package bjc.utils.esodata;

import java.util.function.BiConsumer;
import java.util.function.Consumer;
import java.util.function.Function;

import bjc.utils.funcdata.FunctionalMap;
import bjc.utils.funcdata.IList;
import bjc.utils.funcdata.IMap;

/**
 * A variant of a map where inserting a duplicate key shadows the existing value
 * instead of replacing it.
 *
 * @author EVE
 *
 * @param <KeyType>
 *                The key of the map.
 * @param <ValueType>
 *                The values in the map.
 */
public class PushdownMap<KeyType, ValueType> implements IMap<KeyType, ValueType> {
	private final IMap<KeyType, Stack<ValueType>> backing;

	/**
	 * Create a new empty stack-based map.
	 */
	public PushdownMap() {
		backing = new FunctionalMap<>();
	}

	private PushdownMap(final IMap<KeyType, Stack<ValueType>> back) {
		backing = back;
	}

	@Override
	public void clear() {
		backing.clear();
	}

	@Override
	public boolean containsKey(final KeyType key) {
		return backing.containsKey(key);
	}

	@Override
	public IMap<KeyType, ValueType> extend() {
		return new PushdownMap<>(backing.extend());
	}

	@Override
	public void forEach(final BiConsumer<KeyType, ValueType> action) {
		backing.forEach((key, stk) -> action.accept(key, stk.top()));
	}

	@Override
	public void forEachKey(final Consumer<KeyType> action) {
		backing.forEachKey(action);
	}

	@Override
	public void forEachValue(final Consumer<ValueType> action) {
		backing.forEachValue(stk -> action.accept(stk.top()));
	}

	@Override
	public ValueType get(final KeyType key) {
		return backing.get(key).top();
	}

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

	@Override
	public IList<KeyType> keyList() {
		return backing.keyList();
	}

	@Override
	public <V2> IMap<KeyType, V2> transform(final Function<ValueType, V2> transformer) {
		throw new UnsupportedOperationException("Cannot transform pushdown maps.");
	}

	@Override
	public ValueType put(final KeyType key, final ValueType val) {
		if (backing.containsKey(key)) {
			final Stack<ValueType> stk = backing.get(key);

			final ValueType vl = stk.top();

			stk.push(val);

			return vl;
		} else {
			final Stack<ValueType> stk = new SimpleStack<>();

			stk.push(val);

			return null;
		}
	}

	@Override
	public ValueType remove(final KeyType key) {
		final Stack<ValueType> stk = backing.get(key);

		if (stk.size() > 1)
			return stk.pop();
		else return backing.remove(key).top();
	}

	@Override
	public IList<ValueType> valueList() {
		return backing.valueList().map(stk -> stk.top());
	}

	@Override
	public int hashCode() {
		final int prime = 31;

		int result = 1;
		result = prime * result + (backing == null ? 0 : backing.hashCode());

		return result;
	}

	@Override
	public boolean equals(final Object obj) {
		if (this == obj) return true;
		if (obj == null) return false;
		if (!(obj instanceof PushdownMap<?, ?>)) return false;

		final PushdownMap<?, ?> other = (PushdownMap<?, ?>) obj;

		if (backing == null) {
			if (other.backing != null) return false;
		} else if (!backing.equals(other.backing)) return false;

		return true;
	}

	@Override
	public String toString() {
		return String.format("PushdownMap [backing=%s]", backing);
	}
}