacket);
+        this.sendAvailableEntityIdentifiers();
 
         CreativeContentPacket creativePacket = new CreativeContentPacket();
         creativePacket.setContents(this.itemMappings.getCreativeItems());
@@ -627,6 +632,29 @@ public class GeyserSession implements GeyserConnection, GeyserCommandSource {
         upstream.sendPacket(gamerulePacket);
     }
 
+    public void sendAvailableEntityIdentifiers() {
+        NbtMap nbt = Registries.BEDROCK_ENTITY_IDENTIFIERS.get();
+        List<NbtMap> idlist = nbt.getList("idlist", NbtType.COMPOUND);
+        List<EntityIdentifier> identifiers = new ArrayList<>(idlist.size());
+        for (NbtMap identifier : idlist) {
+            identifiers.add(new GeyserEntityIdentifier(identifier));
+        }
+
+        DefineEntitiesEvent event = new DefineEntitiesEvent(this, identifiers);
+        this.geyser.eventBus().fire(event);
+
+        NbtMapBuilder builder = nbt.toBuilder();
+        builder.putList("idlist", NbtType.COMPOUND, event.identifiers()
+                .stream()
+                .map(identifer -> ((GeyserEntityIdentifier) identifer).nbt())
+                .collect(Collectors.toList())
+        );
+
+        AvailableEntityIdentifiersPacket entityPacket = new AvailableEntityIdentifiersPacket();
+        entityPacket.setIdentifiers(builder.build());
+        upstream.sendPacket(entityPacket);
+    }
+
     public void authenticate(String username) {
         authenticate(username, "");
     }