/**
 * CSE 373, Spring 2011, Jessica Miller
 * A basic graph interface.
 */

import java.util.*;

public interface IGraph<V> {
	/**
	 * Adds a vertex to the graph.
	 * @param v Vertex to add to the graph
	 * @throws IllegalArgumentException if vertex passed is null
	 */
    public void addVertex(V v);
    
	/**
	 * Adds an edge to the graph 
	 * @param v1 source vertex
	 * @param v2 destination vertex
	 * @param weight the weight of the edge
	 * @throws IllegalArgumentException if either vertex passed is null
	 */
    public void addEdge(V v1, V v2, int weight);
    
	/**
	 * Returns whether or not an edge exists between the two vertices.
	 * @param v1 source vertex
	 * @param v2 destination vertex
	 * @return whether or not an edge exists between the two vertices
	 * @throws IllegalArgumentException if either vertex passed is null 
	 * 			or either vertex is not found in the graph 
	 */    
    public boolean hasEdge(V v1, V v2);
    
	/**
	 * Returns the edge between the two vertices.
	 * @param v1 source vertex
	 * @param v2 destination vertex
	 * @return the edge between the two vertices or null if there is no edge
	 * 			between them
	 * @throws IllegalArgumentException if either vertex passed is null 
	 * 			or either vertex is not found in the graph 
	 */      
    public Edge<V> getEdge(V v1, V v2);
    
    public boolean hasPath(V v1, V v2);

    /**
     * Returns a path between the two vertices if one exists.
     * Uses depth-first search algorithm to find the path.
     * @param v1 the source vertex
     * @param v2 the destination vertex
     * @return a path between the two vertices; null if a path does not exist
	 * @throws IllegalArgumentException if either vertex passed is null 
	 * 			or either vertex is not found in the graph 
     */
    public List<V> getDFSPath(V v1, V v2);
    
    public String toString();
}