public class A3Program {
    /*
     *  this program reads in pairs of nodes on separate lines
     *  and creates a directed graph where the pair of nodes are the
     *  edges and all nodes have some edge
     */


    public void start() {
		Graph graph = inputGraph();
		dotifyGraph(graph);
    }

    private void dotifyGraph(Graph graph) {
		NodeSet nodes = graph.getNodeSet();
		EdgeSet edges = graph.getEdgeSet();
		EdgeSet outgoingEdges;

		System.out.println("digraph G {");

		for (int i = 0; i < nodes.length(); i++) {
		    outgoingEdges = graph.getOutgoingEdges(nodes.getNode(i));
		    System.out.print(outgoingEdges.toString());
		}

       	System.out.println("}");
		System.out.println("# nodes = " + nodes.length());
		System.out.println("# edges = " + edges.length());
    }

    private Graph inputGraph() {
		Graph graph = new Graph();

		for (Edge edge = inputEdge(); edge != null; edge = inputEdge()) {
			graph.addEdge(edge);
		}
		return graph;
    }

    private Edge inputEdge() {
		Node source;
		Node target;
		Edge edge;
		source = inputNode();
		if (source == null) {
			return null;   // no more edges
		}
		target = inputNode();
		if (target == null) {    // error: odd number of nodes
			System.out.println("Error: odd number of nodes");
			System.out.println("Error: last node was: "
					   + source.toString());
			return null;
		}
		return new Edge(source, target);
    }

    private Node inputNode() {
		String id;
		String input = Keyboard.readInput();
		while (input != null) {
			id = input.trim();
			if  (id != null && id.length() > 0) {
				return(new Node(id));
			}
			input = Keyboard.readInput();
		}
		return null;
    }

}