Make a PDC view accessible directly from ItemStack

paper-server/src/main/java/io/papermc/paper/persistence/PaperPersistentDataContainerView.java

@@ -0,0 +1,120 @@
+package io.papermc.paper.persistence;
+
+import com.google.common.base.Preconditions;
+import java.io.ByteArrayOutputStream;
+import java.io.DataOutputStream;
+import java.io.IOException;
+import java.util.Collections;
+import java.util.HashSet;
+import java.util.Set;
+import net.minecraft.nbt.CompoundTag;
+import net.minecraft.nbt.NbtIo;
+import net.minecraft.nbt.Tag;
+import org.bukkit.NamespacedKey;
+import org.bukkit.craftbukkit.persistence.CraftPersistentDataAdapterContext;
+import org.bukkit.craftbukkit.persistence.CraftPersistentDataContainer;
+import org.bukkit.craftbukkit.persistence.CraftPersistentDataTypeRegistry;
+import org.bukkit.persistence.PersistentDataAdapterContext;
+import org.bukkit.persistence.PersistentDataContainer;
+import org.bukkit.persistence.PersistentDataType;
+import org.jspecify.annotations.NullMarked;
+import org.jspecify.annotations.Nullable;
+
+@NullMarked
+public abstract class PaperPersistentDataContainerView implements PersistentDataContainerView {
+
+    protected final CraftPersistentDataTypeRegistry registry;
+    protected final CraftPersistentDataAdapterContext adapterContext;
+
+    public PaperPersistentDataContainerView(final CraftPersistentDataTypeRegistry registry) {
+        this.registry = registry;
+        this.adapterContext = new CraftPersistentDataAdapterContext(this.registry);
+    }
+
+    public abstract @Nullable Tag getTag(final String key);
+
+    public abstract CompoundTag toTagCompound();
+
+    @Override
+    public <P, C> boolean has(final NamespacedKey key, final PersistentDataType<P, C> type) {
+        Preconditions.checkArgument(key != null, "The NamespacedKey key cannot be null");
+        Preconditions.checkArgument(type != null, "The provided type cannot be null");
+
+        final Tag value = this.getTag(key.toString());
+        if (value == null) {
+            return false;
+        }
+
+        return this.registry.isInstanceOf(type, value);
+    }
+
+    @Override
+    public boolean has(final NamespacedKey key) {
+        Preconditions.checkArgument(key != null, "The provided key for the custom value was null"); // Paper
+        return this.getTag(key.toString()) != null;
+    }
+
+    @Override
+    public <P, C> @Nullable C get(final NamespacedKey key, final PersistentDataType<P, C> type) {
+        Preconditions.checkArgument(key != null, "The NamespacedKey key cannot be null");
+        Preconditions.checkArgument(type != null, "The provided type cannot be null");
+
+        final Tag value = this.getTag(key.toString());
+        if (value == null) {
+            return null;
+        }
+
+        return type.fromPrimitive(this.registry.extract(type, value), this.adapterContext);
+    }
+
+    @Override
+    public <P, C> C getOrDefault(final NamespacedKey key, final PersistentDataType<P, C> type, final C defaultValue) {
+        final C c = this.get(key, type);
+        return c != null ? c : defaultValue;
+    }
+
+    @Override
+    public Set<NamespacedKey> getKeys() {
+        final Set<String> names = this.toTagCompound().getAllKeys();
+        final Set<NamespacedKey> keys = new HashSet<>(names.size());
+        names.forEach(key -> {
+            final String[] keyPart = key.split(":", 2);
+            if (keyPart.length == 2) {
+                keys.add(new NamespacedKey(keyPart[0], keyPart[1]));
+            }
+        });
+        return Collections.unmodifiableSet(keys);
+    }
+
+    @Override
+    public boolean isEmpty() {
+        return this.toTagCompound().isEmpty();
+    }
+
+    @Override
+    public void copyTo(final PersistentDataContainer other, final boolean replace) {
+        Preconditions.checkArgument(other != null, "The target container cannot be null");
+        final CraftPersistentDataContainer target = (CraftPersistentDataContainer) other;
+        final CompoundTag tag = this.toTagCompound();
+        for (final String key : tag.getAllKeys()) {
+            if (replace || !target.getRaw().containsKey(key)) {
+                target.getRaw().put(key, tag.get(key).copy());
+            }
+        }
+    }
+
+    @Override
+    public PersistentDataAdapterContext getAdapterContext() {
+        return this.adapterContext;
+    }
+
+    @Override
+    public byte[] serializeToBytes() throws IOException {
+        final CompoundTag root = this.toTagCompound();
+        final ByteArrayOutputStream byteArrayOutput = new ByteArrayOutputStream();
+        try (final DataOutputStream dataOutput = new DataOutputStream(byteArrayOutput)) {
+            NbtIo.write(root, dataOutput);
+            return byteArrayOutput.toByteArray();
+        }
+    }
+}