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

 * Top contributors (to current version):

 *   Morgan Deters, Andrew Reynolds, Clark Barrett

 *

 * 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.

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

 *

 * Theory of arrays.

 */

#include "cvc5_private.h"

#ifndef CVC5__THEORY__ARRAYS__THEORY_ARRAYS_H

#define CVC5__THEORY__ARRAYS__THEORY_ARRAYS_H

#include <tuple>

#include <unordered_map>

#include "context/cdhashmap.h"

#include "context/cdhashset.h"

#include "context/cdqueue.h"

#include "theory/arrays/array_info.h"

#include "theory/arrays/inference_manager.h"

#include "theory/arrays/proof_checker.h"

#include "theory/arrays/theory_arrays_rewriter.h"

#include "theory/decision_strategy.h"

#include "theory/theory.h"

#include "theory/theory_state.h"

#include "theory/uf/equality_engine.h"

#include "util/statistics_stats.h"

namespace cvc5 {

namespace theory {

namespace arrays {

/**

 * Decision procedure for arrays.

 *

 * Overview of decision procedure:

 *

 * Preliminary notation:

 *   Stores(a)  = {t | a ~ t and t = store( _ _ _ )}

 *   InStores(a) = {t | t = store (b _ _) and a ~ b }

 *   Indices(a) = {i | there exists a term b[i] such that a ~ b or store(b i v)}

 *   ~ represents the equivalence relation based on the asserted equalities in the

 *   current context.

 *

 * The rules implemented are the following:

 *             store(b i v)

 *     Row1 -------------------

 *          store(b i v)[i] = v

 *

 *           store(b i v)  a'[j]

 *     Row ---------------------- [ a' ~ store(b i v) or a' ~ b ]

 *           i = j OR a[j] = b[j]

 *

 *          a  b same kind arrays

 *     Ext ------------------------ [ a!= b in current context, k new var]

 *           a = b OR a[k] != b[k]p

 *

 *

 *  The Row1 one rule is implemented implicitly as follows:

 *     - for each store(b i v) term add the following equality to the congruence

 *       closure store(b i v)[i] = v

 *     - if one of the literals in a conflict is of the form store(b i v)[i] = v

 *       remove it from the conflict

 *

 *  Because new store terms are not created, we need to check if we need to

 *  instantiate a new Row axiom in the following cases:

 *     1. the congruence relation changes (i.e. two terms get merged)

 *         - when a new equality between array terms a = b is asserted we check if

 *           we can instantiate a Row lemma for all pairs of indices i where a is

 *           being read and stores

 *         - this is only done during full effort check

 *     2. a new read term is created either as a consequences of an Ext lemma or a

 *        Row lemma

 *         - this is implemented in the checkRowForIndex method which is called

 *           when preregistering a term of the form a[i].

 *         - as a consequence lemmas are instantiated even before full effort check

 *

 *  The Ext axiom is instantiated when a disequality is asserted during full effort

 *  check. Ext lemmas are stored in a cache to prevent instantiating essentially

 *  the same lemma multiple times.

 */

{

}

class TheoryArrays : public Theory {

  /////////////////////////////////////////////////////////////////////////////

  // MISC

  /////////////////////////////////////////////////////////////////////////////

 private:

  /** True node for predicates = true */

  Node d_true;

  /** True node for predicates = false */

  Node d_false;

  // Statistics

  /** number of Row lemmas */

  IntStat d_numRow;

  /** number of Ext lemmas */

  IntStat d_numExt;

  /** number of propagations */

  IntStat d_numProp;

  /** number of explanations */

  IntStat d_numExplain;

  /** calls to non-linear */

  IntStat d_numNonLinear;

  /** splits on array variables */

  IntStat d_numSharedArrayVarSplits;

  /** splits in getModelVal */

  IntStat d_numGetModelValSplits;

  /** conflicts in getModelVal */

  IntStat d_numGetModelValConflicts;

  /** splits in setModelVal */

  IntStat d_numSetModelValSplits;

  /** conflicts in setModelVal */

  IntStat d_numSetModelValConflicts;

 public:

  TheoryArrays(Env& env,

               OutputChannel& out,

               Valuation valuation,

               std::string name = "theory::arrays::");

  ~TheoryArrays();

  //--------------------------------- initialization

  /** get the official theory rewriter of this theory */

  TheoryRewriter* getTheoryRewriter() override;

  /** get the proof checker of this theory */

  ProofRuleChecker* getProofChecker() override;

  /**

   * Returns true if we need an equality engine. If so, we initialize the

   * information regarding how it should be setup. For details, see the

   * documentation in Theory::needsEqualityEngine.

   */

  bool needsEqualityEngine(EeSetupInfo& esi) override;

  /** finish initialization */

  void finishInit() override;

  //--------------------------------- end initialization

  /////////////////////////////////////////////////////////////////////////////

  // PREPROCESSING

  /////////////////////////////////////////////////////////////////////////////

 private:

  // PPNotifyClass: dummy template class for d_ppEqualityEngine - notifications not used

  class PPNotifyClass {

  public:

    bool notify(TNode propagation) { return true; }

    void notify(TNode t1, TNode t2) { }

  };

  /** The notify class for d_ppEqualityEngine */

  PPNotifyClass d_ppNotify;

  /** Equaltity engine */

  eq::EqualityEngine d_ppEqualityEngine;

  // List of facts learned by preprocessor - needed for permanent ref for benefit of d_ppEqualityEngine

  context::CDList<Node> d_ppFacts;

  Node preprocessTerm(TNode term);

  Node recursivePreprocessTerm(TNode term);

  bool ppDisequal(TNode a, TNode b);

  Node solveWrite(TNode term, bool solve1, bool solve2, bool ppCheck);

  /** The theory rewriter for this theory. */

  TheoryArraysRewriter d_rewriter;

  /** A (default) theory state object */

  TheoryState d_state;

  /** The arrays inference manager */

  InferenceManager d_im;

 public:

  PPAssertStatus ppAssert(TrustNode tin,

                          TrustSubstitutionMap& outSubstitutions) override;

  TrustNode ppRewrite(TNode atom, std::vector<SkolemLemma>& lems) override;

  /////////////////////////////////////////////////////////////////////////////

  // T-PROPAGATION / REGISTRATION

  /////////////////////////////////////////////////////////////////////////////

 private:

  /** Literals to propagate */

  context::CDList<Node> d_literalsToPropagate;

  /** Index of the next literal to propagate */

  context::CDO<unsigned> d_literalsToPropagateIndex;

  /** Should be called to propagate the literal.  */

  bool propagateLit(TNode literal);

  /** Explain why this literal is true by building an explanation */

  void explain(TNode literal, Node& exp);

  /** For debugging only- checks invariants about when things are preregistered*/

  context::CDHashSet<Node> d_isPreRegistered;

  /** Helper for preRegisterTerm, also used internally */

  void preRegisterTermInternal(TNode n);

 public:

  void preRegisterTerm(TNode n) override;

  TrustNode explain(TNode n) override;

  /////////////////////////////////////////////////////////////////////////////

  // SHARING

  /////////////////////////////////////////////////////////////////////////////

 private:

  class MayEqualNotifyClass {

  public:

    bool notify(TNode propagation) { return true; }

    void notify(TNode t1, TNode t2) { }

  };

  /** The notify class for d_mayEqualEqualityEngine */

  MayEqualNotifyClass d_mayEqualNotify;

  /** Equaltity engine for determining if two arrays might be equal */

  eq::EqualityEngine d_mayEqualEqualityEngine;

  // Helper for computeCareGraph

  void checkPair(TNode r1, TNode r2);

 public:

  void notifySharedTerm(TNode t) override;

  void computeCareGraph() override;

  bool isShared(TNode t)

  {

    return (d_sharedArrays.find(t) != d_sharedArrays.end());

  }

  /////////////////////////////////////////////////////////////////////////////

  // MODEL GENERATION

  /////////////////////////////////////////////////////////////////////////////

 public:

  /** Collect model values in m based on the relevant terms given by termSet */

  bool collectModelValues(TheoryModel* m,

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

  /////////////////////////////////////////////////////////////////////////////

  // NOTIFICATIONS

  /////////////////////////////////////////////////////////////////////////////

  void presolve() override;

  /////////////////////////////////////////////////////////////////////////////

  // MAIN SOLVER

  /////////////////////////////////////////////////////////////////////////////

  //--------------------------------- standard check

  /** Post-check, called after the fact queue of the theory is processed. */

  void postCheck(Effort level) override;

  /** Pre-notify fact, return true if processed. */

  bool preNotifyFact(TNode atom,

                     bool pol,

                     TNode fact,

                     bool isPrereg,

                     bool isInternal) override;

  /** Notify fact */

  void notifyFact(TNode atom, bool pol, TNode fact, bool isInternal) override;

  //--------------------------------- end standard check

 private:

  TNode weakEquivGetRep(TNode node);

  TNode weakEquivGetRepIndex(TNode node, TNode index);

  void visitAllLeaves(TNode reason, std::vector<TNode>& conjunctions);

  void weakEquivBuildCond(TNode node, TNode index, std::vector<TNode>& conjunctions);

  void weakEquivMakeRep(TNode node);

  void weakEquivMakeRepIndex(TNode node);

  void weakEquivAddSecondary(TNode index, TNode arrayFrom, TNode arrayTo, TNode reason);

  void checkWeakEquiv(bool arraysMerged);

  // NotifyClass: template helper class for d_equalityEngine - handles call-back from congruence closure module

    TheoryArrays& d_arrays;

  public:

    {

      // Just forward to arrays

      }

    }

                                     TNode t1,

                                     TNode t2,

                                     bool value) override

    {

        // Propagate equality between shared terms

      }

    }

    {

    {

    {

      }

  };

  /** The notify class for d_equalityEngine */

  NotifyClass d_notify;

  /** The proof checker */

  ArraysProofRuleChecker d_checker;

  /** Conflict when merging constants */

  void conflict(TNode a, TNode b);

  /** The conflict node */

  Node d_conflictNode;

  /**

   * Context dependent map from a congruence class canonical representative of

   * type array to an Info pointer that keeps track of information useful to axiom

   * instantiation

   */

  Backtracker<TNode> d_backtracker;

  ArrayInfo d_infoMap;

  context::CDQueue<Node> d_mergeQueue;

  bool d_mergeInProgress;

  using RowLemmaType = std::tuple<TNode, TNode, TNode, TNode>;

  context::CDQueue<RowLemmaType> d_RowQueue;

  context::CDHashSet<RowLemmaType, RowLemmaTypeHashFunction > d_RowAlreadyAdded;

  typedef context::CDHashSet<Node> CDNodeSet;

  CDNodeSet d_sharedArrays;

  CDNodeSet d_sharedOther;

  context::CDO<bool> d_sharedTerms;

  // Map from constant values to read terms that read from that values equal to that constant value in the current model

  // When a new read term is created, we check the index to see if we know the model value.  If so, we add it to d_constReads (and d_constReadsList)

  // If not, we push it onto d_reads and figure out where it goes at computeCareGraph time.

  // d_constReadsList is used as a backup in case we can't compute the model at computeCareGraph time.

  typedef std::unordered_map<Node, CTNodeList*> CNodeNListMap;

  CNodeNListMap d_constReads;

  context::CDList<TNode> d_reads;

  context::CDList<TNode> d_constReadsList;

  context::Context* d_constReadsContext;

  /** Helper class to keep d_constReadsContext in sync with satContext */

    context::Context* d_satContext;

    context::Context* d_contextToPop;

  protected:

   {

     {

     }

  public:

  };/* class ContextPopper */

  ContextPopper d_contextPopper;

  std::unordered_map<Node, Node> d_skolemCache;

  context::CDO<unsigned> d_skolemIndex;

  std::vector<Node> d_skolemAssertions;

  // The decision requests we have for the core

  context::CDQueue<Node> d_decisionRequests;

  // List of nodes that need permanent references in this context

  context::CDList<Node> d_permRef;

  context::CDList<Node> d_modelConstraints;

  context::CDHashSet<Node> d_lemmasSaved;

  std::vector<Node> d_lemmas;

  // Default values for each mayEqual equivalence class

  typedef context::CDHashMap<Node, Node> DefValMap;

  DefValMap d_defValues;

  typedef std::unordered_map<std::pair<TNode, TNode>, CTNodeList*, TNodePairHashFunction> ReadBucketMap;

  ReadBucketMap d_readBucketTable;

  context::Context* d_readTableContext;

  context::CDList<Node> d_arrayMerges;

  std::vector<CTNodeList*> d_readBucketAllocations;

  Node getSkolem(TNode ref);

  Node mkAnd(std::vector<TNode>& conjunctions, bool invert = false, unsigned startIndex = 0);

  void setNonLinear(TNode a);

  Node removeRepLoops(TNode a, TNode rep);

  Node expandStores(TNode s, std::vector<TNode>& assumptions, bool checkLoop = false, TNode a = TNode(), TNode b = TNode());

  void mergeArrays(TNode a, TNode b);

  void checkStore(TNode a);

  void checkRowForIndex(TNode i, TNode a);

  void checkRowLemmas(TNode a, TNode b);

  void propagateRowLemma(RowLemmaType lem);

  void queueRowLemma(RowLemmaType lem);

  bool dischargeLemmas();

  std::vector<Node> d_decisions;

  bool d_inCheckModel;

  int d_topLevel;

  /**

   * The decision strategy for the theory of arrays, which calls the

   * getNextDecisionEngineRequest function below.

   */

  {

   public:

    TheoryArraysDecisionStrategy(TheoryArrays* ta);

    /** initialize */

    void initialize() override;

    /** get next decision request */

    Node getNextDecisionRequest() override;

    /** identify */

    std::string identify() const override;

   private:

    /** pointer to the theory of arrays */

    TheoryArrays* d_ta;

  };

  /** an instance of the above decision strategy */

  std::unique_ptr<TheoryArraysDecisionStrategy> d_dstrat;

  /** Have we registered the above strategy? (context-independent) */

  bool d_dstratInit;

  /** get the next decision request

   *

   * If the "arrays-eager-index" option is enabled, then whenever a

   * read-over-write lemma is generated, a decision request is also generated

   * for the comparison between the indexes that appears in the lemma.

   */

  Node getNextDecisionRequest();

  /**

   * Compute relevant terms. This includes select nodes for the

   * RIntro1 and RIntro2 rules.

   */

  void computeRelevantTerms(std::set<Node>& termSet) override;

};/* class TheoryArrays */

}  // namespace arrays

}  // namespace theory

}  // namespace cvc5

#endif /* CVC5__THEORY__ARRAYS__THEORY_ARRAYS_H */