/**
 * CSE 373, Spring 2012
 * A class for a directed graph.  
 * Implemented by an adjacency list representation of a graph.
 */
import java.util.*;

public class Graph<V> implements IGraph<V> {
	private Map<V, List<Edge<V>>> adjacencyList;  // [vertices] -> [edge]
	private Map<V, VertexInfo<V>> vertexInfo;

	public Graph() {
		adjacencyList = new HashMap<V, List<Edge<V>>>();
		vertexInfo = new HashMap<V, VertexInfo<V>>();
	}

	public void addVertex(V v) {
		checkForNull(v);

		adjacencyList.put(v, new ArrayList<Edge<V>>());
		vertexInfo.put(v, new VertexInfo<V>(v));
	}

	public void addEdge(V from, V to, int weight) {
		checkVertices(from, to);

		Edge<V> edge = new Edge<V>(from, to, weight);
		adjacencyList.get(from).add(edge);
	}

	public boolean hasEdge(V from, V to) {
		return getEdge(from, to) != null;
	}

	public Edge<V> getEdge(V from, V to) {
		checkVertices(from, to);

		List<Edge<V>> edges = adjacencyList.get(from);

		for (Edge<V> e : edges) {
			if (e.to.equals(to)) {
				return e;
			}
		}

		return null;
	}

	public boolean hasPath(V v1, V v2) {
		return !getDFSPath(v1, v2).isEmpty();
	}

	public List<V> getDFSPath(V v1, V v2) { 
		checkVertices(v1, v2);

		clearVisited();

		List<V> path = new ArrayList<V>();
		return getDFSPath(v1, v2, path);
	}

	private void clearVisited() {
		for (VertexInfo info : vertexInfo.values()) {
			info.clear();
		}
	}

	private List<V> getDFSPath(V v1, V v2, List<V> path) {
		path.add(v1);
		vertexInfo.get(v1).visited = true;

		if (v1.equals(v2)) {
			return path;
		}

		List<Edge<V>> edges = adjacencyList.get(v1);
		for (Edge<V> e : edges) {
			if (vertexInfo.get(e.to).visited) {
				continue;
			}

			if (getDFSPath(e.to, v2, path) != null) {
				return path;
			}
		}

		path.remove(path.size() - 1);

		return null;
	}

	public String toString() {
		Set<V> keys = adjacencyList.keySet();
		String str = "";

		for (V v : keys) {
			str += v + ": ";

			List<Edge<V>> edgeList = adjacencyList.get(v);

			for (Edge<V> edge : edgeList) {
				str += edge + "  ";
			}
			str += "\n";
		}
		return str;
	}    

	private void checkForNull(Object arg) {
		if (arg == null) {
			throw new NullPointerException("Argument must not be null");
		}
	}

	private void checkVertices(V v1, V v2) {
		checkForNull(v1);
		checkForNull(v2);
		if (!adjacencyList.containsKey(v1)) {
			throw new IllegalArgumentException("Vertex not found in graph: " + v1);
		}
		if (!adjacencyList.containsKey(v2)) {
			throw new IllegalArgumentException("Vertex not found in graph: " + v2);
		}        
	} 
}