// Copyright 2004 Michael E. Stillman

#ifndef __f4spairs_h_
#define __f4spairs_h_

#include "memblock.hpp"
#include "moninfo.hpp"
#include "f4-types.hpp"

class F4SPairSet : public our_new_delete
{
 private:
  int determine_next_degree(int &result_number);

  spair *make_spair(spair_type type,
                    int deg,
                    int i,
                    int j);  // CAUTION: lcm is allocated correctly, but is
  // NOT initialized.  That is the caller's responsibility!!

  bool pair_not_needed(spair *p, gbelem *m);

  int remove_unneeded_pairs();
  // returns the number of pairs removed, based on the element gb[gb.size()-1]

  pre_spair *create_pre_spair(int i);

  int construct_pairs(bool remove_disjoints);

 public:
  F4SPairSet(const MonomialInfo *MI0, const gb_array &gb0);

  ~F4SPairSet();

  void insert_generator(int deg, packed_monomial lcm, int column);
  // The lcm is a pointer to the space in the polynomial itself

  void insert_spair(pre_spair *p, int me);

  void delete_spair(spair *p);

  int find_new_pairs(bool remove_disjoints);
  // returns the number of new pairs found, using the last element on this list

  int prepare_next_degree(int max, int &result_number);
  // Returns the (sugar) degree being done next, and collects all (or at
  // most 'max', if max>0) spairs in this lowest degree.
  // Returns the degree, sets result_number.
  // These spairs are not sorted in any way.  Should they be?

  spair *get_next_pair();
  // get the next pair in this degree (the one 'prepare_next_degree' set up')
  // returns 0 if at the end

  void display_spair(spair *p);
  // A debugging routine which displays an spair

  void display();
  // A debugging routine which displays the spairs in the set

  long n_unneeded_pairs() const { return nsaved_unneeded; }
  // Returns how many pairs were created, then later removed due to
  // spair criteria.

 private:
  MemoryBlock<pre_spair> PS;      // passed to constructor routine
  MemoryBlock<varpower_word> VP;  // used for constructing new pairs
  int max_varpower_size;

  const MonomialInfo *M;
  const gb_array &gb;
  spair *heap;  // list of pairs
  spair *this_set;
  stash *spair_stash;

  // stats
  long nsaved_unneeded;
};

#endif

// Local Variables:
//  compile-command: "make -C $M2BUILDDIR/Macaulay2/e "
//  End:
