package bjc.utils.graph;

/**
 * An edge in a weighted graph
 *
 * @author ben
 *
 * @param <T>
 *                The type of the nodes in the graph
 */
public class Edge<T> {
	/*
	 * The distance from initial to terminal node
	 */
	private final int distance;

	/*
	 * The initial and terminal nodes of this edge
	 */
	private final T source, target;

	/**
	 * Create a new edge with set parameters
	 *
	 * @param initial
	 *                The initial node of the edge
	 * @param terminal
	 *                The terminal node of the edge
	 * @param distance
	 *                The distance between initial and terminal edge
	 */
	public Edge(T initial, T terminal, int distance) {
		if(initial == null)
			throw new NullPointerException("Initial node must not be null");
		else if(terminal == null) throw new NullPointerException("Terminal node must not be null");

		this.source = initial;
		this.target = terminal;
		this.distance = distance;
	}

	@Override
	public boolean equals(Object obj) {
		if(this == obj)
			return true;
		else if(obj == null)
			return false;
		else if(getClass() != obj.getClass())
			return false;
		else {
			Edge<?> other = (Edge<?>) obj;

			if(distance != other.distance)
				return false;
			else if(source == null) {
				if(other.source != null) return false;
			} else if(!source.equals(other.source))
				return false;
			else if(target == null) {
				if(other.target != null) return false;
			} else if(!target.equals(other.target)) return false;

			return true;
		}
	}

	/**
	 * Get the distance in this edge
	 *
	 * @return The distance between the initial and terminal nodes of this
	 *         edge
	 */
	public int getDistance() {
		return distance;
	}

	/**
	 * Get the initial node of an edge
	 *
	 * @return The initial node of this edge
	 */
	public T getSource() {
		return source;
	}

	/**
	 * Get the target node of an edge
	 *
	 * @return The target node of this edge
	 */
	public T getTarget() {
		return target;
	}

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

		int result = 1;

		result = prime * result + distance;
		result = prime * result + (source == null ? 0 : source.hashCode());
		result = prime * result + (target == null ? 0 : target.hashCode());

		return result;
	}

	@Override
	public String toString() {
		return " first vertex " + source + " to vertex " + target + " with distance: " + distance;
	}
}