/* -*- C++ -*-

 *

 * This file is a part of LEMON, a generic C++ optimization library

 *

 * Copyright (C) 2003-2006

 * Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport

 * (Egervary Research Group on Combinatorial Optimization, 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 class.

#include <vector>

#include <lemon/bits/invalid.h>

#include <lemon/bits/graph_extender.h>

#include <lemon/bits/utility.h>

#include <lemon/bits/graph_extender.h>

namespace lemon {

  class SmartGraph;

  ///Base of SmartGraph

  ///Base of SmartGraph

  ///

  class SmartGraphBase {

    friend class SmatGraph;

  protected:

    struct NodeT 

    {

      int first_in,first_out;      

      NodeT() : first_in(-1), first_out(-1) {}

    };

    struct EdgeT 

    {

      int target, source, 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) { }

    typedef True NodeNumTag;

    typedef True EdgeNumTag;

    ///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 source(Edge e) const { return edges[e.n].source; }

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

    /// 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; }

    /// \brief Returns the node from its \c id.

    ///

    /// Returns the node from its \c id. If there is not node

    /// with the given id the effect of the function is undefinied.

    static Node nodeFromId(int id) { return Node(id);}

    /// \brief Returns the edge from its \c id.

    ///

    /// Returns the edge from its \c id. If there is not edge

    /// with the given id the effect of the function is undefinied.

    static Edge edgeFromId(int id) { return Edge(id);}

    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].source=u.n; edges[e.n].target=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;

    }

    void clear() {

      edges.clear();

      nodes.clear();

    }

    class Node {

      friend class SmartGraphBase;

      friend class SmartGraph;

    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;

      friend class SmartGraph;

    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;

    }

    Node _split(Node n, bool connect = true)

    {

      Node b = addNode();

      nodes[b.n].first_out=nodes[n.n].first_out;

      nodes[n.n].first_out=-1;

      for(int i=nodes[b.n].first_out;i!=-1;i++) edges[i].source=b.n;

      if(connect) addEdge(n,b);

      return b;

    }

  };

  typedef GraphExtender<SmartGraphBase> ExtendedSmartGraphBase;

  /// \ingroup graphs

  ///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 support only limited (only stack-like)

  ///node and edge deletions</b>.

  ///It conforms to 

  ///the \ref concept::Graph "Graph" concept.

  ///\sa concept::Graph.

  ///

  ///\author Alpar Juttner

  class SmartGraph : public ExtendedSmartGraphBase {

  public:

    typedef ExtendedSmartGraphBase Parent;

    class Snapshot;

    friend class Snapshot;

  protected:

    void restoreSnapshot(const Snapshot &s)

    {

      while(s.edge_num<edges.size()) {

	Parent::getNotifier(Edge()).erase(Edge(edges.size()-1));

	nodes[edges.back().target].first_in=edges.back().next_in;

	nodes[edges.back().source].first_out=edges.back().next_out;

	edges.pop_back();

      }

      //nodes.resize(s.nodes_num);

      while(s.node_num<nodes.size()) {

	Parent::getNotifier(Node()).erase(Node(nodes.size()-1));

	nodes.pop_back();

      }

    }    

  public:

    ///Split a node.

    ///This function splits a node. First a new node is added to the graph,

    ///then the source of each outgoing edge of \c n is moved to this new node.

    ///If \c connect is \c true (this is the default value), then a new edge

    ///from \c n to the newly created node is also added.

    ///\return The newly created node.

    ///

    ///\note The <tt>Edge</tt>s

    ///referencing a moved edge remain

    ///valid. However <tt>InEdge</tt>'s and <tt>OutEdge</tt>'s

    ///may be invalidated.

    ///\warning This functionality cannot be used together with the Snapshot

    ///feature.

    ///\todo It could be implemented in a bit faster way.

    Node split(Node n, bool connect = true) 

    {

      Node b = _split(n,connect);

      return b;

    }

    ///Class to make a snapshot of the graph and to restrore to it later.

    ///Class to make a snapshot of the graph and to restrore to it later.

    ///

    ///The newly added nodes and edges can be removed using the

    ///restore() function.

    ///\note After you restore a state, you cannot restore

    ///a later state, in other word you cannot add again the edges deleted

    ///by restore() using another Snapshot instance.

    ///

    class Snapshot 

    {

      SmartGraph *g;

    protected:

      friend class SmartGraph;

      unsigned int node_num;

      unsigned int edge_num;

    public:

      ///Default constructor.

      ///Default constructor.

      ///To actually make a snapshot you must call save().

      ///

      Snapshot() : g(0) {}

      ///Constructor that immediately makes a snapshot

      ///This constructor immediately makes a snapshot of the graph.

      ///\param _g The graph we make a snapshot of.

      Snapshot(SmartGraph &_g) :g(&_g) {

	node_num=g->nodes.size();

	edge_num=g->edges.size();

      }

      ///Make a snapshot.

      ///Make a snapshot of the graph.

      ///

      ///This function can be called more than once. In case of a repeated

      ///call, the previous snapshot gets lost.

      ///\param _g The graph we make the snapshot of.

      void save(SmartGraph &_g) 

      {

	g=&_g;

	node_num=g->nodes.size();

	edge_num=g->edges.size();

      }

      ///Undo the changes until a snapshot.

      ///Undo the changes until a snapshot created by save().

      ///

      ///\note After you restored a state, you cannot restore

      ///a later state, in other word you cannot add again the edges deleted

      ///by restore().

      ///

      ///\todo This function might be called undo().

      void restore()

      {

	g->restoreSnapshot(*this);

      }

    };

  };

} //namespace lemon

#endif //LEMON_SMART_GRAPH_H