package net.minecraft.core;

import com.google.common.collect.Iterators;
import com.google.common.collect.Lists;
import it.unimi.dsi.fastutil.objects.Reference2IntMap;
import it.unimi.dsi.fastutil.objects.Reference2IntOpenHashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Objects;
import org.jetbrains.annotations.Nullable;

public class IdMapper<T> implements IdMap<T> {
	private int nextId;
	private final Reference2IntMap<T> tToId;
	private final List<T> idToT;

	public IdMapper() {
		this(512);
	}

	public IdMapper(int expectedSize) {
		this.idToT = Lists.<T>newArrayListWithExpectedSize(expectedSize);
		this.tToId = new Reference2IntOpenHashMap<>(expectedSize);
		this.tToId.defaultReturnValue(-1);
	}

	public void addMapping(T key, int value) {
		this.tToId.put(key, value);

		while (this.idToT.size() <= value) {
			this.idToT.add(null);
		}

		this.idToT.set(value, key);
		if (this.nextId <= value) {
			this.nextId = value + 1;
		}
	}

	public void add(T key) {
		this.addMapping(key, this.nextId);
	}

	@Override
	public int getId(T value) {
		return this.tToId.getInt(value);
	}

	@Nullable
	@Override
	public final T byId(int id) {
		return (T)(id >= 0 && id < this.idToT.size() ? this.idToT.get(id) : null);
	}

	public Iterator<T> iterator() {
		return Iterators.filter(this.idToT.iterator(), Objects::nonNull);
	}

	public boolean contains(int id) {
		return this.byId(id) != null;
	}

	@Override
	public int size() {
		return this.tToId.size();
	}
}