package net.minecraft.resources;

import com.google.common.collect.MapMaker;
import com.mojang.serialization.Codec;
import io.netty.buffer.ByteBuf;
import java.util.Optional;
import java.util.concurrent.ConcurrentMap;
import net.minecraft.core.Registry;
import net.minecraft.core.registries.Registries;
import net.minecraft.network.codec.StreamCodec;

/**
 * An immutable key for a resource, in terms of the name of its parent registry and its location in that registry.
 * <p>
 * {@link net.minecraft.core.Registry} uses this to return resource keys for registry objects via {@link net.minecraft.core.Registry#getResourceKey(Object)}. It also uses this class to store its name, with the parent registry name set to {@code minecraft:root}. When used in this way it is usually referred to as a "registry key".</p>
 * <p>
 * @param <T> The type of the resource represented by this {@code ResourceKey}, or the type of the registry if it is a registry key.
 * @see net.minecraft.resources.ResourceLocation
 */
public class ResourceKey<T> {
	private static final ConcurrentMap<ResourceKey.InternKey, ResourceKey<?>> VALUES = new MapMaker().weakValues().makeMap();
	/**
	 * The name of the parent registry of the resource.
	 */
	private final ResourceLocation registryName;
	/**
	 * The location of the resource within the registry.
	 */
	private final ResourceLocation location;

	public static <T> Codec<ResourceKey<T>> codec(ResourceKey<? extends Registry<T>> registryKey) {
		return ResourceLocation.CODEC.xmap(resourceLocation -> create(registryKey, resourceLocation), ResourceKey::location);
	}

	public static <T> StreamCodec<ByteBuf, ResourceKey<T>> streamCodec(ResourceKey<? extends Registry<T>> registryKey) {
		return ResourceLocation.STREAM_CODEC.map(resourceLocation -> create(registryKey, resourceLocation), ResourceKey::location);
	}

	/**
	 * Constructs a new {@code ResourceKey} for a resource with the specified {@code location} within the registry specified by the given {@code registryKey}.
	 * 
	 * @return the created resource key. The registry name is set to the location of the specified {@code registryKey} and with the specified {@code location} as the location of the resource.
	 */
	public static <T> ResourceKey<T> create(ResourceKey<? extends Registry<T>> registryKey, ResourceLocation location) {
		return create(registryKey.location, location);
	}

	/**
	 * @return the created registry key. The registry name is set to {@code minecraft:root} and the location the specified {@code registryName}.
	 */
	public static <T> ResourceKey<Registry<T>> createRegistryKey(ResourceLocation location) {
		return create(Registries.ROOT_REGISTRY_NAME, location);
	}

	private static <T> ResourceKey<T> create(ResourceLocation registryName, ResourceLocation location) {
		return (ResourceKey<T>)VALUES.computeIfAbsent(
			new ResourceKey.InternKey(registryName, location), internKey -> new ResourceKey(internKey.registry, internKey.location)
		);
	}

	private ResourceKey(ResourceLocation registryName, ResourceLocation location) {
		this.registryName = registryName;
		this.location = location;
	}

	public String toString() {
		return "ResourceKey[" + this.registryName + " / " + this.location + "]";
	}

	/**
	 * @return {@code true} if this resource key is a direct child of the specified {@code registryKey}.
	 */
	public boolean isFor(ResourceKey<? extends Registry<?>> registryKey) {
		return this.registryName.equals(registryKey.location());
	}

	public <E> Optional<ResourceKey<E>> cast(ResourceKey<? extends Registry<E>> registryKey) {
		return this.isFor(registryKey) ? Optional.of(this) : Optional.empty();
	}

	public ResourceLocation location() {
		return this.location;
	}

	public ResourceLocation registry() {
		return this.registryName;
	}

	public ResourceKey<Registry<T>> registryKey() {
		return createRegistryKey(this.registryName);
	}

	record InternKey(ResourceLocation registry, ResourceLocation location) {
	}
}