Make a PDC view accessible directly from ItemStack

paper-api/src/main/java/io/papermc/paper/persistence/PersistentDataContainerView.java

@@ -0,0 +1,160 @@
+package io.papermc.paper.persistence;
+
+import java.util.Set;
+import org.bukkit.NamespacedKey;
+import org.bukkit.persistence.PersistentDataAdapterContext;
+import org.bukkit.persistence.PersistentDataContainer;
+import org.bukkit.persistence.PersistentDataHolder;
+import org.bukkit.persistence.PersistentDataType;
+import org.jetbrains.annotations.ApiStatus;
+import org.jspecify.annotations.NullMarked;
+import org.jspecify.annotations.Nullable;
+
+/**
+ * This represents a view of a persistent data container. No
+ * methods on this interface mutate the container.
+ *
+ * @see PersistentDataContainer
+ */
+@NullMarked
+@ApiStatus.NonExtendable
+public interface PersistentDataContainerView {
+
+    /**
+     * Returns if the persistent metadata provider has metadata registered
+     * matching the provided parameters.
+     * <p>
+     * This method will only return true if the found value has the same primitive
+     * data type as the provided key.
+     * <p>
+     * Storing a value using a custom {@link PersistentDataType} implementation
+     * will not store the complex data type. Therefore storing a UUID (by
+     * storing a byte[]) will match has("key" ,
+     * {@link PersistentDataType#BYTE_ARRAY}). Likewise a stored byte[] will
+     * always match your UUID {@link PersistentDataType} even if it is not 16
+     * bytes long.
+     * <p>
+     * This method is only usable for custom object keys. Overwriting existing
+     * tags, like the display name, will not work as the values are stored
+     * using your namespace.
+     *
+     * @param key the key the value is stored under
+     * @param type the type the primative stored value has to match
+     * @param <P> the generic type of the stored primitive
+     * @param <C> the generic type of the eventually created complex object
+     * @return if a value with the provided key and type exists
+     * @throws IllegalArgumentException if the key to look up is null
+     * @throws IllegalArgumentException if the type to cast the found object to is
+     * null
+     */
+    <P, C> boolean has(NamespacedKey key, PersistentDataType<P, C> type);
+
+    /**
+     * Returns if the persistent metadata provider has metadata registered matching
+     * the provided parameters.
+     * <p>
+     * This method will return true as long as a value with the given key exists,
+     * regardless of its type.
+     * <p>
+     * This method is only usable for custom object keys. Overwriting existing tags,
+     * like the display name, will not work as the values are stored using your
+     * namespace.
+     *
+     * @param key the key the value is stored under
+     * @return if a value with the provided key exists
+     * @throws IllegalArgumentException if the key to look up is null
+     */
+    boolean has(NamespacedKey key);
+
+    /**
+     * Returns the metadata value that is stored on the
+     * {@link PersistentDataHolder} instance.
+     *
+     * @param key the key to look up in the custom tag map
+     * @param type the type the value must have and will be casted to
+     * @param <P> the generic type of the stored primitive
+     * @param <C> the generic type of the eventually created complex object
+     * @return the value or {@code null} if no value was mapped under the given
+     * value
+     * @throws IllegalArgumentException if the key to look up is null
+     * @throws IllegalArgumentException if the type to cast the found object to is
+     * null
+     * @throws IllegalArgumentException if a value exists under the given key,
+     * but cannot be accessed using the given type
+     * @throws IllegalArgumentException if no suitable adapter was found for
+     * the {@link
+     * PersistentDataType#getPrimitiveType()}
+     */
+    <P, C> @Nullable C get(NamespacedKey key, PersistentDataType<P, C> type);
+
+    /**
+     * Returns the metadata value that is stored on the
+     * {@link PersistentDataHolder} instance. If the value does not exist in the
+     * container, the default value provided is returned.
+     *
+     * @param key the key to look up in the custom tag map
+     * @param type the type the value must have and will be casted to
+     * @param defaultValue the default value to return if no value was found for
+     * the provided key
+     * @param <P> the generic type of the stored primitive
+     * @param <C> the generic type of the eventually created complex object
+     * @return the value or the default value if no value was mapped under the
+     * given key
+     * @throws IllegalArgumentException if the key to look up is null
+     * @throws IllegalArgumentException if the type to cast the found object to is
+     * null
+     * @throws IllegalArgumentException if a value exists under the given key,
+     * but cannot be accessed using the given type
+     * @throws IllegalArgumentException if no suitable adapter was found for
+     * the {@link PersistentDataType#getPrimitiveType()}
+     */
+    <P, C> C getOrDefault(NamespacedKey key, PersistentDataType<P, C> type, C defaultValue);
+
+    /**
+     * Get the set of keys present on this {@link PersistentDataContainer}
+     * instance.
+     * <p>
+     * Any changes made to the returned set will not be reflected on the
+     * instance.
+     *
+     * @return the key set
+     */
+    Set<NamespacedKey> getKeys();
+
+    /**
+     * Returns if the container instance is empty, therefore has no entries
+     * inside it.
+     *
+     * @return the boolean
+     */
+    boolean isEmpty();
+
+    /**
+     * Copies all values from this {@link PersistentDataContainer} to the provided
+     * container.
+     * <p>
+     * This method only copies custom object keys. Existing tags, like the display
+     * name, will not be copied as the values are stored using your namespace.
+     *
+     * @param other the container to copy to
+     * @param replace whether to replace any matching values in the target container
+     * @throws IllegalArgumentException if the other container is null
+     */
+    void copyTo(PersistentDataContainer other, boolean replace);
+
+    /**
+     * Returns the adapter context this tag container uses.
+     *
+     * @return the tag context
+     */
+    PersistentDataAdapterContext getAdapterContext();
+
+    /**
+     * Serialize this {@link PersistentDataContainer} instance to a
+     * byte array.
+     *
+     * @return a binary representation of this container
+     * @throws java.io.IOException if we fail to write this container to a byte array
+     */
+    byte[] serializeToBytes() throws java.io.IOException;
+}

paper-api/src/main/java/io/papermc/paper/persistence/PersistentDataViewHolder.java

@@ -0,0 +1,24 @@
+package io.papermc.paper.persistence;
+
+import org.jetbrains.annotations.ApiStatus;
+import org.jspecify.annotations.NullMarked;
+
+/**
+ * The {@link PersistentDataViewHolder} interface defines an object that can view
+ * custom persistent data on it.
+ */
+@NullMarked
+@ApiStatus.NonExtendable
+public interface PersistentDataViewHolder {
+
+    /**
+     * Returns a custom tag container view capable of viewing tags on the object.
+     * <p>
+     * Note that the tags stored on this container are all stored under their
+     * own custom namespace therefore modifying default tags using this
+     * {@link PersistentDataViewHolder} is impossible.
+     *
+     * @return the persistent data container view
+     */
+    PersistentDataContainerView getPersistentDataContainer();
+}