package algs64;
import  stdlib.*;

/* ***********************************************************************
 *  Compilation:  javac FlowEdge.java
 *  Execution:    java FlowEdge
 *
 *  Capacitated edge with a flow in a flow network.
 *
 *************************************************************************/

/**
 *  The {@code FlowEdge} class represents a capacitated edge with a flow
 *  in a digraph.
 *  <p>
 *  For additional documentation, see <a href="/algs4/74or">Section 7.4</a> of
 *  <i>Algorithms, 4th Edition</i> by Robert Sedgewick and Kevin Wayne.
 */


public class FlowEdge {
	private final int v;             // from
	private final int w;             // to
	private final double capacity;   // capacity
	private double flow;             // flow

	public FlowEdge(int v, int w, double capacity) {
		if (capacity < 0) throw new IllegalArgumentException("Negative edge capacity");
		this.v         = v;
		this.w         = w;
		this.capacity  = capacity;
		this.flow      = 0;
	}

	public FlowEdge(int v, int w, double capacity, double flow) {
		if (capacity < 0) throw new IllegalArgumentException("Negative edge capacity");
		this.v         = v;
		this.w         = w;
		this.capacity  = capacity;
		this.flow      = flow;
	}

	// copy constructor
	public FlowEdge(FlowEdge e) {
		this.v         = e.v;
		this.w         = e.w;
		this.capacity  = e.capacity;
		this.flow      = e.flow;
	}

	// accessor methods
	public int from()         { return v;        }
	public int to()           { return w;        }
	public double capacity()  { return capacity; }
	public double flow()      { return flow;     }


	public int other(int vertex) {
		if      (vertex == v) return w;
		else if (vertex == w) return v;
		else throw new IllegalArgumentException("Illegal endpoint");
	}

	public double residualCapacityTo(int vertex) {
		if      (vertex == v) return flow;              // backward edge
		else if (vertex == w) return capacity - flow;   // forward edge
		else throw new IllegalArgumentException("Illegal endpoint");
	}

	public void addResidualFlowTo(int vertex, double delta) {
		if      (vertex == v) flow -= delta;           // backward edge
		else if (vertex == w) flow += delta;           // forward edge
		else throw new IllegalArgumentException("Illegal endpoint");
	}


	public String toString() {
		return v + "->" + w + " " + flow + "/" + capacity;
	}


	/**
	 * Test client.
	 */
	public static void main(String[] args) {
		FlowEdge e = new FlowEdge(12, 23, 3.14);
		StdOut.println(e);
	}

}