/* -*- 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/clearable_graph_extender.h>

#include <lemon/extendable_graph_extender.h>

#include <lemon/iterable_graph_extender.h>

#include <lemon/alteration_observer_registry.h>

#include <lemon/default_map.h>

#include <lemon/utility.h>

namespace lemon {

  /// \addtogroup graphs

  /// @{

  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 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) { }

    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 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;

    }

    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].tail!=v.n) e = edges[e].next_out;

      prev.n=e;

      return prev;

    }

  };

  typedef AlterableGraphExtender<SmartGraphBase> AlterableSmartGraphBase;

  typedef IterableGraphExtender<AlterableSmartGraphBase> IterableSmartGraphBase;

  typedef DefaultMappableGraphExtender<IterableSmartGraphBase> 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 support only limited (only stack-like)

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

  ///It conforms to 

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

  ///\sa concept::ExtendableGraph.

  ///

  ///\todo Some member functions could be \c static.

  ///

  ///\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);

    }

    ///Internal data structure to store snapshots

    ///\ingroup graphs

    ///\sa makeSnapShot()

    ///\sa rollBack()

    struct SnapShot 

    {

      unsigned int node_num;

      unsigned int edge_num;

    };

    ///Make a snapshot of the graph.

    ///Make a snapshot of the graph.

    ///

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

    ///rollBack() function.

    ///

    ///\return An stucture SnapShot describing the pesent state of the

    ///graph.

    ///\note After you rolled back to a state, you cannot roll "back" to

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

    ///by rollBack().

    ///\todo This function might be called saveState() or getState().

    SnapShot makeSnapShot() 

    {

      SnapShot s;

      s.node_num=nodes.size();

      s.edge_num=edges.size();

      return s;

    }

    ///Undo the changes until a snapshot.

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

    ///

    ///\param s an internal stucture given back by makeSnapShot()

    ///\note After you rolled back to a state, you cannot "roll forward" to

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

    ///by rollBack().

    ///

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

    void rollBack(const SnapShot &s)

    {

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

	edge_observers.erase(Edge(edges.size()-1));

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

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

	edges.pop_back();

      }

      //nodes.resize(s.nodes_num);

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

	node_observers.erase(Node(nodes.size()-1));

	nodes.pop_back();

      }

    }

  };

  /// @}  

} //namespace lemon

#endif //LEMON_SMART_GRAPH_H