/*
    * Created on Oct 18, 2005
    *
    * Copyright (c) 2005, the JUNG Project and the Regents of the University 
    * of California
    * All rights reserved.
    *
    * This software is open-source under the BSD license; see either
    * "license.txt" or
   * http://jung.sourceforge.net/license.txt for a description.
   */
  package edu.uci.ics.jung.graph;
  
  import java.util.Collection;
  import java.util.Collections;
  import java.util.HashMap;
  import java.util.HashSet;
  import java.util.Map;
  import java.util.Set;
  
  import org.apache.commons.collections15.Factory;
  
  import edu.uci.ics.jung.graph.util.EdgeType;
  import edu.uci.ics.jung.graph.util.Pair;
  
  /**
   * An implementation of <code>Graph</code> that is suitable for sparse graphs
   * and permits directed, undirected, and parallel edges.
   */
  @SuppressWarnings("serial")
  public class SparseMultigraph<V,E> 
      extends AbstractGraph<V,E>
      implements MultiGraph<V,E> {
  	
      /**
       * Returns a {@code Factory} that creates an instance of this graph type.
       * @param <V> the vertex type for the graph factory
       * @param <E> the edge type for the graph factory
       */
  	public static <V,E> Factory<Graph<V,E>> getFactory() { 
  		return new Factory<Graph<V,E>> () {
  			public Graph<V,E> create() {
  				return new SparseMultigraph<V,E>();
  			}
  		};
  	}
      
      // TODO: refactor internal representation: right now directed edges each have two references (in vertices and directedEdges)
      // and undirected also have two (incoming and outgoing).  
      protected Map<V, Pair<Set<E>>> vertices; // Map of vertices to Pair of adjacency sets {incoming, outgoing}
      protected Map<E, Pair<V>> edges;            // Map of edges to incident vertex pairs
      protected Set<E> directedEdges;
  
      /**
       * Creates a new instance.
       */
      public SparseMultigraph()
      {
          vertices = new HashMap<V, Pair<Set<E>>>();
          edges = new HashMap<E, Pair<V>>();
          directedEdges = new HashSet<E>();
      }
  
      public Collection<E> getEdges()
      {
          return Collections.unmodifiableCollection(edges.keySet());
      }
  
      public Collection<V> getVertices()
      {
          return Collections.unmodifiableCollection(vertices.keySet());
      }
      
      public boolean containsVertex(V vertex) {
      	return vertices.keySet().contains(vertex);
      }
      
      public boolean containsEdge(E edge) {
      	return edges.keySet().contains(edge);
      }
  
      protected Collection<E> getIncoming_internal(V vertex)
      {
          return vertices.get(vertex).getFirst();
      }
      
      protected Collection<E> getOutgoing_internal(V vertex)
      {
          return vertices.get(vertex).getSecond();
      }
      
      public boolean addVertex(V vertex) {
          if(vertex == null) {
              throw new IllegalArgumentException("vertex may not be null");
          }
          if (!vertices.containsKey(vertex)) {
              vertices.put(vertex, new Pair<Set<E>>(new HashSet<E>(), new HashSet<E>()));
              return true;
          } else {
         	return false;
         }
     }
 
     public boolean removeVertex(V vertex) {
         if (!containsVertex(vertex))
             return false;
         
         // copy to avoid concurrent modification in removeEdge
         Set<E> incident = new HashSet<E>(getIncoming_internal(vertex));
         incident.addAll(getOutgoing_internal(vertex));
         
         for (E edge : incident)
             removeEdge(edge);
         
         vertices.remove(vertex);
         
         return true;
     }
     
     @Override
     public boolean addEdge(E edge, Pair<? extends V> endpoints, EdgeType edgeType) {
 
         Pair<V> new_endpoints = getValidatedEndpoints(edge, endpoints);
         if (new_endpoints == null)
             return false;
         
         V v1 = new_endpoints.getFirst();
         V v2 = new_endpoints.getSecond();
         
         if (!vertices.containsKey(v1))
             this.addVertex(v1);
         
         if (!vertices.containsKey(v2))
             this.addVertex(v2);
         
 
         vertices.get(v1).getSecond().add(edge);        
         vertices.get(v2).getFirst().add(edge);        
         edges.put(edge, new_endpoints);
         if(edgeType == EdgeType.DIRECTED) {
         	directedEdges.add(edge);
         } else {
           vertices.get(v1).getFirst().add(edge);        
           vertices.get(v2).getSecond().add(edge);        
         }
         return true;
     }
     
     public boolean removeEdge(E edge)
     {
         if (!containsEdge(edge)) {
             return false;
         }
         
         Pair<V> endpoints = getEndpoints(edge);
         V v1 = endpoints.getFirst();
         V v2 = endpoints.getSecond();
         
         // remove edge from incident vertices' adjacency sets
         vertices.get(v1).getSecond().remove(edge);
         vertices.get(v2).getFirst().remove(edge);
 
         if(directedEdges.remove(edge) == false) {
         	
         	// its an undirected edge, remove the other ends
             vertices.get(v2).getSecond().remove(edge);
             vertices.get(v1).getFirst().remove(edge);
         }
         edges.remove(edge);
         return true;
     }
     
     public Collection<E> getInEdges(V vertex)
     {
     	if (!containsVertex(vertex))
     		return null;
         return Collections.unmodifiableCollection(vertices.get(vertex).getFirst());
     }
 
     public Collection<E> getOutEdges(V vertex)
     {
     	if (!containsVertex(vertex))
     		return null;
         return Collections.unmodifiableCollection(vertices.get(vertex).getSecond());
     }
 
     // TODO: this will need to get changed if we modify the internal representation
     public Collection<V> getPredecessors(V vertex)
     {
     	if (!containsVertex(vertex))
     		return null;
 
         Set<V> preds = new HashSet<V>();
         for (E edge : getIncoming_internal(vertex)) {
         	if(getEdgeType(edge) == EdgeType.DIRECTED) {
         		preds.add(this.getSource(edge));
         	} else {
         		preds.add(getOpposite(vertex, edge));
         	}
         }
         return Collections.unmodifiableCollection(preds);
     }
 
     // TODO: this will need to get changed if we modify the internal representation
     public Collection<V> getSuccessors(V vertex)
     {
     	if (!containsVertex(vertex))
     		return null;
         Set<V> succs = new HashSet<V>();
         for (E edge : getOutgoing_internal(vertex)) {
         	if(getEdgeType(edge) == EdgeType.DIRECTED) {
         		succs.add(this.getDest(edge));
         	} else {
         		succs.add(getOpposite(vertex, edge));
         	}
         }
         return Collections.unmodifiableCollection(succs);
     }
 
     public Collection<V> getNeighbors(V vertex)
     {
     	if (!containsVertex(vertex))
     		return null;
         Collection<V> out = new HashSet<V>();
         out.addAll(this.getPredecessors(vertex));
         out.addAll(this.getSuccessors(vertex));
         return out;
     }
 
     public Collection<E> getIncidentEdges(V vertex)
     {
     	if (!containsVertex(vertex))
     		return null;
         Collection<E> out = new HashSet<E>();
         out.addAll(this.getInEdges(vertex));
         out.addAll(this.getOutEdges(vertex));
         return out;
     }
 
     @Override
     public E findEdge(V v1, V v2)
     {
     	if (!containsVertex(v1) || !containsVertex(v2))
     		return null;
         for (E edge : getOutgoing_internal(v1))
             if (this.getOpposite(v1, edge).equals(v2))
                 return edge;
         
         return null;
     }
 
     public Pair<V> getEndpoints(E edge)
     {
         return edges.get(edge);
     }
 
     public V getSource(E edge) {
     	if(directedEdges.contains(edge)) {
     		return this.getEndpoints(edge).getFirst();
     	}
     	return null;
     }
 
     public V getDest(E edge) {
     	if(directedEdges.contains(edge)) {
     		return this.getEndpoints(edge).getSecond();
     	}
     	return null;
     }
 
     public boolean isSource(V vertex, E edge) {
     	if (!containsEdge(edge) || !containsVertex(vertex))
     		return false;
         return getSource(edge).equals(vertex);
     }
 
     public boolean isDest(V vertex, E edge) {
     	if (!containsEdge(edge) || !containsVertex(vertex))
     		return false;
         return getDest(edge).equals(vertex);
     }
 
     public EdgeType getEdgeType(E edge) {
     	return directedEdges.contains(edge) ?
     		EdgeType.DIRECTED :
     			EdgeType.UNDIRECTED;
     }
 
 	@SuppressWarnings("unchecked")
 	public Collection<E> getEdges(EdgeType edgeType) {
 		if(edgeType == EdgeType.DIRECTED) {
 			return Collections.unmodifiableSet(this.directedEdges);
 		} else if(edgeType == EdgeType.UNDIRECTED) {
 			Collection<E> edges = new HashSet<E>(getEdges());
 			edges.removeAll(directedEdges);
 			return edges;
 		} else {
 			return Collections.EMPTY_SET;
 		}
 		
 	}
 
 	public int getEdgeCount() {
 		return edges.keySet().size();
 	}
 
 	public int getVertexCount() {
 		return vertices.keySet().size();
 	}
 
     public int getEdgeCount(EdgeType edge_type)
     {
         return getEdges(edge_type).size();
     }
 
 	public EdgeType getDefaultEdgeType() 
 	{
 		return EdgeType.UNDIRECTED;
 	}
 }