/* -*- C++ -*-
 * src/lemon/smart_graph.h - Part of LEMON, a generic C++ optimization library
 *
 * Copyright (C) 2004 Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport
 * (Egervary Combinatorial Optimization Research Group, EGRES).
 *
 * Permission to use, modify and distribute this software is granted
 * provided that this copyright notice appears in all copies. For
 * precise terms see the accompanying LICENSE file.
 *
 * This software is provided "AS IS" with no warranty of any kind,
 * express or implied, and with no claim as to its suitability for any
 * purpose.
 *
 */

#ifndef LEMON_SMART_GRAPH_H
#define LEMON_SMART_GRAPH_H

///\ingroup graphs
///\file
///\brief SmartGraph and SymSmartGraph classes.

#include <vector>

#include <lemon/invalid.h>

#include <lemon/erasable_graph_extender.h>
#include <lemon/clearable_graph_extender.h>
#include <lemon/extendable_graph_extender.h>

#include <lemon/idmappable_graph_extender.h>

#include <lemon/iterable_graph_extender.h>

#include <lemon/alteration_observer_registry.h>
#include <lemon/default_map.h>


#include <lemon/graph_utils.h>


namespace lemon {

  /// \addtogroup graphs
  /// @{

  class SmartGraphBase {

    struct NodeT 
    {
      int first_in,first_out;      
      NodeT() : first_in(-1), first_out(-1) {}
    };
    struct EdgeT 
    {
      int head, tail, next_in, next_out;      
      //FIXME: is this necessary?
      EdgeT() : next_in(-1), next_out(-1) {}  
    };

    std::vector<NodeT> nodes;

    std::vector<EdgeT> edges;
    
    
  public:

    typedef SmartGraphBase Graph;

    class Node;
    class Edge;

    
  public:

    SmartGraphBase() : nodes(), edges() { }
    SmartGraphBase(const SmartGraphBase &_g) : nodes(_g.nodes), edges(_g.edges) { }
    
    ///Number of nodes.
    int nodeNum() const { return nodes.size(); }
    ///Number of edges.
    int edgeNum() const { return edges.size(); }

    /// Maximum node ID.
    
    /// Maximum node ID.
    ///\sa id(Node)
    int maxNodeId() const { return nodes.size()-1; }
    /// Maximum edge ID.
    
    /// Maximum edge ID.
    ///\sa id(Edge)
    int maxEdgeId() const { return edges.size()-1; }

    Node tail(Edge e) const { return edges[e.n].tail; }
    Node head(Edge e) const { return edges[e.n].head; }

    /// Node ID.
    
    /// The ID of a valid Node is a nonnegative integer not greater than
    /// \ref maxNodeId(). The range of the ID's is not surely continuous
    /// and the greatest node ID can be actually less then \ref maxNodeId().
    ///
    /// The ID of the \ref INVALID node is -1.
    ///\return The ID of the node \c v. 
    static int id(Node v) { return v.n; }
    /// Edge ID.
    
    /// The ID of a valid Edge is a nonnegative integer not greater than
    /// \ref maxEdgeId(). The range of the ID's is not surely continuous
    /// and the greatest edge ID can be actually less then \ref maxEdgeId().
    ///
    /// The ID of the \ref INVALID edge is -1.
    ///\return The ID of the edge \c e. 
    static int id(Edge e) { return e.n; }

    Node addNode() {
      Node n; n.n=nodes.size();
      nodes.push_back(NodeT()); //FIXME: Hmmm...
      return n;
    }
    
    Edge addEdge(Node u, Node v) {
      Edge e; e.n=edges.size(); edges.push_back(EdgeT()); //FIXME: Hmmm...
      edges[e.n].tail=u.n; edges[e.n].head=v.n;
      edges[e.n].next_out=nodes[u.n].first_out;
      edges[e.n].next_in=nodes[v.n].first_in;
      nodes[u.n].first_out=nodes[v.n].first_in=e.n;

      return e;
    }

    /// Finds an edge between two nodes.

    /// Finds an edge from node \c u to node \c v.
    ///
    /// If \c prev is \ref INVALID (this is the default value), then
    /// It finds the first edge from \c u to \c v. Otherwise it looks for
    /// the next edge from \c u to \c v after \c prev.
    /// \return The found edge or INVALID if there is no such an edge.
    Edge findEdge(Node u,Node v, Edge prev = INVALID) 
    {
      int e = (prev.n==-1)? nodes[u.n].first_out : edges[prev.n].next_out;
      while(e!=-1 && edges[e].tail!=v.n) e = edges[e].next_out;
      prev.n=e;
      return prev;
    }
    
    void clear() {
      edges.clear();
      nodes.clear();
    }


    class Node {
      friend class SmartGraphBase;

    protected:
      int n;
      Node(int nn) {n=nn;}
    public:
      Node() {}
      Node (Invalid) { n=-1; }
      bool operator==(const Node i) const {return n==i.n;}
      bool operator!=(const Node i) const {return n!=i.n;}
      bool operator<(const Node i) const {return n<i.n;}
    };
    

    class Edge {
      friend class SmartGraphBase;

    protected:
      int n;
      Edge(int nn) {n=nn;}
    public:
      Edge() { }
      Edge (Invalid) { n=-1; }
      bool operator==(const Edge i) const {return n==i.n;}
      bool operator!=(const Edge i) const {return n!=i.n;}
      bool operator<(const Edge i) const {return n<i.n;}
    };

    void first(Node& node) const {
      node.n = nodes.size() - 1;
    }

    static void next(Node& node) {
      --node.n;
    }

    void first(Edge& edge) const {
      edge.n = edges.size() - 1;
    }

    static void next(Edge& edge) {
      --edge.n;
    }

    void firstOut(Edge& edge, const Node& node) const {
      edge.n = nodes[node.n].first_out;
    }

    void nextOut(Edge& edge) const {
      edge.n = edges[edge.n].next_out;
    }

    void firstIn(Edge& edge, const Node& node) const {
      edge.n = nodes[node.n].first_in;
    }
    
    void nextIn(Edge& edge) const {
      edge.n = edges[edge.n].next_in;
    }

  };

  typedef AlterableGraphExtender<SmartGraphBase> AlterableSmartGraphBase;
  typedef IterableGraphExtender<AlterableSmartGraphBase> IterableSmartGraphBase;
  typedef IdMappableGraphExtender<IterableSmartGraphBase> IdMappableSmartGraphBase;
  typedef DefaultMappableGraphExtender<IdMappableSmartGraphBase> MappableSmartGraphBase;
  typedef ExtendableGraphExtender<MappableSmartGraphBase> ExtendableSmartGraphBase;
  typedef ClearableGraphExtender<ExtendableSmartGraphBase> ClearableSmartGraphBase;

  ///A smart graph class.

  ///This is a simple and fast graph implementation.
  ///It is also quite memory efficient, but at the price
  ///that <b> it does not support node and edge deletion</b>.
  ///It conforms to 
  ///the \ref skeleton::ExtendableGraph "ExtendableGraph" concept.
  ///\sa skeleton::ExtendableGraph.
  ///
  ///\todo Some member functions could be \c static.
  ///
  ///\todo A possibly useful functionality: a function saveState()
  ///(or snapshot() ) would
  ///give back a data sturcture X and then the function restoreState(X)
  ///(or rollBack() )
  ///would remove the nodes and edges added after the call of saveState().
  ///Of course it should be used as a stack. (Maybe X is not necessary.)
  ///
  ///\author Alpar Juttner
  class SmartGraph :public ClearableSmartGraphBase { };
  
  template <>
  int countNodes<SmartGraph>(const SmartGraph& graph) {
    return graph.nodeNum();
  }

  template <>
  int countEdges<SmartGraph>(const SmartGraph& graph) {
    return graph.edgeNum();
  }

  /// @}  
} //namespace lemon




#endif //LEMON_SMART_GRAPH_H