package net.minecraft.util;

import com.google.common.collect.ImmutableList;
import com.google.common.collect.Iterators;
import com.google.common.collect.Lists;
import com.google.common.collect.Maps;
import java.util.AbstractCollection;
import java.util.Collection;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;

public class ClassInstanceMultiMap<T> extends AbstractCollection<T> {
	private final Map<Class<?>, List<T>> byClass = Maps.newHashMap();
	private final Class<T> baseClass;
	private final List<T> allInstances = Lists.newArrayList();

	public ClassInstanceMultiMap(final Class<T> baseClass) {
		this.baseClass = baseClass;
		this.byClass.put(baseClass, this.allInstances);
	}

	@Override
	public boolean add(final T instance) {
		boolean success = false;

		for (Entry<Class<?>, List<T>> entry : this.byClass.entrySet()) {
			if (entry.getKey().isInstance(instance)) {
				success |= entry.getValue().add(instance);
			}
		}

		return success;
	}

	@Override
	public boolean remove(final Object object) {
		boolean success = false;

		for (Entry<Class<?>, List<T>> entry : this.byClass.entrySet()) {
			if (entry.getKey().isInstance(object)) {
				List<T> list = entry.getValue();
				success |= list.remove(object);
			}
		}

		return success;
	}

	@Override
	public boolean contains(final Object o) {
		return this.find(o.getClass()).contains(o);
	}

	public <S> Collection<S> find(final Class<S> index) {
		if (!this.baseClass.isAssignableFrom(index)) {
			throw new IllegalArgumentException("Don't know how to search for " + index);
		}

		List<? extends T> instances = this.byClass.computeIfAbsent(index, k -> this.allInstances.stream().filter(k::isInstance).collect(Util.toMutableList()));
		return (Collection<S>)Collections.unmodifiableCollection(instances);
	}

	@Override
	public Iterator<T> iterator() {
		return this.allInstances.isEmpty() ? Collections.emptyIterator() : Iterators.unmodifiableIterator(this.allInstances.iterator());
	}

	public List<T> getAllInstances() {
		return ImmutableList.copyOf(this.allInstances);
	}

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