path: root/patches/server/1054-Registry-Modification-API.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Jake Potrebic <jake.m.potrebic@gmail.com>
Date: Mon, 27 Feb 2023 18:28:39 -0800
Subject: [PATCH] Registry Modification API

== AT ==
public net.minecraft.server.RegistryLayer STATIC_ACCESS
public net.minecraft.core.MappedRegistry validateWrite(Lnet/minecraft/resources/ResourceKey;)V

diff --git a/src/main/java/io/papermc/paper/registry/PaperRegistries.java b/src/main/java/io/papermc/paper/registry/PaperRegistries.java
index e68ac2a9710c9e0ac248ce65b6e0d21fa7033fec..9342f034ef590594db046cd9b0810bd4075d8e6b 100644
--- a/src/main/java/io/papermc/paper/registry/PaperRegistries.java
+++ b/src/main/java/io/papermc/paper/registry/PaperRegistries.java
@@ -42,6 +42,7 @@ import org.checkerframework.framework.qual.DefaultQualifier;
 
 import static io.papermc.paper.registry.entry.RegistryEntry.apiOnly;
 import static io.papermc.paper.registry.entry.RegistryEntry.entry;
+import static io.papermc.paper.registry.entry.RegistryEntry.writable;
 
 @DefaultQualifier(NonNull.class)
 public final class PaperRegistries {
diff --git a/src/main/java/io/papermc/paper/registry/PaperRegistryAccess.java b/src/main/java/io/papermc/paper/registry/PaperRegistryAccess.java
index c34cffd369ead2b3e43464a02d4f8fb98ca969c1..a70d1d8b2aef96c2dff7e20670afa8b82027ebf3 100644
--- a/src/main/java/io/papermc/paper/registry/PaperRegistryAccess.java
+++ b/src/main/java/io/papermc/paper/registry/PaperRegistryAccess.java
@@ -85,6 +85,14 @@ public class PaperRegistryAccess implements RegistryAccess {
         return possiblyUnwrap(registryHolder.get());
     }
 
+    public <M, T extends Keyed, B extends PaperRegistryBuilder<M, T>> WritableCraftRegistry<M, T, B> getWritableRegistry(final RegistryKey<T> key) {
+        final Registry<T> registry = this.getRegistry(key);
+        if (registry instanceof WritableCraftRegistry<?, T, ?>) {
+            return (WritableCraftRegistry<M, T, B>) registry;
+        }
+        throw new IllegalArgumentException(key + " does not point to a writable registry");
+    }
+
     private static <T extends Keyed> Registry<T> possiblyUnwrap(final Registry<T> registry) {
         if (registry instanceof final DelayedRegistry<T, ?> delayedRegistry) { // if not coming from legacy, unwrap the delayed registry
             return delayedRegistry.delegate();
diff --git a/src/main/java/io/papermc/paper/registry/PaperRegistryBuilder.java b/src/main/java/io/papermc/paper/registry/PaperRegistryBuilder.java
new file mode 100644
index 0000000000000000000000000000000000000000..4cf32102a134ebef67d3893cfd24bf0add321eb9
--- /dev/null
+++ b/src/main/java/io/papermc/paper/registry/PaperRegistryBuilder.java
@@ -0,0 +1,24 @@
+package io.papermc.paper.registry;
+
+import org.checkerframework.checker.nullness.qual.Nullable;
+
+public interface PaperRegistryBuilder<M, T> extends RegistryBuilder<T> {
+
+    M build();
+
+    @FunctionalInterface
+    interface Filler<M, T, B extends PaperRegistryBuilder<M, T>> {
+
+        B fill(final TypedKey<T> key, final @Nullable M nms);
+
+        default Factory<M, T, B> asFactory() {
+            return key -> this.fill(key, null);
+        }
+    }
+
+    @FunctionalInterface
+    interface Factory<M, T, B extends PaperRegistryBuilder<M, T>> {
+
+        B create(final TypedKey<T> key);
+    }
+}
diff --git a/src/main/java/io/papermc/paper/registry/PaperRegistryListenerManager.java b/src/main/java/io/papermc/paper/registry/PaperRegistryListenerManager.java
new file mode 100644
index 0000000000000000000000000000000000000000..6b3ba059b4f530b9e3d1c3d6bbc033e96c6a9bc2
--- /dev/null
+++ b/src/main/java/io/papermc/paper/registry/PaperRegistryListenerManager.java
@@ -0,0 +1,167 @@
+package io.papermc.paper.registry;
+
+import com.google.common.base.Preconditions;
+import io.papermc.paper.plugin.bootstrap.BootstrapContext;
+import io.papermc.paper.plugin.entrypoint.Entrypoint;
+import io.papermc.paper.plugin.entrypoint.LaunchEntryPointHandler;
+import io.papermc.paper.plugin.lifecycle.event.LifecycleEventRunner;
+import io.papermc.paper.plugin.lifecycle.event.types.LifecycleEventType;
+import io.papermc.paper.registry.entry.RegistryEntry;
+import io.papermc.paper.registry.entry.RegistryEntryInfo;
+import io.papermc.paper.registry.event.RegistryEntryAddEventImpl;
+import io.papermc.paper.registry.event.RegistryEventMap;
+import io.papermc.paper.registry.event.RegistryEventProvider;
+import io.papermc.paper.registry.event.RegistryFreezeEvent;
+import io.papermc.paper.registry.event.RegistryFreezeEventImpl;
+import io.papermc.paper.registry.event.type.RegistryEntryAddEventType;
+import io.papermc.paper.registry.event.type.RegistryEntryAddEventTypeImpl;
+import io.papermc.paper.registry.event.type.RegistryLifecycleEventType;
+import net.kyori.adventure.key.Key;
+import net.minecraft.core.Holder;
+import net.minecraft.core.MappedRegistry;
+import net.minecraft.core.RegistrationInfo;
+import net.minecraft.core.Registry;
+import net.minecraft.core.WritableRegistry;
+import net.minecraft.resources.ResourceKey;
+import net.minecraft.resources.ResourceLocation;
+import org.checkerframework.checker.nullness.qual.Nullable;
+import org.intellij.lang.annotations.Subst;
+
+public final class PaperRegistryListenerManager {
+
+    public static final PaperRegistryListenerManager INSTANCE = new PaperRegistryListenerManager();
+
+    public final RegistryEventMap valueAddHooks = new RegistryEventMap("value add");
+    public final RegistryEventMap freezeHooks = new RegistryEventMap("freeze");
+
+    private PaperRegistryListenerManager() {
+    }
+
+    /**
+     * For {@link Registry#register(Registry, String, Object)}
+     */
+    public <M> M registerWithListeners(final Registry<M> registry, final String id, final M nms) {
+        return this.registerWithListeners(registry, new ResourceLocation(id), nms);
+    }
+
+    /**
+     * For {@link Registry#register(Registry, ResourceLocation, Object)}
+     */
+    public <M> M registerWithListeners(final Registry<M> registry, final ResourceLocation loc, final M nms) {
+        return this.registerWithListeners(registry, ResourceKey.create(registry.key(), loc), nms);
+    }
+
+    /**
+     * For {@link Registry#register(Registry, ResourceKey, Object)}
+     */
+    public <M> M registerWithListeners(final Registry<M> registry, final ResourceKey<M> key, final M nms) {
+        return this.registerWithListeners(registry, key, nms, RegistrationInfo.BUILT_IN, PaperRegistryListenerManager::registerWithInstance);
+    }
+
+    /**
+     * For {@link Registry#registerForHolder(Registry, ResourceLocation, Object)}
+     */
+    public <M> Holder.Reference<M> registerForHolderWithListeners(final Registry<M> registry, final ResourceLocation loc, final M nms) {
+        return this.registerForHolderWithListeners(registry, ResourceKey.create(registry.key(), loc), nms);
+    }
+
+    /**
+     * For {@link Registry#registerForHolder(Registry, ResourceKey, Object)}
+     */
+    public <M> Holder.Reference<M> registerForHolderWithListeners(final Registry<M> registry, final ResourceKey<M> key, final M nms) {
+        return this.registerWithListeners(registry, key, nms, RegistrationInfo.BUILT_IN, WritableRegistry::register);
+    }
+
+    public <M, T extends org.bukkit.Keyed, B extends PaperRegistryBuilder<M, T>> void registerWithListeners(
+        final Registry<M> registry,
+        final ResourceKey<M> key,
+        final M nms,
+        final RegistrationInfo registrationInfo
+    ) {
+        this.registerWithListeners(registry, key, nms, registrationInfo, WritableRegistry::register);
+    }
+
+    public <M, T extends org.bukkit.Keyed, B extends PaperRegistryBuilder<M, T>, R> R registerWithListeners(
+        final Registry<M> registry,
+        final ResourceKey<M> key,
+        final M nms,
+        final RegistrationInfo registrationInfo,
+        final RegisterMethod<M, R> registerMethod
+    ) {
+        Preconditions.checkState(LaunchEntryPointHandler.INSTANCE.hasEntered(Entrypoint.BOOTSTRAPPER), registry.key() + " tried to run modification listeners before bootstrappers have been called"); // verify that bootstrappers have been called
+        final @Nullable RegistryEntryInfo<M, T> entry = PaperRegistries.getEntry(registry.key());
+        if (!(entry instanceof RegistryEntry.Modifiable<?, ?, ?>) || !this.valueAddHooks.hasHooks(entry.apiKey())) {
+            return registerMethod.register((WritableRegistry<M>) registry, key, nms, registrationInfo);
+        }
+        final RegistryEntry.Modifiable<M, T, B> modifiableEntry = (RegistryEntry.Modifiable<M, T, B>) entry;
+        @SuppressWarnings("PatternValidation") final TypedKey<T> typedKey = TypedKey.create(entry.apiKey(), Key.key(key.location().getNamespace(), key.location().getPath()));
+        final B builder = modifiableEntry.fillBuilder(typedKey, nms);
+        return this.registerWithListeners(registry, modifiableEntry, key, nms, builder, registrationInfo, registerMethod);
+    }
+
+    public <M, T extends org.bukkit.Keyed, B extends PaperRegistryBuilder<M, T>> void registerWithListeners(
+        final Registry<M> registry,
+        final RegistryEntry.Modifiable<M, T, B> entry,
+        final ResourceKey<M> key,
+        final @Nullable M oldNms,
+        final B builder,
+        final RegistrationInfo registrationInfo
+    ) {
+        this.registerWithListeners(registry, entry, key, oldNms, builder, registrationInfo, WritableRegistry::register);
+    }
+
+    public <M, T extends org.bukkit.Keyed, B extends PaperRegistryBuilder<M, T>, R> R registerWithListeners(
+        final Registry<M> registry,
+        final RegistryEntry.Modifiable<M, T, B> entry,
+        final ResourceKey<M> key,
+        final @Nullable M oldNms,
+        final B builder,
+        final RegistrationInfo registrationInfo,
+        final RegisterMethod<M, R> registerMethod
+    ) {
+        @Subst("namespace:key") final ResourceLocation beingAdded = key.location();
+        @SuppressWarnings("PatternValidation") final TypedKey<T> typedKey = TypedKey.create(entry.apiKey(), Key.key(beingAdded.getNamespace(), beingAdded.getPath()));
+        final RegistryEntryAddEventImpl<T, B> event = entry.createEntryAddEvent(typedKey, builder);
+        LifecycleEventRunner.INSTANCE.callEvent(this.valueAddHooks.getHook(entry.apiKey()), event);
+        if (oldNms != null) {
+            ((MappedRegistry<M>) registry).clearIntrusiveHolder(oldNms);
+        }
+        final M newNms = event.builder().build();
+        return registerMethod.register((WritableRegistry<M>) registry, key, newNms, registrationInfo);
+    }
+
+    private static <M> M registerWithInstance(final WritableRegistry<M> writableRegistry, final ResourceKey<M> key, final M value, final RegistrationInfo registrationInfo) {
+        writableRegistry.register(key, value, registrationInfo);
+        return value;
+    }
+
+    @FunctionalInterface
+    public interface RegisterMethod<M, R> {
+
+        R register(WritableRegistry<M> writableRegistry, ResourceKey<M> key, M value, RegistrationInfo registrationInfo);
+    }
+
+    public <M, T extends org.bukkit.Keyed, B extends PaperRegistryBuilder<M, T>> void runFreezeListeners(final ResourceKey<? extends Registry<M>> resourceKey) {
+        final @Nullable RegistryEntryInfo<M, T> entry = PaperRegistries.getEntry(resourceKey);
+        if (!(entry instanceof RegistryEntry.Writable<?, ?, ?>) || !this.freezeHooks.hasHooks(entry.apiKey())) {
+            return;
+        }
+        final RegistryEntry.Writable<M, T, B> writableEntry = (RegistryEntry.Writable<M, T, B>) entry;
+        final RegistryFreezeEventImpl<T, B> event = writableEntry.createFreezeEvent(PaperRegistryAccess.instance().getWritableRegistry(entry.apiKey()));
+        LifecycleEventRunner.INSTANCE.callEvent(this.freezeHooks.getHook(entry.apiKey()), event);
+    }
+
+    public <T, B extends RegistryBuilder<T>> RegistryEntryAddEventType<T, B> getRegistryValueAddEventType(final RegistryEventProvider<T, B> type) {
+        if (!(PaperRegistries.getEntry(type.registryKey()) instanceof RegistryEntry.Modifiable)) {
+            throw new IllegalArgumentException(type.registryKey() + " does not support RegistryAdditionEvent");
+        }
+        return this.valueAddHooks.getOrCreate(type, RegistryEntryAddEventTypeImpl::new);
+    }
+
+    public <T, B extends RegistryBuilder<T>> LifecycleEventType.Prioritizable<BootstrapContext, RegistryFreezeEvent<T, B>> getRegistryFreezeEventType(final RegistryEventProvider<T, B> type) {
+        if (!(PaperRegistries.getEntry(type.registryKey()) instanceof RegistryEntry.Writable)) {
+            throw new IllegalArgumentException(type.registryKey() + " does not support RegistryPreFreezeEvent");
+        }
+        return this.freezeHooks.getOrCreate(type, RegistryLifecycleEventType::new);
+    }
+}
diff --git a/src/main/java/io/papermc/paper/registry/WritableCraftRegistry.java b/src/main/java/io/papermc/paper/registry/WritableCraftRegistry.java
new file mode 100644
index 0000000000000000000000000000000000000000..aff4895d5add72e22ae9f723b77843435ff044aa
--- /dev/null
+++ b/src/main/java/io/papermc/paper/registry/WritableCraftRegistry.java
@@ -0,0 +1,85 @@
+package io.papermc.paper.registry;
+
+import com.mojang.serialization.Lifecycle;
+import io.papermc.paper.adventure.PaperAdventure;
+import io.papermc.paper.registry.entry.RegistryEntry;
+import io.papermc.paper.registry.event.WritableRegistry;
+import java.util.Optional;
+import java.util.function.BiFunction;
+import java.util.function.Consumer;
+import net.minecraft.core.MappedRegistry;
+import net.minecraft.core.RegistrationInfo;
+import net.minecraft.resources.ResourceKey;
+import org.bukkit.Keyed;
+import org.bukkit.NamespacedKey;
+import org.bukkit.craftbukkit.CraftRegistry;
+import org.bukkit.craftbukkit.util.ApiVersion;
+import org.checkerframework.checker.nullness.qual.Nullable;
+
+public class WritableCraftRegistry<M, T extends Keyed, B extends PaperRegistryBuilder<M, T>> extends CraftRegistry<T, M> {
+
+    private static final RegistrationInfo FROM_PLUGIN = new RegistrationInfo(Optional.empty(), Lifecycle.experimental());
+
+    private final RegistryEntry.BuilderHolder<M, T, B> entry;
+    private final MappedRegistry<M> registry;
+    public final WritableRegistry<T, B> apiWritableRegistry = new ApiWritableRegistry();
+    private final PaperRegistryBuilder.Factory<M, T, ? extends B> builderFactory;
+    private final BiFunction<? super NamespacedKey, M, T> minecraftToBukkit;
+
+    public WritableCraftRegistry(
+        final RegistryEntry.BuilderHolder<M, T, B> entry,
+        final Class<?> classToPreload,
+        final MappedRegistry<M> registry,
+        final BiFunction<NamespacedKey, ApiVersion, NamespacedKey> serializationUpdater,
+        final PaperRegistryBuilder.Factory<M, T, ? extends B> builderFactory,
+        final BiFunction<? super NamespacedKey, M, T> minecraftToBukkit
+    ) {
+        super(classToPreload, registry, null, serializationUpdater);
+        this.entry = entry;
+        this.registry = registry;
+        this.builderFactory = builderFactory;
+        this.minecraftToBukkit = minecraftToBukkit;
+    }
+
+    public void register(final TypedKey<T> key, final Consumer<? super B> value) {
+        final ResourceKey<M> resourceKey = ResourceKey.create(this.registry.key(), PaperAdventure.asVanilla(key.key()));
+        this.registry.validateWrite(resourceKey);
+        final B builder = this.newBuilder(key);
+        value.accept(builder);
+        if (this.entry instanceof final RegistryEntry.Modifiable<M, T, B> modifiable && PaperRegistryListenerManager.INSTANCE.valueAddHooks.hasHooks(this.entry.apiKey())) {
+            PaperRegistryListenerManager.INSTANCE.registerWithListeners(
+                this.registry,
+                modifiable,
+                resourceKey,
+                null,
+                builder,
+                FROM_PLUGIN
+            );
+        } else {
+            this.registry.register(resourceKey, builder.build(), FROM_PLUGIN);
+        }
+    }
+
+    @Override
+    public final @Nullable T createBukkit(final NamespacedKey namespacedKey, final @Nullable M minecraft) {
+        if (minecraft == null) {
+            return null;
+        }
+        return this.minecraftToBukkit(namespacedKey, minecraft);
+    }
+
+    public T minecraftToBukkit(final NamespacedKey namespacedKey, final M minecraft) {
+        return this.minecraftToBukkit.apply(namespacedKey, minecraft);
+    }
+
+    protected B newBuilder(final TypedKey<T> key) {
+        return this.builderFactory.create(key);
+    }
+
+    public class ApiWritableRegistry implements WritableRegistry<T, B> {
+        @Override
+        public void register(final TypedKey<T> key, final Consumer<? super B> value) {
+            WritableCraftRegistry.this.register(key, value);
+        }
+    }
+}
diff --git a/src/main/java/io/papermc/paper/registry/entry/AddableRegistryEntry.java b/src/main/java/io/papermc/paper/registry/entry/AddableRegistryEntry.java
new file mode 100644
index 0000000000000000000000000000000000000000..a0f24d396e3a258be1978b2baa3f8e07ff54538f
--- /dev/null
+++ b/src/main/java/io/papermc/paper/registry/entry/AddableRegistryEntry.java
@@ -0,0 +1,43 @@
+package io.papermc.paper.registry.entry;
+
+import io.papermc.paper.registry.PaperRegistryBuilder;
+import io.papermc.paper.registry.RegistryHolder;
+import io.papermc.paper.registry.RegistryKey;
+import io.papermc.paper.registry.TypedKey;
+import io.papermc.paper.registry.WritableCraftRegistry;
+import java.util.function.BiFunction;
+import net.minecraft.core.MappedRegistry;
+import net.minecraft.core.Registry;
+import net.minecraft.resources.ResourceKey;
+import org.bukkit.Keyed;
+import org.bukkit.NamespacedKey;
+
+public class AddableRegistryEntry<M, T extends Keyed, B extends PaperRegistryBuilder<M, T>> extends CraftRegistryEntry<M, T> implements RegistryEntry.Addable<M, T, B> {
+
+    private final PaperRegistryBuilder.Filler<M, T, B> builderFiller;
+
+    protected AddableRegistryEntry(
+        final ResourceKey<? extends Registry<M>> mcKey,
+        final RegistryKey<T> apiKey,
+        final Class<?> classToPreload,
+        final BiFunction<NamespacedKey, M, T> minecraftToBukkit,
+        final PaperRegistryBuilder.Filler<M, T, B> builderFiller
+    ) {
+        super(mcKey, apiKey, classToPreload, minecraftToBukkit);
+        this.builderFiller = builderFiller;
+    }
+
+    private WritableCraftRegistry<M, T, B> createRegistry(final Registry<M> registry) {
+        return new WritableCraftRegistry<>(this, this.classToPreload, (MappedRegistry<M>) registry, this.updater, this.builderFiller.asFactory(), this.minecraftToBukkit);
+    }
+
+    @Override
+    public RegistryHolder<T> createRegistryHolder(final Registry<M> nmsRegistry) {
+        return new RegistryHolder.Memoized<>(() -> this.createRegistry(nmsRegistry));
+    }
+
+    @Override
+    public B fillBuilder(final TypedKey<T> key, final M nms) {
+        return this.builderFiller.fill(key, nms);
+    }
+}
diff --git a/src/main/java/io/papermc/paper/registry/entry/ModifiableRegistryEntry.java b/src/main/java/io/papermc/paper/registry/entry/ModifiableRegistryEntry.java
new file mode 100644
index 0000000000000000000000000000000000000000..df10008f6bde1047c8a13523c0a8fc01222a4e62
--- /dev/null
+++ b/src/main/java/io/papermc/paper/registry/entry/ModifiableRegistryEntry.java
@@ -0,0 +1,31 @@
+package io.papermc.paper.registry.entry;
+
+import io.papermc.paper.registry.PaperRegistryBuilder;
+import io.papermc.paper.registry.RegistryKey;
+import io.papermc.paper.registry.TypedKey;
+import java.util.function.BiFunction;
+import net.minecraft.core.Registry;
+import net.minecraft.resources.ResourceKey;
+import org.bukkit.Keyed;
+import org.bukkit.NamespacedKey;
+
+public class ModifiableRegistryEntry<M, T extends Keyed, B extends PaperRegistryBuilder<M, T>> extends CraftRegistryEntry<M, T> implements RegistryEntry.Modifiable<M, T, B> {
+
+    protected final PaperRegistryBuilder.Filler<M, T, B> builderFiller;
+
+    protected ModifiableRegistryEntry(
+        final ResourceKey<? extends Registry<M>> mcKey,
+        final RegistryKey<T> apiKey,
+        final Class<?> toPreload,
+        final BiFunction<NamespacedKey, M, T> minecraftToBukkit,
+        final PaperRegistryBuilder.Filler<M, T, B> builderFiller
+    ) {
+        super(mcKey, apiKey, toPreload, minecraftToBukkit);
+        this.builderFiller = builderFiller;
+    }
+
+    @Override
+    public B fillBuilder(final TypedKey<T> key, final M nms) {
+        return this.builderFiller.fill(key, nms);
+    }
+}
diff --git a/src/main/java/io/papermc/paper/registry/entry/RegistryEntry.java b/src/main/java/io/papermc/paper/registry/entry/RegistryEntry.java
index 15991bf13894d850f360a520d1815711d25973ec..c49170d469dca809dc42421168d14e57e24d734b 100644
--- a/src/main/java/io/papermc/paper/registry/entry/RegistryEntry.java
+++ b/src/main/java/io/papermc/paper/registry/entry/RegistryEntry.java
@@ -1,7 +1,12 @@
 package io.papermc.paper.registry.entry;
 
+import io.papermc.paper.registry.PaperRegistryBuilder;
 import io.papermc.paper.registry.RegistryHolder;
 import io.papermc.paper.registry.RegistryKey;
+import io.papermc.paper.registry.TypedKey;
+import io.papermc.paper.registry.WritableCraftRegistry;
+import io.papermc.paper.registry.event.RegistryEntryAddEventImpl;
+import io.papermc.paper.registry.event.RegistryFreezeEventImpl;
 import io.papermc.paper.registry.legacy.DelayedRegistryEntry;
 import java.util.function.BiFunction;
 import java.util.function.Supplier;
@@ -32,6 +37,37 @@ public interface RegistryEntry<M, B extends Keyed> extends RegistryEntryInfo<M,
         return new DelayedRegistryEntry<>(this);
     }
 
+    interface BuilderHolder<M, T, B extends PaperRegistryBuilder<M, T>> extends RegistryEntryInfo<M, T> {
+
+        B fillBuilder(TypedKey<T> key, M nms);
+    }
+
+    /**
+     * Can mutate values being added to the registry
+     */
+    interface Modifiable<M, T, B extends PaperRegistryBuilder<M, T>> extends BuilderHolder<M, T, B> {
+
+        default RegistryEntryAddEventImpl<T, B> createEntryAddEvent(final TypedKey<T> key, final B initialBuilder) {
+            return new RegistryEntryAddEventImpl<>(key, initialBuilder, this.apiKey());
+        }
+    }
+
+    /**
+     * Can only add new values to the registry, not modify any values.
+     */
+    interface Addable<M, T extends Keyed, B extends PaperRegistryBuilder<M, T>> extends BuilderHolder<M, T, B> { // TODO remove Keyed
+
+        default RegistryFreezeEventImpl<T, B> createFreezeEvent(final WritableCraftRegistry<M, T, B> writableRegistry) {
+            return new RegistryFreezeEventImpl<>(this.apiKey(), writableRegistry.apiWritableRegistry);
+        }
+    }
+
+    /**
+     * Can mutate values and add new values.
+     */
+    interface Writable<M, T extends Keyed, B extends PaperRegistryBuilder<M, T>> extends Modifiable<M, T, B>, Addable<M, T, B> { // TODO remove Keyed
+    }
+
     static <M, B extends Keyed> RegistryEntry<M, B> entry(
         final ResourceKey<? extends Registry<M>> mcKey,
         final RegistryKey<B> apiKey,
@@ -48,4 +84,24 @@ public interface RegistryEntry<M, B extends Keyed> extends RegistryEntryInfo<M,
     ) {
         return new ApiRegistryEntry<>(mcKey, apiKey, apiRegistrySupplier);
     }
+
+    static <M, T extends Keyed, B extends PaperRegistryBuilder<M, T>> RegistryEntry<M, T> modifiable(
+        final ResourceKey<? extends Registry<M>> mcKey,
+        final RegistryKey<T> apiKey,
+        final Class<?> toPreload,
+        final BiFunction<NamespacedKey, M, T> minecraftToBukkit,
+        final PaperRegistryBuilder.Filler<M, T, B> filler
+    ) {
+        return new ModifiableRegistryEntry<>(mcKey, apiKey, toPreload, minecraftToBukkit, filler);
+    }
+
+    static <M, T extends Keyed, B extends PaperRegistryBuilder<M, T>> RegistryEntry<M, T> writable(
+        final ResourceKey<? extends Registry<M>> mcKey,
+        final RegistryKey<T> apiKey,
+        final Class<?> toPreload,
+        final BiFunction<NamespacedKey, M, T> minecraftToBukkit,
+        final PaperRegistryBuilder.Filler<M, T, B> filler
+    ) {
+        return new WritableRegistryEntry<>(mcKey, apiKey, toPreload, minecraftToBukkit, filler);
+    }
 }
diff --git a/src/main/java/io/papermc/paper/registry/entry/WritableRegistryEntry.java b/src/main/java/io/papermc/paper/registry/entry/WritableRegistryEntry.java
new file mode 100644
index 0000000000000000000000000000000000000000..562accce731630327d116afd1c9d559df7e386bd
--- /dev/null
+++ b/src/main/java/io/papermc/paper/registry/entry/WritableRegistryEntry.java
@@ -0,0 +1,22 @@
+package io.papermc.paper.registry.entry;
+
+import io.papermc.paper.registry.PaperRegistryBuilder;
+import io.papermc.paper.registry.RegistryKey;
+import java.util.function.BiFunction;
+import net.minecraft.core.Registry;
+import net.minecraft.resources.ResourceKey;
+import org.bukkit.Keyed;
+import org.bukkit.NamespacedKey;
+
+public class WritableRegistryEntry<M, T extends Keyed, B extends PaperRegistryBuilder<M, T>> extends AddableRegistryEntry<M, T, B> implements RegistryEntry.Writable<M, T, B> { // TODO remove Keyed
+
+    protected WritableRegistryEntry(
+        final ResourceKey<? extends Registry<M>> mcKey,
+        final RegistryKey<T> apiKey,
+        final Class<?> classToPreload,
+        final BiFunction<NamespacedKey, M, T> minecraftToBukkit,
+        final PaperRegistryBuilder.Filler<M, T, B> builderFiller
+    ) {
+        super(mcKey, apiKey, classToPreload, minecraftToBukkit, builderFiller);
+    }
+}
diff --git a/src/main/java/io/papermc/paper/registry/event/RegistryEntryAddEventImpl.java b/src/main/java/io/papermc/paper/registry/event/RegistryEntryAddEventImpl.java
new file mode 100644
index 0000000000000000000000000000000000000000..a1d747c1a46d3aa8bcdef82bebb48f1fd760e61f
--- /dev/null
+++ b/src/main/java/io/papermc/paper/registry/event/RegistryEntryAddEventImpl.java
@@ -0,0 +1,13 @@
+package io.papermc.paper.registry.event;
+
+import io.papermc.paper.plugin.lifecycle.event.PaperLifecycleEvent;
+import io.papermc.paper.registry.RegistryBuilder;
+import io.papermc.paper.registry.RegistryKey;
+import io.papermc.paper.registry.TypedKey;
+
+public record RegistryEntryAddEventImpl<T, B extends RegistryBuilder<T>>(
+    TypedKey<T> key,
+    B builder,
+    RegistryKey<T> registryKey
+) implements RegistryEntryAddEvent<T, B>, PaperLifecycleEvent {
+}
diff --git a/src/main/java/io/papermc/paper/registry/event/RegistryEventMap.java b/src/main/java/io/papermc/paper/registry/event/RegistryEventMap.java
new file mode 100644
index 0000000000000000000000000000000000000000..f5ea23173dcbe491742c3dd051c147ef397307a0
--- /dev/null
+++ b/src/main/java/io/papermc/paper/registry/event/RegistryEventMap.java
@@ -0,0 +1,44 @@
+package io.papermc.paper.registry.event;
+
+import io.papermc.paper.plugin.bootstrap.BootstrapContext;
+import io.papermc.paper.plugin.lifecycle.event.LifecycleEventRunner;
+import io.papermc.paper.plugin.lifecycle.event.types.LifecycleEventType;
+import io.papermc.paper.registry.RegistryBuilder;
+import io.papermc.paper.registry.RegistryKey;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Objects;
+import java.util.function.BiFunction;
+
+public final class RegistryEventMap {
+
+    private final Map<RegistryKey<?>, LifecycleEventType<BootstrapContext, ? extends RegistryEvent<?>, ?>> hooks = new HashMap<>();
+    private final String name;
+
+    public RegistryEventMap(final String name) {
+        this.name = name;
+    }
+
+    @SuppressWarnings("unchecked")
+    public <T, B extends RegistryBuilder<T>, E extends RegistryEvent<T>, ET extends LifecycleEventType<BootstrapContext, E, ?>> ET getOrCreate(final RegistryEventProvider<T, B> type, final BiFunction<? super RegistryEventProvider<T, B>, ? super String, ET> eventTypeCreator) {
+        final ET registerHook;
+        if (this.hooks.containsKey(type.registryKey())) {
+            registerHook = (ET) this.hooks.get(type.registryKey());
+        } else {
+            registerHook = eventTypeCreator.apply(type, this.name);
+            LifecycleEventRunner.INSTANCE.addEventType(registerHook);
+            this.hooks.put(type.registryKey(), registerHook);
+        }
+        return registerHook;
+    }
+
+    @SuppressWarnings("unchecked")
+    public <T, E extends RegistryEvent<T>> LifecycleEventType<BootstrapContext, E, ?> getHook(final RegistryKey<T> registryKey) {
+        return (LifecycleEventType<BootstrapContext, E, ?>) Objects.requireNonNull(this.hooks.get(registryKey), "No hook for " + registryKey);
+    }
+
+    public boolean hasHooks(final RegistryKey<?> registryKey) {
+        return this.hooks.containsKey(registryKey);
+    }
+
+}
diff --git a/src/main/java/io/papermc/paper/registry/event/RegistryEventTypeProviderImpl.java b/src/main/java/io/papermc/paper/registry/event/RegistryEventTypeProviderImpl.java
new file mode 100644
index 0000000000000000000000000000000000000000..34c842ffa355e3c8001dd7b8551bcb49229a6391
--- /dev/null
+++ b/src/main/java/io/papermc/paper/registry/event/RegistryEventTypeProviderImpl.java
@@ -0,0 +1,24 @@
+package io.papermc.paper.registry.event;
+
+import io.papermc.paper.plugin.bootstrap.BootstrapContext;
+import io.papermc.paper.plugin.lifecycle.event.types.LifecycleEventType;
+import io.papermc.paper.registry.PaperRegistryListenerManager;
+import io.papermc.paper.registry.RegistryBuilder;
+import io.papermc.paper.registry.event.type.RegistryEntryAddEventType;
+
+public class RegistryEventTypeProviderImpl implements RegistryEventTypeProvider {
+
+    public static RegistryEventTypeProviderImpl instance() {
+        return (RegistryEventTypeProviderImpl) RegistryEventTypeProvider.provider();
+    }
+
+    @Override
+    public <T, B extends RegistryBuilder<T>> RegistryEntryAddEventType<T, B> registryEntryAdd(final RegistryEventProvider<T, B> type) {
+        return PaperRegistryListenerManager.INSTANCE.getRegistryValueAddEventType(type);
+    }
+
+    @Override
+    public <T, B extends RegistryBuilder<T>> LifecycleEventType.Prioritizable<BootstrapContext, RegistryFreezeEvent<T, B>> registryFreeze(final RegistryEventProvider<T, B> type) {
+        return PaperRegistryListenerManager.INSTANCE.getRegistryFreezeEventType(type);
+    }
+}
diff --git a/src/main/java/io/papermc/paper/registry/event/RegistryFreezeEventImpl.java b/src/main/java/io/papermc/paper/registry/event/RegistryFreezeEventImpl.java
new file mode 100644
index 0000000000000000000000000000000000000000..2db5d33d0b72ec3c9ff1c3042d9246dfa4344346
--- /dev/null
+++ b/src/main/java/io/papermc/paper/registry/event/RegistryFreezeEventImpl.java
@@ -0,0 +1,11 @@
+package io.papermc.paper.registry.event;
+
+import io.papermc.paper.plugin.lifecycle.event.PaperLifecycleEvent;
+import io.papermc.paper.registry.RegistryBuilder;
+import io.papermc.paper.registry.RegistryKey;
+
+public record RegistryFreezeEventImpl<T, B extends RegistryBuilder<T>>(
+    RegistryKey<T> registryKey,
+    WritableRegistry<T, B> registry
+) implements RegistryFreezeEvent<T, B>, PaperLifecycleEvent {
+}
diff --git a/src/main/java/io/papermc/paper/registry/event/package-info.java b/src/main/java/io/papermc/paper/registry/event/package-info.java
new file mode 100644
index 0000000000000000000000000000000000000000..14d2d9766b8dee763f220c397aba3ad432d02aaa
--- /dev/null
+++ b/src/main/java/io/papermc/paper/registry/event/package-info.java
@@ -0,0 +1,5 @@
+@DefaultQualifier(NonNull.class)
+package io.papermc.paper.registry.event;
+
+import org.checkerframework.checker.nullness.qual.NonNull;
+import org.checkerframework.framework.qual.DefaultQualifier;
diff --git a/src/main/java/io/papermc/paper/registry/event/type/RegistryEntryAddEventTypeImpl.java b/src/main/java/io/papermc/paper/registry/event/type/RegistryEntryAddEventTypeImpl.java
new file mode 100644
index 0000000000000000000000000000000000000000..32303ea9b3da736cbe26d06e57f5dcc3aa32a99b
--- /dev/null
+++ b/src/main/java/io/papermc/paper/registry/event/type/RegistryEntryAddEventTypeImpl.java
@@ -0,0 +1,32 @@
+package io.papermc.paper.registry.event.type;
+
+import io.papermc.paper.plugin.bootstrap.BootstrapContext;
+import io.papermc.paper.plugin.lifecycle.event.handler.LifecycleEventHandler;
+import io.papermc.paper.plugin.lifecycle.event.types.PrioritizableLifecycleEventType;
+import io.papermc.paper.registry.RegistryBuilder;
+import io.papermc.paper.registry.event.RegistryEntryAddEvent;
+import io.papermc.paper.registry.event.RegistryEventProvider;
+import java.util.function.Consumer;
+import java.util.function.Predicate;
+
+public class RegistryEntryAddEventTypeImpl<T, B extends RegistryBuilder<T>> extends PrioritizableLifecycleEventType<BootstrapContext, RegistryEntryAddEvent<T, B>, RegistryEntryAddConfiguration<T>> implements RegistryEntryAddEventType<T, B> {
+
+    public RegistryEntryAddEventTypeImpl(final RegistryEventProvider<T, B> type, final String eventName) {
+        super(type.registryKey() + " / " + eventName, BootstrapContext.class);
+    }
+
+    @Override
+    public RegistryEntryAddConfiguration<T> newHandler(final LifecycleEventHandler<? super RegistryEntryAddEvent<T, B>> handler) {
+        return new RegistryEntryAddHandlerConfiguration<>(handler, this);
+    }
+
+    @Override
+    public void forEachHandler(final RegistryEntryAddEvent<T, B> event, final Consumer<RegisteredHandler<BootstrapContext, RegistryEntryAddEvent<T, B>>> consumer, final Predicate<RegisteredHandler<BootstrapContext, RegistryEntryAddEvent<T, B>>> predicate) {
+        super.forEachHandler(event, consumer, predicate.and(handler -> this.matchesTarget(event, handler)));
+    }
+
+    private boolean matchesTarget(final RegistryEntryAddEvent<T, B> event, final RegisteredHandler<BootstrapContext, RegistryEntryAddEvent<T, B>> handler) {
+        final RegistryEntryAddHandlerConfiguration<T, B> config = (RegistryEntryAddHandlerConfiguration<T, B>) handler.config();
+        return config.target() == null || event.key().equals(config.target());
+    }
+}
diff --git a/src/main/java/io/papermc/paper/registry/event/type/RegistryEntryAddHandlerConfiguration.java b/src/main/java/io/papermc/paper/registry/event/type/RegistryEntryAddHandlerConfiguration.java
new file mode 100644
index 0000000000000000000000000000000000000000..53df2dd1a9e1cef90bd8504c717b1cc6374b6f4e
--- /dev/null
+++ b/src/main/java/io/papermc/paper/registry/event/type/RegistryEntryAddHandlerConfiguration.java
@@ -0,0 +1,39 @@
+package io.papermc.paper.registry.event.type;
+
+import io.papermc.paper.plugin.bootstrap.BootstrapContext;
+import io.papermc.paper.plugin.lifecycle.event.handler.LifecycleEventHandler;
+import io.papermc.paper.plugin.lifecycle.event.handler.configuration.PrioritizedLifecycleEventHandlerConfigurationImpl;
+import io.papermc.paper.plugin.lifecycle.event.types.AbstractLifecycleEventType;
+import io.papermc.paper.registry.RegistryBuilder;
+import io.papermc.paper.registry.TypedKey;
+import io.papermc.paper.registry.event.RegistryEntryAddEvent;
+import org.checkerframework.checker.nullness.qual.Nullable;
+
+public class RegistryEntryAddHandlerConfiguration<T, B extends RegistryBuilder<T>> extends PrioritizedLifecycleEventHandlerConfigurationImpl<BootstrapContext, RegistryEntryAddEvent<T, B>> implements RegistryEntryAddConfiguration<T> {
+
+    private @Nullable TypedKey<T> target;
+
+    public RegistryEntryAddHandlerConfiguration(final LifecycleEventHandler<? super RegistryEntryAddEvent<T, B>> handler, final AbstractLifecycleEventType<BootstrapContext, RegistryEntryAddEvent<T, B>, ?> eventType) {
+        super(handler, eventType);
+    }
+
+    public @Nullable TypedKey<T> target() {
+        return this.target;
+    }
+
+    @Override
+    public RegistryEntryAddConfiguration<T> onlyFor(final TypedKey<T> key) {
+        this.target = key;
+        return this;
+    }
+
+    @Override
+    public RegistryEntryAddConfiguration<T> priority(final int priority) {
+        return (RegistryEntryAddConfiguration<T>) super.priority(priority);
+    }
+
+    @Override
+    public RegistryEntryAddConfiguration<T> monitor() {
+        return (RegistryEntryAddConfiguration<T>) super.monitor();
+    }
+}
diff --git a/src/main/java/io/papermc/paper/registry/event/type/RegistryLifecycleEventType.java b/src/main/java/io/papermc/paper/registry/event/type/RegistryLifecycleEventType.java
new file mode 100644
index 0000000000000000000000000000000000000000..dcc0f6b337840a78d38abdf2eb3f4bbd1676f58f
--- /dev/null
+++ b/src/main/java/io/papermc/paper/registry/event/type/RegistryLifecycleEventType.java
@@ -0,0 +1,14 @@
+package io.papermc.paper.registry.event.type;
+
+import io.papermc.paper.plugin.bootstrap.BootstrapContext;
+import io.papermc.paper.plugin.lifecycle.event.types.PrioritizableLifecycleEventType;
+import io.papermc.paper.registry.RegistryBuilder;
+import io.papermc.paper.registry.event.RegistryEvent;
+import io.papermc.paper.registry.event.RegistryEventProvider;
+
+public final class RegistryLifecycleEventType<T, B extends RegistryBuilder<T>, E extends RegistryEvent<T>> extends PrioritizableLifecycleEventType.Simple<BootstrapContext, E> {
+
+    public RegistryLifecycleEventType(final RegistryEventProvider<T, B> type, final String eventName) {
+        super(type.registryKey() + " / " + eventName, BootstrapContext.class);
+    }
+}
diff --git a/src/main/java/io/papermc/paper/registry/package-info.java b/src/main/java/io/papermc/paper/registry/package-info.java
new file mode 100644
index 0000000000000000000000000000000000000000..0b80179ff90e085568d7ceafd9b17511789dc99b
--- /dev/null
+++ b/src/main/java/io/papermc/paper/registry/package-info.java
@@ -0,0 +1,5 @@
+@DefaultQualifier(NonNull.class)
+package io.papermc.paper.registry;
+
+import org.checkerframework.checker.nullness.qual.NonNull;
+import org.checkerframework.framework.qual.DefaultQualifier;
diff --git a/src/main/java/net/minecraft/core/MappedRegistry.java b/src/main/java/net/minecraft/core/MappedRegistry.java
index 72c0c4a12aea39fa1c1967fa0277ed117471107e..68f575602476dd5127af773e4af098196091ca70 100644
--- a/src/main/java/net/minecraft/core/MappedRegistry.java
+++ b/src/main/java/net/minecraft/core/MappedRegistry.java
@@ -436,4 +436,12 @@ public class MappedRegistry<T> implements WritableRegistry<T> {
     public HolderLookup.RegistryLookup<T> asLookup() {
         return this.lookup;
     }
+    // Paper start
+    // used to clear intrusive holders from GameEvent, Item, Block, EntityType, and Fluid from unused instances of those types
+    public void clearIntrusiveHolder(final T instance) {
+        if (this.unregisteredIntrusiveHolders != null) {
+            this.unregisteredIntrusiveHolders.remove(instance);
+        }
+    }
+    // Paper end
 }
diff --git a/src/main/java/net/minecraft/core/registries/BuiltInRegistries.java b/src/main/java/net/minecraft/core/registries/BuiltInRegistries.java
index 8daee5a7935e3253834c4cbe81d5e8886f776dad..d7da62360d48d8c12c489296b4ee2ee44c0c2d93 100644
--- a/src/main/java/net/minecraft/core/registries/BuiltInRegistries.java
+++ b/src/main/java/net/minecraft/core/registries/BuiltInRegistries.java
@@ -310,6 +310,7 @@ public class BuiltInRegistries {
     }
     public static void bootStrap(Runnable runnable) {
         // Paper end
+        REGISTRY.freeze(); // Paper - freeze main registry early
         createContents();
         runnable.run(); // Paper
         freeze();
@@ -328,6 +329,7 @@ public class BuiltInRegistries {
         REGISTRY.freeze();
 
         for (Registry<?> registry : REGISTRY) {
+            io.papermc.paper.registry.PaperRegistryListenerManager.INSTANCE.runFreezeListeners(registry.key()); // Paper
             registry.freeze();
         }
     }
diff --git a/src/main/java/net/minecraft/resources/RegistryDataLoader.java b/src/main/java/net/minecraft/resources/RegistryDataLoader.java
index d59356df2d98de873fc5accc749f87fa3d685267..9414cadb2766c3b8f50bf811d3408402e9f57670 100644
--- a/src/main/java/net/minecraft/resources/RegistryDataLoader.java
+++ b/src/main/java/net/minecraft/resources/RegistryDataLoader.java
@@ -125,6 +125,7 @@ public class RegistryDataLoader {
         list.forEach(loader -> loadable.apply((RegistryDataLoader.Loader<?>)loader, registryInfoLookup));
         list.forEach(loader -> {
             Registry<?> registry = loader.registry();
+            io.papermc.paper.registry.PaperRegistryListenerManager.INSTANCE.runFreezeListeners(loader.registry.key()); // Paper - run pre-freeze listeners
 
             try {
                 registry.freeze();
@@ -188,7 +189,7 @@ public class RegistryDataLoader {
             JsonElement jsonElement = JsonParser.parseReader(reader);
             DataResult<E> dataResult = decoder.parse(ops, jsonElement);
             E object = dataResult.getOrThrow();
-            registry.register(key, object, entryInfo);
+            io.papermc.paper.registry.PaperRegistryListenerManager.INSTANCE.registerWithListeners(registry, key, object, entryInfo); // Paper
         }
     }
 
diff --git a/src/main/java/org/bukkit/craftbukkit/CraftRegistry.java b/src/main/java/org/bukkit/craftbukkit/CraftRegistry.java
index 4a5778d1751b774c825bbce0e870e2998278afe3..55d459731a9d7ab8debfdd6d27f874dba6c41436 100644
--- a/src/main/java/org/bukkit/craftbukkit/CraftRegistry.java
+++ b/src/main/java/org/bukkit/craftbukkit/CraftRegistry.java
@@ -155,11 +155,11 @@ public class CraftRegistry<B extends Keyed, M> implements Registry<B> {
     private final Map<NamespacedKey, B> cache = new HashMap<>();
     private final Map<B, NamespacedKey> byValue = new java.util.IdentityHashMap<>(); // Paper - improve Registry
     private final net.minecraft.core.Registry<M> minecraftRegistry;
-    private final BiFunction<NamespacedKey, M, B> minecraftToBukkit;
+    private final BiFunction<? super NamespacedKey, M, B> minecraftToBukkit; // Paper
     private final BiFunction<NamespacedKey, ApiVersion, NamespacedKey> serializationUpdater; // Paper - rename to make it *clear* what it is *only* for
     private boolean init;
 
-    public CraftRegistry(Class<?> bukkitClass, net.minecraft.core.Registry<M> minecraftRegistry, BiFunction<NamespacedKey, M, B> minecraftToBukkit, BiFunction<NamespacedKey, ApiVersion, NamespacedKey> serializationUpdater) { // Paper - relax preload class
+    public CraftRegistry(Class<?> bukkitClass, net.minecraft.core.Registry<M> minecraftRegistry, BiFunction<? super NamespacedKey, M, B> minecraftToBukkit, BiFunction<NamespacedKey, ApiVersion, NamespacedKey> serializationUpdater) { // Paper - relax preload class
         this.bukkitClass = bukkitClass;
         this.minecraftRegistry = minecraftRegistry;
         this.minecraftToBukkit = minecraftToBukkit;
diff --git a/src/main/resources/META-INF/services/io.papermc.paper.registry.event.RegistryEventTypeProvider b/src/main/resources/META-INF/services/io.papermc.paper.registry.event.RegistryEventTypeProvider
new file mode 100644
index 0000000000000000000000000000000000000000..8bee1a5ed877a04e4d027593df1f42cefdd824e7
--- /dev/null
+++ b/src/main/resources/META-INF/services/io.papermc.paper.registry.event.RegistryEventTypeProvider
@@ -0,0 +1 @@
+io.papermc.paper.registry.event.RegistryEventTypeProviderImpl