package hw4;

import java.util.Iterator;

/**
 * Graph represents a mutable, directed, labeled multi-graph. Graphs are a
 * collection of nodes and edges, each labeled by a String
 *
 * Nodes are uniquely defined by their label, no two nodes have the same label
 * Edges are directed and are not unique (two edges may be identical)
 */
public class Graph {
    // private T adjList;

    // Abstraction function:
    // Representation invariant:

    /**
     * @effects Constructs a new, empty Graph (no nodes and no edges)
     */
    public Graph() {
        throw new RuntimeException("Graph constructor is not yet implemented");
    }

    /**
     * @param label The String representing the node to be added
     * @modifies this
     * @effects Adds a node represented by the String label to the graph. If
     *          node already exists in the graph, does nothing
     */
    public void addNode(String label) {
        throw new RuntimeException("Graph.addNode() is not yet implemented");
    }

    /**
     * @param parent The node from which the added edge starts from
     * @param child The node to which the added edge goes
     * @param label The String which the new edge will be labeled with
     * @modifies this
     * @effects Adds an edge from parent to child labeled label. If
     *          either parent or child does not exist, does nothing.
     */
    public void addEdge(String parent, String child, String label) {
        throw new RuntimeException("Graph.addEdge() is not yet implemented");
    }

    /**
     * @return Iterator which returns all the nodes in lexicographical order.
     */
    public Iterator<String> listNodes() {
        throw new RuntimeException("Graph.listNodes() is not yet implemented");
    }

    /**
     * @param parent The node whose children are to be found
     * @return Iterator which returns a list of childNode(edgeLabel) in lexicographic
     *          order by node name and secondarily by edge label.
     */
    public Iterator<String> listChildren(String parent) {
        throw new RuntimeException("Graph.listChildren() is not yet implemented");
    }
}