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

 * 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.

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

 *

 * Proof checker utility.

 */

#include "cvc5_private.h"

#ifndef CVC5__EXPR__PROOF_CHECKER_H

#define CVC5__EXPR__PROOF_CHECKER_H

#include <map>

#include "expr/node.h"

#include "expr/proof_rule.h"

#include "util/statistics_stats.h"

namespace cvc5 {

class ProofChecker;

class ProofNode;

/** A virtual base class for checking a proof rule */

class ProofRuleChecker

{

 public:

  /**

   * This checks a single step in a proof.

   *

   * Return the formula that is proven by a proof node with the given id,

   * premises and arguments, or null if such a proof node is not well-formed.

   *

   * Note that the input/output of this method expects to be terms in *Skolem

   * form*, which is passed to checkInternal below. Rule checkers may

   * convert premises to witness form when necessary.

   *

   * @param id The id of the proof node to check

   * @param children The premises of the proof node to check. These are nodes

   * corresponding to the conclusion (ProofNode::getResult) of the children

   * of the proof node we are checking in Skolem form.

   * @param args The arguments of the proof node to check

   * @return The conclusion of the proof node, in Skolem form, if successful or

   * null if such a proof node is malformed.

   */

  Node check(PfRule id,

             const std::vector<Node>& children,

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

  /** get an index from a node, return false if we fail */

  static bool getUInt32(TNode n, uint32_t& i);

  /** get a Boolean from a node, return false if we fail */

  static bool getBool(TNode n, bool& b);

  /** get a Kind from a node, return false if we fail */

  static bool getKind(TNode n, Kind& k);

  /** Make a Kind into a node */

  static Node mkKindNode(Kind k);

  /** Register all rules owned by this rule checker into pc. */

 protected:

  /**

   * This checks a single step in a proof.

   *

   * @param id The id of the proof node to check

   * @param children The premises of the proof node to check. These are nodes

   * corresponding to the conclusion (ProofNode::getResult) of the children

   * of the proof node we are checking.

   * @param args The arguments of the proof node to check

   * @return The conclusion of the proof node if successful or null if such a

   * proof node is malformed.

   */

  virtual Node checkInternal(PfRule id,

                             const std::vector<Node>& children,

                             const std::vector<Node>& args) = 0;

};

/** Statistics class */

class ProofCheckerStatistics

{

 public:

  ProofCheckerStatistics();

  /** Counts the number of checks for each kind of proof rule */

  HistogramStat<PfRule> d_ruleChecks;

  /** Total number of rule checks */

  IntStat d_totalRuleChecks;

};

/** A class for checking proofs */

class ProofChecker

{

 public:

  /**

   * Return the formula that is proven by proof node pn, or null if pn is not

   * well-formed. If expected is non-null, then we return null if pn does not

   * prove expected.

   *

   * @param pn The proof node to check

   * @param expected The (optional) formula that is the expected conclusion of

   * the proof node.

   * @return The conclusion of the proof node if successful or null if the

   * proof is malformed, or if no checker is available for id.

   */

  Node check(ProofNode* pn, Node expected = Node::null());

  /** Same as above, with explicit arguments

   *

   * @param id The id of the proof node to check

   * @param children The children of the proof node to check

   * @param args The arguments of the proof node to check

   * @param expected The (optional) formula that is the expected conclusion of

   * the proof node.

   * @return The conclusion of the proof node if successful or null if the

   * proof is malformed, or if no checker is available for id.

   */

  Node check(PfRule id,

             const std::vector<std::shared_ptr<ProofNode>>& children,

             const std::vector<Node>& args,

             Node expected = Node::null());

  /**

   * Same as above, without conclusions instead of proof node children. This

   * is used for debugging. In particular, this function does not throw an

   * assertion failure when a proof step is malformed and can be used without

   * constructing proof nodes.

   *

   * @param id The id of the proof node to check

   * @param children The conclusions of the children of the proof node to check

   * @param args The arguments of the proof node to check

   * @param expected The (optional) formula that is the expected conclusion of

   * the proof node.

   * @param traceTag The trace tag to print debug information to

   * @return The conclusion of the proof node if successful or null if the

   * proof is malformed, or if no checker is available for id.

   */

  Node checkDebug(PfRule id,

                  const std::vector<Node>& cchildren,

                  const std::vector<Node>& args,

                  Node expected = Node::null(),

                  const char* traceTag = "");

  /** Indicate that psc is the checker for proof rule id */

  void registerChecker(PfRule id, ProofRuleChecker* psc);

  /**

   * Indicate that id is a trusted rule with the given pedantic level, e.g.:

   *  0: (mandatory) always a failure to use the given id

   *  1: (major) failure on all (non-zero) pedantic levels

   * 10: (minor) failure only on pedantic levels >= 10.

   */

  void registerTrustedChecker(PfRule id,

                              ProofRuleChecker* psc,

                              uint32_t plevel = 10);

  /** get checker for */

  ProofRuleChecker* getCheckerFor(PfRule id);

  /**

   * Get the pedantic level for id if it has been assigned a pedantic

   * level via registerTrustedChecker above, or zero otherwise.

   */

  uint32_t getPedanticLevel(PfRule id) const;

  /**

   * Is pedantic failure? If so, we return true and write a debug message on the

   * output stream out if enableOutput is true.

   */

  bool isPedanticFailure(PfRule id,

                         std::ostream& out,

                         bool enableOutput = true) const;

 private:

  /** statistics class */

  ProofCheckerStatistics d_stats;

  /** Maps proof rules to their checker */

  std::map<PfRule, ProofRuleChecker*> d_checker;

  /** Maps proof trusted rules to their pedantic level */

  std::map<PfRule, uint32_t> d_plevel;

  /** The pedantic level of this checker */

  uint32_t d_pclevel;

  /**

   * Check internal. This is used by check and checkDebug above. It writes

   * checking errors on out when enableOutput is true. We treat trusted checkers

   * (nullptr in the range of the map d_checker) as failures if

   * useTrustedChecker = false.

   */

  Node checkInternal(PfRule id,

                     const std::vector<Node>& cchildren,

                     const std::vector<Node>& args,

                     Node expected,

                     std::stringstream& out,

                     bool useTrustedChecker,

                     bool enableOutput);

};

}  // namespace cvc5

#endif /* CVC5__EXPR__PROOF_CHECKER_H */