Add Item serialization as json api (#11235)

* Item serialization as json

* Add ItemStackAdapter for Gson

* A javadoc note at #serialize() and #deserialize()

* Rebase

* Move serialize closer to deserialize

* Add explaining comment about SERIALIZE_CUSTOM_AS_SNBT usage

* Apply lynxplay requests

* Forgot `@NotNull`

* Very important diff was removed

* Rebase

* Javadocs

---------

Co-authored-by: Bjarne Koll <lynxplay101@gmail.com>

patches/api/0490-Item-serialization-as-json.patch

@@ -0,0 +1,47 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: masmc05 <masmc05@gmail.com>
+Date: Sun, 11 Aug 2024 03:01:52 +0300
+Subject: [PATCH] Item serialization as json
+
+
+diff --git a/src/main/java/org/bukkit/UnsafeValues.java b/src/main/java/org/bukkit/UnsafeValues.java
+index c80e0ef587a001ee6de3f5c182cc9696d58bafeb..10c87b7c19ed3eab28fdce5f225df3767292ee0a 100644
+--- a/src/main/java/org/bukkit/UnsafeValues.java
++++ b/src/main/java/org/bukkit/UnsafeValues.java
+@@ -174,6 +174,36 @@ public interface UnsafeValues {
+ 
+     ItemStack deserializeItem(byte[] data);
+ 
++    /**
++     * Serializes this itemstack to json format.
++     * It is safe for data migrations as it will use the built-in data converter instead of bukkit's
++     * dangerous serialization system.
++     * <p>
++     * The emitted json object's format will inherently change across versions and hence should not be used for
++     * non-development purposes like plugin configurations or end-user input.
++     *
++     * @return json object representing this item.
++     * @see #deserializeItemFromJson(com.google.gson.JsonObject)
++     * @throws IllegalArgumentException if the passed itemstack is {@link ItemStack#empty()}.
++     */
++    @NotNull
++    com.google.gson.JsonObject serializeItemAsJson(@NotNull ItemStack itemStack);
++
++    /**
++     * Creates an itemstack from a json object.
++     * <p>
++     * This method expects a json object in the format emitted by {@link #serializeItemAsJson(ItemStack)}.
++     * <p>
++     * The emitted json object's format will inherently change across versions and hence should not be used for
++     * non-development purposes like plugin configurations or end-user input.
++     *
++     * @param data object representing an item in Json format
++     * @return the deserialize item stack, migrated to the latest data version if needed.
++     * @throws IllegalArgumentException if the json object is not a valid item
++     * @see #serializeItemAsJson(ItemStack)
++     */
++    @NotNull ItemStack deserializeItemFromJson(@NotNull com.google.gson.JsonObject data) throws IllegalArgumentException;
++
+     byte[] serializeEntity(org.bukkit.entity.Entity entity);
+ 
+     default org.bukkit.entity.Entity deserializeEntity(byte[] data, World world) {

patches/server/1060-Item-serialization-as-json.patch

@@ -0,0 +1,73 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: masmc05 <masmc05@gmail.com>
+Date: Sun, 11 Aug 2024 03:01:52 +0300
+Subject: [PATCH] Item serialization as json
+
+
+diff --git a/src/main/java/net/minecraft/world/item/component/CustomData.java b/src/main/java/net/minecraft/world/item/component/CustomData.java
+index 6b7245cf05ea4b6ce05462eb3164bce7f5d76a03..ac1914438307e8a7cc3a3b6352e88a0638f8a33b 100644
+--- a/src/main/java/net/minecraft/world/item/component/CustomData.java
++++ b/src/main/java/net/minecraft/world/item/component/CustomData.java
+@@ -28,7 +28,17 @@ import org.slf4j.Logger;
+ public final class CustomData {
+     private static final Logger LOGGER = LogUtils.getLogger();
+     public static final CustomData EMPTY = new CustomData(new CompoundTag());
+-    public static final Codec<CustomData> CODEC = Codec.withAlternative(CompoundTag.CODEC, TagParser.AS_CODEC)
++    // Paper start - Item serialization as json
++    public static ThreadLocal<Boolean> SERIALIZE_CUSTOM_AS_SNBT = ThreadLocal.withInitial(() -> false);
++    public static final Codec<CustomData> CODEC = Codec.either(CompoundTag.CODEC, TagParser.AS_CODEC)
++        .xmap(com.mojang.datafixers.util.Either::unwrap, data -> { // Both will be used for deserialization, but we decide which one to use for serialization
++            if (!SERIALIZE_CUSTOM_AS_SNBT.get()) {
++                return com.mojang.datafixers.util.Either.left(data); // First codec
++            } else {
++                return com.mojang.datafixers.util.Either.right(data); // Second codec
++            }
++        })
++        // Paper end - Item serialization as json
+         .xmap(CustomData::new, component -> component.tag);
+     public static final Codec<CustomData> CODEC_WITH_ID = CODEC.validate(
+         component -> component.getUnsafe().contains("id", 8) ? DataResult.success(component) : DataResult.error(() -> "Missing id for entity in: " + component)
+diff --git a/src/main/java/org/bukkit/craftbukkit/util/CraftMagicNumbers.java b/src/main/java/org/bukkit/craftbukkit/util/CraftMagicNumbers.java
+index 7d32c032b63b9c4674489b30c845fe2de8275808..f78744b6d6075f584d9a88612661854f3f04aed1 100644
+--- a/src/main/java/org/bukkit/craftbukkit/util/CraftMagicNumbers.java
++++ b/src/main/java/org/bukkit/craftbukkit/util/CraftMagicNumbers.java
+@@ -505,6 +505,39 @@ public final class CraftMagicNumbers implements UnsafeValues {
+         return CraftItemStack.asCraftMirror(net.minecraft.world.item.ItemStack.parse(MinecraftServer.getServer().registryAccess(), compound).orElseThrow());
+     }
+ 
++    @Override
++    public com.google.gson.JsonObject serializeItemAsJson(ItemStack itemStack) {
++        Preconditions.checkNotNull(itemStack, "Cannot serialize empty ItemStack");
++        Preconditions.checkArgument(!itemStack.isEmpty(), "Cannot serialize empty ItemStack");
++
++        net.minecraft.core.RegistryAccess.Frozen reg = net.minecraft.server.MinecraftServer.getServer().registryAccess();
++        com.mojang.serialization.DynamicOps<com.google.gson.JsonElement> ops = reg.createSerializationContext(com.mojang.serialization.JsonOps.INSTANCE);
++        com.google.gson.JsonObject item;
++        // Serialize as SNBT to preserve exact NBT types; vanilla codecs already can handle such deserialization.
++        net.minecraft.world.item.component.CustomData.SERIALIZE_CUSTOM_AS_SNBT.set(true);
++        try {
++            item = net.minecraft.world.item.ItemStack.CODEC.encodeStart(ops, CraftItemStack.unwrap(itemStack)).getOrThrow().getAsJsonObject();
++        } finally {
++            net.minecraft.world.item.component.CustomData.SERIALIZE_CUSTOM_AS_SNBT.set(false);
++        }
++        item.addProperty("DataVersion", this.getDataVersion());
++        return item;
++    }
++
++    @Override
++    public ItemStack deserializeItemFromJson(com.google.gson.JsonObject data) throws IllegalArgumentException {
++        Preconditions.checkNotNull(data, "null cannot be deserialized");
++
++        final int dataVersion = data.get("DataVersion").getAsInt();
++        final int currentVersion = org.bukkit.craftbukkit.util.CraftMagicNumbers.INSTANCE.getDataVersion();
++        data = ca.spottedleaf.dataconverter.minecraft.MCDataConverter.convertJson(
++            ca.spottedleaf.dataconverter.minecraft.datatypes.MCTypeRegistry.ITEM_STACK,
++            data, false, dataVersion, currentVersion
++        );
++        com.mojang.serialization.DynamicOps<com.google.gson.JsonElement> ops = MinecraftServer.getServer().registryAccess().createSerializationContext(com.mojang.serialization.JsonOps.INSTANCE);
++        return CraftItemStack.asCraftMirror(net.minecraft.world.item.ItemStack.CODEC.parse(ops, data).getOrThrow(IllegalArgumentException::new));
++    }
++
+     @Override
+     public byte[] serializeEntity(org.bukkit.entity.Entity entity) {
+         Preconditions.checkNotNull(entity, "null cannot be serialized");