#include "internal.h"
#include "gates.h"
#include "logging.h"

bool
kissat_find_equivalence_gate (kissat * solver, unsigned lit)
{
  if (!GET_OPTION (equivalences))
    return false;
  if (!kissat_mark_binaries (solver, lit))
    return false;
  value *marks = solver->marks;
  unsigned not_lit = NOT (lit);
  watches *watches = &WATCHES (not_lit);
  unsigned replace = INVALID_LIT;
  for (all_binary_large_watches (watch, *watches))
    {
      if (!watch.type.binary)
	continue;
      const unsigned other = watch.binary.lit;
      const unsigned not_other = NOT (other);
      if (!marks[not_other])
	continue;
      replace = other;
      break;
    }
  kissat_unmark_binaries (solver, lit);
  if (replace == INVALID_LIT)
    return false;
  LOG ("found equivalence gate %s = %s", LOGLIT (lit), LOGLIT (replace));

  const watch watch1 = kissat_binary_watch (replace, false, false);
  PUSH_STACK (solver->gates[1], watch1);

  const watch watch0 = kissat_binary_watch (NOT (replace), false, false);
  PUSH_STACK (solver->gates[0], watch0);
  solver->gate_eliminated = GATE_ELIMINATED (equivalences);
  return true;
}