#ifndef VERTEX_PARENT_H
#define VERTEX_PARENT_H

#include <limits.h>
#include <stdio.h>
#include <assert.h>

#include "utils.h"
#include "vertex.h"

// ===================================================================
// VertexParent

// useful when you need to track the hierarchy of vertices.  this data
// structure can be placed in a Bag, and then accessed with the
// extract function to find the child vertex (if it exists) when given
// two parents.

// ===================================================================

class VertexParent { 

public:

  // ========================
  // CONSTRUCTORS & DESTRUCTOR
  VertexParent(Vertex *_p1, Vertex *_p2, Vertex *_v) {
    assert (_p1 != NULL && _p2 != NULL && _v != NULL);
    assert (_p1 != _p2 && _p1 != _v && _p2 != _v);
    p1 = _p1;
    p2 = _p2;
    v = _v;
  }
  ~VertexParent();
  
  // to be put in a bag...
  static void extract_func(VertexParent *e, int &a, int &b, int &c, int &d) {
    a = min2(e->p1->getIndex(),e->p2->getIndex());
    b = max2(e->p1->getIndex(),e->p2->getIndex());
    c = 0;
    d = 0;
  }
 
  // =========
  // ACCESSORS
  Vertex* get() const { return v; }

protected:

  VertexParent(const VertexParent&) { assert(0); }
  VertexParent& operator=(const VertexParent&) { assert(0); }

  // ==============
  // REPRESENTATION
  Vertex *p1;
  Vertex *p2;
  Vertex *v;
};

// ===================================================================

#endif