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

 * Top contributors (to current version):

 *   Andrew Reynolds, 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.

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

 *

 * Inference to proof conversion.

 */

#include "cvc5_private.h"

#ifndef CVC5__THEORY__STRINGS__INFER_PROOF_CONS_H

#define CVC5__THEORY__STRINGS__INFER_PROOF_CONS_H

#include <vector>

#include "expr/node.h"

#include "proof/proof_checker.h"

#include "proof/proof_rule.h"

#include "proof/theory_proof_step_buffer.h"

#include "theory/builtin/proof_checker.h"

#include "theory/strings/infer_info.h"

#include "theory/strings/sequences_stats.h"

#include "theory/uf/proof_equality_engine.h"

namespace cvc5 {

namespace theory {

namespace strings {

/**

 * Converts between the strings-specific (untrustworthy) InferInfo class and

 * information about how to construct a trustworthy proof step

 * (PfRule, children, args). It acts as a (lazy) proof generator where the

 * former is registered via notifyFact and the latter is asked for in

 * getProofFor, typically by the proof equality engine.

 *

 * The main (private) method of this class is convert below, which is

 * called when we need to construct a proof node from an InferInfo.

 */

class InferProofCons : public ProofGenerator

{

  typedef context::CDHashMap<Node, std::shared_ptr<InferInfo>> NodeInferInfoMap;

 public:

  InferProofCons(context::Context* c,

                 ProofNodeManager* pnm,

                 SequencesStatistics& statistics);

  /**

   * This is called to notify that ii is an inference that may need a proof

   * in the future.

   *

   * In detail, this class should be prepared to respond to a call to:

   *   getProofFor(ii.d_conc)

   * in the remainder of the SAT context. This method copies ii and stores it

   * in the context-dependent map d_lazyFactMap below.

   *

   * This is used for lazy proof construction, where proofs are constructed

   * only for facts that are explained.

   */

  void notifyFact(const InferInfo& ii);

  /**

   * This returns the proof for fact. This is required for using this class as

   * a lazy proof generator.

   *

   * It should be the case that a call was made to notifyFact(ii) where

   * ii.d_conc is fact in this SAT context.

   */

  std::shared_ptr<ProofNode> getProofFor(Node fact) override;

  /** Identify this generator (for debugging, etc..) */

  virtual std::string identify() const override;

 private:

  /** convert

   *

   * This method is called when the theory of strings makes an inference

   * described by an InferInfo, whose fields are given by the first four

   * arguments of this method.

   *

   * This method converts this call to instructions on what the proof rule

   * step(s) are for concluding the conclusion of the inference. This

   * information is either:

   *

   * (A) stored in the argument ps, which consists of:

   * - A proof rule identifier (ProofStep::d_rule).

   * - The premises of the proof step (ProofStep::d_children).

   * - Arguments to the proof step (ProofStep::d_args).

   *

   * (B) If the proof for the inference cannot be captured by a single

   * step, then the d_rule field of ps is not set, and useBuffer is set to

   * true. In this case, the argument psb is updated to contain (possibly

   * multiple) proof steps for how to construct a proof for the given inference.

   * In particular, psb will contain a set of steps that form a proof

   * whose conclusion is ii.d_conc and whose free assumptions are ii.d_ant.

   */

  void convert(InferenceId infer,

               bool isRev,

               Node conc,

               const std::vector<Node>& exp,

               ProofStep& ps,

               TheoryProofStepBuffer& psb,

               bool& useBuffer);

  /**

   * Convert length proof. If this method returns true, it adds proof step(s)

   * to the buffer psb that conclude lenReq from premises lenExp.

   */

  bool convertLengthPf(Node lenReq,

                       const std::vector<Node>& lenExp,

                       TheoryProofStepBuffer& psb);

  /**

   * Helper method, adds the proof of (TRANS eqa eqb) into the proof step

   * buffer psb, where eqa and eqb are flipped as needed. Returns the

   * conclusion, or null if we were not able to construct a TRANS step.

   */

  Node convertTrans(Node eqa, Node eqb, TheoryProofStepBuffer& psb);

  /** the proof node manager */

  ProofNodeManager* d_pnm;

  /** The lazy fact map */

  NodeInferInfoMap d_lazyFactMap;

  /** Reference to the statistics for the theory of strings/sequences. */

  SequencesStatistics& d_statistics;

};

}  // namespace strings

}  // namespace theory

}  // namespace cvc5

#endif /* CVC5__THEORY__STRINGS__INFER_PROOF_CONS_H */