package com.github.dexecutor.executor.graph;
   
   import java.util.ArrayList;
   import java.util.Collection;
   import java.util.HashMap;
   import java.util.LinkedHashSet;
   import java.util.Map;
   import java.util.Set;
   
  /**
   * Default implementation of Graph
   * 
   * @author Nadeem Mohammad
   *
   * @param <T>
   */
  public final class DefaultGraph<T extends Comparable<T>> implements Graph<T> {
  
  	private Map<T, Node<T>> nodes = new HashMap<T, Node<T>>();
  
  	public void addIndependent(T nodeValue) {
  		doAdd(nodeValue);
  	}
  
  	public void addDependency(final T evalFirstNode, final T evalLaterNode) {
  		Node<T> firstNode = doAdd(evalFirstNode);
  		Node<T> afterNode = doAdd(evalLaterNode);
  
  		if (!firstNode.equals(afterNode)) {
  			firstNode.addOutGoingNode(afterNode);
  			afterNode.addInComingNode(firstNode);			
  		}
  	}
  
  	private Node<T> doAdd(final T nodeValue) {
  		Node<T> graphNode = null;
  		if (nodes.containsKey(nodeValue)) {
  			graphNode = nodes.get(nodeValue);
  		} else {
  			graphNode = createNode(nodeValue);
  			nodes.put(nodeValue, graphNode);
  		}
  		return graphNode;
  	}
  
  	private Node<T> createNode(final T value) {
  		Node<T> node = new Node<T>(value);
  		return node;
  	}
  
  	public Set<Node<T>> getInitialNodes() {
  		Set<Node<T>> initialNodes = new LinkedHashSet<Node<T>>();
  		Set<T> keys = nodes.keySet();
  		for (T key : keys) {
  			Node<T> node = nodes.get(key);
  			if (node.getInComingNodes().isEmpty()) {				
  				initialNodes.add(node);
  			}
  		}
  		return initialNodes;
  	}
  
  	public int size() {
  		return nodes.size();
  	}
  
  	public Collection<Graph.Node<T>> allNodes() {
  		return new ArrayList<Graph.Node<T>>(this.nodes.values());
  	}
  
  	public Set<Graph.Node<T>> getLeafNodes() {
  		Set<Node<T>> leafNodes = new LinkedHashSet<Node<T>>();
  		Set<T> keys = nodes.keySet();
  		for (T key : keys) {
  			Node<T> node = nodes.get(key);
  			if (node.getOutGoingNodes().isEmpty()) {				
  				leafNodes.add(node);
  			}
  		}
  		return leafNodes;
  	}
  }