/*********************                                                        */
/*! \file infer_proof_cons.h
 ** \verbatim
 ** Top contributors (to current version):
 **   Andrew Reynolds, Gereon Kremer
 ** This file is part of the CVC4 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.\endverbatim
 **
 ** \brief Inference to proof conversion
 **/

#include "cvc4_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 "expr/proof_checker.h"
#include "expr/proof_rule.h"
#include "theory/builtin/proof_checker.h"
#include "theory/strings/infer_info.h"
#include "theory/strings/sequences_stats.h"
#include "theory/theory_proof_step_buffer.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>, NodeHashFunction>
      NodeInferInfoMap;

 public:
  InferProofCons(context::Context* c,
                 ProofNodeManager* pnm,
                 SequencesStatistics& statistics);
  ~InferProofCons() {}
  /**
   * 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 */