Custom item support for extensions (#2822)

Co-authored-by: Camotoy <20743703+Camotoy@users.noreply.github.com>

.gitignore

@@ -249,4 +249,5 @@ locales/
 /packs/
 /dump.json
 /saved-refresh-tokens.json
+/custom_mappings/
 /languages/

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

@@ -116,7 +116,7 @@ public interface GeyserApi extends GeyserApiBase {
     EventBus eventBus();
 
     /**
-     * Get's the default {@link RemoteServer} configured
+     * Gets the default {@link RemoteServer} configured
      * within the config file that is used by default.
      *
      * @return the default remote server used within Geyser

api/geyser/src/main/java/org/geysermc/geyser/api/event/EventBus.java

@@ -76,7 +76,7 @@ public interface EventBus {
      void unregisterAll(@NonNull Extension extension);
 
     /**
-     * Fires the given {@link Event}.
+     * Fires the given {@link Event} and returns the result.
      *
      * @param event the event to fire
      *

api/geyser/src/main/java/org/geysermc/geyser/api/event/lifecycle/GeyserDefineCustomItemsEvent.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.api.event.lifecycle;
+
+import com.google.common.collect.Multimap;
+import org.checkerframework.checker.nullness.qual.NonNull;
+import org.geysermc.geyser.api.event.Event;
+import org.geysermc.geyser.api.item.custom.CustomItemData;
+import org.geysermc.geyser.api.item.custom.NonVanillaCustomItemData;
+
+import java.util.*;
+
+/**
+ * Called on Geyser's startup when looking for custom items. Custom items must be registered through this event.
+ *
+ * This event will not be called if the "add non-Bedrock items" setting is disabled in the Geyser config.
+ */
+public abstract class GeyserDefineCustomItemsEvent implements Event {
+    private final Multimap<String, CustomItemData> customItems;
+    private final List<NonVanillaCustomItemData> nonVanillaCustomItems;
+
+    public GeyserDefineCustomItemsEvent(Multimap<String, CustomItemData> customItems, List<NonVanillaCustomItemData> nonVanillaCustomItems) {
+        this.customItems = customItems;
+        this.nonVanillaCustomItems = nonVanillaCustomItems;
+    }
+
+    /**
+     * Gets a multimap of all the already registered custom items indexed by the item's extended java item's identifier.
+     *
+     * @return a multimap of all the already registered custom items
+     */
+    public Map<String, Collection<CustomItemData>> getExistingCustomItems() {
+        return Collections.unmodifiableMap(this.customItems.asMap());
+    }
+
+    /**
+     * Gets the list of the already registered non-vanilla custom items.
+     *
+     * @return the list of the already registered non-vanilla custom items
+     */
+    public List<NonVanillaCustomItemData> getExistingNonVanillaCustomItems() {
+        return Collections.unmodifiableList(this.nonVanillaCustomItems);
+    }
+
+    /**
+     * Registers a custom item with a base Java item. This is used to register items with custom textures and properties
+     * based on NBT data.
+     *
+     * @param identifier the base (java) item
+     * @param customItemData the custom item data to register
+     * @return if the item was registered
+     */
+    public abstract boolean register(@NonNull String identifier, @NonNull CustomItemData customItemData);
+
+    /**
+     * Registers a custom item with no base item. This is used for mods.
+     *
+     * @param customItemData the custom item data to register
+     * @return if the item was registered
+     */
+    public abstract boolean register(@NonNull NonVanillaCustomItemData customItemData);
+}

api/geyser/src/main/java/org/geysermc/geyser/api/event/lifecycle/GeyserLoadResourcePacksEvent.java

@@ -0,0 +1,40 @@
+/*
+ * 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.lifecycle;
+
+import org.checkerframework.checker.nullness.qual.NonNull;
+import org.geysermc.geyser.api.event.Event;
+
+import java.nio.file.Path;
+import java.util.List;
+
+/**
+ * Called when resource packs are loaded within Geyser.
+ *
+ * @param resourcePacks a mutable list of the currently listed resource packs
+ */
+public record GeyserLoadResourcePacksEvent(@NonNull List<Path> resourcePacks) implements Event {
+}

api/geyser/src/main/java/org/geysermc/geyser/api/item/custom/CustomItemData.java

@@ -0,0 +1,109 @@
+/*
+ * 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.item.custom;
+
+import org.checkerframework.checker.nullness.qual.NonNull;
+import org.checkerframework.checker.nullness.qual.Nullable;
+import org.geysermc.geyser.api.GeyserApi;
+
+/**
+ * This is used to store data for a custom item.
+ */
+public interface CustomItemData {
+    /**
+     * Gets the item's name.
+     *
+     * @return the item's name
+     */
+    @NonNull String name();
+
+    /**
+     * Gets the custom item options of the item.
+     *
+     * @return the custom item options of the item.
+     */
+    CustomItemOptions customItemOptions();
+
+    /**
+     * Gets the item's display name. By default, this is the item's name.
+     *
+     * @return the item's display name
+     */
+    @NonNull String displayName();
+
+    /**
+     * Gets the item's icon. By default, this is the item's name.
+     *
+     * @return the item's icon
+     */
+    @NonNull String icon();
+
+    /**
+     * Gets if the item is allowed to be put into the offhand.
+     *
+     * @return true if the item is allowed to be used in the offhand, false otherwise
+     */
+    boolean allowOffhand();
+
+    /**
+     * Gets the item's texture size. This is to resize the item if the texture is not 16x16.
+     *
+     * @return the item's texture size
+     */
+    int textureSize();
+
+    /**
+     * Gets the item's render offsets. If it is null, the item will be rendered normally, with no offsets.
+     *
+     * @return the item's render offsets
+     */
+    @Nullable CustomRenderOffsets renderOffsets();
+
+    static CustomItemData.Builder builder() {
+        return GeyserApi.api().providerManager().builderProvider().provideBuilder(CustomItemData.Builder.class);
+    }
+
+    interface Builder {
+        /**
+         * Will also set the display name and icon to the provided parameter, if it is currently not set.
+         */
+        Builder name(@NonNull String name);
+
+        Builder customItemOptions(@NonNull CustomItemOptions customItemOptions);
+
+        Builder displayName(@NonNull String displayName);
+
+        Builder icon(@NonNull String icon);
+
+        Builder allowOffhand(boolean allowOffhand);
+
+        Builder textureSize(int textureSize);
+
+        Builder renderOffsets(@Nullable CustomRenderOffsets renderOffsets);
+
+        CustomItemData build();
+    }
+}

api/geyser/src/main/java/org/geysermc/geyser/api/item/custom/CustomItemOptions.java

@@ -0,0 +1,83 @@
+/*
+ * 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.item.custom;
+
+import org.checkerframework.checker.nullness.qual.NonNull;
+import org.geysermc.geyser.api.GeyserApi;
+import org.geysermc.geyser.api.util.TriState;
+
+import java.util.OptionalInt;
+
+/**
+ * This class represents the different ways you can register custom items
+ */
+public interface CustomItemOptions {
+    /**
+     * Gets if the item should be unbreakable.
+     *
+     * @return if the item should be unbreakable
+     */
+    @NonNull TriState unbreakable();
+
+    /**
+     * Gets the item's custom model data predicate.
+     *
+     * @return the item's custom model data
+     */
+    @NonNull OptionalInt customModelData();
+
+    /**
+     * Gets the item's damage predicate.
+     *
+     * @return the item's damage predicate
+     */
+    @NonNull OptionalInt damagePredicate();
+
+    /**
+     * Checks if the item has at least one option set
+     *
+     * @return true if the item at least one options set
+     */
+    default boolean hasCustomItemOptions() {
+        return this.unbreakable() != TriState.NOT_SET ||
+                this.customModelData().isPresent() ||
+                this.damagePredicate().isPresent();
+    }
+
+    static CustomItemOptions.Builder builder() {
+        return GeyserApi.api().providerManager().builderProvider().provideBuilder(CustomItemOptions.Builder.class);
+    }
+
+    interface Builder {
+        Builder unbreakable(boolean unbreakable);
+
+        Builder customModelData(int customModelData);
+
+        Builder damagePredicate(int damagePredicate);
+
+        CustomItemOptions build();
+    }
+}

api/geyser/src/main/java/org/geysermc/geyser/api/item/custom/CustomRenderOffsets.java

@@ -0,0 +1,51 @@
+/*
+ * 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.item.custom;
+
+import org.checkerframework.checker.nullness.qual.Nullable;
+
+/**
+ * This class is used to store the render offsets of custom items.
+ */
+public record CustomRenderOffsets(@Nullable Hand mainHand, @Nullable Hand offhand) {
+    /**
+     * The hand that is used for the offset.
+     */
+    public record Hand(@Nullable Offset firstPerson, @Nullable Offset thirdPerson) {
+    }
+
+    /**
+     * The offset of the item.
+     */
+    public record Offset(@Nullable OffsetXYZ position, @Nullable OffsetXYZ rotation, @Nullable OffsetXYZ scale) {
+    }
+
+    /**
+     * X, Y and Z positions for the offset.
+     */
+    public record OffsetXYZ(float x, float y, float z) {
+    }
+}

api/geyser/src/main/java/org/geysermc/geyser/api/item/custom/NonVanillaCustomItemData.java

@@ -0,0 +1,188 @@
+/*
+ * 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.item.custom;
+
+import org.checkerframework.checker.index.qual.NonNegative;
+import org.checkerframework.checker.nullness.qual.NonNull;
+import org.checkerframework.checker.nullness.qual.Nullable;
+import org.geysermc.geyser.api.GeyserApi;
+
+import java.util.OptionalInt;
+import java.util.Set;
+
+/**
+ * Represents a completely custom item that is not based on an existing vanilla Minecraft item.
+ */
+public interface NonVanillaCustomItemData extends CustomItemData {
+    /**
+     * Gets the java identifier for this item.
+     *
+     * @return The java identifier for this item.
+     */
+    @NonNull String identifier();
+
+    /**
+     * Gets the java item id of the item.
+     *
+     * @return the java item id of the item
+     */
+    @NonNegative int javaId();
+
+    /**
+     * Gets the stack size of the item.
+     *
+     * @return the stack size of the item
+     */
+    @NonNegative int stackSize();
+
+    /**
+     * Gets the max damage of the item.
+     *
+     * @return the max damage of the item
+     */
+    int maxDamage();
+
+    /**
+     * Gets the tool type of the item.
+     *
+     * @return the tool type of the item
+     */
+    @Nullable String toolType();
+
+    /**
+     * Gets the tool tier of the item.
+     *
+     * @return the tool tier of the item
+     */
+    @Nullable String toolTier();
+
+    /**
+     * Gets the armor type of the item.
+     *
+     * @return the armor type of the item
+     */
+    @Nullable String armorType();
+
+    /**
+     * Gets the armor protection value of the item.
+     *
+     * @return the armor protection value of the item
+     */
+    int protectionValue();
+
+    /**
+     * Gets the item's translation string.
+     *
+     * @return the item's translation string
+     */
+    @Nullable String translationString();
+
+    /**
+     * Gets the repair materials of the item.
+     *
+     * @return the repair materials of the item
+     */
+    @Nullable Set<String> repairMaterials();
+
+    /**
+     * Gets the item's creative category, or tab id.
+     *
+     * @return the item's creative category
+     */
+    @NonNull OptionalInt creativeCategory();
+
+    /**
+     * Gets the item's creative group.
+     *
+     * @return the item's creative group
+     */
+    @Nullable String creativeGroup();
+
+    /**
+     * Gets if the item is a hat. This is used to determine if the item should be rendered on the player's head, and
+     * normally allow the player to equip it. This is not meant for armor.
+     *
+     * @return if the item is a hat
+     */
+    boolean isHat();
+
+    /**
+     * Gets if the item is a tool. This is used to set the render type of the item, if the item is handheld.
+     *
+     * @return if the item is a tool
+     */
+    boolean isTool();
+
+    static NonVanillaCustomItemData.Builder builder() {
+        return GeyserApi.api().providerManager().builderProvider().provideBuilder(NonVanillaCustomItemData.Builder.class);
+    }
+
+    interface Builder extends CustomItemData.Builder {
+        Builder name(@NonNull String name);
+
+        Builder identifier(@NonNull String identifier);
+
+        Builder javaId(@NonNegative int javaId);
+
+        Builder stackSize(@NonNegative int stackSize);
+
+        Builder maxDamage(int maxDamage);
+
+        Builder toolType(@Nullable String toolType);
+
+        Builder toolTier(@Nullable String toolTier);
+
+        Builder armorType(@Nullable String armorType);
+
+        Builder protectionValue(int protectionValue);
+
+        Builder translationString(@Nullable String translationString);
+
+        Builder repairMaterials(@Nullable Set<String> repairMaterials);
+
+        Builder creativeCategory(int creativeCategory);
+
+        Builder creativeGroup(@Nullable String creativeGroup);
+
+        Builder hat(boolean isHat);
+
+        Builder tool(boolean isTool);
+
+        @Override
+        Builder displayName(@NonNull String displayName);
+
+        @Override
+        Builder allowOffhand(boolean allowOffhand);
+
+        @Override
+        Builder textureSize(int textureSize);
+
+        @Override
+        Builder renderOffsets(@Nullable CustomRenderOffsets renderOffsets);
+
+        NonVanillaCustomItemData build();
+    }
+}

api/geyser/src/main/java/org/geysermc/geyser/api/util/TriState.java

@@ -0,0 +1,83 @@
+/*
+ * 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.util;
+
+import org.checkerframework.checker.nullness.qual.NonNull;
+import org.checkerframework.checker.nullness.qual.Nullable;
+
+/**
+ * This is a way to represent a boolean, but with a non set value added.
+ * This class was inspired by adventure's version https://github.com/KyoriPowered/adventure/blob/main/4/api/src/main/java/net/kyori/adventure/util/TriState.java
+ */
+public enum TriState {
+    /**
+     * Describes a value that is not set, null, or not present.
+     */
+    NOT_SET,
+
+    /**
+     * Describes a true value.
+     */
+    TRUE,
+
+    /**
+     * Describes a false value.
+     */
+    FALSE;
+
+    /**
+     * Converts the TriState to a boolean.
+     *
+     * @return the boolean value of the TriState
+     */
+    public @Nullable Boolean toBoolean() {
+        return switch (this) {
+            case TRUE -> true;
+            case FALSE -> false;
+            default -> null;
+        };
+    }
+
+    /**
+     * Creates a TriState from a boolean.
+     *
+     * @param value the Boolean value
+     * @return the created TriState
+     */
+    public static @NonNull TriState fromBoolean(@Nullable Boolean value) {
+        return value == null ? NOT_SET : fromBoolean(value.booleanValue());
+    }
+
+    /**
+     * Creates a TriState from a primitive boolean.
+     *
+     * @param value the boolean value
+     * @return the created TriState
+     */
+    public @NonNull static TriState fromBoolean(boolean value) {
+        return value ? TRUE : FALSE;
+    }
+}

bootstrap/standalone/build.gradle.kts

@@ -1,7 +1,7 @@
 import com.github.jengelman.gradle.plugins.shadow.transformers.Log4j2PluginsCacheFileTransformer
 
 val terminalConsoleVersion = "1.2.0"
-val jlineVersion = "3.10.0"
+val jlineVersion = "3.21.0"
 
 dependencies {
     api(projects.core)

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

@@ -180,22 +180,26 @@ public class GeyserImpl implements GeyserApi {
         logger.info("");
         logger.info("******************************************");
 
-        /* Initialize translators and registries */
+        /* Initialize event bus */
-        BlockRegistries.init();
+        this.eventBus = new GeyserEventBus();
-        Registries.init();
 
+        /* Load Extensions */
+        this.extensionManager = new GeyserExtensionManager();
+        this.extensionManager.init();
+
+        this.extensionManager.enableExtensions();
+        this.eventBus.fire(new GeyserPreInitializeEvent(this.extensionManager, this.eventBus));
+
+        /* Initialize registries */
+        Registries.init();
+        BlockRegistries.init();
+
+        /* Initialize translators */
         EntityDefinitions.init();
         ItemTranslator.init();
         MessageTranslator.init();
         MinecraftLocale.init();
 
-        /* Load Extensions */
-        this.eventBus = new GeyserEventBus();
-        this.extensionManager = new GeyserExtensionManager();
-        this.extensionManager.init();
-
-        this.eventBus.fire(new GeyserPreInitializeEvent(this.extensionManager, this.eventBus));
-
         start();
 
         GeyserConfiguration config = bootstrap.getGeyserConfig();
@@ -256,8 +260,6 @@ public class GeyserImpl implements GeyserApi {
 
         ResourcePack.loadPacks();
 
-        this.extensionManager.enableExtensions();
-
         if (platformType != PlatformType.STANDALONE && config.getRemote().getAddress().equals("auto")) {
             // Set the remote address to localhost since that is where we are always connecting
             try {
@@ -580,6 +582,7 @@ public class GeyserImpl implements GeyserApi {
     @Override
     public void reload() {
         shutdown();
+        this.extensionManager.enableExtensions();
         bootstrap.onEnable();
     }
 
@@ -615,7 +618,6 @@ public class GeyserImpl implements GeyserApi {
         return this.eventBus;
     }
 
-    @Override
     public RemoteServer defaultRemoteServer() {
         return this.remoteServer;
     }

core/src/main/java/org/geysermc/geyser/entity/type/ItemFrameEntity.java

@@ -40,7 +40,6 @@ import com.nukkitx.protocol.bedrock.packet.BlockEntityDataPacket;
 import com.nukkitx.protocol.bedrock.packet.UpdateBlockPacket;
 import lombok.Getter;
 import org.geysermc.geyser.entity.EntityDefinition;
-import org.geysermc.geyser.registry.type.ItemMapping;
 import org.geysermc.geyser.session.GeyserSession;
 import org.geysermc.geyser.translator.inventory.item.ItemTranslator;
 import org.geysermc.geyser.util.InteractionResult;
@@ -114,7 +113,9 @@ public class ItemFrameEntity extends Entity {
         if (entityMetadata.getValue() != null) {
             this.heldItem = entityMetadata.getValue();
             ItemData itemData = ItemTranslator.translateToBedrock(session, heldItem);
-            ItemMapping mapping = session.getItemMappings().getMapping(entityMetadata.getValue());
+
+            String customIdentifier = session.getItemMappings().getCustomIdMappings().get(itemData.getId());
+
             NbtMapBuilder builder = NbtMap.builder();
 
             builder.putByte("Count", (byte) itemData.getCount());
@@ -122,7 +123,7 @@ public class ItemFrameEntity extends Entity {
                 builder.put("tag", itemData.getTag());
             }
             builder.putShort("Damage", (short) itemData.getDamage());
-            builder.putString("Name", mapping.getBedrockIdentifier());
+            builder.putString("Name", customIdentifier != null ? customIdentifier : session.getItemMappings().getMapping(entityMetadata.getValue()).getBedrockIdentifier());
             NbtMapBuilder tag = getDefaultTag().toBuilder();
             tag.put("Item", builder.build());
             tag.putFloat("ItemDropChance", 1.0f);

core/src/main/java/org/geysermc/geyser/extension/GeyserExtensionManager.java

@@ -25,6 +25,7 @@
 
 package org.geysermc.geyser.extension;
 
+import it.unimi.dsi.fastutil.objects.Object2ObjectOpenHashMap;
 import net.kyori.adventure.key.Key;
 import org.checkerframework.checker.nullness.qual.NonNull;
 import org.checkerframework.checker.nullness.qual.Nullable;
@@ -32,7 +33,6 @@ import org.geysermc.geyser.GeyserImpl;
 import org.geysermc.geyser.api.extension.Extension;
 import org.geysermc.geyser.api.extension.ExtensionLoader;
 import org.geysermc.geyser.api.extension.ExtensionManager;
-import org.geysermc.geyser.registry.Registries;
 import org.geysermc.geyser.text.GeyserLocale;
 
 import java.util.Collection;
@@ -44,13 +44,15 @@ import java.util.stream.Collectors;
 public class GeyserExtensionManager extends ExtensionManager {
     private static final Key BASE_EXTENSION_LOADER_KEY = Key.key("geysermc", "base");
 
+    private final Map<Key, ExtensionLoader> extensionLoaderTypes = new Object2ObjectOpenHashMap<>();
+
     private final Map<String, Extension> extensions = new LinkedHashMap<>();
     private final Map<Extension, ExtensionLoader> extensionsLoaders = new LinkedHashMap<>();
 
     public void init() {
         GeyserImpl.getInstance().getLogger().info(GeyserLocale.getLocaleStringLog("geyser.extensions.load.loading"));
 
-        Registries.EXTENSION_LOADERS.register(BASE_EXTENSION_LOADER_KEY, new GeyserExtensionLoader());
+        extensionLoaderTypes.put(BASE_EXTENSION_LOADER_KEY, new GeyserExtensionLoader());
         for (ExtensionLoader loader : this.extensionLoaders().values()) {
             this.loadAllExtensions(loader);
         }
@@ -98,6 +100,12 @@ public class GeyserExtensionManager extends ExtensionManager {
         }
     }
 
+    public void enableExtensions() {
+        for (Extension extension : this.extensions()) {
+            this.enable(extension);
+        }
+    }
+
     private void disableExtension(@NonNull Extension extension) {
         if (extension.isEnabled()) {
             GeyserImpl.getInstance().eventBus().unregisterAll(extension);
@@ -107,12 +115,6 @@ public class GeyserExtensionManager extends ExtensionManager {
         }
     }
 
-    public void enableExtensions() {
-        for (Extension extension : this.extensions()) {
-            this.enable(extension);
-        }
-    }
-
     public void disableExtensions() {
         for (Extension extension : this.extensions()) {
             this.disable(extension);
@@ -133,18 +135,18 @@ public class GeyserExtensionManager extends ExtensionManager {
     @Nullable
     @Override
     public ExtensionLoader extensionLoader(@NonNull String identifier) {
-        return Registries.EXTENSION_LOADERS.get(Key.key(identifier));
+        return this.extensionLoaderTypes.get(Key.key(identifier));
     }
 
     @Override
     public void registerExtensionLoader(@NonNull String identifier, @NonNull ExtensionLoader extensionLoader) {
-        Registries.EXTENSION_LOADERS.register(Key.key(identifier), extensionLoader);
+        this.extensionLoaderTypes.put(Key.key(identifier), extensionLoader);
     }
 
     @NonNull
     @Override
     public Map<String, ExtensionLoader> extensionLoaders() {
-        return Registries.EXTENSION_LOADERS.get().entrySet().stream().collect(Collectors.toMap(key -> key.getKey().asString(), Map.Entry::getValue));
+        return this.extensionLoaderTypes.entrySet().stream().collect(Collectors.toMap(key -> key.getKey().asString(), Map.Entry::getValue));
     }
 
     @Override

core/src/main/java/org/geysermc/geyser/item/GeyserCustomItemData.java

@@ -0,0 +1,158 @@
+/*
+ * 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.item;
+
+import lombok.EqualsAndHashCode;
+import lombok.ToString;
+import org.checkerframework.checker.nullness.qual.NonNull;
+import org.geysermc.geyser.api.item.custom.CustomItemData;
+import org.geysermc.geyser.api.item.custom.CustomItemOptions;
+import org.geysermc.geyser.api.item.custom.CustomRenderOffsets;
+import org.jetbrains.annotations.NotNull;
+
+@EqualsAndHashCode
+@ToString
+public class GeyserCustomItemData implements CustomItemData {
+    private final String name;
+    private final CustomItemOptions customItemOptions;
+    private final String displayName;
+    private final String icon;
+    private final boolean allowOffhand;
+    private final int textureSize;
+    private final CustomRenderOffsets renderOffsets;
+
+    public GeyserCustomItemData(String name,
+                                CustomItemOptions customItemOptions,
+                                String displayName,
+                                String icon,
+                                boolean allowOffhand,
+                                int textureSize,
+                                CustomRenderOffsets renderOffsets) {
+        this.name = name;
+        this.customItemOptions = customItemOptions;
+        this.displayName = displayName;
+        this.icon = icon;
+        this.allowOffhand = allowOffhand;
+        this.textureSize = textureSize;
+        this.renderOffsets = renderOffsets;
+    }
+
+    public @NotNull String name() {
+        return name;
+    }
+
+    public CustomItemOptions customItemOptions() {
+        return customItemOptions;
+    }
+
+    public @NotNull String displayName() {
+        return displayName;
+    }
+
+    public @NotNull String icon() {
+        return icon;
+    }
+
+    public boolean allowOffhand() {
+        return allowOffhand;
+    }
+
+    public int textureSize() {
+        return textureSize;
+    }
+
+    public CustomRenderOffsets renderOffsets() {
+        return renderOffsets;
+    }
+
+    public static class CustomItemDataBuilder implements Builder {
+        protected String name = null;
+        protected CustomItemOptions customItemOptions = null;
+
+        protected String displayName = null;
+        protected String icon = null;
+        protected boolean allowOffhand = true; // Bedrock doesn't give items offhand allowance unless they serve gameplay purpose, but we want to be friendly with Java
+        protected int textureSize = 16;
+        protected CustomRenderOffsets renderOffsets = null;
+
+        @Override
+        public Builder name(@NonNull String name) {
+            this.name = name;
+            return this;
+        }
+
+        @Override
+        public Builder customItemOptions(@NonNull CustomItemOptions customItemOptions) {
+            this.customItemOptions = customItemOptions;
+            return this;
+        }
+
+        @Override
+        public Builder displayName(@NonNull String displayName) {
+            this.displayName = displayName;
+            return this;
+        }
+
+        @Override
+        public Builder icon(@NonNull String icon) {
+            this.icon = icon;
+            return this;
+        }
+
+        @Override
+        public Builder allowOffhand(boolean allowOffhand) {
+            this.allowOffhand = allowOffhand;
+            return this;
+        }
+
+        @Override
+        public Builder textureSize(int textureSize) {
+            this.textureSize = textureSize;
+            return this;
+        }
+
+        @Override
+        public Builder renderOffsets(CustomRenderOffsets renderOffsets) {
+            this.renderOffsets = renderOffsets;
+            return this;
+        }
+
+        @Override
+        public CustomItemData build() {
+            if (this.name == null || this.customItemOptions == null) {
+                throw new IllegalArgumentException("Name and custom item options must be set");
+            }
+
+            if (this.displayName == null) {
+                this.displayName = this.name;
+            }
+            if (this.icon == null) {
+                this.icon = this.name;
+            }
+            return new GeyserCustomItemData(this.name, this.customItemOptions, this.displayName, this.icon, this.allowOffhand, this.textureSize, this.renderOffsets);
+        }
+    }
+}

core/src/main/java/org/geysermc/geyser/item/GeyserCustomItemOptions.java

@@ -0,0 +1,69 @@
+/*
+ * 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.item;
+
+import org.geysermc.geyser.api.item.custom.CustomItemOptions;
+import org.geysermc.geyser.api.util.TriState;
+
+import java.util.OptionalInt;
+
+public record GeyserCustomItemOptions(TriState unbreakable,
+                                      OptionalInt customModelData,
+                                      OptionalInt damagePredicate) implements CustomItemOptions {
+
+    public static class CustomItemOptionsBuilder implements CustomItemOptions.Builder {
+        private TriState unbreakable = TriState.NOT_SET;
+        private OptionalInt customModelData = OptionalInt.empty();
+        private OptionalInt damagePredicate = OptionalInt.empty();
+
+        @Override
+        public Builder unbreakable(boolean unbreakable) {
+            if (unbreakable) {
+                this.unbreakable = TriState.TRUE;
+            } else {
+                this.unbreakable = TriState.FALSE;
+            }
+            return this;
+        }
+
+        @Override
+        public Builder customModelData(int customModelData) {
+            this.customModelData = OptionalInt.of(customModelData);
+            return this;
+        }
+
+        @Override
+        public Builder damagePredicate(int damagePredicate) {
+            this.damagePredicate = OptionalInt.of(damagePredicate);
+            return this;
+        }
+
+        @Override
+        public CustomItemOptions build() {
+            return new GeyserCustomItemOptions(unbreakable, customModelData, damagePredicate);
+        }
+    }
+}

core/src/main/java/org/geysermc/geyser/item/GeyserCustomMappingData.java

@@ -0,0 +1,32 @@
+/*
+ * 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.item;
+
+import com.nukkitx.protocol.bedrock.data.inventory.ComponentItemData;
+import com.nukkitx.protocol.bedrock.packet.StartGamePacket;
+
+public record GeyserCustomMappingData(ComponentItemData componentItemData, StartGamePacket.ItemEntry startGamePacketItemEntry, String stringId, int integerId) {
+}

core/src/main/java/org/geysermc/geyser/item/GeyserNonVanillaCustomItemData.java

@@ -0,0 +1,303 @@
+/*
+ * 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.item;
+
+import lombok.EqualsAndHashCode;
+import lombok.ToString;
+import org.checkerframework.checker.nullness.qual.NonNull;
+import org.checkerframework.checker.nullness.qual.Nullable;
+import org.geysermc.geyser.api.item.custom.CustomItemOptions;
+import org.geysermc.geyser.api.item.custom.CustomRenderOffsets;
+import org.geysermc.geyser.api.item.custom.NonVanillaCustomItemData;
+import org.jetbrains.annotations.NotNull;
+
+import java.util.OptionalInt;
+import java.util.Set;
+
+@EqualsAndHashCode(callSuper = true)
+@ToString
+public final class GeyserNonVanillaCustomItemData extends GeyserCustomItemData implements NonVanillaCustomItemData {
+    private final String identifier;
+    private final int javaId;
+    private final int stackSize;
+    private final int maxDamage;
+    private final String toolType;
+    private final String toolTier;
+    private final String armorType;
+    private final int protectionValue;
+    private final String translationString;
+    private final Set<String> repairMaterials;
+    private final OptionalInt creativeCategory;
+    private final String creativeGroup;
+    private final boolean isHat;
+    private final boolean isTool;
+
+    public GeyserNonVanillaCustomItemData(NonVanillaCustomItemDataBuilder builder) {
+        super(builder.name, builder.customItemOptions, builder.displayName, builder.icon, builder.allowOffhand,
+                builder.textureSize, builder.renderOffsets);
+
+        this.identifier = builder.identifier;
+        this.javaId = builder.javaId;
+        this.stackSize = builder.stackSize;
+        this.maxDamage = builder.maxDamage;
+        this.toolType = builder.toolType;
+        this.toolTier = builder.toolTier;
+        this.armorType = builder.armorType;
+        this.protectionValue = builder.protectionValue;
+        this.translationString = builder.translationString;
+        this.repairMaterials = builder.repairMaterials;
+        this.creativeCategory = builder.creativeCategory;
+        this.creativeGroup = builder.creativeGroup;
+        this.isHat = builder.hat;
+        this.isTool = builder.tool;
+    }
+
+    @Override
+    public @NotNull String identifier() {
+        return identifier;
+    }
+
+    @Override
+    public int javaId() {
+        return javaId;
+    }
+
+    @Override
+    public int stackSize() {
+        return stackSize;
+    }
+
+    @Override
+    public int maxDamage() {
+        return maxDamage;
+    }
+
+    @Override
+    public String toolType() {
+        return toolType;
+    }
+
+    @Override
+    public String toolTier() {
+        return toolTier;
+    }
+
+    @Override
+    public @Nullable String armorType() {
+        return armorType;
+    }
+
+    @Override
+    public int protectionValue() {
+        return protectionValue;
+    }
+
+    @Override
+    public String translationString() {
+        return translationString;
+    }
+
+    @Override
+    public Set<String> repairMaterials() {
+        return repairMaterials;
+    }
+
+    @Override
+    public @NotNull OptionalInt creativeCategory() {
+        return creativeCategory;
+    }
+
+    @Override
+    public String creativeGroup() {
+        return creativeGroup;
+    }
+
+    @Override
+    public boolean isHat() {
+        return isHat;
+    }
+
+    @Override
+    public boolean isTool() {
+        return isTool;
+    }
+
+    public static class NonVanillaCustomItemDataBuilder extends GeyserCustomItemData.CustomItemDataBuilder implements NonVanillaCustomItemData.Builder {
+        private String identifier = null;
+        private int javaId = -1;
+
+        private int stackSize = 64;
+
+        private int maxDamage = 0;
+
+        private String toolType = null;
+        private String toolTier = null;
+
+        private String armorType = null;
+        private int protectionValue = 0;
+
+        private String translationString;
+
+        private Set<String> repairMaterials;
+
+        private OptionalInt creativeCategory = OptionalInt.empty();
+        private String creativeGroup = null;
+
+        private boolean hat = false;
+        private boolean tool = false;
+
+        @Override
+        public NonVanillaCustomItemData.Builder name(@NonNull String name) {
+            return (NonVanillaCustomItemData.Builder) super.name(name);
+        }
+
+        @Override
+        public NonVanillaCustomItemData.Builder customItemOptions(@NonNull CustomItemOptions customItemOptions) {
+            //Do nothing, as that value won't be read
+            return this;
+        }
+
+        @Override
+        public NonVanillaCustomItemData.Builder allowOffhand(boolean allowOffhand) {
+            return (NonVanillaCustomItemData.Builder) super.allowOffhand(allowOffhand);
+        }
+
+        @Override
+        public NonVanillaCustomItemData.Builder displayName(@NonNull String displayName) {
+            return (NonVanillaCustomItemData.Builder) super.displayName(displayName);
+        }
+
+        @Override
+        public NonVanillaCustomItemData.Builder icon(@NonNull String icon) {
+            return (NonVanillaCustomItemData.Builder) super.icon(icon);
+        }
+
+        @Override
+        public NonVanillaCustomItemData.Builder textureSize(int textureSize) {
+            return (NonVanillaCustomItemData.Builder) super.textureSize(textureSize);
+        }
+
+        @Override
+        public NonVanillaCustomItemData.Builder renderOffsets(CustomRenderOffsets renderOffsets) {
+            return (NonVanillaCustomItemData.Builder) super.renderOffsets(renderOffsets);
+        }
+
+        @Override
+        public NonVanillaCustomItemData.Builder identifier(@NonNull String identifier) {
+            this.identifier = identifier;
+            return this;
+        }
+
+        @Override
+        public NonVanillaCustomItemData.Builder javaId(int javaId) {
+            this.javaId = javaId;
+            return this;
+        }
+
+        @Override
+        public NonVanillaCustomItemData.Builder stackSize(int stackSize) {
+            this.stackSize = stackSize;
+            return this;
+        }
+
+        @Override
+        public NonVanillaCustomItemData.Builder maxDamage(int maxDamage) {
+            this.maxDamage = maxDamage;
+            return this;
+        }
+
+        @Override
+        public NonVanillaCustomItemData.Builder toolType(@Nullable String toolType) {
+            this.toolType = toolType;
+            return this;
+        }
+
+        @Override
+        public NonVanillaCustomItemData.Builder toolTier(@Nullable String toolTier) {
+            this.toolTier = toolTier;
+            return this;
+        }
+
+        @Override
+        public NonVanillaCustomItemData.Builder armorType(@Nullable String armorType) {
+            this.armorType = armorType;
+            return this;
+        }
+
+        @Override
+        public NonVanillaCustomItemData.Builder protectionValue(int protectionValue) {
+            this.protectionValue = protectionValue;
+            return this;
+        }
+
+        @Override
+        public NonVanillaCustomItemData.Builder translationString(@Nullable String translationString) {
+            this.translationString = translationString;
+            return this;
+        }
+
+        @Override
+        public NonVanillaCustomItemData.Builder repairMaterials(@Nullable Set<String> repairMaterials) {
+            this.repairMaterials = repairMaterials;
+            return this;
+        }
+
+        @Override
+        public NonVanillaCustomItemData.Builder creativeCategory(int creativeCategory) {
+            this.creativeCategory = OptionalInt.of(creativeCategory);
+            return this;
+        }
+
+        @Override
+        public NonVanillaCustomItemData.Builder creativeGroup(@Nullable String creativeGroup) {
+            this.creativeGroup = creativeGroup;
+            return this;
+        }
+
+        @Override
+        public NonVanillaCustomItemData.Builder hat(boolean isHat) {
+            this.hat = isHat;
+            return this;
+        }
+
+        @Override
+        public NonVanillaCustomItemData.Builder tool(boolean isTool) {
+            this.tool = isTool;
+            return this;
+        }
+
+        @Override
+        public NonVanillaCustomItemData build() {
+            if (identifier == null || javaId == -1) {
+                throw new IllegalArgumentException("Identifier and javaId must be set");
+            }
+
+            super.customItemOptions(CustomItemOptions.builder().build());
+            super.build();
+            return new GeyserNonVanillaCustomItemData(this);
+        }
+    }
+}

core/src/main/java/org/geysermc/geyser/item/components/ToolBreakSpeedsUtils.java

@@ -0,0 +1,174 @@
+/*
+ * 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.item.components;
+
+import com.nukkitx.nbt.NbtMap;
+import com.nukkitx.nbt.NbtType;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class ToolBreakSpeedsUtils {
+    public static int toolTierToSpeed(String toolTier) {
+        ToolTier tier = ToolTier.getByName(toolTier);
+        if (tier != null) {
+            return tier.getSpeed();
+        }
+
+        return 0;
+    }
+
+    private static NbtMap createTagBreakSpeed(int speed, String... tags) {
+        StringBuilder builder = new StringBuilder("query.any_tag('");
+        builder.append(tags[0]);
+        for (int i = 1; i < tags.length; i++) {
+            builder.append("', '").append(tags[i]);
+        }
+        builder.append("')");
+
+        return NbtMap.builder()
+                .putCompound("block", NbtMap.builder()
+                        .putString("tags", builder.toString())
+                        .build())
+                .putCompound("on_dig", NbtMap.builder()
+                        .putCompound("condition", NbtMap.builder()
+                                .putString("expression", "")
+                                .putInt("version", -1)
+                                .build())
+                        .putString("event", "tool_durability")
+                        .putString("target", "self")
+                        .build())
+                .putInt("speed", speed)
+                .build();
+    }
+
+    private static NbtMap createBreakSpeed(int speed, String block) {
+        return NbtMap.builder()
+                .putCompound("block", NbtMap.builder()
+                        .putString("name", block).build())
+                .putCompound("on_dig", NbtMap.builder()
+                        .putCompound("condition", NbtMap.builder()
+                                .putString("expression", "")
+                                .putInt("version", -1)
+                                .build())
+                        .putString("event", "tool_durability")
+                        .putString("target", "self")
+                        .build())
+                .putInt("speed", speed)
+                .build();
+    }
+
+    private static NbtMap createDigger(List<NbtMap> speeds) {
+        return NbtMap.builder()
+                .putList("destroy_speeds", NbtType.COMPOUND, speeds)
+                .putCompound("on_dig", NbtMap.builder()
+                        .putCompound("condition", NbtMap.builder()
+                                .putString("expression", "")
+                                .putInt("version", -1)
+                                .build())
+                        .putString("event", "tool_durability")
+                        .putString("target", "self")
+                        .build())
+                .putBoolean("use_efficiency", true)
+                .build();
+    }
+
+    public static NbtMap getAxeDigger(int speed) {
+        List<NbtMap> speeds = new ArrayList<>();
+        speeds.add(createTagBreakSpeed(speed, "wood", "pumpkin", "plant"));
+
+        return createDigger(speeds);
+    }
+
+    public static NbtMap getPickaxeDigger(int speed, String toolTier) {
+        List<NbtMap> speeds = new ArrayList<>();
+        if (toolTier.equals(ToolTier.DIAMOND.toString()) || toolTier.equals(ToolTier.NETHERITE.toString())) {
+            speeds.add(createTagBreakSpeed(speed, "iron_pick_diggable", "diamond_pick_diggable"));
+        } else {
+            speeds.add(createTagBreakSpeed(speed, "iron_pick_diggable"));
+        }
+        speeds.add(createTagBreakSpeed(speed, "stone", "metal", "rail", "mob_spawner"));
+
+        return createDigger(speeds);
+    }
+
+    public static NbtMap getShovelDigger(int speed) {
+        List<NbtMap> speeds = new ArrayList<>();
+        speeds.add(createTagBreakSpeed(speed, "dirt", "sand", "gravel", "grass", "snow"));
+
+        return createDigger(speeds);
+    }
+
+    public static NbtMap getSwordDigger(int speed) {
+        List<NbtMap> speeds = new ArrayList<>();
+        speeds.add(createBreakSpeed(speed, "minecraft:web"));
+        speeds.add(createBreakSpeed(speed, "minecraft:bamboo"));
+
+        return createDigger(speeds);
+    }
+
+    public static NbtMap getHoeDigger(int speed) {
+        List<NbtMap> speeds = new ArrayList<>();
+        speeds.add(createBreakSpeed(speed, "minecraft:leaves"));
+        speeds.add(createBreakSpeed(speed, "minecraft:leaves2"));
+        speeds.add(createBreakSpeed(speed, "minecraft:azalea_leaves"));
+        speeds.add(createBreakSpeed(speed, "minecraft:azalea_leaves_flowered"));
+
+        speeds.add(createBreakSpeed(speed, "minecraft:sculk"));
+        speeds.add(createBreakSpeed(speed, "minecraft:sculk_catalyst"));
+        speeds.add(createBreakSpeed(speed, "minecraft:sculk_sensor"));
+        speeds.add(createBreakSpeed(speed, "minecraft:sculk_shrieker"));
+        speeds.add(createBreakSpeed(speed, "minecraft:sculk_vein"));
+
+        speeds.add(createBreakSpeed(speed, "minecraft:nether_wart_block"));
+        speeds.add(createBreakSpeed(speed, "minecraft:warped_wart_block"));
+
+        speeds.add(createBreakSpeed(speed, "minecraft:hay_block"));
+        speeds.add(createBreakSpeed(speed, "minecraft:moss_block"));
+        speeds.add(createBreakSpeed(speed, "minecraft:shroomlight"));
+        speeds.add(createBreakSpeed(speed, "minecraft:sponge"));
+        speeds.add(createBreakSpeed(speed, "minecraft:target"));
+
+        return createDigger(speeds);
+    }
+
+    public static NbtMap getShearsDigger(int speed) {
+        List<NbtMap> speeds = new ArrayList<>();
+        speeds.add(createBreakSpeed(speed, "minecraft:web"));
+
+        speeds.add(createBreakSpeed(speed, "minecraft:leaves"));
+        speeds.add(createBreakSpeed(speed, "minecraft:leaves2"));
+        speeds.add(createBreakSpeed(speed, "minecraft:azalea_leaves"));
+        speeds.add(createBreakSpeed(speed, "minecraft:azalea_leaves_flowered"));
+
+        speeds.add(createBreakSpeed(speed, "minecraft:wool"));
+
+        speeds.add(createBreakSpeed(speed, "minecraft:glow_lichen"));
+        speeds.add(createBreakSpeed(speed, "minecraft:vine"));
+
+        return createDigger(speeds);
+    }
+}

core/src/main/java/org/geysermc/geyser/item/components/ToolTier.java

@@ -0,0 +1,66 @@
+/*
+ * 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.item.components;
+
+import org.checkerframework.checker.nullness.qual.NonNull;
+
+import java.util.Locale;
+
+public enum ToolTier {
+    WOODEN(2),
+    STONE(4),
+    IRON(6),
+    GOLDEN(12),
+    DIAMOND(8),
+    NETHERITE(9);
+
+    public static final ToolTier[] VALUES = values();
+
+    private final int speed;
+
+    ToolTier(int speed) {
+        this.speed = speed;
+    }
+
+    public int getSpeed() {
+        return speed;
+    }
+
+    @Override
+    public String toString() {
+        return this.name().toLowerCase(Locale.ROOT);
+    }
+
+    public static ToolTier getByName(@NonNull String name) {
+        String upperCase = name.toUpperCase(Locale.ROOT);
+        for (ToolTier tier : VALUES) {
+            if (tier.name().equals(upperCase)) {
+                return tier;
+            }
+        }
+        return null;
+    }
+}

core/src/main/java/org/geysermc/geyser/item/components/WearableSlot.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.item.components;
+
+import com.nukkitx.nbt.NbtMap;
+
+import java.util.Locale;
+
+public enum WearableSlot {
+    HEAD,
+    CHEST,
+    LEGS,
+    FEET;
+
+    private final NbtMap slotNbt;
+
+    WearableSlot() {
+        this.slotNbt = NbtMap.builder().putString("slot", "slot.armor." + this.name().toLowerCase(Locale.ROOT)).build();
+    }
+
+    public NbtMap getSlotNbt() {
+        return slotNbt;
+    }
+}

core/src/main/java/org/geysermc/geyser/item/exception/InvalidCustomMappingsFileException.java

@@ -0,0 +1,40 @@
+/*
+ * 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.item.exception;
+
+public class InvalidCustomMappingsFileException extends Exception {
+    public InvalidCustomMappingsFileException(Throwable cause) {
+        super(cause);
+    }
+
+    public InvalidCustomMappingsFileException(String message) {
+        super(message);
+    }
+
+    public InvalidCustomMappingsFileException(String message, Throwable cause) {
+        super(message, cause);
+    }
+}

core/src/main/java/org/geysermc/geyser/item/mappings/MappingsConfigReader.java

@@ -0,0 +1,98 @@
+/*
+ * 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.item.mappings;
+
+import com.fasterxml.jackson.databind.JsonNode;
+import it.unimi.dsi.fastutil.ints.Int2ObjectMap;
+import it.unimi.dsi.fastutil.ints.Int2ObjectOpenHashMap;
+import org.geysermc.geyser.GeyserImpl;
+import org.geysermc.geyser.api.item.custom.CustomItemData;
+import org.geysermc.geyser.item.mappings.versions.MappingsReader;
+import org.geysermc.geyser.item.mappings.versions.MappingsReader_v1;
+
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.function.BiConsumer;
+
+public class MappingsConfigReader {
+    private final Int2ObjectMap<MappingsReader> mappingReaders = new Int2ObjectOpenHashMap<>();
+    private final Path customMappingsDirectory = GeyserImpl.getInstance().getBootstrap().getConfigFolder().resolve("custom_mappings");
+
+    public MappingsConfigReader() {
+        this.mappingReaders.put(1, new MappingsReader_v1());
+    }
+
+    public Path[] getCustomMappingsFiles() {
+        try {
+            return Files.walk(this.customMappingsDirectory)
+                    .filter(child -> child.toString().endsWith(".json"))
+                    .toArray(Path[]::new);
+        } catch (IOException e) {
+            return new Path[0];
+        }
+    }
+
+    public void loadMappingsFromJson(BiConsumer<String, CustomItemData> consumer) {
+        Path customMappingsDirectory = this.customMappingsDirectory;
+        if (!Files.exists(customMappingsDirectory)) {
+            try {
+                Files.createDirectories(customMappingsDirectory);
+            } catch (IOException e) {
+                GeyserImpl.getInstance().getLogger().error("Failed to create custom mappings directory", e);
+                return;
+            }
+        }
+
+        Path[] mappingsFiles = this.getCustomMappingsFiles();
+        for (Path mappingsFile : mappingsFiles) {
+            this.readMappingsFromJson(mappingsFile, consumer);
+        }
+    }
+
+    public void readMappingsFromJson(Path file, BiConsumer<String, CustomItemData> consumer) {
+        JsonNode mappingsRoot;
+        try {
+            mappingsRoot = GeyserImpl.JSON_MAPPER.readTree(file.toFile());
+        } catch (IOException e) {
+            GeyserImpl.getInstance().getLogger().error("Failed to read custom mapping file: " + file, e);
+            return;
+        }
+
+        if (!mappingsRoot.has("format_version")) {
+            GeyserImpl.getInstance().getLogger().error("Mappings file " + file + " is missing the format version field!");
+            return;
+        }
+
+        int formatVersion = mappingsRoot.get("format_version").asInt();
+        if (!this.mappingReaders.containsKey(formatVersion)) {
+            GeyserImpl.getInstance().getLogger().error("Mappings file " + file + " has an unknown format version: " + formatVersion);
+            return;
+        }
+
+        this.mappingReaders.get(formatVersion).readMappings(file, mappingsRoot, consumer);
+    }
+}

core/src/main/java/org/geysermc/geyser/item/mappings/versions/MappingsReader.java

@@ -0,0 +1,93 @@
+/*
+ * 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.item.mappings.versions;
+
+import com.fasterxml.jackson.databind.JsonNode;
+import org.geysermc.geyser.api.item.custom.CustomItemData;
+import org.geysermc.geyser.api.item.custom.CustomRenderOffsets;
+import org.geysermc.geyser.item.exception.InvalidCustomMappingsFileException;
+
+import java.nio.file.Path;
+import java.util.function.BiConsumer;
+
+public abstract class MappingsReader {
+    public abstract void readMappings(Path file, JsonNode mappingsRoot, BiConsumer<String, CustomItemData> consumer);
+
+    public abstract CustomItemData readItemMappingEntry(JsonNode node) throws InvalidCustomMappingsFileException;
+
+    protected CustomRenderOffsets fromJsonNode(JsonNode node) {
+        if (node == null || !node.isObject()) {
+            return null;
+        }
+
+        return new CustomRenderOffsets(
+                getHandOffsets(node, "main_hand"),
+                getHandOffsets(node, "off_hand")
+        );
+    }
+
+    protected CustomRenderOffsets.Hand getHandOffsets(JsonNode node, String hand) {
+        JsonNode tmpNode = node.get(hand);
+        if (tmpNode == null || !tmpNode.isObject()) {
+            return null;
+        }
+
+        return new CustomRenderOffsets.Hand(
+                getPerspectiveOffsets(tmpNode, "first_person"),
+                getPerspectiveOffsets(tmpNode, "third_person")
+        );
+    }
+
+    protected CustomRenderOffsets.Offset getPerspectiveOffsets(JsonNode node, String perspective) {
+        JsonNode tmpNode = node.get(perspective);
+        if (tmpNode == null || !tmpNode.isObject()) {
+            return null;
+        }
+
+        return new CustomRenderOffsets.Offset(
+                getOffsetXYZ(tmpNode, "position"),
+                getOffsetXYZ(tmpNode, "rotation"),
+                getOffsetXYZ(tmpNode, "scale")
+        );
+    }
+
+    protected CustomRenderOffsets.OffsetXYZ getOffsetXYZ(JsonNode node, String offsetType) {
+        JsonNode tmpNode = node.get(offsetType);
+        if (tmpNode == null || !tmpNode.isObject()) {
+            return null;
+        }
+
+        if (!tmpNode.has("x") || !tmpNode.has("y") || !tmpNode.has("z")) {
+            return null;
+        }
+
+        return new CustomRenderOffsets.OffsetXYZ(
+                tmpNode.get("x").floatValue(),
+                tmpNode.get("y").floatValue(),
+                tmpNode.get("z").floatValue()
+        );
+    }
+}

core/src/main/java/org/geysermc/geyser/item/mappings/versions/MappingsReader_v1.java

@@ -0,0 +1,123 @@
+/*
+ * 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.item.mappings.versions;
+
+import com.fasterxml.jackson.databind.JsonNode;
+import org.geysermc.geyser.GeyserImpl;
+import org.geysermc.geyser.api.item.custom.CustomItemData;
+import org.geysermc.geyser.api.item.custom.CustomItemOptions;
+import org.geysermc.geyser.item.exception.InvalidCustomMappingsFileException;
+
+import java.nio.file.Path;
+import java.util.function.BiConsumer;
+
+public class MappingsReader_v1 extends MappingsReader {
+    @Override
+    public void readMappings(Path file, JsonNode mappingsRoot, BiConsumer<String, CustomItemData> consumer) {
+        this.readItemMappings(file, mappingsRoot, consumer);
+    }
+
+    public void readItemMappings(Path file, JsonNode mappingsRoot, BiConsumer<String, CustomItemData> consumer) {
+        JsonNode itemsNode = mappingsRoot.get("items");
+
+        if (itemsNode != null && itemsNode.isObject()) {
+            itemsNode.fields().forEachRemaining(entry -> {
+                if (entry.getValue().isArray()) {
+                    entry.getValue().forEach(data -> {
+                        try {
+                            CustomItemData customItemData = this.readItemMappingEntry(data);
+                            consumer.accept(entry.getKey(), customItemData);
+                        } catch (InvalidCustomMappingsFileException e) {
+                            GeyserImpl.getInstance().getLogger().error("Error in custom mapping file: " + file.toString(), e);
+                        }
+                    });
+                }
+            });
+        }
+    }
+
+    private CustomItemOptions readItemCustomItemOptions(JsonNode node) {
+        CustomItemOptions.Builder customItemOptions = CustomItemOptions.builder();
+
+        JsonNode customModelData = node.get("custom_model_data");
+        if (customModelData != null && customModelData.isInt()) {
+            customItemOptions.customModelData(customModelData.asInt());
+        }
+
+        JsonNode damagePredicate = node.get("damage_predicate");
+        if (damagePredicate != null && damagePredicate.isInt()) {
+            customItemOptions.damagePredicate(damagePredicate.asInt());
+        }
+
+        JsonNode unbreakable = node.get("unbreakable");
+        if (unbreakable != null && unbreakable.isBoolean()) {
+            customItemOptions.unbreakable(unbreakable.asBoolean());
+        }
+
+        return customItemOptions.build();
+    }
+
+    @Override
+    public CustomItemData readItemMappingEntry(JsonNode node) throws InvalidCustomMappingsFileException {
+        if (node == null || !node.isObject()) {
+            throw new InvalidCustomMappingsFileException("Invalid item mappings entry");
+        }
+
+        String name = node.get("name").asText();
+        if (name == null || name.isEmpty()) {
+            throw new InvalidCustomMappingsFileException("An item entry has no name");
+        }
+
+        CustomItemData.Builder customItemData = CustomItemData.builder()
+                .name(name)
+                .customItemOptions(this.readItemCustomItemOptions(node));
+
+        //The next entries are optional
+        if (node.has("display_name")) {
+            customItemData.displayName(node.get("display_name").asText());
+        }
+
+        if (node.has("icon")) {
+            customItemData.icon(node.get("icon").asText());
+        }
+
+        if (node.has("allow_offhand")) {
+            customItemData.allowOffhand(node.get("allow_offhand").asBoolean());
+        }
+
+        if (node.has("texture_size")) {
+            customItemData.textureSize(node.get("texture_size").asInt());
+        }
+
+        if (node.has("render_offsets")) {
+            JsonNode tmpNode = node.get("render_offsets");
+
+            customItemData.renderOffsets(fromJsonNode(tmpNode));
+        }
+
+        return customItemData.build();
+    }
+}

core/src/main/java/org/geysermc/geyser/network/UpstreamPacketHandler.java

@@ -31,6 +31,7 @@ import com.nukkitx.protocol.bedrock.data.ExperimentData;
 import com.nukkitx.protocol.bedrock.data.ResourcePackType;
 import com.nukkitx.protocol.bedrock.packet.*;
 import org.geysermc.geyser.GeyserImpl;
+import org.geysermc.geyser.session.PendingMicrosoftAuthentication;
 import org.geysermc.geyser.api.network.AuthType;
 import org.geysermc.geyser.configuration.GeyserConfiguration;
 import org.geysermc.geyser.pack.ResourcePack;
@@ -38,7 +39,6 @@ import org.geysermc.geyser.pack.ResourcePackManifest;
 import org.geysermc.geyser.registry.BlockRegistries;
 import org.geysermc.geyser.registry.Registries;
 import org.geysermc.geyser.session.GeyserSession;
-import org.geysermc.geyser.session.PendingMicrosoftAuthentication;
 import org.geysermc.geyser.text.GeyserLocale;
 import org.geysermc.geyser.util.LoginEncryptionUtils;
 import org.geysermc.geyser.util.MathUtils;
@@ -160,7 +160,7 @@ public class UpstreamPacketHandler extends LoggingPacketHandler {
                     stackPacket.getResourcePacks().add(new ResourcePackStackPacket.Entry(header.getUuid().toString(), header.getVersionString(), ""));
                 }
 
-                if (session.getItemMappings().getFurnaceMinecartData() != null) {
+                if (GeyserImpl.getInstance().getConfig().isAddNonBedrockItems()) {
                     // Allow custom items to work
                     stackPacket.getExperiments().add(new ExperimentData("data_driven_items", true));
                 }

core/src/main/java/org/geysermc/geyser/pack/ResourcePack.java

@@ -26,12 +26,16 @@
 package org.geysermc.geyser.pack;
 
 import org.geysermc.geyser.GeyserImpl;
-import org.geysermc.geyser.text.GeyserLocale;
+import org.geysermc.geyser.api.event.lifecycle.GeyserLoadResourcePacksEvent;
 import org.geysermc.geyser.util.FileUtils;
+import org.geysermc.geyser.text.GeyserLocale;
 
 import java.io.File;
-import java.util.HashMap;
+import java.io.IOException;
-import java.util.Map;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.*;
+import java.util.stream.Collectors;
 import java.util.stream.Stream;
 import java.util.zip.ZipEntry;
 import java.util.zip.ZipFile;
@@ -59,16 +63,33 @@ public class ResourcePack {
      * Loop through the packs directory and locate valid resource pack files
      */
     public static void loadPacks() {
-        File directory = GeyserImpl.getInstance().getBootstrap().getConfigFolder().resolve("packs").toFile();
+        Path directory = GeyserImpl.getInstance().getBootstrap().getConfigFolder().resolve("packs");
 
-        if (!directory.exists()) {
+        if (!Files.exists(directory)) {
-            directory.mkdir();
+            try {
+                Files.createDirectory(directory);
+            } catch (IOException e) {
+                GeyserImpl.getInstance().getLogger().error("Could not create packs directory", e);
+            }
 
             // As we just created the directory it will be empty
             return;
         }
 
-        for (File file : directory.listFiles()) {
+        List<Path> resourcePacks;
+        try {
+            resourcePacks = Files.walk(directory).collect(Collectors.toList());
+        } catch (IOException e) {
+            GeyserImpl.getInstance().getLogger().error("Could not list packs directory", e);
+            return;
+        }
+
+        GeyserLoadResourcePacksEvent event = new GeyserLoadResourcePacksEvent(resourcePacks);
+        GeyserImpl.getInstance().eventBus().fire(event);
+
+        for (Path path : event.resourcePacks()) {
+            File file = path.toFile();
+
             if (file.getName().endsWith(".zip") || file.getName().endsWith(".mcpack")) {
                 ResourcePack pack = new ResourcePack();
 

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

@@ -113,11 +113,6 @@ public final class Registries {
      */
     public static final SimpleMappedRegistry<EntityType, EntityDefinition<?>> ENTITY_DEFINITIONS = SimpleMappedRegistry.create(RegistryLoaders.empty(() -> new EnumMap<>(EntityType.class)));
 
-    /**
-     * A map containing all the extension loaders.
-     */
-    public static final SimpleMappedRegistry<Key, ExtensionLoader> EXTENSION_LOADERS = SimpleMappedRegistry.create(RegistryLoaders.empty(Object2ObjectOpenHashMap::new));
-
     /**
      * A map containing all Java entity identifiers and their respective Geyser definitions
      */

core/src/main/java/org/geysermc/geyser/registry/populator/CustomItemRegistryPopulator.java

@@ -0,0 +1,360 @@
+/*
+ * 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.populator;
+
+import com.nukkitx.nbt.NbtMap;
+import com.nukkitx.nbt.NbtMapBuilder;
+import com.nukkitx.nbt.NbtType;
+import com.nukkitx.protocol.bedrock.data.inventory.ComponentItemData;
+import com.nukkitx.protocol.bedrock.packet.StartGamePacket;
+import it.unimi.dsi.fastutil.objects.Object2IntMaps;
+import org.geysermc.geyser.GeyserImpl;
+import org.geysermc.geyser.api.item.custom.CustomItemData;
+import org.geysermc.geyser.api.item.custom.CustomRenderOffsets;
+import org.geysermc.geyser.api.item.custom.NonVanillaCustomItemData;
+import org.geysermc.geyser.item.GeyserCustomMappingData;
+import org.geysermc.geyser.item.components.ToolBreakSpeedsUtils;
+import org.geysermc.geyser.item.components.WearableSlot;
+import org.geysermc.geyser.registry.type.GeyserMappingItem;
+import org.geysermc.geyser.registry.type.ItemMapping;
+import org.geysermc.geyser.registry.type.NonVanillaItemRegistration;
+
+import javax.annotation.Nullable;
+import java.util.List;
+import java.util.Map;
+import java.util.OptionalInt;
+
+public class CustomItemRegistryPopulator {
+    public static GeyserCustomMappingData registerCustomItem(String customItemName, GeyserMappingItem javaItem, CustomItemData customItemData, int bedrockId) {
+        StartGamePacket.ItemEntry startGamePacketItemEntry = new StartGamePacket.ItemEntry(customItemName, (short) bedrockId, true);
+
+        NbtMapBuilder builder = createComponentNbt(customItemData, javaItem, customItemName, bedrockId);
+        ComponentItemData componentItemData = new ComponentItemData(customItemName, builder.build());
+
+        return new GeyserCustomMappingData(componentItemData, startGamePacketItemEntry, customItemName, bedrockId);
+    }
+
+    static boolean initialCheck(String identifier, CustomItemData item, Map<String, GeyserMappingItem> mappings) {
+        if (!mappings.containsKey(identifier)) {
+            GeyserImpl.getInstance().getLogger().error("Could not find the Java item to add custom item properties to for " + item.name());
+            return false;
+        }
+        if (!item.customItemOptions().hasCustomItemOptions()) {
+            GeyserImpl.getInstance().getLogger().error("The custom item " + item.name() + " has no registration types");
+        }
+        return true;
+    }
+
+    public static NonVanillaItemRegistration registerCustomItem(NonVanillaCustomItemData customItemData, int customItemId) {
+        String customIdentifier = customItemData.identifier();
+
+        ItemMapping customItemMapping = ItemMapping.builder()
+                .javaIdentifier(customIdentifier)
+                .bedrockIdentifier(customIdentifier)
+                .javaId(customItemData.javaId())
+                .bedrockId(customItemId)
+                .bedrockData(0)
+                .bedrockBlockId(0)
+                .stackSize(customItemData.stackSize())
+                .toolType(customItemData.toolType())
+                .toolTier(customItemData.toolTier())
+                .translationString(customItemData.translationString())
+                .maxDamage(customItemData.maxDamage())
+                .repairMaterials(customItemData.repairMaterials())
+                .hasSuspiciousStewEffect(false)
+                .customItemOptions(Object2IntMaps.emptyMap())
+                .build();
+
+        NbtMapBuilder builder = createComponentNbt(customItemData, customItemData.identifier(), customItemId,
+                customItemData.creativeCategory(), customItemData.creativeGroup(), customItemData.isHat(), customItemData.isTool());
+        ComponentItemData componentItemData = new ComponentItemData(customIdentifier, builder.build());
+
+        return new NonVanillaItemRegistration(componentItemData, customItemMapping);
+    }
+
+    private static NbtMapBuilder createComponentNbt(CustomItemData customItemData, GeyserMappingItem mapping,
+                                                    String customItemName, int customItemId) {
+        NbtMapBuilder builder = NbtMap.builder();
+        builder.putString("name", customItemName)
+                .putInt("id", customItemId);
+
+        NbtMapBuilder itemProperties = NbtMap.builder();
+        NbtMapBuilder componentBuilder = NbtMap.builder();
+
+        setupBasicItemInfo(mapping.getMaxDamage(), mapping.getStackSize(), mapping.getToolType() != null, customItemData, itemProperties, componentBuilder);
+
+        boolean canDestroyInCreative = true;
+        if (mapping.getToolType() != null) { // This is not using the isTool boolean because it is not just a render type here.
+            canDestroyInCreative = computeToolProperties(mapping.getToolTier(), mapping.getToolType(), itemProperties, componentBuilder);
+        }
+        itemProperties.putBoolean("can_destroy_in_creative", canDestroyInCreative);
+
+        if (mapping.getArmorType() != null) {
+            computeArmorProperties(mapping.getArmorType(), mapping.getProtectionValue(), componentBuilder);
+        }
+
+        computeRenderOffsets(false, customItemData, componentBuilder);
+
+        componentBuilder.putCompound("item_properties", itemProperties.build());
+        builder.putCompound("components", componentBuilder.build());
+
+        return builder;
+    }
+
+    private static NbtMapBuilder createComponentNbt(NonVanillaCustomItemData customItemData, String customItemName,
+                                                    int customItemId, OptionalInt creativeCategory,
+                                                    String creativeGroup, boolean isHat, boolean isTool) {
+        NbtMapBuilder builder = NbtMap.builder();
+        builder.putString("name", customItemName)
+                .putInt("id", customItemId);
+
+        NbtMapBuilder itemProperties = NbtMap.builder();
+        NbtMapBuilder componentBuilder = NbtMap.builder();
+
+        setupBasicItemInfo(customItemData.maxDamage(), customItemData.stackSize(), isTool, customItemData, itemProperties, componentBuilder);
+
+        boolean canDestroyInCreative = true;
+        if (customItemData.toolType() != null) { // This is not using the isTool boolean because it is not just a render type here.
+            canDestroyInCreative = computeToolProperties(customItemData.toolTier(), customItemData.toolType(), itemProperties, componentBuilder);
+        }
+        itemProperties.putBoolean("can_destroy_in_creative", canDestroyInCreative);
+
+        String armorType = customItemData.armorType();
+        if (armorType != null) {
+            computeArmorProperties(armorType, customItemData.protectionValue(), componentBuilder);
+        }
+
+        computeRenderOffsets(isHat, customItemData, componentBuilder);
+
+        if (creativeGroup != null) {
+            itemProperties.putString("creative_group", creativeGroup);
+        }
+        if (creativeCategory.isPresent()) {
+            itemProperties.putInt("creative_category", creativeCategory.getAsInt());
+        }
+
+        componentBuilder.putCompound("item_properties", itemProperties.build());
+        builder.putCompound("components", componentBuilder.build());
+
+        return builder;
+    }
+
+    private static void setupBasicItemInfo(int maxDamage, int stackSize, boolean isTool, CustomItemData customItemData, NbtMapBuilder itemProperties, NbtMapBuilder componentBuilder) {
+        itemProperties.putCompound("minecraft:icon", NbtMap.builder()
+                .putString("texture", customItemData.icon())
+                .build());
+        componentBuilder.putCompound("minecraft:display_name", NbtMap.builder().putString("value", customItemData.displayName()).build());
+
+        itemProperties.putBoolean("allow_off_hand", customItemData.allowOffhand());
+        itemProperties.putBoolean("hand_equipped", isTool);
+        itemProperties.putInt("max_stack_size", stackSize);
+        if (maxDamage > 0) {
+            componentBuilder.putCompound("minecraft:durability", NbtMap.builder()
+                    .putCompound("damage_chance", NbtMap.builder()
+                            .putInt("max", 1)
+                            .putInt("min", 1)
+                            .build())
+                    .putInt("max_durability", maxDamage)
+                    .build());
+            itemProperties.putBoolean("use_duration", true);
+        }
+    }
+
+    /**
+     * @return can destroy in creative
+     */
+    private static boolean computeToolProperties(String toolTier, String toolType, NbtMapBuilder itemProperties, NbtMapBuilder componentBuilder) {
+        boolean canDestroyInCreative = true;
+        float miningSpeed = 1.0f;
+
+        if (toolType.equals("shears")) {
+            componentBuilder.putCompound("minecraft:digger", ToolBreakSpeedsUtils.getShearsDigger(15));
+        } else {
+            int toolSpeed = ToolBreakSpeedsUtils.toolTierToSpeed(toolTier);
+            switch (toolType) {
+                case "sword" -> {
+                    miningSpeed = 1.5f;
+                    canDestroyInCreative = false;
+                    componentBuilder.putCompound("minecraft:digger", ToolBreakSpeedsUtils.getSwordDigger(toolSpeed));
+                    componentBuilder.putCompound("minecraft:weapon", NbtMap.EMPTY);
+                }
+                case "pickaxe" -> {
+                    componentBuilder.putCompound("minecraft:digger", ToolBreakSpeedsUtils.getPickaxeDigger(toolSpeed, toolTier));
+                    setItemTag(componentBuilder, "pickaxe");
+                }
+                case "axe" -> {
+                    componentBuilder.putCompound("minecraft:digger", ToolBreakSpeedsUtils.getAxeDigger(toolSpeed));
+                    setItemTag(componentBuilder, "axe");
+                }
+                case "shovel" -> {
+                    componentBuilder.putCompound("minecraft:digger", ToolBreakSpeedsUtils.getShovelDigger(toolSpeed));
+                    setItemTag(componentBuilder, "shovel");
+                }
+                case "hoe" -> {
+                    componentBuilder.putCompound("minecraft:digger", ToolBreakSpeedsUtils.getHoeDigger(toolSpeed));
+                    setItemTag(componentBuilder, "hoe");
+                }
+            }
+        }
+
+        itemProperties.putBoolean("hand_equipped", true);
+        itemProperties.putFloat("mining_speed", miningSpeed);
+
+        return canDestroyInCreative;
+    }
+
+    private static void computeArmorProperties(String armorType, int protectionValue, NbtMapBuilder componentBuilder) {
+        switch (armorType) {
+            case "boots" -> {
+                componentBuilder.putString("minecraft:render_offsets", "boots");
+                componentBuilder.putCompound("minecraft:wearable", WearableSlot.FEET.getSlotNbt());
+                componentBuilder.putCompound("minecraft:armor", NbtMap.builder().putInt("protection", protectionValue).build());
+            }
+            case "chestplate" -> {
+                componentBuilder.putString("minecraft:render_offsets", "chestplates");
+                componentBuilder.putCompound("minecraft:wearable", WearableSlot.CHEST.getSlotNbt());
+                componentBuilder.putCompound("minecraft:armor", NbtMap.builder().putInt("protection", protectionValue).build());
+            }
+            case "leggings" -> {
+                componentBuilder.putString("minecraft:render_offsets", "leggings");
+                componentBuilder.putCompound("minecraft:wearable", WearableSlot.LEGS.getSlotNbt());
+                componentBuilder.putCompound("minecraft:armor", NbtMap.builder().putInt("protection", protectionValue).build());
+            }
+            case "helmet" -> {
+                componentBuilder.putString("minecraft:render_offsets", "helmets");
+                componentBuilder.putCompound("minecraft:wearable", WearableSlot.HEAD.getSlotNbt());
+                componentBuilder.putCompound("minecraft:armor", NbtMap.builder().putInt("protection", protectionValue).build());
+            }
+        }
+    }
+
+    private static void computeRenderOffsets(boolean isHat, CustomItemData customItemData, NbtMapBuilder componentBuilder) {
+        if (isHat) {
+            componentBuilder.remove("minecraft:render_offsets");
+            componentBuilder.putString("minecraft:render_offsets", "helmets");
+
+            componentBuilder.remove("minecraft:wearable");
+            componentBuilder.putCompound("minecraft:wearable", WearableSlot.HEAD.getSlotNbt());
+        }
+
+        CustomRenderOffsets renderOffsets = customItemData.renderOffsets();
+        if (renderOffsets != null) {
+            componentBuilder.remove("minecraft:render_offsets");
+            componentBuilder.putCompound("minecraft:render_offsets", toNbtMap(renderOffsets));
+        } else if (customItemData.textureSize() != 16 && !componentBuilder.containsKey("minecraft:render_offsets")) {
+            float scale1 = (float) (0.075 / (customItemData.textureSize() / 16f));
+            float scale2 = (float) (0.125 / (customItemData.textureSize() / 16f));
+            float scale3 = (float) (0.075 / (customItemData.textureSize() / 16f * 2.4f));
+
+            componentBuilder.putCompound("minecraft:render_offsets",
+                    NbtMap.builder().putCompound("main_hand", NbtMap.builder()
+                                    .putCompound("first_person", xyzToScaleList(scale3, scale3, scale3))
+                                    .putCompound("third_person", xyzToScaleList(scale1, scale2, scale1)).build())
+                            .putCompound("off_hand", NbtMap.builder()
+                                    .putCompound("first_person", xyzToScaleList(scale1, scale2, scale1))
+                                    .putCompound("third_person", xyzToScaleList(scale1, scale2, scale1)).build()).build());
+        }
+    }
+
+    private static NbtMap toNbtMap(CustomRenderOffsets renderOffsets) {
+        NbtMapBuilder builder = NbtMap.builder();
+
+        CustomRenderOffsets.Hand mainHand = renderOffsets.mainHand();
+        if (mainHand != null) {
+            NbtMap nbt = toNbtMap(mainHand);
+            if (nbt != null) {
+                builder.putCompound("main_hand", nbt);
+            }
+        }
+        CustomRenderOffsets.Hand offhand = renderOffsets.offhand();
+        if (offhand != null) {
+            NbtMap nbt = toNbtMap(offhand);
+            if (nbt != null) {
+                builder.putCompound("off_hand", nbt);
+            }
+        }
+
+        return builder.build();
+    }
+
+    private static NbtMap toNbtMap(CustomRenderOffsets.Hand hand) {
+        NbtMap firstPerson = toNbtMap(hand.firstPerson());
+        NbtMap thirdPerson = toNbtMap(hand.thirdPerson());
+
+        if (firstPerson == null && thirdPerson == null) {
+            return null;
+        }
+
+        NbtMapBuilder builder = NbtMap.builder();
+        if (firstPerson != null) {
+            builder.putCompound("first_person", firstPerson);
+        }
+        if (thirdPerson != null) {
+            builder.putCompound("third_person", thirdPerson);
+        }
+
+        return builder.build();
+    }
+
+    private static NbtMap toNbtMap(@Nullable CustomRenderOffsets.Offset offset) {
+        if (offset == null) {
+            return null;
+        }
+
+        CustomRenderOffsets.OffsetXYZ position = offset.position();
+        CustomRenderOffsets.OffsetXYZ rotation = offset.rotation();
+        CustomRenderOffsets.OffsetXYZ scale = offset.scale();
+
+        if (position == null && rotation == null && scale == null) {
+            return null;
+        }
+
+        NbtMapBuilder builder = NbtMap.builder();
+        if (position != null) {
+            builder.putList("position", NbtType.FLOAT, toList(position));
+        }
+        if (rotation != null) {
+            builder.putList("rotation", NbtType.FLOAT, toList(rotation));
+        }
+        if (scale != null) {
+            builder.putList("scale", NbtType.FLOAT, toList(scale));
+        }
+
+        return builder.build();
+    }
+
+    private static List<Float> toList(CustomRenderOffsets.OffsetXYZ xyz) {
+        return List.of(xyz.x(), xyz.y(), xyz.z());
+    }
+
+    private static void setItemTag(NbtMapBuilder builder, String tag) {
+        builder.putList("item_tags", NbtType.STRING, List.of("minecraft:is_" + tag));
+    }
+
+    private static NbtMap xyzToScaleList(float x, float y, float z) {
+        return NbtMap.builder().putList("scale", NbtType.FLOAT, List.of(x, y, z)).build();
+    }
+}

core/src/main/java/org/geysermc/geyser/registry/populator/ItemRegistryPopulator.java

@@ -27,6 +27,8 @@ package org.geysermc.geyser.registry.populator;
 
 import com.fasterxml.jackson.core.type.TypeReference;
 import com.fasterxml.jackson.databind.JsonNode;
+import com.google.common.collect.Multimap;
+import com.google.common.collect.MultimapBuilder;
 import com.nukkitx.nbt.NbtMap;
 import com.nukkitx.nbt.NbtMapBuilder;
 import com.nukkitx.nbt.NbtType;
@@ -35,14 +37,22 @@ import com.nukkitx.protocol.bedrock.data.SoundEvent;
 import com.nukkitx.protocol.bedrock.data.inventory.ComponentItemData;
 import com.nukkitx.protocol.bedrock.data.inventory.ItemData;
 import com.nukkitx.protocol.bedrock.packet.StartGamePacket;
+import it.unimi.dsi.fastutil.ints.*;
 import com.nukkitx.protocol.bedrock.v527.Bedrock_v527;
 import it.unimi.dsi.fastutil.ints.Int2IntMap;
 import it.unimi.dsi.fastutil.ints.IntArrayList;
 import it.unimi.dsi.fastutil.ints.IntList;
 import it.unimi.dsi.fastutil.objects.*;
+import org.checkerframework.checker.nullness.qual.NonNull;
 import org.geysermc.geyser.GeyserBootstrap;
 import org.geysermc.geyser.GeyserImpl;
+import org.geysermc.geyser.api.event.lifecycle.GeyserDefineCustomItemsEvent;
+import org.geysermc.geyser.api.item.custom.CustomItemData;
+import org.geysermc.geyser.api.item.custom.CustomItemOptions;
+import org.geysermc.geyser.api.item.custom.NonVanillaCustomItemData;
 import org.geysermc.geyser.inventory.item.StoredItemMappings;
+import org.geysermc.geyser.item.GeyserCustomMappingData;
+import org.geysermc.geyser.item.mappings.MappingsConfigReader;
 import org.geysermc.geyser.registry.BlockRegistries;
 import org.geysermc.geyser.registry.Registries;
 import org.geysermc.geyser.registry.type.*;
@@ -78,6 +88,58 @@ public class ItemRegistryPopulator {
             throw new AssertionError("Unable to load Java runtime item IDs", e);
         }
 
+        boolean customItemsAllowed = GeyserImpl.getInstance().getConfig().isAddNonBedrockItems();
+
+        Multimap<String, CustomItemData> customItems = MultimapBuilder.hashKeys().hashSetValues().build();
+        List<NonVanillaCustomItemData> nonVanillaCustomItems;
+
+        MappingsConfigReader mappingsConfigReader = new MappingsConfigReader();
+        if (customItemsAllowed) {
+            // Load custom items from mappings files
+            mappingsConfigReader.loadMappingsFromJson((key, item) -> {
+                if (CustomItemRegistryPopulator.initialCheck(key, item, items)) {
+                    customItems.get(key).add(item);
+                }
+            });
+
+            nonVanillaCustomItems = new ObjectArrayList<>();
+            GeyserImpl.getInstance().eventBus().fire(new GeyserDefineCustomItemsEvent(customItems, nonVanillaCustomItems) {
+                @Override
+                public boolean register(@NonNull String identifier, @NonNull CustomItemData customItemData) {
+                    if (CustomItemRegistryPopulator.initialCheck(identifier, customItemData, items)) {
+                        customItems.get(identifier).add(customItemData);
+                        return true;
+                    }
+                    return false;
+                }
+
+                @Override
+                public boolean register(@NonNull NonVanillaCustomItemData customItemData) {
+                    if (customItemData.identifier().startsWith("minecraft:")) {
+                        GeyserImpl.getInstance().getLogger().error("The custom item " + customItemData.identifier() +
+                                " is attempting to masquerade as a vanilla Minecraft item!");
+                        return false;
+                    }
+
+                    if (customItemData.javaId() < items.size()) {
+                        // Attempting to overwrite an item that already exists in the protocol
+                        GeyserImpl.getInstance().getLogger().error("The custom item " + customItemData.identifier() +
+                                " is attempting to overwrite a vanilla Minecraft item!");
+                        return false;
+                    }
+                    nonVanillaCustomItems.add(customItemData);
+                    return true;
+                }
+            });
+        } else {
+            nonVanillaCustomItems = Collections.emptyList();
+        }
+
+        int customItemCount = customItems.size() + nonVanillaCustomItems.size();
+        if (customItemCount > 0) {
+            GeyserImpl.getInstance().getLogger().info("Registered " + customItemCount + " custom items");
+        }
+
         // We can reduce some operations as Java information is the same across all palette versions
         boolean firstMappingsPass = true;
         Int2IntMap dyeColors = new FixedInt2IntMap();
@@ -99,11 +161,20 @@ public class ItemRegistryPopulator {
                 throw new AssertionError("Unable to load Bedrock runtime item IDs", e);
             }
 
+            // Used for custom items
+            int nextFreeBedrockId = 0;
+            List<ComponentItemData> componentItemData = new ObjectArrayList<>();
+
             Map<String, StartGamePacket.ItemEntry> entries = new Object2ObjectOpenHashMap<>();
 
             for (PaletteItem entry : itemEntries) {
-                entries.put(entry.getName(), new StartGamePacket.ItemEntry(entry.getName(), (short) entry.getId()));
+                int id = entry.getId();
-                bedrockIdentifierToId.put(entry.getName(), entry.getId());
+                if (id >= nextFreeBedrockId) {
+                    nextFreeBedrockId = id + 1;
+                }
+
+                entries.put(entry.getName(), new StartGamePacket.ItemEntry(entry.getName(), (short) id));
+                bedrockIdentifierToId.put(entry.getName(), id);
             }
 
             Object2IntMap<String> bedrockBlockIdOverrides = new Object2IntOpenHashMap<>();
@@ -203,18 +274,20 @@ public class ItemRegistryPopulator {
 
             int itemIndex = 0;
             int javaFurnaceMinecartId = 0;
-            boolean usingFurnaceMinecart = GeyserImpl.getInstance().getConfig().isAddNonBedrockItems();
 
             Set<String> javaOnlyItems = new ObjectOpenHashSet<>();
             Collections.addAll(javaOnlyItems, "minecraft:spectral_arrow", "minecraft:debug_stick",
                     "minecraft:knowledge_book", "minecraft:tipped_arrow", "minecraft:trader_llama_spawn_egg",
                     "minecraft:bundle");
-            if (!usingFurnaceMinecart) {
+            if (!customItemsAllowed) {
                 javaOnlyItems.add("minecraft:furnace_minecart");
             }
             // Java-only items for this version
             javaOnlyItems.addAll(palette.getValue().additionalTranslatedItems().keySet());
 
+            Int2ObjectMap<String> customIdMappings = new Int2ObjectOpenHashMap<>();
+            Set<String> registeredItemNames = new ObjectOpenHashSet<>(); // This is used to check for duplicate item names
+
             for (Map.Entry<String, GeyserMappingItem> entry : items.entrySet()) {
                 String javaIdentifier = entry.getKey().intern();
                 GeyserMappingItem mappingItem;
@@ -226,7 +299,7 @@ public class ItemRegistryPopulator {
                     mappingItem = entry.getValue();
                 }
 
-                if (usingFurnaceMinecart && javaIdentifier.equals("minecraft:furnace_minecart")) {
+                if (customItemsAllowed && javaIdentifier.equals("minecraft:furnace_minecart")) {
                     javaFurnaceMinecartId = itemIndex;
                     itemIndex++;
                     // Will be added later
@@ -380,12 +453,46 @@ public class ItemRegistryPopulator {
                                 .toolTier("");
                     }
                 }
+
                 if (javaOnlyItems.contains(javaIdentifier)) {
                     // These items don't exist on Bedrock, so set up a variable that indicates they should have custom names
                     mappingBuilder = mappingBuilder.translationString((bedrockBlockId != -1 ? "block." : "item.") + entry.getKey().replace(":", "."));
                     GeyserImpl.getInstance().getLogger().debug("Adding " + entry.getKey() + " as an item that needs to be translated.");
                 }
 
+                // Add the custom item properties, if applicable
+                Object2IntMap<CustomItemOptions> customItemOptions;
+                Collection<CustomItemData> customItemsToLoad = customItems.get(javaIdentifier);
+                if (customItemsAllowed && !customItemsToLoad.isEmpty()) {
+                    customItemOptions = new Object2IntOpenHashMap<>(customItemsToLoad.size());
+
+                    for (CustomItemData customItem : customItemsToLoad) {
+                        int customProtocolId = nextFreeBedrockId++;
+
+                        String customItemName = "geyser_custom:" + customItem.name();
+                        if (!registeredItemNames.add(customItemName)) {
+                            if (firstMappingsPass) {
+                                GeyserImpl.getInstance().getLogger().error("Custom item name '" + customItem.name() + "' already exists and was registered again! Skipping...");
+                            }
+                            continue;
+                        }
+
+                        GeyserCustomMappingData customMapping = CustomItemRegistryPopulator.registerCustomItem(
+                                customItemName, mappingItem, customItem, customProtocolId
+                        );
+                        // StartGamePacket entry - needed for Bedrock to recognize the item through the protocol
+                        entries.put(customMapping.stringId(), customMapping.startGamePacketItemEntry());
+                        // ComponentItemData - used to register some custom properties
+                        componentItemData.add(customMapping.componentItemData());
+                        customItemOptions.put(customItem.customItemOptions(), customProtocolId);
+
+                        customIdMappings.put(customMapping.integerId(), customMapping.stringId());
+                    }
+                } else {
+                    customItemOptions = Object2IntMaps.emptyMap();
+                }
+                mappingBuilder.customItemOptions(customItemOptions);
+
                 ItemMapping mapping = mappingBuilder.build();
 
                 if (javaIdentifier.contains("boat")) {
@@ -436,12 +543,12 @@ public class ItemRegistryPopulator {
                     .bedrockData(0)
                     .bedrockBlockId(-1)
                     .stackSize(1)
+                    .customItemOptions(Object2IntMaps.emptyMap())
                     .build();
 
-            ComponentItemData furnaceMinecartData = null;
+            if (customItemsAllowed) {
-            if (usingFurnaceMinecart) {
                 // Add the furnace minecart as a custom item
-                int furnaceMinecartId = mappings.size() + 1;
+                int furnaceMinecartId = nextFreeBedrockId++;
 
                 entries.put("geysermc:furnace_minecart", new StartGamePacket.ItemEntry("geysermc:furnace_minecart", (short) furnaceMinecartId, true));
 
@@ -456,7 +563,7 @@ public class ItemRegistryPopulator {
                         .build());
 
                 creativeItems.add(ItemData.builder()
-                        .netId(netId)
+                        .netId(netId++)
                         .id(furnaceMinecartId)
                         .count(1).build());
 
@@ -492,7 +599,36 @@ public class ItemRegistryPopulator {
 
                 componentBuilder.putCompound("item_properties", itemProperties.build());
                 builder.putCompound("components", componentBuilder.build());
-                furnaceMinecartData = new ComponentItemData("geysermc:furnace_minecart", builder.build());
+                componentItemData.add(new ComponentItemData("geysermc:furnace_minecart", builder.build()));
+
+                // Register any completely custom items given to us
+                IntSet registeredJavaIds = new IntOpenHashSet(); // Used to check for duplicate item java ids
+                for (NonVanillaCustomItemData customItem : nonVanillaCustomItems) {
+                    if (!registeredJavaIds.add(customItem.javaId())) {
+                        if (firstMappingsPass) {
+                            GeyserImpl.getInstance().getLogger().error("Custom item java id " + customItem.javaId() + " already exists and was registered again! Skipping...");
+                        }
+                        continue;
+                    }
+
+                    int customItemId = nextFreeBedrockId++;
+                    NonVanillaItemRegistration registration = CustomItemRegistryPopulator.registerCustomItem(customItem, customItemId);
+
+                    componentItemData.add(registration.componentItemData());
+                    ItemMapping mapping = registration.mapping();
+                    while (mapping.getJavaId() >= mappings.size()) {
+                        // Fill with empty to get to the correct size
+                        mappings.add(ItemMapping.AIR);
+                    }
+                    mappings.set(mapping.getJavaId(), mapping);
+
+                    if (customItem.creativeGroup() != null || customItem.creativeCategory().isPresent()) {
+                        creativeItems.add(ItemData.builder()
+                                .id(customItemId)
+                                .netId(netId++)
+                                .count(1).build());
+                    }
+                }
             }
 
             ItemMappings itemMappings = ItemMappings.builder()
@@ -506,8 +642,9 @@ public class ItemRegistryPopulator {
                     .boatIds(boats)
                     .spawnEggIds(spawnEggs)
                     .carpets(carpets)
-                    .furnaceMinecartData(furnaceMinecartData)
+                    .componentItemData(componentItemData)
                     .lodestoneCompass(lodestoneEntry)
+                    .customIdMappings(customIdMappings)
                     .build();
 
             Registries.ITEMS.register(palette.getValue().protocolVersion(), itemMappings);

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

@@ -29,8 +29,14 @@ 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.item.custom.CustomItemData;
+import org.geysermc.geyser.api.item.custom.CustomItemOptions;
+import org.geysermc.geyser.api.item.custom.NonVanillaCustomItemData;
 import org.geysermc.geyser.api.provider.BuilderProvider;
 import org.geysermc.geyser.command.GeyserCommandManager;
+import org.geysermc.geyser.item.GeyserCustomItemData;
+import org.geysermc.geyser.item.GeyserCustomItemOptions;
+import org.geysermc.geyser.item.GeyserNonVanillaCustomItemData;
 import org.geysermc.geyser.registry.ProviderRegistries;
 import org.geysermc.geyser.registry.SimpleMappedRegistry;
 
@@ -46,6 +52,9 @@ public class GeyserBuilderProvider extends AbstractProvider implements BuilderPr
     @Override
     public void registerProviders(Map<Class<?>, ProviderSupplier> providers) {
         providers.put(Command.Builder.class, args -> new GeyserCommandManager.CommandBuilder<>((Class<? extends CommandSource>) args[0]));
+        providers.put(CustomItemData.Builder.class, args -> new GeyserCustomItemData.CustomItemDataBuilder());
+        providers.put(CustomItemOptions.Builder.class, args -> new GeyserCustomItemOptions.CustomItemOptionsBuilder());
+        providers.put(NonVanillaCustomItemData.Builder.class, args -> new GeyserNonVanillaCustomItemData.NonVanillaCustomItemDataBuilder());
     }
 
     @Override

core/src/main/java/org/geysermc/geyser/registry/type/GeyserMappingItem.java

@@ -42,6 +42,8 @@ public class GeyserMappingItem {
     @JsonProperty("stack_size") int stackSize = 64;
     @JsonProperty("tool_type") String toolType;
     @JsonProperty("tool_tier") String toolTier;
+    @JsonProperty("armor_type") String armorType;
+    @JsonProperty("protection_value") int protectionValue;
     @JsonProperty("max_damage") int maxDamage = 0;
     @JsonProperty("repair_materials") List<String> repairMaterials;
     @JsonProperty("has_suspicious_stew_effect") boolean hasSuspiciousStewEffect = false;

core/src/main/java/org/geysermc/geyser/registry/type/ItemMapping.java

@@ -25,9 +25,12 @@
 
 package org.geysermc.geyser.registry.type;
 
+import it.unimi.dsi.fastutil.objects.Object2IntMap;
+import it.unimi.dsi.fastutil.objects.Object2IntMaps;
 import lombok.Builder;
 import lombok.EqualsAndHashCode;
 import lombok.Value;
+import org.geysermc.geyser.api.item.custom.CustomItemOptions;
 import org.geysermc.geyser.network.GameProtocol;
 import org.geysermc.geyser.registry.BlockRegistries;
 
@@ -39,7 +42,7 @@ import java.util.Set;
 public class ItemMapping {
     public static final ItemMapping AIR = new ItemMapping("minecraft:air", "minecraft:air", 0, 0, 0,
             BlockRegistries.BLOCKS.forVersion(GameProtocol.DEFAULT_BEDROCK_CODEC.getProtocolVersion()).getBedrockAirId(),
-            64, null, null, null, 0, null, false);
+            64, null, null, null, Object2IntMaps.emptyMap(), 0, null, false);
 
     String javaIdentifier;
     String bedrockIdentifier;
@@ -59,6 +62,8 @@ public class ItemMapping {
 
     String translationString;
 
+    Object2IntMap<CustomItemOptions> customItemOptions;
+
     int maxDamage;
 
     Set<String> repairMaterials;

core/src/main/java/org/geysermc/geyser/registry/type/ItemMappings.java

@@ -29,6 +29,7 @@ import com.github.steveice10.mc.protocol.data.game.entity.metadata.ItemStack;
 import com.nukkitx.protocol.bedrock.data.inventory.ComponentItemData;
 import com.nukkitx.protocol.bedrock.data.inventory.ItemData;
 import com.nukkitx.protocol.bedrock.packet.StartGamePacket;
+import it.unimi.dsi.fastutil.ints.Int2ObjectMap;
 import it.unimi.dsi.fastutil.ints.IntList;
 import lombok.Builder;
 import lombok.Value;
@@ -36,7 +37,6 @@ import org.geysermc.geyser.GeyserImpl;
 import org.geysermc.geyser.inventory.item.StoredItemMappings;
 
 import javax.annotation.Nonnull;
-import javax.annotation.Nullable;
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
@@ -67,7 +67,8 @@ public class ItemMappings {
     IntList spawnEggIds;
     List<ItemData> carpets;
 
-    @Nullable ComponentItemData furnaceMinecartData;
+    List<ComponentItemData> componentItemData;
+    Int2ObjectMap<String> customIdMappings;
 
     /**
      * Gets an {@link ItemMapping} from the given {@link ItemStack}.

core/src/main/java/org/geysermc/geyser/registry/type/NonVanillaItemRegistration.java

@@ -0,0 +1,34 @@
+/*
+ * 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.type;
+
+import com.nukkitx.protocol.bedrock.data.inventory.ComponentItemData;
+
+/**
+ * The return data of a successful registration of a custom item.
+ */
+public record NonVanillaItemRegistration(ComponentItemData componentItemData, ItemMapping mapping) {
+}

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

@@ -594,9 +594,9 @@ public class GeyserSession implements GeyserConnection, GeyserCommandSource {
         // Set the hardcoded shield ID to the ID we just defined in StartGamePacket
         upstream.getSession().getHardcodedBlockingId().set(this.itemMappings.getStoredItems().shield().getBedrockId());
 
-        if (this.itemMappings.getFurnaceMinecartData() != null) {
+        if (GeyserImpl.getInstance().getConfig().isAddNonBedrockItems()) {
             ItemComponentPacket componentPacket = new ItemComponentPacket();
-            componentPacket.getItems().add(this.itemMappings.getFurnaceMinecartData());
+            componentPacket.getItems().addAll(itemMappings.getComponentItemData());
             upstream.sendPacket(componentPacket);
         }
 
@@ -1465,7 +1465,9 @@ public class GeyserSession implements GeyserConnection, GeyserCommandSource {
         // startGamePacket.setCurrentTick(0);
         startGamePacket.setEnchantmentSeed(0);
         startGamePacket.setMultiplayerCorrelationId("");
+
         startGamePacket.setItemEntries(this.itemMappings.getItemEntries());
+
         startGamePacket.setVanillaVersion("*");
         startGamePacket.setInventoriesServerAuthoritative(true);
         startGamePacket.setServerEngine(""); // Do we want to fill this in?

core/src/main/java/org/geysermc/geyser/translator/inventory/item/CompassTranslator.java

@@ -79,8 +79,7 @@ public class CompassTranslator extends ItemTranslator {
 
     @Override
     public List<ItemMapping> getAppliedItems() {
-        return Arrays.stream(Registries.ITEMS.forVersion(GameProtocol.DEFAULT_BEDROCK_CODEC.getProtocolVersion())
+        return Arrays.stream(Registries.ITEMS.forVersion(GameProtocol.DEFAULT_BEDROCK_CODEC.getProtocolVersion()).getItems())
-                        .getItems())
                 .filter(entry -> entry.getJavaIdentifier().endsWith("compass"))
                 .collect(Collectors.toList());
     }

core/src/main/java/org/geysermc/geyser/translator/inventory/item/ItemTranslator.java

@@ -34,9 +34,12 @@ import com.nukkitx.nbt.NbtType;
 import com.nukkitx.protocol.bedrock.data.inventory.ItemData;
 import it.unimi.dsi.fastutil.ints.Int2ObjectMap;
 import it.unimi.dsi.fastutil.ints.Int2ObjectOpenHashMap;
+import it.unimi.dsi.fastutil.objects.Object2IntMap;
 import net.kyori.adventure.text.Component;
 import net.kyori.adventure.text.format.NamedTextColor;
 import org.geysermc.geyser.GeyserImpl;
+import org.geysermc.geyser.api.item.custom.CustomItemOptions;
+import org.geysermc.geyser.api.util.TriState;
 import org.geysermc.geyser.inventory.GeyserItemStack;
 import org.geysermc.geyser.registry.BlockRegistries;
 import org.geysermc.geyser.registry.type.ItemMapping;
@@ -122,7 +125,7 @@ public abstract class ItemTranslator {
                 }
             }
             if (itemStack.getNbt().isEmpty()) {
-                // Otherwise, seems to causes issues with villagers accepting books, and I don't see how this will break anything else. - Camotoy
+                // Otherwise, seems to cause issues with villagers accepting books, and I don't see how this will break anything else. - Camotoy
                 itemStack = new ItemStack(itemStack.getId(), itemStack.getAmount(), null);
             }
         }
@@ -170,6 +173,8 @@ public abstract class ItemTranslator {
             builder.blockRuntimeId(bedrockItem.getBedrockBlockId());
         }
 
+        translateCustomItem(nbt, builder, bedrockItem);
+
         if (nbt != null) {
             // Translate the canDestroy and canPlaceOn Java NBT
             ListTag canDestroy = nbt.get("CanDestroy");
@@ -292,6 +297,10 @@ public abstract class ItemTranslator {
         if (itemStack.getNbt() != null) {
             builder.tag(this.translateNbtToBedrock(itemStack.getNbt()));
         }
+
+        CompoundTag nbt = itemStack.getNbt();
+        translateCustomItem(nbt, builder, mapping);
+
         return builder;
     }
 
@@ -524,6 +533,48 @@ public abstract class ItemTranslator {
         return tag;
     }
 
+    /**
+     * Translates the custom model data of an item
+     */
+    private static void translateCustomItem(CompoundTag nbt, ItemData.Builder builder, ItemMapping mapping) {
+        int bedrockId = getCustomItem(nbt, mapping);
+        if (bedrockId != -1) {
+            builder.id(bedrockId);
+        }
+    }
+
+    private static int getCustomItem(CompoundTag nbt, ItemMapping mapping) {
+        if (nbt == null) {
+            return -1;
+        }
+        Object2IntMap<CustomItemOptions> customMappings = mapping.getCustomItemOptions();
+        if (customMappings.isEmpty()) {
+            return -1;
+        }
+        int customModelData = nbt.get("CustomModelData") instanceof IntTag customModelDataTag ? customModelDataTag.getValue() : 0;
+        TriState unbreakable = TriState.fromBoolean(nbt.get("Unbreakable") instanceof ByteTag unbreakableTag && unbreakableTag.getValue() == 1);
+        int damage = nbt.get("Damage") instanceof IntTag damageTag ? damageTag.getValue() : 0;
+        for (Object2IntMap.Entry<CustomItemOptions> mappingTypes : customMappings.object2IntEntrySet()) {
+            CustomItemOptions options = mappingTypes.getKey();
+
+            TriState unbreakableOption = options.unbreakable();
+            if (unbreakableOption == unbreakable) { // Implementation note: if the option is NOT_SET then this comparison will always be false because of how the item unbreaking TriState is created
+                return mappingTypes.getIntValue();
+            }
+
+            OptionalInt customModelDataOption = options.customModelData();
+            if (customModelDataOption.isPresent() && customModelDataOption.getAsInt() == customModelData) {
+                return mappingTypes.getIntValue();
+            }
+
+            OptionalInt damagePredicate = options.damagePredicate();
+            if (damagePredicate.isPresent() && damagePredicate.getAsInt() == damage) {
+                return mappingTypes.getIntValue();
+            }
+        }
+        return -1;
+    }
+
     /**
      * Checks if an {@link ItemStack} is equal to another item stack
      *

core/src/main/java/org/geysermc/geyser/translator/inventory/item/PotionTranslator.java

@@ -74,8 +74,7 @@ public class PotionTranslator extends ItemTranslator {
 
     @Override
     public List<ItemMapping> getAppliedItems() {
-        return Arrays.stream(Registries.ITEMS.forVersion(GameProtocol.DEFAULT_BEDROCK_CODEC.getProtocolVersion())
+        return Arrays.stream(Registries.ITEMS.forVersion(GameProtocol.DEFAULT_BEDROCK_CODEC.getProtocolVersion()).getItems())
-                        .getItems())
                 .filter(entry -> entry.getJavaIdentifier().endsWith("potion"))
                 .collect(Collectors.toList());
     }

core/src/main/java/org/geysermc/geyser/translator/inventory/item/TippedArrowTranslator.java

@@ -81,8 +81,7 @@ public class TippedArrowTranslator extends ItemTranslator {
 
     @Override
     public List<ItemMapping> getAppliedItems() {
-        return Arrays.stream(Registries.ITEMS.forVersion(GameProtocol.DEFAULT_BEDROCK_CODEC.getProtocolVersion())
+        return Arrays.stream(Registries.ITEMS.forVersion(GameProtocol.DEFAULT_BEDROCK_CODEC.getProtocolVersion()).getItems())
-                        .getItems())
                 .filter(entry -> entry.getJavaIdentifier().contains("arrow")
                         && !entry.getJavaIdentifier().contains("spectral"))
                 .collect(Collectors.toList());

core/src/main/java/org/geysermc/geyser/translator/inventory/item/nbt/BannerTranslator.java

@@ -76,8 +76,7 @@ public class BannerTranslator extends NbtItemStackTranslator {
     }
 
     public BannerTranslator() {
-        appliedItems = Arrays.stream(Registries.ITEMS.forVersion(GameProtocol.DEFAULT_BEDROCK_CODEC.getProtocolVersion())
+        appliedItems = Arrays.stream(Registries.ITEMS.forVersion(GameProtocol.DEFAULT_BEDROCK_CODEC.getProtocolVersion()).getItems())
-                        .getItems())
                 .filter(entry -> entry.getJavaIdentifier().endsWith("banner"))
                 .collect(Collectors.toList());
     }

core/src/main/java/org/geysermc/geyser/translator/protocol/java/inventory/JavaMerchantOffersTranslator.java

@@ -168,11 +168,12 @@ public class JavaMerchantOffersTranslator extends PacketTranslator<ClientboundMe
 
     private static NbtMap getItemTag(GeyserSession session, ItemStack stack, ItemMapping mapping, int count) {
         ItemData itemData = ItemTranslator.translateToBedrock(session, stack);
+        String customIdentifier = session.getItemMappings().getCustomIdMappings().get(itemData.getId());
 
         NbtMapBuilder builder = NbtMap.builder();
         builder.putByte("Count", (byte) count);
         builder.putShort("Damage", (short) itemData.getDamage());
-        builder.putString("Name", mapping.getBedrockIdentifier());
+        builder.putString("Name", customIdentifier != null ? customIdentifier : mapping.getBedrockIdentifier());
         if (itemData.getTag() != null) {
             NbtMap tag = itemData.getTag().toBuilder().build();
             builder.put("tag", tag);

core/src/main/resources/mappings

@@ -1 +1 @@
-Subproject commit 99a1f8070e844d059454dacbb6e8b203521eed23
+Subproject commit 919908f4825e9fa1bb7b5a2f5e09218f0a3f72f3