/* -*- C++ -*-
 * lemon/smart_graph.h - Part of LEMON, a generic C++ optimization library
 *
 * Copyright (C) 2005 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 and SymSmartGraph classes.

#include <vector>

#include <lemon/invalid.h>

#include <lemon/bits/clearable_graph_extender.h>
#include <lemon/bits/extendable_graph_extender.h>
#include <lemon/bits/iterable_graph_extender.h>
#include <lemon/bits/alteration_notifier.h>
#include <lemon/bits/default_map.h>

#include <lemon/bits/undir_graph_extender.h>

#include <lemon/utility.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 maxId(Node = INVALID) const { return nodes.size()-1; }
    /// Maximum edge ID.
    
    /// Maximum edge ID.
    ///\sa id(Edge)
    int maxId(Edge = INVALID) 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; }

    static Node fromId(int id, Node) { return Node(id);}

    static Edge fromId(int id, Edge) { 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;
      ///\todo It should be removed (or at least define a setToId() instead).
      ///
      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;
      ///\todo It should be removed (or at least define a setToId() instead).
      ///
      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;
    }

    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].target!=v.n) e = edges[e].next_out;
      prev.n=e;
      return prev;
    }

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

  /// \addtogroup 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::ExtendableGraph "ExtendableGraph" concept.
  ///\sa concept::ExtendableGraph.
  ///
  ///\author Alpar Juttner
  class SmartGraph : public ClearableSmartGraphBase {
  public:
    /// 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 \ref INVALID if there is no such an edge.
    ///
    /// Thus you can iterate through each edge from \c u to \c v as it follows.
    /// \code
    /// for(Edge e=G.findEdge(u,v);e!=INVALID;e=G.findEdge(u,v,e)) {
    ///   ...
    /// }
    /// \endcode
    /// \todo Possibly it should be a global function.
    Edge findEdge(Node u,Node v, Edge prev = INVALID) 
    {
      return _findEdge(u,v,prev);
    }
    
    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) 
    {
      return _split(n,connect);
    }
  

    ///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().
      ///
      ///\param s an internal stucture given back 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);
      }
    };
  };


  /**************** Undirected List Graph ****************/

  typedef ClearableUndirGraphExtender<
    ExtendableUndirGraphExtender<
    MappableUndirGraphExtender<
    IterableUndirGraphExtender<
    AlterableUndirGraphExtender<
    UndirGraphExtender<SmartGraphBase> > > > > > UndirSmartGraphBase;

  ///A smart undirected graph class.

  ///This is a simple and fast undirected 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>.
  ///Except from this it conforms to 
  ///the \ref concept::UndirGraph "UndirGraph" concept.
  ///\sa concept::UndirGraph.
  ///
  ///\todo SnapShot hasn't been implemented yet.
  ///
  class UndirSmartGraph : public UndirSmartGraphBase {
  };

  
  /// @}  
} //namespace lemon


#endif //LEMON_SMART_GRAPH_H