/* -*- 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_LIST_GRAPH_H
#define LEMON_LIST_GRAPH_H

///\ingroup graphs
///\file
///\brief ListGraph class.

#include <lemon/bits/graph_extender.h>

#include <vector>
#include <list>

namespace lemon {

  class ListGraphBase {

  protected:
    struct NodeT {
      int first_in, first_out;
      int prev, next;
    };
 
    struct EdgeT {
      int target, source;
      int prev_in, prev_out;
      int next_in, next_out;
    };

    std::vector<NodeT> nodes;

    int first_node;

    int first_free_node;

    std::vector<EdgeT> edges;

    int first_free_edge;
    
  public:
    
    typedef ListGraphBase Graph;
    
    class Node {
      friend class ListGraphBase;
    protected:

      int id;
      explicit Node(int pid) { id = pid;}

    public:
      Node() {}
      Node (Invalid) { id = -1; }
      bool operator==(const Node& node) const {return id == node.id;}
      bool operator!=(const Node& node) const {return id != node.id;}
      bool operator<(const Node& node) const {return id < node.id;}
    };

    class Edge {
      friend class ListGraphBase;
    protected:

      int id;
      explicit Edge(int pid) { id = pid;}

    public:
      Edge() {}
      Edge (Invalid) { id = -1; }
      bool operator==(const Edge& edge) const {return id == edge.id;}
      bool operator!=(const Edge& edge) const {return id != edge.id;}
      bool operator<(const Edge& edge) const {return id < edge.id;}
    };



    ListGraphBase()
      : nodes(), first_node(-1),
	first_free_node(-1), edges(), first_free_edge(-1) {}

    
    /// 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 Node(edges[e.id].source); }
    Node target(Edge e) const { return Node(edges[e.id].target); }


    void first(Node& node) const { 
      node.id = first_node;
    }

    void next(Node& node) const {
      node.id = nodes[node.id].next;
    }


    void first(Edge& e) const { 
      int n;
      for(n = first_node; 
	  n!=-1 && nodes[n].first_in == -1; 
	  n = nodes[n].next);
      e.id = (n == -1) ? -1 : nodes[n].first_in;
    }

    void next(Edge& edge) const {
      if (edges[edge.id].next_in != -1) {
	edge.id = edges[edge.id].next_in;
      } else {
	int n;
	for(n = nodes[edges[edge.id].target].next;
	  n!=-1 && nodes[n].first_in == -1; 
	  n = nodes[n].next);
	edge.id = (n == -1) ? -1 : nodes[n].first_in;
      }      
    }

    void firstOut(Edge &e, const Node& v) const {
      e.id = nodes[v.id].first_out;
    }
    void nextOut(Edge &e) const {
      e.id=edges[e.id].next_out;
    }

    void firstIn(Edge &e, const Node& v) const {
      e.id = nodes[v.id].first_in;
    }
    void nextIn(Edge &e) const {
      e.id=edges[e.id].next_in;
    }

    
    static int id(Node v) { return v.id; }
    static int id(Edge e) { return e.id; }

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

    /// Adds a new node to the graph.

    /// \warning It adds the new node to the front of the list.
    /// (i.e. the lastly added node becomes the first.)
    Node addNode() {     
      int n;
      
      if(first_free_node==-1) {
	n = nodes.size();
	nodes.push_back(NodeT());
      } else {
	n = first_free_node;
	first_free_node = nodes[n].next;
      }
      
      nodes[n].next = first_node;
      if(first_node != -1) nodes[first_node].prev = n;
      first_node = n;
      nodes[n].prev = -1;
      
      nodes[n].first_in = nodes[n].first_out = -1;
      
      return Node(n);
    }
    
    Edge addEdge(Node u, Node v) {
      int n;      

      if (first_free_edge == -1) {
	n = edges.size();
	edges.push_back(EdgeT());
      } else {
	n = first_free_edge;
	first_free_edge = edges[n].next_in;
      }
      
      edges[n].source = u.id; 
      edges[n].target = v.id;

      edges[n].next_out = nodes[u.id].first_out;
      if(nodes[u.id].first_out != -1) {
	edges[nodes[u.id].first_out].prev_out = n;
      }
      
      edges[n].next_in = nodes[v.id].first_in;
      if(nodes[v.id].first_in != -1) {
	edges[nodes[v.id].first_in].prev_in = n;
      }
      
      edges[n].prev_in = edges[n].prev_out = -1;
	
      nodes[u.id].first_out = nodes[v.id].first_in = n;

      return Edge(n);
    }
    
    void erase(const Node& node) {
      int n = node.id;
      
      if(nodes[n].next != -1) {
	nodes[nodes[n].next].prev = nodes[n].prev;
      }
      
      if(nodes[n].prev != -1) {
	nodes[nodes[n].prev].next = nodes[n].next;
      } else {
	first_node = nodes[n].next;
      }
      
      nodes[n].next = first_free_node;
      first_free_node = n;

    }
    
    void erase(const Edge& edge) {
      int n = edge.id;
      
      if(edges[n].next_in!=-1) {
	edges[edges[n].next_in].prev_in = edges[n].prev_in;
      }

      if(edges[n].prev_in!=-1) {
	edges[edges[n].prev_in].next_in = edges[n].next_in;
      } else {
	nodes[edges[n].target].first_in = edges[n].next_in;
      }

      
      if(edges[n].next_out!=-1) {
	edges[edges[n].next_out].prev_out = edges[n].prev_out;
      } 

      if(edges[n].prev_out!=-1) {
	edges[edges[n].prev_out].next_out = edges[n].next_out;
      } else {
	nodes[edges[n].source].first_out = edges[n].next_out;
      }
      
      edges[n].next_in = first_free_edge;
      first_free_edge = n;      

    }

    void clear() {
      edges.clear();
      nodes.clear();
      first_node = first_free_node = first_free_edge = -1;
    }

  protected:
    void changeTarget(Edge e, Node n) 
    {
      if(edges[e.id].next_in != -1)
	edges[edges[e.id].next_in].prev_in = edges[e.id].prev_in;
      if(edges[e.id].prev_in != -1)
	edges[edges[e.id].prev_in].next_in = edges[e.id].next_in;
      else nodes[edges[e.id].target].first_in = edges[e.id].next_in;
      if (nodes[n.id].first_in != -1) {
	edges[nodes[n.id].first_in].prev_in = e.id;
      }
      edges[e.id].target = n.id;
      edges[e.id].prev_in = -1;
      edges[e.id].next_in = nodes[n.id].first_in;
      nodes[n.id].first_in = e.id;
    }
    void changeSource(Edge e, Node n) 
    {
      if(edges[e.id].next_out != -1)
	edges[edges[e.id].next_out].prev_out = edges[e.id].prev_out;
      if(edges[e.id].prev_out != -1)
	edges[edges[e.id].prev_out].next_out = edges[e.id].next_out;
      else nodes[edges[e.id].source].first_out = edges[e.id].next_out;
      if (nodes[n.id].first_out != -1) {
	edges[nodes[n.id].first_out].prev_out = e.id;
      }
      edges[e.id].source = n.id;
      edges[e.id].prev_out = -1;
      edges[e.id].next_out = nodes[n.id].first_out;
      nodes[n.id].first_out = e.id;
    }

  };

  typedef GraphExtender<ListGraphBase> ExtendedListGraphBase;

  /// \ingroup graphs

  ///A list graph class.

  ///This is a simple and fast erasable graph implementation.
  ///
  ///It conforms to the \ref concept::Graph "Graph" concept and it
  ///also provides several additional useful extra functionalities.
  ///The most of the member functions and nested classes are
  ///documented only in the concept class.
  ///\sa concept::Graph.

  class ListGraph : public ExtendedListGraphBase {
  public:

    typedef ExtendedListGraphBase Parent;

    ///Add a new node to the graph.
    
    /// \return the new node.
    ///
    Node addNode() { return Parent::addNode(); }

    ///Add a new edge to the graph.
    
    ///Add a new edge to the graph with source node \c s
    ///and target node \c t.
    ///\return the new edge.
    Edge addEdge(const Node& s, const Node& t) { 
      return Parent::addEdge(s, t); 
    }

    /// Changes the target of \c e to \c n

    /// Changes the target of \c e to \c n
    ///
    ///\note The <tt>Edge</tt>s and <tt>OutEdgeIt</tt>s referencing
    ///the changed edge remain valid. However <tt>InEdgeIt</tt>s are
    ///invalidated.
    void changeTarget(Edge e, Node n) { 
      Parent::changeTarget(e,n); 
    }
    /// Changes the source of \c e to \c n

    /// Changes the source of \c e to \c n
    ///
    ///\note The <tt>Edge</tt>s and <tt>InEdgeIt</tt>s referencing
    ///the changed edge remain valid. However <tt>OutEdgeIt</tt>s are
    ///invalidated.
    void changeSource(Edge e, Node n) { 
      Parent::changeSource(e,n);
    }

    /// Invert the direction of an edge.

    ///\note The <tt>Edge</tt>s referencing the changed edge remain
    ///valid. However <tt>OutEdgeIt</tt>s and <tt>InEdgeIt</tt>s are
    ///invalidated.
    void reverseEdge(Edge e) {
      Node t=target(e);
      changeTarget(e,source(e));
      changeSource(e,t);
    }

    /// \brief Using this it is possible to avoid the superfluous memory
    /// allocation.

    ///Using this it is possible to avoid the superfluous memory
    ///allocation: if you know that the graph you want to build will
    ///contain at least 10 million nodes then it is worth to reserve
    ///space for this amount before starting to build the graph.
    void reserveNode(int n) { nodes.reserve(n); };

    /// \brief Using this it is possible to avoid the superfluous memory
    /// allocation.

    ///Using this it is possible to avoid the superfluous memory
    ///allocation: see the \ref reserveNode function.
    void reserveEdge(int n) { edges.reserve(n); };


    ///Contract two nodes.

    ///This function contracts two nodes.
    ///
    ///Node \p b will be removed but instead of deleting
    ///incident edges, they will be joined to \p a.
    ///The last parameter \p r controls whether to remove loops. \c true
    ///means that loops will be removed.
    ///
    ///\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.
    void contract(Node a, Node b, bool r = true) 
    {
      for(OutEdgeIt e(*this,b);e!=INVALID;) {
	OutEdgeIt f=e;
	++f;
	if(r && target(e)==a) erase(e);
	else changeSource(e,a);
	e=f;
      }
      for(InEdgeIt e(*this,b);e!=INVALID;) {
	InEdgeIt f=e;
	++f;
	if(r && source(e)==a) erase(e);
	else changeTarget(e,a);
	e=f;
      }
      erase(b);
    }

    ///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 = addNode();
      for(OutEdgeIt e(*this,n);e!=INVALID;) {
 	OutEdgeIt f=e;
	++f;
	changeSource(e,b);
	e=f;
      }
      if (connect) addEdge(n,b);
      return b;
    }
      
    ///Split an edge.

    ///This function splits an edge. First a new node \c b is added to
    ///the graph, then the original edge is re-targeted to \c
    ///b. Finally an edge from \c b to the original target is added.
    ///\return The newly created node.  
    ///\warning This functionality
    ///cannot be used together with the Snapshot feature.
    Node split(Edge e) {
      Node b = addNode();
      addEdge(b,target(e));
      changeTarget(e,b);
      return b;
    }
      
    /// \brief Class to make a snapshot of the graph and restore
    /// to it later.
    ///
    /// Class to make a snapshot of the graph and to restore it
    /// later.
    ///
    /// The newly added nodes and edges can be removed using the
    /// restore() function.
    ///
    /// \warning Edge and node deletions cannot be restored.
    class Snapshot {
    public:
      
      class UnsupportedOperation : public LogicError {
      public:
	virtual const char* exceptionName() const {
	  return "lemon::ListGraph::Snapshot::UnsupportedOperation";
	}
      };
            

    protected:

      typedef Parent::NodeNotifier NodeNotifier;

      class NodeObserverProxy : public NodeNotifier::ObserverBase {
      public:

        NodeObserverProxy(Snapshot& _snapshot)
          : snapshot(_snapshot) {}

        using NodeNotifier::ObserverBase::attach;
        using NodeNotifier::ObserverBase::detach;
        using NodeNotifier::ObserverBase::attached;
        
      protected:
        
        virtual void add(const Node& node) {
          snapshot.addNode(node);
        }
        virtual void add(const std::vector<Node>& nodes) {
          for (int i = nodes.size() - 1; i >= 0; ++i) {
            snapshot.addNode(nodes[i]);
          }
        }
        virtual void erase(const Node& node) {
          snapshot.eraseNode(node);
        }
        virtual void erase(const std::vector<Node>& nodes) {
          for (int i = 0; i < (int)nodes.size(); ++i) {
            if (!snapshot.eraseNode(nodes[i])) break;
          }
        }
        virtual void build() {
          NodeNotifier* notifier = getNotifier();
          Node node;
          std::vector<Node> nodes;
          for (notifier->first(node); node != INVALID; notifier->next(node)) {
            nodes.push_back(node);
          }
          for (int i = nodes.size() - 1; i >= 0; --i) {
            snapshot.addNode(nodes[i]);
          }
        }
        virtual void clear() {
          NodeNotifier* notifier = getNotifier();
          Node node;
          for (notifier->first(node); node != INVALID; notifier->next(node)) {
            if (!snapshot.eraseNode(node)) break;
          }
        }

        Snapshot& snapshot;
      };

      class EdgeObserverProxy : public EdgeNotifier::ObserverBase {
      public:

        EdgeObserverProxy(Snapshot& _snapshot)
          : snapshot(_snapshot) {}

        using EdgeNotifier::ObserverBase::attach;
        using EdgeNotifier::ObserverBase::detach;
        using EdgeNotifier::ObserverBase::attached;
        
      protected:

        virtual void add(const Edge& edge) {
          snapshot.addEdge(edge);
        }
        virtual void add(const std::vector<Edge>& edges) {
          for (int i = edges.size() - 1; i >= 0; ++i) {
            snapshot.addEdge(edges[i]);
          }
        }
        virtual void erase(const Edge& edge) {
          snapshot.eraseEdge(edge);
        }
        virtual void erase(const std::vector<Edge>& edges) {
          for (int i = 0; i < (int)edges.size(); ++i) {
            if (!snapshot.eraseEdge(edges[i])) break;
          }
        }
        virtual void build() {
          EdgeNotifier* notifier = getNotifier();
          Edge edge;
          std::vector<Edge> edges;
          for (notifier->first(edge); edge != INVALID; notifier->next(edge)) {
            edges.push_back(edge);
          }
          for (int i = edges.size() - 1; i >= 0; --i) {
            snapshot.addEdge(edges[i]);
          }
        }
        virtual void clear() {
          EdgeNotifier* notifier = getNotifier();
          Edge edge;
          for (notifier->first(edge); edge != INVALID; notifier->next(edge)) {
            if (!snapshot.eraseEdge(edge)) break;
          }
        }

        Snapshot& snapshot;
      };
      
      ListGraph *graph;

      NodeObserverProxy node_observer_proxy;
      EdgeObserverProxy edge_observer_proxy;

      std::list<Node> added_nodes;
      std::list<Edge> added_edges;


      void addNode(const Node& node) {
        added_nodes.push_front(node);        
      }
      bool eraseNode(const Node& node) {
        std::list<Node>::iterator it = 
          std::find(added_nodes.begin(), added_nodes.end(), node);
        if (it == added_nodes.end()) {
          clear();
          return false;
        } else {
          added_nodes.erase(it);
          return true;
        }
      }

      void addEdge(const Edge& edge) {
        added_edges.push_front(edge);        
      }
      bool eraseEdge(const Edge& edge) {
        std::list<Edge>::iterator it = 
          std::find(added_edges.begin(), added_edges.end(), edge);
        if (it == added_edges.end()) {
          clear();
          return false;
        } else {
          added_edges.erase(it);
          return true;
        }        
      }

      void attach(ListGraph &_graph) {
	graph = &_graph;
	node_observer_proxy.attach(graph->getNotifier(Node()));
        edge_observer_proxy.attach(graph->getNotifier(Edge()));
      }
            
      void detach() {
	node_observer_proxy.detach();
	edge_observer_proxy.detach();
      }

      void clear() {
        detach();
        added_nodes.clear();
        added_edges.clear();        
      }

    public:

      /// \brief Default constructur.
      ///
      /// Default constructor.
      /// To actually make a snapshot you must call save().
      Snapshot() 
        : graph(0), node_observer_proxy(*this), 
          edge_observer_proxy(*this) {}
      
      /// \brief Constructor that immediately makes a snapshot.
      ///      
      /// This constructor immediately makes a snapshot of the graph.
      /// \param _graph The graph we make a snapshot of.
      Snapshot(ListGraph &_graph) 
        : node_observer_proxy(*this), 
          edge_observer_proxy(*this) {
	attach(_graph);
      }
      
      /// \brief 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 _graph The graph we make the snapshot of.
      void save(ListGraph &_graph) {
        clear();
        attach(_graph);
      }
      
      /// \brief Undo the changes until the last snapshot.
      // 
      /// Undo the changes until last snapshot created by save().
      ///
      /// \todo This function might be called undo().
      void restore() {
	detach();
	while(!added_edges.empty()) {
	  graph->erase(added_edges.front());
	  added_edges.pop_front();
	}
 	while(!added_nodes.empty()) {
	  graph->erase(added_nodes.front());
	  added_nodes.pop_front();
	}
      }

      /// \brief Gives back true when the snapshot is valid.
      ///
      /// Gives back true when the snapshot is valid.
      bool valid() const {
        return node_observer_proxy.attached();
      }
    };
    
  };

} //namespace lemon
  

#endif