/******************************************************************************

 * Top contributors (to current version):

 *   Liana Hadarean, Mathias Preiner, Morgan Deters

 *

 * This file is part of the cvc5 project.

 *

 * Copyright (c) 2009-2021 by the authors listed in the file AUTHORS

 * in the top-level source directory and their institutional affiliations.

 * All rights reserved.  See the file COPYING in the top-level source

 * directory for licensing information.

 * ****************************************************************************

 *

 * Sandboxed SAT solver for bv quickchecks.

 */

#include "cvc5_private.h"

#ifndef CVC5__BV_QUICK_CHECK_H

#define CVC5__BV_QUICK_CHECK_H

#include <unordered_set>

#include <vector>

#include "context/cdo.h"

#include "expr/node.h"

#include "prop/sat_solver_types.h"

#include "theory/bv/theory_bv_utils.h"

#include "util/statistics_stats.h"

namespace cvc5 {

namespace theory {

class TheoryModel;

namespace bv {

class TLazyBitblaster;

class BVSolverLayered;

class BVQuickCheck

{

  context::Context d_ctx;

  std::unique_ptr<TLazyBitblaster> d_bitblaster;

  Node d_conflict;

  context::CDO<bool> d_inConflict;

  void setConflict();

 public:

  BVQuickCheck(const std::string& name, theory::bv::BVSolverLayered* bv);

  ~BVQuickCheck();

  bool inConflict();

  /**

   * Checks the satisfiability for a given set of assumptions.

   *

   * @param assumptions literals assumed true

   * @param budget max number of conflicts

   *

   * @return

   */

  prop::SatValue checkSat(std::vector<Node>& assumptions, unsigned long budget);

  /**

   * Checks the satisfiability of given assertions.

   *

   * @param budget max number of conflicts

   *

   * @return

   */

  prop::SatValue checkSat(unsigned long budget);

  /**

   * Convert to CNF and assert the given literal.

   *

   * @param assumption bv literal

   *

   * @return false if a conflict has been found via bcp.

   */

  bool addAssertion(TNode assumption);

  void push();

  void pop();

  void popToZero();

  /**

   * Deletes the SAT solver and CNF stream, but maintains the

   * bit-blasting term cache.

   *

   */

  void clearSolver();

  /**

   * Computes the size of the circuit required to bit-blast

   * atom, by not recounting the nodes in seen.

   *

   * @param node

   * @param seen

   *

   * @return

   */

  uint64_t computeAtomWeight(TNode atom, NodeSet& seen);

  bool collectModelValues(theory::TheoryModel* model,

                          const std::set<Node>& termSet);

  typedef std::unordered_set<TNode>::const_iterator vars_iterator;

  vars_iterator beginVars();

  vars_iterator endVars();

  Node getVarValue(TNode var, bool fullModel);

};

class QuickXPlain

{

  struct Statistics

  {

    TimerStat d_xplainTime;

    IntStat d_numSolved;

    IntStat d_numUnknown;

    IntStat d_numUnknownWasUnsat;

    IntStat d_numConflictsMinimized;

    IntStat d_finalPeriod;

    AverageStat d_avgMinimizationRatio;

    Statistics(const std::string& name);

  };

  BVQuickCheck* d_solver;

  unsigned long d_budget;

  // crazy heuristic variables

  unsigned d_numCalled;  // number of times called

  double d_minRatioSum;  // sum of minimization ratio for computing average min

                         // ratio

  unsigned d_numConflicts;  // number of conflicts (including when minimization

                            // not applied)

  // unsigned d_period; // after how many conflicts to try minimizing again

  // double d_thresh; // if minimization ratio is less, increase period

  // double d_hardThresh; // decrease period if minimization ratio is greater

  // than this

  Statistics d_statistics;

  /**

   * Uses solve with assumptions unsat core feature to

   * further minimize a conflict. The minimized conflict

   * will be between low and the returned value in conflict.

   *

   * @param low

   * @param high

   * @param conflict

   *

   * @return

   */

  unsigned selectUnsatCore(unsigned low,

                           unsigned high,

                           std::vector<TNode>& conflict);

  /**

   * Internal conflict  minimization, attempts to minimize

   * literals in conflict between low and high and adds the

   * result in new_conflict.

   *

   * @param low

   * @param high

   * @param conflict

   * @param new_conflict

   */

  void minimizeConflictInternal(unsigned low,

                                unsigned high,

                                std::vector<TNode>& conflict,

                                std::vector<TNode>& new_conflict);

  bool useHeuristic();

 public:

  QuickXPlain(const std::string& name,

              BVQuickCheck* solver,

              unsigned long budged = 10000);

  ~QuickXPlain();

  Node minimizeConflict(TNode conflict);

};

}  // namespace bv

}  // namespace theory

}  // namespace cvc5

#endif /* CVC5__BV_QUICK_CHECK_H */