Add basic Datapack API

Co-authored-by: Jake Potrebic <jake.m.potrebic@gmail.com>

paper-api/src/main/java/io/papermc/paper/datapack/Datapack.java

@@ -0,0 +1,99 @@
+package io.papermc.paper.datapack;
+
+import java.util.Set;
+import net.kyori.adventure.text.Component;
+import org.bukkit.FeatureFlag;
+import org.jetbrains.annotations.Contract;
+import org.jetbrains.annotations.Unmodifiable;
+import org.jspecify.annotations.NullMarked;
+
+/**
+ * This is a snapshot of a datapack on the server. It
+ * won't be updated as datapacks are updated.
+ */
+@NullMarked
+public interface Datapack {
+
+    /**
+     * Gets the name/id of this datapack.
+     *
+     * @return the name of the pack
+     */
+    @Contract(pure = true)
+    String getName();
+
+    /**
+     * Gets the title component of this datapack.
+     *
+     * @return the title
+     */
+    Component getTitle();
+
+    /**
+     * Gets the description component of this datapack.
+     *
+     * @return the description
+     */
+    Component getDescription();
+
+    /**
+     * Gets if this datapack is required to be enabled.
+     *
+     * @return true if the pack is required
+     */
+    boolean isRequired();
+
+    /**
+     * Gets the compatibility status of this pack.
+     *
+     * @return the compatibility of the pack
+     */
+    Compatibility getCompatibility();
+
+    /**
+     * Gets the set of required features for this datapack.
+     *
+     * @return the set of required features
+     */
+    @Unmodifiable Set<FeatureFlag> getRequiredFeatures();
+
+    /**
+     * Gets the enabled state of this pack.
+     *
+     * @return whether the pack is currently enabled
+     */
+    boolean isEnabled();
+
+    /**
+     * Changes the enabled state of this pack. Will
+     * cause a reload of resources ({@code /minecraft:reload}) if
+     * any change happens.
+     *
+     * @param enabled true to enable, false to disable
+     * @apiNote This method may be deprecated in the future as setters on a "snapshot" type are undesirable.
+     */
+    void setEnabled(boolean enabled);
+
+    /**
+     * Gets the source for this datapack.
+     *
+     * @return the pack source
+     */
+    DatapackSource getSource();
+
+    /**
+     * Computes the component vanilla Minecraft uses
+     * to display this datapack. Includes the {@link #getSource()},
+     * {@link #getDescription()}, {@link #getName()}, and the enabled state.
+     *
+     * @return a new component
+     */
+    @Contract(pure = true, value = "-> new")
+    Component computeDisplayName();
+
+    enum Compatibility {
+        TOO_OLD,
+        TOO_NEW,
+        COMPATIBLE,
+    }
+}

paper-api/src/main/java/io/papermc/paper/datapack/DatapackManager.java

@@ -0,0 +1,43 @@
+package io.papermc.paper.datapack;
+
+import java.util.Collection;
+import org.jetbrains.annotations.Unmodifiable;
+import org.jspecify.annotations.NullMarked;
+import org.jspecify.annotations.Nullable;
+
+@NullMarked
+public interface DatapackManager {
+
+    /**
+     * Triggers a refresh of the available and selected datapacks. This
+     * can find new datapacks, remove old ones, and update the metadata for
+     * existing datapacks. Some of these changes will only take effect
+     * after the next {@link org.bukkit.Server#reloadData()} or {@code /minecraft:reload}.
+     */
+    void refreshPacks();
+
+    /**
+     * Gets a datapack by name. May require calling {@link #refreshPacks()} before
+     * to get the latest pack information.
+     *
+     * @param name the name/id of the datapack
+     * @return the datapack, or null if not found
+     */
+    @Nullable Datapack getPack(String name);
+
+    /**
+     * Gets the available datapacks. May require calling {@link #refreshPacks()} before
+     * to get the latest pack information.
+     *
+     * @return all the packs known to the server
+     */
+    @Unmodifiable Collection<Datapack> getPacks();
+
+    /**
+     * Gets the enabled datapacks. May require calling {@link #refreshPacks()} before
+     * to get the latest pack information.
+     *
+     * @return all the packs which are currently enabled
+     */
+    @Unmodifiable Collection<Datapack> getEnabledPacks();
+}

paper-api/src/main/java/io/papermc/paper/datapack/DatapackSource.java

@@ -0,0 +1,20 @@
+package io.papermc.paper.datapack;
+
+import org.jspecify.annotations.NullMarked;
+
+/**
+ * Source of a datapack.
+ */
+@NullMarked
+public sealed interface DatapackSource permits DatapackSourceImpl {
+
+    DatapackSource DEFAULT = create("default");
+    DatapackSource BUILT_IN = create("built_in");
+    DatapackSource FEATURE = create("feature");
+    DatapackSource WORLD = create("world");
+    DatapackSource SERVER = create("server");
+
+    private static DatapackSource create(final String name) {
+        return new DatapackSourceImpl(name);
+    }
+}

paper-api/src/main/java/io/papermc/paper/datapack/DatapackSourceImpl.java

@@ -0,0 +1,14 @@
+package io.papermc.paper.datapack;
+
+import org.jetbrains.annotations.ApiStatus;
+import org.jspecify.annotations.NullMarked;
+
+@ApiStatus.Internal
+@NullMarked
+record DatapackSourceImpl(String name) implements DatapackSource {
+
+    @Override
+    public String toString() {
+        return this.name;
+    }
+}