/**
 * Graph represented an an adjacency list. 
 * @author ggtowell
 * Created: dec 1: 2021
 */

import java.util.ArrayList;
import java.util.HashMap;

public class AdjList<G> {
    /** 
     * Nodes in the array
     */
    private class Node<H> {
        // Node content
        public H payload;
        // hold the list
        public ArrayList<Edge<G>> edges;

        public Node(H payl) {
            this.payload = payl;
            this.edges = new ArrayList<Edge<G>>();
        }

        public void addEdge(Node<G> n, double w) {
            edges.add(new Edge<G>(n, w));
        }

        public String toString() {
            StringBuffer sb = new StringBuffer();
            for (Edge<G> eg : edges) {
                sb.append(String.format("[%s->%s:%.3f]", payload, eg.too.payload,eg.weight));
            }
            return sb.toString();
        }
    }

    //Edges in the graph
    private class Edge<J> {
        Node<J> too;
        double weight;
        public Edge(Node<J> t2, double w) {
            this.too = t2;
            this.weight = w;
        }

    }
    // nodes are stored in a hashmap so they are quickly and easily found
    private HashMap<G, Node<G>> nodeHash;

    public AdjList() {
        nodeHash = new HashMap<G, Node<G>>();
    }

    @Override
    public String toString() {
        StringBuffer sb = new StringBuffer();
        for (Node<G> gn : nodeHash.values()) {
            sb.append(gn.toString());
        }
        return sb.toString();
    }

    public static void main(String[] args) {
        AdjList<String> adjl = new AdjList<>();
        adjl.addNode("A");
        adjl.addNode("B");
        adjl.addNode("C");
        adjl.addNode("D");
        adjl.addEdge("A", "B");
        adjl.addEdge("A", "D");
        adjl.addEdge("B", "D");
        adjl.addEdge("C", "D");
        adjl.addEdge("C", "B");
        adjl.addEdge("C", "A");
        adjl.addEdge("D", "B");
        System.out.println(adjl);

        AdjList<Integer> adji = new AdjList<>();
        adji.addNode(1);
        adji.addNode(2);
        adji.addEdge(1, 2);
        adji.addEdge(1, 1);
        System.out.println(adji);
    }
    
    /**
     *  Add a node to the Graph
    * Note that initially the node my be unconnected
    * @param g == the payload of the node
    **/
    public void addNode(G g) {
        nodeHash.put(g, new Node<G>(g));
    }

    /**
     * Add an edge with a weight of 1
     * @param fr the payload of the node from
     * @param t2 the payload of the node too
     */
    public void addEdge(G fr, G t2) {
        addEdge(fr, t2, 1.0);
    }
    
    /**
     * Add an edge with a weight
     * @param fr the payload of the node from
     * @param t2 the payload of the node too
     * @param w the weight of the edge
     */
    public void addEdge(G fr, G t2, double w) {
        Node<G> frn = nodeHash.get(fr);
        Node<G> t2n = nodeHash.get(t2);
        if (frn == null || t2n == null)
            return;
        frn.addEdge(t2n, w);
    }
    
    
}