// -*- c++ -*-
#ifndef LEMON_ITERABLE_GRAPH_EXTENDER_H
#define LEMON_ITERABLE_GRAPH_EXTENDER_H

#include <lemon/invalid.h>

namespace lemon {
  
  template <typename _Base>
  class IterableGraphExtender : public _Base {
  public:

    typedef _Base Parent;
    typedef IterableGraphExtender<_Base> Graph;

    typedef typename Parent::Node Node;
    typedef typename Parent::Edge Edge;


    class NodeIt : public Node { 
      const Graph* graph;
    public:

      NodeIt() {}

      NodeIt(Invalid i) : Node(i) { }

      explicit NodeIt(const Graph& _graph) : graph(&_graph) {
	_graph.first(*static_cast<Node*>(this));
      }

      NodeIt(const Graph& _graph, const Node& node) 
	: Node(node), graph(&_graph) {}

      NodeIt& operator++() { 
	graph->next(*this);
	return *this; 
      }

    };


    class EdgeIt : public Edge { 
      const Graph* graph;
    public:

      EdgeIt() { }

      EdgeIt(Invalid i) : Edge(i) { }

      explicit EdgeIt(const Graph& _graph) : graph(&_graph) {
	_graph.first(*static_cast<Edge*>(this));
      }

      EdgeIt(const Graph& _graph, const Edge& e) : 
	Edge(e), graph(&_graph) { }

      EdgeIt& operator++() { 
	graph->next(*this);
	return *this; 
      }

    };


    class OutEdgeIt : public Edge { 
      const Graph* graph;
    public:

      OutEdgeIt() { }

      OutEdgeIt(Invalid i) : Edge(i) { }

      OutEdgeIt(const Graph& _graph, const Node& node) 
	: graph(&_graph) {
	_graph.firstOut(*this, node);
      }

      OutEdgeIt(const Graph& _graph, const Edge& edge) 
	: Edge(edge), graph(&_graph) {}

      OutEdgeIt& operator++() { 
	graph->nextOut(*this);
	return *this; 
      }

    };


    class InEdgeIt : public Edge { 
      const Graph* graph;
    public:

      InEdgeIt() { }

      InEdgeIt(Invalid i) : Edge(i) { }

      InEdgeIt(const Graph& _graph, const Node& node) 
	: graph(&_graph) {
	_graph.firstIn(*this, node);
      }

      InEdgeIt(const Graph& _graph, const Edge& edge) : 
	Edge(edge), graph(&_graph) {}

      InEdgeIt& operator++() { 
	graph->nextIn(*this);
	return *this; 
      }

    };

    using Parent::first;

  private:

    /// \todo When (and if) we change the iterators concept to use operator*,
    /// then the following shadowed methods will become superfluous.
    /// But for now these are important safety measures.

    void first(NodeIt &) const;
    void first(EdgeIt &) const;
    void first(OutEdgeIt &) const;
    void first(InEdgeIt &) const;

  };
  
  template <typename _Base>
  class IterableUndirGraphExtender : public IterableGraphExtender<_Base> {
  public:

    typedef IterableGraphExtender<_Base> Parent;
    typedef IterableUndirGraphExtender<_Base> Graph;
    typedef typename Parent::Node Node;

    typedef typename Parent::UndirEdge UndirEdge;

    class UndirEdgeIt : public UndirEdge { 
      const Graph* graph;
    public:

      UndirEdgeIt() { }

      UndirEdgeIt(Invalid i) : UndirEdge(i) { }

      explicit UndirEdgeIt(const Graph& _graph) : graph(&_graph) {
	_graph.first(*static_cast<UndirEdge*>(this));
      }

      UndirEdgeIt(const Graph& _graph, const UndirEdge& e) : 
	UndirEdge(e), graph(&_graph) { }

      UndirEdgeIt& operator++() { 
	graph->next(*this);
	return *this; 
      }

    };

    class IncEdgeIt : public UndirEdge { 
      const Graph* graph;
      bool forward;
      friend class IterableUndirGraphExtender;
      template <typename G>
      friend class UndirGraphExtender;
    public:

      IncEdgeIt() { }

      IncEdgeIt(Invalid i) : UndirEdge(i), forward(false) { }

      explicit IncEdgeIt(const Graph& _graph, const Node &n)
	: graph(&_graph)
      {
	_graph._dirFirstOut(*this, n);
      }

      // FIXME: Do we need this type of constructor here?
      // IncEdgeIt(const Graph& _graph, const Edge& e) : 
      //   UndirEdge(e), graph(&_graph), forward(_graph.forward(e)) { }
      // or
      // IncEdgeIt(const Graph& _graph, const Node& n,
      //    Const UndirEdge &e) ... ?

      IncEdgeIt& operator++() {
	graph->_dirNextOut(*this);
	return *this; 
      }
    };

    Node source(const IncEdgeIt &e) const {
      return _dirSource(e);
    }

    /// \todo Shouldn't the "source" of an undirected edge be called "aNode"
    /// or something???
    using Parent::source;

    /// Target of the given Edge.
    Node target(const IncEdgeIt &e) const {
      return _dirTarget(e);
    }

    /// \todo Shouldn't the "target" of an undirected edge be called "bNode"
    /// or something???
    using Parent::target;

  };
}

#endif // LEMON_GRAPH_EXTENDER_H