From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Jake Potrebic <jake.m.potrebic@gmail.com>
Date: Thu, 20 Jun 2024 09:40:53 -0700
Subject: [PATCH] Tag Lifecycle Events


diff --git a/src/main/java/io/papermc/paper/plugin/lifecycle/event/types/LifecycleEventTypeProvider.java b/src/main/java/io/papermc/paper/plugin/lifecycle/event/types/LifecycleEventTypeProvider.java
index 3b17f056d162dd42cae0d33cbbb22fece82fe525..a52ab9e09420768d89385c881fb7a4c424e5b8d6 100644
--- a/src/main/java/io/papermc/paper/plugin/lifecycle/event/types/LifecycleEventTypeProvider.java
+++ b/src/main/java/io/papermc/paper/plugin/lifecycle/event/types/LifecycleEventTypeProvider.java
@@ -19,4 +19,6 @@ interface LifecycleEventTypeProvider {
     <O extends LifecycleEventOwner, E extends LifecycleEvent> LifecycleEventType.Monitorable<O, E> monitor(String name, Class<? extends O> ownerType);
 
     <O extends LifecycleEventOwner, E extends LifecycleEvent> LifecycleEventType.Prioritizable<O, E> prioritized(String name, Class<? extends O> ownerType);
+
+    TagEventTypeProvider tagProvider();
 }
diff --git a/src/main/java/io/papermc/paper/plugin/lifecycle/event/types/LifecycleEvents.java b/src/main/java/io/papermc/paper/plugin/lifecycle/event/types/LifecycleEvents.java
index dae4935d8e9f46c52f700927a43a9202dac13df6..720fe2546015838708ce794c291ca187cf7bca9c 100644
--- a/src/main/java/io/papermc/paper/plugin/lifecycle/event/types/LifecycleEvents.java
+++ b/src/main/java/io/papermc/paper/plugin/lifecycle/event/types/LifecycleEvents.java
@@ -24,6 +24,12 @@ public final class LifecycleEvents {
      */
     public static final LifecycleEventType.Prioritizable<LifecycleEventOwner, ReloadableRegistrarEvent<Commands>> COMMANDS = prioritized("commands", LifecycleEventOwner.class);
 
+    /**
+     * These events are for registering tags to the server's tag system. You can register a handler for these events
+     * only in {@link io.papermc.paper.plugin.bootstrap.PluginBootstrap#bootstrap(BootstrapContext)}.
+     */
+    public static final TagEventTypeProvider TAGS = LifecycleEventTypeProvider.provider().tagProvider();
+
     //<editor-fold desc="helper methods" defaultstate="collapsed">
     @ApiStatus.Internal
     static <E extends LifecycleEvent> LifecycleEventType.Monitorable<Plugin, E> plugin(final String name) {
diff --git a/src/main/java/io/papermc/paper/plugin/lifecycle/event/types/TagEventTypeProvider.java b/src/main/java/io/papermc/paper/plugin/lifecycle/event/types/TagEventTypeProvider.java
new file mode 100644
index 0000000000000000000000000000000000000000..61c5f6cc6986193eab596ee55e1a414afcf4fbd1
--- /dev/null
+++ b/src/main/java/io/papermc/paper/plugin/lifecycle/event/types/TagEventTypeProvider.java
@@ -0,0 +1,40 @@
+package io.papermc.paper.plugin.lifecycle.event.types;
+
+import io.papermc.paper.plugin.bootstrap.BootstrapContext;
+import io.papermc.paper.plugin.lifecycle.event.registrar.ReloadableRegistrarEvent;
+import io.papermc.paper.registry.RegistryKey;
+import io.papermc.paper.tag.PostFlattenTagRegistrar;
+import io.papermc.paper.tag.PreFlattenTagRegistrar;
+import org.checkerframework.checker.nullness.qual.NonNull;
+import org.jetbrains.annotations.ApiStatus;
+
+/**
+ * Provides event types for tag registration.
+ *
+ * @see PreFlattenTagRegistrar
+ * @see PostFlattenTagRegistrar
+ */
+@ApiStatus.Experimental
+@ApiStatus.NonExtendable
+public interface TagEventTypeProvider {
+
+    /**
+     * Get a prioritizable, reloadable registrar event for tags before they are flattened.
+     *
+     * @param registryKey the registry key for the tag type
+     * @return the registry event type
+     * @param <T> the type of value in the tag
+     * @see PreFlattenTagRegistrar
+     */
+    <T> LifecycleEventType.@NonNull Prioritizable<BootstrapContext, ReloadableRegistrarEvent<PreFlattenTagRegistrar<T>>> preFlatten(@NonNull RegistryKey<T> registryKey);
+
+    /**
+     * Get a prioritizable, reloadable registrar event for tags after they are flattened.
+     *
+     * @param registryKey the registry key for the tag type
+     * @return the registry event type
+     * @param <T> the type of value in the tag
+     * @see PostFlattenTagRegistrar
+     */
+    <T> LifecycleEventType.@NonNull Prioritizable<BootstrapContext, ReloadableRegistrarEvent<PostFlattenTagRegistrar<T>>> postFlatten(@NonNull RegistryKey<T> registryKey);
+}
diff --git a/src/main/java/io/papermc/paper/tag/PostFlattenTagRegistrar.java b/src/main/java/io/papermc/paper/tag/PostFlattenTagRegistrar.java
new file mode 100644
index 0000000000000000000000000000000000000000..32d79dac18c402c3d95edb642eef1563eddf5e9e
--- /dev/null
+++ b/src/main/java/io/papermc/paper/tag/PostFlattenTagRegistrar.java
@@ -0,0 +1,103 @@
+package io.papermc.paper.tag;
+
+import io.papermc.paper.plugin.lifecycle.event.registrar.Registrar;
+import io.papermc.paper.registry.RegistryKey;
+import io.papermc.paper.registry.TypedKey;
+import io.papermc.paper.registry.tag.TagKey;
+import java.util.Collection;
+import java.util.Map;
+import org.checkerframework.checker.nullness.qual.NonNull;
+import org.jetbrains.annotations.ApiStatus;
+import org.jetbrains.annotations.Contract;
+import org.jetbrains.annotations.Unmodifiable;
+
+/**
+ * Registrar for tags after they have been flattened. Flattened
+ * tags are tags which have any nested tags resolved to the tagged
+ * values the nested tags point to. This registrar, being a post-flatten
+ * registrar, allows for modification after that flattening has happened, when
+ * tags only point to individual entries and not other nested tags.
+ * <p>
+ * An example of a custom enchant being registered to the vanilla
+ * {@code #minecraft:in_enchanting_table} tag.
+ * <pre>{@code
+ * class YourBootstrapClass implements PluginBootstrap {
+ *
+ *     @Override
+ *     public void bootstrap(@NotNull BootstrapContext context) {
+ *         LifecycleEventManager<BootstrapContext> manager = context.getLifecycleManager();
+ *         manager.registerEventHandler(LifecycleEvents.TAGS.postFlatten(RegistryKey.ENCHANTMENT), event -> {
+ *             final PostFlattenTagRegistrar<Enchantment> registrar = event.registrar();
+ *             registrar.addToTag(
+ *                 EnchantmentTagKeys.IN_ENCHANTING_TABLE,
+ *                 Set.of(CUSTOM_ENCHANT)
+ *             );
+ *         });
+ *     }
+ * }
+ * }</pre>
+ *
+ * @param <T> the type of value in the tag
+ * @see PreFlattenTagRegistrar
+ */
+@ApiStatus.Experimental
+@ApiStatus.NonExtendable
+public interface PostFlattenTagRegistrar<T> extends Registrar {
+
+    /**
+     * Get the registry key for this tag registrar.
+     *
+     * @return the registry key
+     */
+    @NonNull RegistryKey<T> registryKey();
+
+    /**
+     * Get a copy of all tags currently held in this registrar.
+     *
+     * @return an immutable map of all tags
+     */
+    @Contract(value = "-> new", pure = true)
+    @Unmodifiable @NonNull Map<TagKey<T>, Collection<TypedKey<T>>> getAllTags();
+
+    /**
+     * Checks if this registrar has a tag with the given key.
+     *
+     * @param tagKey the key to check for
+     * @return true if the tag exists, false otherwise
+     */
+    @Contract(pure = true)
+    boolean hasTag(@NonNull TagKey<T> tagKey);
+
+    /**
+     * Get the tag with the given key. Use {@link #hasTag(TagKey)} to check
+     * if a tag exists first.
+     *
+     * @param tagKey the key of the tag to get
+     * @return an immutable list of tag entries
+     * @throws java.util.NoSuchElementException if the tag does not exist
+     * @see #hasTag(TagKey)
+     */
+    @Contract(value = "_ -> new", pure = true)
+    @Unmodifiable @NonNull Collection<TypedKey<T>> getTag(@NonNull TagKey<T> tagKey);
+
+    /**
+     * Adds values to the given tag. If the tag does not exist, it will be created.
+     *
+     * @param tagKey the key of the tag to add to
+     * @param values the values to add
+     * @see #setTag(TagKey, Collection)
+     */
+    @Contract(mutates = "this")
+    void addToTag(@NonNull TagKey<T> tagKey, @NonNull Collection<TypedKey<T>> values);
+
+    /**
+     * Sets the values of the given tag. If the tag does not exist, it will be created.
+     * If the tag does exist, it will be overwritten.
+     *
+     * @param tagKey the key of the tag to set
+     * @param values the values to set
+     * @see #addToTag(TagKey, Collection)
+     */
+    @Contract(mutates = "this")
+    void setTag(@NonNull TagKey<T> tagKey, @NonNull Collection<TypedKey<T>> values);
+}
diff --git a/src/main/java/io/papermc/paper/tag/PreFlattenTagRegistrar.java b/src/main/java/io/papermc/paper/tag/PreFlattenTagRegistrar.java
new file mode 100644
index 0000000000000000000000000000000000000000..44f7a9d3c2734fb00d11890ece9dc4ce2fafa796
--- /dev/null
+++ b/src/main/java/io/papermc/paper/tag/PreFlattenTagRegistrar.java
@@ -0,0 +1,102 @@
+package io.papermc.paper.tag;
+
+import io.papermc.paper.plugin.lifecycle.event.registrar.Registrar;
+import io.papermc.paper.registry.RegistryKey;
+import io.papermc.paper.registry.tag.TagKey;
+import java.util.Collection;
+import java.util.List;
+import java.util.Map;
+import org.checkerframework.checker.nullness.qual.NonNull;
+import org.jetbrains.annotations.ApiStatus;
+import org.jetbrains.annotations.Contract;
+import org.jetbrains.annotations.Unmodifiable;
+
+/**
+ * Registrar for tags before they are flattened. Flattened
+ * tags are tags which have any nested tags resolved to the tagged
+ * values the nested tags point to. This registrar, being a pre-flatten
+ * registrar, allows for modification before that flattening has happened, when
+ * tags both point to individual entries and other nested tags.
+ * <p>
+ * An example of a tag being created in a pre-flatten registrar:
+ * <pre>{@code
+ * class YourBootstrapClass implements PluginBootstrap {
+ *
+ *     @Override
+ *     public void bootstrap(@NotNull BootstrapContext context) {
+ *         LifecycleEventManager<BootstrapContext> manager = context.getLifecycleManager();
+ *         manager.registerEventHandler(LifecycleEvents.TAGS.preFlatten(RegistryKey.ITEM), event -> {
+ *             final PreFlattenTagRegistrar<ItemType> registrar = event.registrar();
+ *             registrar.setTag(AXE_PICKAXE, Set.of(
+ *                 TagEntry.tagEntry(ItemTypeTagKeys.PICKAXES),
+ *                 TagEntry.tagEntry(ItemTypeTagKeys.AXES)
+ *             ));
+ *         });
+ *     }
+ * }
+ * }</pre>
+ *
+ * @param <T> the type of value in the tag
+ * @see PostFlattenTagRegistrar
+ */
+@ApiStatus.Experimental
+@ApiStatus.NonExtendable
+public interface PreFlattenTagRegistrar<T> extends Registrar {
+
+    /**
+     * Get the registry key for this tag registrar.
+     *
+     * @return the registry key
+     */
+    @NonNull RegistryKey<T> registryKey();
+
+    /**
+     * Get a copy of all tags currently held in this registrar.
+     *
+     * @return an immutable map of all tags
+     */
+    @Contract(value = "-> new", pure = true)
+    @Unmodifiable @NonNull Map<TagKey<T>, Collection<TagEntry<T>>> getAllTags();
+
+    /**
+     * Checks if this registrar has a tag with the given key.
+     *
+     * @param tagKey the key to check for
+     * @return true if the tag exists, false otherwise
+     */
+    @Contract(pure = true)
+    boolean hasTag(@NonNull TagKey<T> tagKey);
+
+    /**
+     * Get the tag with the given key. Use {@link #hasTag(TagKey)} to check
+     * if a tag exists first.
+     *
+     * @param tagKey the key of the tag to get
+     * @return an immutable list of tag entries
+     * @throws java.util.NoSuchElementException if the tag does not exist
+     * @see #hasTag(TagKey)
+     */
+    @Contract(value = "_ -> new", pure = true)
+    @Unmodifiable @NonNull List<TagEntry<T>> getTag(@NonNull TagKey<T> tagKey);
+
+    /**
+     * Adds entries to the given tag. If the tag does not exist, it will be created.
+     *
+     * @param tagKey the key of the tag to add to
+     * @param entries the entries to add
+     * @see #setTag(TagKey, Collection)
+     */
+    @Contract(mutates = "this")
+    void addToTag(@NonNull TagKey<T> tagKey, @NonNull Collection<TagEntry<T>> entries);
+
+    /**
+     * Sets the entries of the given tag. If the tag does not exist, it will be created.
+     * If the tag does exist, it will be overwritten.
+     *
+     * @param tagKey the key of the tag to set
+     * @param entries the entries to set
+     * @see #addToTag(TagKey, Collection)
+     */
+    @Contract(mutates = "this")
+    void setTag(@NonNull TagKey<T> tagKey, @NonNull Collection<TagEntry<T>> entries);
+}
diff --git a/src/main/java/io/papermc/paper/tag/TagEntry.java b/src/main/java/io/papermc/paper/tag/TagEntry.java
new file mode 100644
index 0000000000000000000000000000000000000000..436b701f1231354a78a9e0ab04ffd9097343ecfc
--- /dev/null
+++ b/src/main/java/io/papermc/paper/tag/TagEntry.java
@@ -0,0 +1,89 @@
+package io.papermc.paper.tag;
+
+import io.papermc.paper.registry.TypedKey;
+import io.papermc.paper.registry.tag.TagKey;
+import net.kyori.adventure.key.Keyed;
+import org.checkerframework.checker.nullness.qual.NonNull;
+import org.jetbrains.annotations.ApiStatus;
+import org.jetbrains.annotations.Contract;
+
+/**
+ * An entry is a pre-flattened tag. Represents
+ * either an individual registry entry or a whole tag.
+ *
+ * @param <T> the type of value in the tag
+ * @see PreFlattenTagRegistrar
+ */
+@ApiStatus.Experimental
+@ApiStatus.NonExtendable
+public interface TagEntry<T> extends Keyed {
+
+    /**
+     * Create required tag entry for a single value.
+     *
+     * @param entryKey the key of the entry
+     * @return a new tag entry for a value
+     * @param <T> the type of value
+     */
+    @Contract(value = "_ -> new", pure = true)
+    static <T> @NonNull TagEntry<T> valueEntry(final @NonNull TypedKey<T> entryKey) {
+        return valueEntry(entryKey, true);
+    }
+
+    /**
+     * Create tag entry for a single value.
+     *
+     * @param entryKey the key of the entry
+     * @param isRequired if this entry is required (see {@link #isRequired()})
+     * @return a new tag entry for a value
+     * @param <T> the type of value
+     */
+    @Contract(value = "_, _ -> new", pure = true)
+    static <T> @NonNull TagEntry<T> valueEntry(final @NonNull TypedKey<T> entryKey, final boolean isRequired) {
+        return new TagEntryImpl<>(entryKey.key(), false, isRequired);
+    }
+
+    /**
+     * Create a required tag entry for a nested tag.
+     *
+     * @param tagKey they key for the tag
+     * @return a new tag entry for a tag
+     * @param <T> the type of value
+     */
+    @Contract(value = "_ -> new", pure = true)
+    static <T> @NonNull TagEntry<T> tagEntry(final @NonNull TagKey<T> tagKey) {
+        return tagEntry(tagKey, true);
+    }
+
+    /**
+     * Create a tag entry for a nested tag.
+     *
+     * @param tagKey they key for the tag
+     * @param isRequired if this entry is required (see {@link #isRequired()})
+     * @return a new tag entry for a tag
+     * @param <T> the type of value
+     */
+    @Contract(value = "_, _ -> new", pure = true)
+    static <T> @NonNull TagEntry<T> tagEntry(final @NonNull TagKey<T> tagKey, final boolean isRequired) {
+        return new TagEntryImpl<>(tagKey.key(), true, isRequired);
+    }
+
+    /**
+     * Returns if this entry represents a tag.
+     *
+     * @return true if this entry is a tag, false if it is an individual entry
+     */
+    @Contract(pure = true)
+    boolean isTag();
+
+    /**
+     * Returns if this entry is required. If an entry is required,
+     * the value or tag must exist on the server in order for the tag
+     * to load correctly. A missing value will prevent the tag holding
+     * that missing value from being created.
+     *
+     * @return true if this entry is required, false if it is optional
+     */
+    @Contract(pure = true)
+    boolean isRequired();
+}
diff --git a/src/main/java/io/papermc/paper/tag/TagEntryImpl.java b/src/main/java/io/papermc/paper/tag/TagEntryImpl.java
new file mode 100644
index 0000000000000000000000000000000000000000..c0ffd2b9f814d92d0d9b370dfa7e352f1241f614
--- /dev/null
+++ b/src/main/java/io/papermc/paper/tag/TagEntryImpl.java
@@ -0,0 +1,8 @@
+package io.papermc.paper.tag;
+
+import net.kyori.adventure.key.Key;
+import org.jetbrains.annotations.ApiStatus;
+
+@ApiStatus.Internal
+record TagEntryImpl<T>(Key key, boolean isTag, boolean isRequired) implements TagEntry<T> {
+}