/*
 * Created on Oct 17, 2005
 *
 * Copyright (c) 2005, the JUNG Project and the Regents of the University 
 * of California
 * All rights reserved.
 *
 * This software is open-source under the BSD license; see either
 * "license.txt" or
 * http://jung.sourceforge.net/license.txt for a description.
 */
package edu.uci.ics.jung.graph;

import java.util.Collection;
import java.util.Collections;
import java.util.LinkedHashMap;
import java.util.LinkedHashSet;
import java.util.Set;

import org.apache.commons.collections15.Factory;

import edu.uci.ics.jung.graph.util.Pair;

/**
 * An implementation of <code>DirectedGraph</code>, suitable for sparse graphs,
 * that orders its vertex and edge collections according to insertion time.
 */
@SuppressWarnings("serial")
public class DirectedOrderedSparseMultigraph<V, E>
		extends DirectedSparseMultigraph<V, E>
		implements DirectedGraph<V, E>, MultiGraph<V, E> {
	/**
	 * Returns a {@code Factory} that creates an instance of this graph type.
	 * 
	 * @param <V>
	 *            the vertex type for the graph factory
	 * @param <E>
	 *            the edge type for the graph factory
	 */
	public static <V, E> Factory<DirectedGraph<V, E>> getFactory() {
		return new Factory<DirectedGraph<V, E>>() {
			@Override
			public DirectedGraph<V, E> create() {
				return new DirectedOrderedSparseMultigraph<V, E>();
			}
		};
	}

	/**
	 * Creates a new instance.
	 */
	public DirectedOrderedSparseMultigraph() {
		vertices = new LinkedHashMap<V, Pair<Set<E>>>();
		edges = new LinkedHashMap<E, Pair<V>>();
	}

	@Override
	public boolean addVertex(V vertex) {
		if (vertex == null) {
			throw new IllegalArgumentException("vertex may not be null");
		}
		if (!containsVertex(vertex)) {
			vertices.put(vertex, new Pair<Set<E>>(new LinkedHashSet<E>(),
					new LinkedHashSet<E>()));
			return true;
		}
		return false;
	}

	@Override
	public Collection<V> getPredecessors(V vertex) {
		if (!containsVertex(vertex)) {
			return null;
		}
		Set<V> preds = new LinkedHashSet<V>();
		for (E edge : getIncoming_internal(vertex)) {
			preds.add(this.getSource(edge));
		}

		return Collections.unmodifiableCollection(preds);
	}

	@Override
	public Collection<V> getSuccessors(V vertex) {
		if (!containsVertex(vertex)) {
			return null;
		}
		Set<V> succs = new LinkedHashSet<V>();
		for (E edge : getOutgoing_internal(vertex)) {
			succs.add(this.getDest(edge));
		}

		return Collections.unmodifiableCollection(succs);
	}

	@Override
	public Collection<V> getNeighbors(V vertex) {
		if (!containsVertex(vertex)) {
			return null;
		}
		Collection<V> neighbors = new LinkedHashSet<V>();
		for (E edge : getIncoming_internal(vertex)) {
			neighbors.add(this.getSource(edge));
		}
		for (E edge : getOutgoing_internal(vertex)) {
			neighbors.add(this.getDest(edge));
		}
		return Collections.unmodifiableCollection(neighbors);
	}

	@Override
	public Collection<E> getIncidentEdges(V vertex) {
		if (!containsVertex(vertex)) {
			return null;
		}
		Collection<E> incident = new LinkedHashSet<E>();
		incident.addAll(getIncoming_internal(vertex));
		incident.addAll(getOutgoing_internal(vertex));
		return incident;
	}

}