minecraft-src/net/minecraft/world/level/storage/loot/LootContext.java

package net.minecraft.world.level.storage.loot;

import com.google.common.collect.Sets;
import java.util.Optional;
import java.util.Set;
import java.util.function.Consumer;
import net.minecraft.core.HolderGetter;
import net.minecraft.resources.ResourceLocation;
import net.minecraft.server.MinecraftServer;
import net.minecraft.server.level.ServerLevel;
import net.minecraft.util.RandomSource;
import net.minecraft.util.StringRepresentable;
import net.minecraft.util.context.ContextKey;
import net.minecraft.world.entity.Entity;
import net.minecraft.world.item.ItemStack;
import net.minecraft.world.level.storage.loot.functions.LootItemFunction;
import net.minecraft.world.level.storage.loot.parameters.LootContextParams;
import net.minecraft.world.level.storage.loot.predicates.LootItemCondition;
import org.jetbrains.annotations.Nullable;

/**
 * LootContext stores various context information for loot generation.
 * This includes the Level as well as any known {@link LootContextParam}s.
 */
public class LootContext {
	private final LootParams params;
	private final RandomSource random;
	private final HolderGetter.Provider lootDataResolver;
	private final Set<LootContext.VisitedEntry<?>> visitedElements = Sets.<LootContext.VisitedEntry<?>>newLinkedHashSet();

	LootContext(LootParams params, RandomSource random, HolderGetter.Provider lootDataResolver) {
		this.params = params;
		this.random = random;
		this.lootDataResolver = lootDataResolver;
	}

	public boolean hasParameter(ContextKey<?> parameter) {
		return this.params.contextMap().has(parameter);
	}

	public <T> T getParameter(ContextKey<T> parameter) {
		return this.params.contextMap().getOrThrow(parameter);
	}

	@Nullable
	public <T> T getOptionalParameter(ContextKey<T> parameter) {
		return this.params.contextMap().getOptional(parameter);
	}

	/**
	 * Add the dynamic drops for the given dynamic drops name to the given consumer.
	 * If no dynamic drops provider for the given name has been registered to this LootContext, nothing is generated.
	 * 
	 * @see DynamicDrops
	 */
	public void addDynamicDrops(ResourceLocation name, Consumer<ItemStack> consumer) {
		this.params.addDynamicDrops(name, consumer);
	}

	public boolean hasVisitedElement(LootContext.VisitedEntry<?> element) {
		return this.visitedElements.contains(element);
	}

	public boolean pushVisitedElement(LootContext.VisitedEntry<?> element) {
		return this.visitedElements.add(element);
	}

	public void popVisitedElement(LootContext.VisitedEntry<?> element) {
		this.visitedElements.remove(element);
	}

	public HolderGetter.Provider getResolver() {
		return this.lootDataResolver;
	}

	public RandomSource getRandom() {
		return this.random;
	}

	/**
	 * The luck value for this loot context. This is usually just the player's {@linkplain Attributes#LUCK luck value}, however it may be modified depending on the context of the looting.
	 * When fishing for example it is increased based on the Luck of the Sea enchantment.
	 */
	public float getLuck() {
		return this.params.getLuck();
	}

	public ServerLevel getLevel() {
		return this.params.getLevel();
	}

	public static LootContext.VisitedEntry<LootTable> createVisitedEntry(LootTable lootTable) {
		return new LootContext.VisitedEntry<>(LootDataType.TABLE, lootTable);
	}

	public static LootContext.VisitedEntry<LootItemCondition> createVisitedEntry(LootItemCondition predicate) {
		return new LootContext.VisitedEntry<>(LootDataType.PREDICATE, predicate);
	}

	public static LootContext.VisitedEntry<LootItemFunction> createVisitedEntry(LootItemFunction modifier) {
		return new LootContext.VisitedEntry<>(LootDataType.MODIFIER, modifier);
	}

	public static class Builder {
		private final LootParams params;
		@Nullable
		private RandomSource random;

		public Builder(LootParams params) {
			this.params = params;
		}

		public LootContext.Builder withOptionalRandomSeed(long seed) {
			if (seed != 0L) {
				this.random = RandomSource.create(seed);
			}

			return this;
		}

		public LootContext.Builder withOptionalRandomSource(RandomSource random) {
			this.random = random;
			return this;
		}

		public ServerLevel getLevel() {
			return this.params.getLevel();
		}

		public LootContext create(Optional<ResourceLocation> sequence) {
			ServerLevel serverLevel = this.getLevel();
			MinecraftServer minecraftServer = serverLevel.getServer();
			RandomSource randomSource = (RandomSource)Optional.ofNullable(this.random)
				.or(() -> sequence.map(serverLevel::getRandomSequence))
				.orElseGet(serverLevel::getRandom);
			return new LootContext(this.params, randomSource, minecraftServer.reloadableRegistries().lookup());
		}
	}

	/**
	 * Represents a type of entity that can be looked up in a {@link LootContext} using a {@link LootContextParam}.
	 */
	public static enum EntityTarget implements StringRepresentable {
		/**
		 * Looks up {@link LootContextParams#THIS_ENTITY}.
		 */
		THIS("this", LootContextParams.THIS_ENTITY),
		ATTACKER("attacker", LootContextParams.ATTACKING_ENTITY),
		DIRECT_ATTACKER("direct_attacker", LootContextParams.DIRECT_ATTACKING_ENTITY),
		ATTACKING_PLAYER("attacking_player", LootContextParams.LAST_DAMAGE_PLAYER);

		public static final StringRepresentable.EnumCodec<LootContext.EntityTarget> CODEC = StringRepresentable.fromEnum(LootContext.EntityTarget::values);
		private final String name;
		private final ContextKey<? extends Entity> param;

		private EntityTarget(final String name, final ContextKey<? extends Entity> param) {
			this.name = name;
			this.param = param;
		}

		public ContextKey<? extends Entity> getParam() {
			return this.param;
		}

		public static LootContext.EntityTarget getByName(String name) {
			LootContext.EntityTarget entityTarget = (LootContext.EntityTarget)CODEC.byName(name);
			if (entityTarget != null) {
				return entityTarget;
			} else {
				throw new IllegalArgumentException("Invalid entity target " + name);
			}
		}

		@Override
		public String getSerializedName() {
			return this.name;
		}
	}

	public record VisitedEntry<T>(LootDataType<T> type, T value) {
	}
}