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

 * Top contributors (to current version):

 *   Andrew Reynolds, Mathias Preiner, Gereon Kremer

 *

 * 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.

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

 *

 * sygus_repair_const

 */

#include "cvc5_private.h"

#ifndef CVC5__THEORY__QUANTIFIERS__SYGUS_REPAIR_CONST_H

#define CVC5__THEORY__QUANTIFIERS__SYGUS_REPAIR_CONST_H

#include <unordered_set>

#include "expr/node.h"

namespace cvc5 {

class LogicInfo;

namespace theory {

namespace quantifiers {

class TermDbSygus;

/** SygusRepairConst

 *

 * This module is used to repair portions of candidate solutions. In particular,

 * given a synthesis conjecture:

 *   exists f. forall x. P( f, x )

 * and a candidate solution f = \x. t[x,r] where r are repairable terms, this

 * function checks whether there exists a term of the form \x. t[x,c'] for some

 * constants c' such that:

 *   forall x. P( (\x. t[x,c']), x )  [***]

 * is satisfiable, where notice that the above formula after beta-reduction may

 * be one in pure first-order logic in a decidable theory (say linear

 * arithmetic). To check this, we invoke a separate instance of the SmtEngine

 * within repairSolution(...) below, which if satisfiable gives us the

 * valuation for c'.

 */

class SygusRepairConst

{

 public:

  SygusRepairConst(TermDbSygus* tds);

  /** initialize

   *

   * Initialize this class with the base instantiation (body) of the sygus

   * conjecture (see SynthConjecture::d_base_inst) and its candidate variables

   * (see SynthConjecture::d_candidates).

   */

  void initialize(Node base_inst, const std::vector<Node>& candidates);

  /** repair solution

   *

   * This function is called when candidates -> candidate_values is a (failed)

   * candidate solution for the synthesis conjecture.

   *

   * If this function returns true, then this class adds to repair_cv the

   * repaired version of the solution candidate_values for each candidate,

   * where for each index i, repair_cv[i] is obtained by replacing constant

   * subterms in candidate_values[i] with others, and

   *    candidates -> repair_cv

   * is a solution for the synthesis conjecture associated with this class.

   * Moreover, it is the case that

   *    repair_cv[j] != candidate_values[j], for at least one j.

   * We always consider applications of the "any constant" constructors in

   * candidate_values to be repairable. In addition, if the flag

   * useConstantsAsHoles is true, we consider all constants whose (sygus) type

   * admit alls constants to be repairable.

   * The repaired solution has the property that it satisfies the synthesis

   * conjecture whose body is given by sygusBody.

   */

  bool repairSolution(Node sygusBody,

                      const std::vector<Node>& candidates,

                      const std::vector<Node>& candidate_values,

                      std::vector<Node>& repair_cv,

                      bool useConstantsAsHoles = false);

  /**

   * Same as above, but where sygusBody is the body (base_inst) provided to the

   * call to initialize of this class.

   */

  bool repairSolution(const std::vector<Node>& candidates,

                      const std::vector<Node>& candidate_values,

                      std::vector<Node>& repair_cv,

                      bool useConstantsAsHoles = false);

  /**

   * Return whether this module has the possibility to repair solutions. This is

   * true if this module has been initialized, and at least one candidate has

   * an "any constant" constructor.

   */

  bool isActive() const;

  /** must repair?

   *

   * This returns true if n must be repaired for it to be a valid solution.

   * This corresponds to whether n contains a subterm that is a symbolic

   * constructor like the "any constant" constructor.

   */

  static bool mustRepair(Node n);

 private:

  /** pointer to the sygus term database of d_qe */

  TermDbSygus* d_tds;

  /**

   * The "base instantiation" of the deep embedding form of the synthesis

   * conjecture associated with this class, see CegConjecture::d_base_inst.

   */

  Node d_base_inst;

  /**

   * whether any sygus type for the candidate variables of d_base_inst (the

   * syntactic restrictions) allows all constants. If this flag is false, then

   * this class is a no-op.

   */

  bool d_allow_constant_grammar;

  /** map from skeleton variables to first-order variables */

  std::map<Node, Node> d_sk_to_fo;

  /** reverse map of d_sk_to_fo */

  std::map<Node, Node> d_fo_to_sk;

  /** a cache of satisfiability queries of the form [***] above we have tried */

  std::unordered_set<Node> d_queries;

  /**

   * Register information for sygus type tn, tprocessed stores the set of

   * already registered types.

   */

  void registerSygusType(TypeNode tn, std::map<TypeNode, bool>& tprocessed);

  /** is repairable?

   *

   * This returns true if n can be repaired by this class. In particular, we

   * return true if n is an "any constant" constructor, or it is a constructor

   * for a constant in a type that allows all constants and useConstantsAsHoles

   * is true.

   */

  static bool isRepairable(Node n, bool useConstantsAsHoles);

  /** get skeleton

   *

   * Returns a skeleton for sygus datatype value n, where the subterms of n that

   * are repairable are replaced by free variables. Since we are interested in

   * returning canonical skeletons, the free variables we use in this

   * replacement are taken from TermDbSygus, where we track indices

   * in free_var_count. Variables we introduce in this way are added to sk_vars.

   * The mapping sk_vars_to_subs contains entries v -> c, where v is a

   * variable in sk_vars, and c is the term in n that it replaced. The flag

   * useConstantsAsHoles affects which terms we consider to be repairable.

   */

  Node getSkeleton(Node n,

                   std::map<TypeNode, int>& free_var_count,

                   std::vector<Node>& sk_vars,

                   std::map<Node, Node>& sk_vars_to_subs,

                   bool useConstantsAsHoles);

  /** get first-order query

   *

   * This function returns a formula that is equivalent to the negation of the

   * synthesis conjecture whose body is given in the first argument, where

   * candidates are replaced by candidate_skeletons,

   * whose free variables are in the set sk_vars. The returned formula

   * is a first-order (quantified) formula in the background logic, without UF,

   * of the form [***] above.

   */

  Node getFoQuery(Node body,

                  const std::vector<Node>& candidates,

                  const std::vector<Node>& candidate_skeletons,

                  const std::vector<Node>& sk_vars);

  /** fit to logic

   *

   * This function ensures that a query of the form [***] above fits the given

   * logic. In our approach for constant repair, replacing constants by

   * variables may introduce e.g. non-linearity. If non-linear arithmetic is

   * not enabled, we must undo some of the variables we introduced when

   * inferring candidate skeletons.

   *

   * body is the (sygus) form of the original synthesis conjecture we are

   * considering in this call.

   *

   * This function may remove variables from sk_vars and the map

   * sk_vars_to_subs. The skeletons candidate_skeletons are obtained by

   * getSkeleton(...) on the resulting vectors. If this function returns a

   * non-null node n', then n' is getFoQuery(...) on the resulting vectors, and

   * n' is in the given logic. The function may return null if it is not

   * possible to find a n' of this form.

   *

   * It uses the function below to choose which variables to remove from

   * sk_vars.

   */

  Node fitToLogic(Node body,

                  LogicInfo& logic,

                  Node n,

                  const std::vector<Node>& candidates,

                  std::vector<Node>& candidate_skeletons,

                  std::vector<Node>& sk_vars,

                  std::map<Node, Node>& sk_vars_to_subs);

  /** get fit to logic exclusion variable

   *

   * If n is not in the given logic, then this method either returns false,

   * or returns true and sets exvar to some variable in the domain of

   * d_fo_to_sk, that must be replaced by a constant for n to be in the given

   * logic. For example, for logic linear arithemic, for input:

   *    x * y = 5

   * where x is in the domain of d_fo_to_sk, this function returns true and sets

   * exvar to x.

   * If n is in the given logic, this method returns true.

   */

  bool getFitToLogicExcludeVar(LogicInfo& logic, Node n, Node& exvar);

};

}  // namespace quantifiers

}  // namespace theory

}  // namespace cvc5

#endif /* CVC5__THEORY__QUANTIFIERS__SYGUS_REPAIR_CONST_H */