Add basic Datapack API

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

paper-server/src/main/java/io/papermc/paper/datapack/PaperDatapack.java

@@ -0,0 +1,103 @@
+package io.papermc.paper.datapack;
+
+import io.papermc.paper.adventure.PaperAdventure;
+import io.papermc.paper.event.server.ServerResourcesReloadedEvent;
+import io.papermc.paper.world.flag.PaperFeatureFlagProviderImpl;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+import java.util.concurrent.ConcurrentHashMap;
+import net.kyori.adventure.text.Component;
+import net.minecraft.server.MinecraftServer;
+import net.minecraft.server.packs.repository.Pack;
+import net.minecraft.server.packs.repository.PackSource;
+import org.bukkit.FeatureFlag;
+import org.checkerframework.checker.nullness.qual.NonNull;
+import org.checkerframework.checker.nullness.qual.Nullable;
+import org.checkerframework.framework.qual.DefaultQualifier;
+
+@DefaultQualifier(NonNull.class)
+public class PaperDatapack implements Datapack {
+
+    private static final Map<PackSource, DatapackSource> PACK_SOURCES = new ConcurrentHashMap<>();
+    static {
+        PACK_SOURCES.put(PackSource.DEFAULT, DatapackSource.DEFAULT);
+        PACK_SOURCES.put(PackSource.BUILT_IN, DatapackSource.BUILT_IN);
+        PACK_SOURCES.put(PackSource.FEATURE, DatapackSource.FEATURE);
+        PACK_SOURCES.put(PackSource.WORLD, DatapackSource.WORLD);
+        PACK_SOURCES.put(PackSource.SERVER, DatapackSource.SERVER);
+    }
+
+    private final Pack pack;
+    private final boolean enabled;
+
+    PaperDatapack(final Pack pack, final boolean enabled) {
+        this.pack = pack;
+        this.enabled = enabled;
+    }
+
+    @Override
+    public String getName() {
+        return this.pack.getId();
+    }
+
+    @Override
+    public Component getTitle() {
+        return PaperAdventure.asAdventure(this.pack.getTitle());
+    }
+
+    @Override
+    public Component getDescription() {
+        return PaperAdventure.asAdventure(this.pack.getDescription());
+    }
+
+    @Override
+    public boolean isRequired() {
+        return this.pack.isRequired();
+    }
+
+    @Override
+    public Compatibility getCompatibility() {
+        return Datapack.Compatibility.valueOf(this.pack.getCompatibility().name());
+    }
+
+    @Override
+    public Set<FeatureFlag> getRequiredFeatures() {
+        return PaperFeatureFlagProviderImpl.fromNms(this.pack.getRequestedFeatures());
+    }
+
+    @Override
+    public boolean isEnabled() {
+        return this.enabled;
+    }
+
+    @Override
+    public void setEnabled(final boolean enabled) {
+        final MinecraftServer server = MinecraftServer.getServer();
+        final List<Pack> enabledPacks = new ArrayList<>(server.getPackRepository().getSelectedPacks());
+        final @Nullable Pack packToChange = server.getPackRepository().getPack(this.getName());
+        if (packToChange == null) {
+            throw new IllegalStateException("Cannot toggle state of pack that doesn't exist: " + this.getName());
+        }
+        if (enabled == enabledPacks.contains(packToChange)) {
+            return;
+        }
+        if (enabled) {
+            packToChange.getDefaultPosition().insert(enabledPacks, packToChange, Pack::selectionConfig, false); // modeled off the default /datapack enable logic
+        } else {
+            enabledPacks.remove(packToChange);
+        }
+        server.reloadResources(enabledPacks.stream().map(Pack::getId).toList(), ServerResourcesReloadedEvent.Cause.PLUGIN);
+    }
+
+    @Override
+    public DatapackSource getSource() {
+        return PACK_SOURCES.computeIfAbsent(this.pack.location().source(), source -> new DatapackSourceImpl(source.toString()));
+    }
+
+    @Override
+    public Component computeDisplayName() {
+        return PaperAdventure.asAdventure(this.pack.getChatLink(this.enabled));
+    }
+}