package it.univr.di.cstnu.util;

import it.unimi.dsi.fastutil.objects.*;
import it.univr.di.cstnu.graph.LabeledNode;
import it.univr.di.labeledvalue.Constants;

import javax.annotation.Nonnull;

/**
 * Implementation based on two nested hash maps.
 */
public class GraphDistancesImpl implements GraphDistances {

	/**
	 * Maintains the distances from a node to each reachable node.
	 */
	private final Object2ObjectMap<LabeledNode, Object2IntMap<LabeledNode>> distancesMatrix;

	/**
	 * Default constructor
	 */
	public GraphDistancesImpl() {
		distancesMatrix = new Object2ObjectOpenHashMap<>();
	}

	/**
	 *
	 */
	@Override
	public int getDistance(@Nonnull LabeledNode source, @Nonnull LabeledNode destination) {
		final Object2IntMap<LabeledNode> subMap = distancesMatrix.get(source);
		if (subMap == null) {
			return Constants.INT_POS_INFINITE;
		}
		return subMap.getInt(destination);
	}

	/**
	 *
	 */
	@Override
	public ObjectSet<LabeledNode> getNodes() {
		ObjectSet<LabeledNode> list = new ObjectArraySet<>();
		if (distancesMatrix.size() > 0) {
			list = distancesMatrix.keySet();
		}
		return list;
	}

	/**
	 *
	 */
	@Override
	public Object2IntMap<LabeledNode> getReachable(@Nonnull LabeledNode node) {
		final Object2IntMap<LabeledNode> subMap = distancesMatrix.get(node);
		if (subMap == null) {
			return new Object2IntOpenHashMap<>();
		}
		return subMap;
	}

	/**
	 *
	 */
	@Override
	public void putDistance(@Nonnull LabeledNode source, @Nonnull LabeledNode destination, int distance) {
		Object2IntMap<LabeledNode> subMap = distancesMatrix.get(source);
		if (subMap == null) {
			subMap = new Object2IntOpenHashMap<>();
			subMap.defaultReturnValue(Constants.INT_POS_INFINITE);
			distancesMatrix.put(source, subMap);
		}
		subMap.put(destination, distance);
	}

	/**
	 *
	 */
	@Override
	public void putDistances(@Nonnull LabeledNode source, @Nonnull Object2IntMap<LabeledNode> destinations) {
		destinations.defaultReturnValue(Constants.INT_POS_INFINITE);
		distancesMatrix.put(source, destinations);
	}

	/**
	 *
	 */
	@Override
	public void removeDistance(@Nonnull LabeledNode source, @Nonnull LabeledNode destination) {
		final Object2IntMap<LabeledNode> subMap = distancesMatrix.get(source);
		if (subMap == null) {
			return;
		}
		subMap.removeInt(destination);
	}

	/*
	 * @return a string representation ordered by the node's natural order.
	 */

	@Override
	public String toString() {
		final Object2ObjectSortedMap<LabeledNode, Object2IntMap<LabeledNode>> orderedMap = new Object2ObjectAVLTreeMap<>(distancesMatrix);
		final StringBuilder sb = new StringBuilder(80);
		sb.append("{").append("\n");
		for (final LabeledNode node : orderedMap.keySet()) {
			final Object2IntSortedMap<LabeledNode> subMap = new Object2IntAVLTreeMap<>(orderedMap.get(node));
			sb.append(node).append(" -> ").append(subMap).append("\n");
		}
		sb.append("}");
		return sb.toString();
	}
}