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//===- TypoCorrection.h - Class for typo correction results -----*- C++ -*-===//

//

// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.

// See https://llvm.org/LICENSE.txt for license information.

// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception

//

//===----------------------------------------------------------------------===//

//

// This file defines the TypoCorrection class, which stores the results of

// Sema's typo correction (Sema::CorrectTypo).

//

//===----------------------------------------------------------------------===//

#ifndef LLVM_CLANG_SEMA_TYPOCORRECTION_H

#define LLVM_CLANG_SEMA_TYPOCORRECTION_H

#include "clang/AST/Decl.h"

#include "clang/AST/DeclarationName.h"

#include "clang/Basic/LLVM.h"

#include "clang/Basic/PartialDiagnostic.h"

#include "clang/Basic/SourceLocation.h"

#include "clang/Sema/DeclSpec.h"

#include "llvm/ADT/ArrayRef.h"

#include "llvm/ADT/SmallVector.h"

#include "llvm/Support/Casting.h"

#include <cstddef>

#include <limits>

#include <string>

#include <utility>

#include <vector>

namespace clang {

class DeclContext;

class IdentifierInfo;

class LangOptions;

class MemberExpr;

class NestedNameSpecifier;

class Sema;

/// Simple class containing the result of Sema::CorrectTypo

class TypoCorrection {

public:

  // "Distance" for unusable corrections

  static const unsigned InvalidDistance = std::numeric_limits<unsigned>::max();

  // The largest distance still considered valid (larger edit distances are

  // mapped to InvalidDistance by getEditDistance).

  static const unsigned MaximumDistance = 10000U;

  // Relative weightings of the "edit distance" components. The higher the

  // weight, the more of a penalty to fitness the component will give (higher

  // weights mean greater contribution to the total edit distance, with the

  // best correction candidates having the lowest edit distance).

  static const unsigned CharDistanceWeight = 100U;

  static const unsigned QualifierDistanceWeight = 110U;

  static const unsigned CallbackDistanceWeight = 150U;

  TypoCorrection(const DeclarationName &Name, NamedDecl *NameDecl,

                 NestedNameSpecifier *NNS = nullptr, unsigned CharDistance = 0,

                 unsigned QualifierDistance = 0)

      : CorrectionName(Name), CorrectionNameSpec(NNS),

        CharDistance(CharDistance), QualifierDistance(QualifierDistance) {

    if (NameDecl)

      CorrectionDecls.push_back(NameDecl);

  }

  TypoCorrection(NamedDecl *Name, NestedNameSpecifier *NNS = nullptr,

                 unsigned CharDistance = 0)

      : CorrectionName(Name->getDeclName()), CorrectionNameSpec(NNS),

        CharDistance(CharDistance) {

    if (Name)

      CorrectionDecls.push_back(Name);

  }

  TypoCorrection(DeclarationName Name, NestedNameSpecifier *NNS = nullptr,

                 unsigned CharDistance = 0)

      : CorrectionName(Name), CorrectionNameSpec(NNS),

        CharDistance(CharDistance) {}

  TypoCorrection() = default;

  /// Gets the DeclarationName of the typo correction

  DeclarationName getCorrection() const { return CorrectionName; }

  IdentifierInfo *getCorrectionAsIdentifierInfo() const {

    return CorrectionName.getAsIdentifierInfo();

  }

  /// Gets the NestedNameSpecifier needed to use the typo correction

  NestedNameSpecifier *getCorrectionSpecifier() const {

    return CorrectionNameSpec;

  }

  void setCorrectionSpecifier(NestedNameSpecifier *NNS) {

    CorrectionNameSpec = NNS;

    ForceSpecifierReplacement = (NNS != nullptr);

  }

  void WillReplaceSpecifier(bool ForceReplacement) {

    ForceSpecifierReplacement = ForceReplacement;

  }

  bool WillReplaceSpecifier() const {

    return ForceSpecifierReplacement;

  }

  void setQualifierDistance(unsigned ED) {

    QualifierDistance = ED;

  }

  void setCallbackDistance(unsigned ED) {

    CallbackDistance = ED;

  }

  // Convert the given weighted edit distance to a roughly equivalent number of

  // single-character edits (typically for comparison to the length of the

  // string being edited).

  static unsigned NormalizeEditDistance(unsigned ED) {

    if (ED > MaximumDistance)

      return InvalidDistance;

    return (ED + CharDistanceWeight / 2) / CharDistanceWeight;

  }

  /// Gets the "edit distance" of the typo correction from the typo.

  /// If Normalized is true, scale the distance down by the CharDistanceWeight

  /// to return the edit distance in terms of single-character edits.

  unsigned getEditDistance(bool Normalized = true) const {

    if (CharDistance > MaximumDistance || QualifierDistance > MaximumDistance ||

        CallbackDistance > MaximumDistance)

      return InvalidDistance;

    unsigned ED =

        CharDistance * CharDistanceWeight +

        QualifierDistance * QualifierDistanceWeight +

        CallbackDistance * CallbackDistanceWeight;

    if (ED > MaximumDistance)

      return InvalidDistance;

    // Half the CharDistanceWeight is added to ED to simulate rounding since

    // integer division truncates the value (i.e. round-to-nearest-int instead

    // of round-to-zero).

    return Normalized ? NormalizeEditDistance(ED) : ED;

  }

  /// Get the correction declaration found by name lookup (before we

  /// looked through using shadow declarations and the like).

  NamedDecl *getFoundDecl() const {

    return hasCorrectionDecl() ? *(CorrectionDecls.begin()) : nullptr;

  }

  /// Gets the pointer to the declaration of the typo correction

  NamedDecl *getCorrectionDecl() const {

    auto *D = getFoundDecl();

    return D ? D->getUnderlyingDecl() : nullptr;

  }

  template <class DeclClass>

  DeclClass *getCorrectionDeclAs() const {

    return dyn_cast_or_null<DeclClass>(getCorrectionDecl());

  }

  /// Clears the list of NamedDecls.

  void ClearCorrectionDecls() {

    CorrectionDecls.clear();

  }

  /// Clears the list of NamedDecls before adding the new one.

  void setCorrectionDecl(NamedDecl *CDecl) {

    CorrectionDecls.clear();

    addCorrectionDecl(CDecl);

  }

  /// Clears the list of NamedDecls and adds the given set.

  void setCorrectionDecls(ArrayRef<NamedDecl*> Decls) {

    CorrectionDecls.clear();

    CorrectionDecls.insert(CorrectionDecls.begin(), Decls.begin(), Decls.end());

  }

  /// Add the given NamedDecl to the list of NamedDecls that are the

  /// declarations associated with the DeclarationName of this TypoCorrection

  void addCorrectionDecl(NamedDecl *CDecl);

  std::string getAsString(const LangOptions &LO) const;

  std::string getQuoted(const LangOptions &LO) const {

    return "'" + getAsString(LO) + "'";

  }

  /// Returns whether this TypoCorrection has a non-empty DeclarationName

  explicit operator bool() const { return bool(CorrectionName); }

  /// Mark this TypoCorrection as being a keyword.

  /// Since addCorrectionDeclsand setCorrectionDecl don't allow NULL to be

  /// added to the list of the correction's NamedDecl pointers, NULL is added

  /// as the only element in the list to mark this TypoCorrection as a keyword.

  void makeKeyword() {

    CorrectionDecls.clear();

    CorrectionDecls.push_back(nullptr);

    ForceSpecifierReplacement = true;

  }

  // Check if this TypoCorrection is a keyword by checking if the first

  // item in CorrectionDecls is NULL.

  bool isKeyword() const {

    return !CorrectionDecls.empty() && CorrectionDecls.front() == nullptr;

  }

  // Check if this TypoCorrection is the given keyword.

  template<std::size_t StrLen>

  bool isKeyword(const char (&Str)[StrLen]) const {

    return isKeyword() && getCorrectionAsIdentifierInfo()->isStr(Str);

  }

  // Returns true if the correction either is a keyword or has a known decl.

  bool isResolved() const { return !CorrectionDecls.empty(); }

  bool isOverloaded() const {

    return CorrectionDecls.size() > 1;

  }

  void setCorrectionRange(CXXScopeSpec *SS,

                          const DeclarationNameInfo &TypoName) {

    CorrectionRange = TypoName.getSourceRange();

    if (ForceSpecifierReplacement && SS && !SS->isEmpty())

      CorrectionRange.setBegin(SS->getBeginLoc());

  }

  SourceRange getCorrectionRange() const {

    return CorrectionRange;

  }

  using decl_iterator = SmallVectorImpl<NamedDecl *>::iterator;

  decl_iterator begin() {

    return isKeyword() ? CorrectionDecls.end() : CorrectionDecls.begin();

  }

  decl_iterator end() { return CorrectionDecls.end(); }

  using const_decl_iterator = SmallVectorImpl<NamedDecl *>::const_iterator;

  const_decl_iterator begin() const {

    return isKeyword() ? CorrectionDecls.end() : CorrectionDecls.begin();

  }

  const_decl_iterator end() const { return CorrectionDecls.end(); }

  /// Returns whether this typo correction is correcting to a

  /// declaration that was declared in a module that has not been imported.

  bool requiresImport() const { return RequiresImport; }

  void setRequiresImport(bool Req) { RequiresImport = Req; }

  /// Extra diagnostics are printed after the first diagnostic for the typo.

  /// This can be used to attach external notes to the diag.

  void addExtraDiagnostic(PartialDiagnostic PD) {

    ExtraDiagnostics.push_back(std::move(PD));

  }

  ArrayRef<PartialDiagnostic> getExtraDiagnostics() const {

    return ExtraDiagnostics;

  }

private:

  bool hasCorrectionDecl() const {

    return (!isKeyword() && !CorrectionDecls.empty());

  }

  // Results.

  DeclarationName CorrectionName;

  NestedNameSpecifier *CorrectionNameSpec = nullptr;

  SmallVector<NamedDecl *, 1> CorrectionDecls;

  unsigned CharDistance = 0;

  unsigned QualifierDistance = 0;

  unsigned CallbackDistance = 0;

  SourceRange CorrectionRange;

  bool ForceSpecifierReplacement = false;

  bool RequiresImport = false;

  std::vector<PartialDiagnostic> ExtraDiagnostics;

};

/// Base class for callback objects used by Sema::CorrectTypo to check

/// the validity of a potential typo correction.

class CorrectionCandidateCallback {

public:

  static const unsigned InvalidDistance = TypoCorrection::InvalidDistance;

  explicit CorrectionCandidateCallback(IdentifierInfo *Typo = nullptr,

                                       NestedNameSpecifier *TypoNNS = nullptr)

      : Typo(Typo), TypoNNS(TypoNNS) {}

  virtual ~CorrectionCandidateCallback() = default;

  /// Simple predicate used by the default RankCandidate to

  /// determine whether to return an edit distance of 0 or InvalidDistance.

  /// This can be overridden by validators that only need to determine if a

  /// candidate is viable, without ranking potentially viable candidates.

  /// Only ValidateCandidate or RankCandidate need to be overridden by a

  /// callback wishing to check the viability of correction candidates.

  /// The default predicate always returns true if the candidate is not a type

  /// name or keyword, true for types if WantTypeSpecifiers is true, and true

  /// for keywords if WantTypeSpecifiers, WantExpressionKeywords,

  /// WantCXXNamedCasts, WantRemainingKeywords, or WantObjCSuper is true.

  virtual bool ValidateCandidate(const TypoCorrection &candidate);

  /// Method used by Sema::CorrectTypo to assign an "edit distance" rank

  /// to a candidate (where a lower value represents a better candidate), or

  /// returning InvalidDistance if the candidate is not at all viable. For

  /// validation callbacks that only need to determine if a candidate is viable,

  /// the default RankCandidate returns either 0 or InvalidDistance depending

  /// whether ValidateCandidate returns true or false.

  virtual unsigned RankCandidate(const TypoCorrection &candidate) {

    return (!MatchesTypo(candidate) && ValidateCandidate(candidate))

               ? 0

               : InvalidDistance;

  }

  /// Clone this CorrectionCandidateCallback. CorrectionCandidateCallbacks are

  /// initially stack-allocated. However in case where delayed typo-correction

  /// is done we need to move the callback to storage with a longer lifetime.

  /// Every class deriving from CorrectionCandidateCallback must implement

  /// this method.

  virtual std::unique_ptr<CorrectionCandidateCallback> clone() = 0;

  void setTypoName(IdentifierInfo *II) { Typo = II; }

  void setTypoNNS(NestedNameSpecifier *NNS) { TypoNNS = NNS; }

  // Flags for context-dependent keywords. WantFunctionLikeCasts is only

  // used/meaningful when WantCXXNamedCasts is false.

  // TODO: Expand these to apply to non-keywords or possibly remove them.

  bool WantTypeSpecifiers = true;

  bool WantExpressionKeywords = true;

  bool WantCXXNamedCasts = true;

  bool WantFunctionLikeCasts = true;

  bool WantRemainingKeywords = true;

  bool WantObjCSuper = false;

  // Temporary hack for the one case where a CorrectTypoContext enum is used

  // when looking up results.

  bool IsObjCIvarLookup = false;

  bool IsAddressOfOperand = false;

protected:

  bool MatchesTypo(const TypoCorrection &candidate) {

    return Typo && candidate.isResolved() && !candidate.requiresImport() &&

           candidate.getCorrectionAsIdentifierInfo() == Typo &&

           // FIXME: This probably does not return true when both

           // NestedNameSpecifiers have the same textual representation.

           candidate.getCorrectionSpecifier() == TypoNNS;

  }

  IdentifierInfo *Typo;

  NestedNameSpecifier *TypoNNS;

};

class DefaultFilterCCC final : public CorrectionCandidateCallback {

public:

  explicit DefaultFilterCCC(IdentifierInfo *Typo = nullptr,

                            NestedNameSpecifier *TypoNNS = nullptr)

      : CorrectionCandidateCallback(Typo, TypoNNS) {}

  std::unique_ptr<CorrectionCandidateCallback> clone() override {

    return std::make_unique<DefaultFilterCCC>(*this);

  }

};

/// Simple template class for restricting typo correction candidates

/// to ones having a single Decl* of the given type.

template <class C>

class DeclFilterCCC final : public CorrectionCandidateCallback {

public:

  bool ValidateCandidate(const TypoCorrection &candidate) override {

    return candidate.getCorrectionDeclAs<C>();

  }

  std::unique_ptr<CorrectionCandidateCallback> clone() override {

    return std::make_unique<DeclFilterCCC>(*this);

  }

};

// Callback class to limit the allowed keywords and to only accept typo

// corrections that are keywords or whose decls refer to functions (or template

// functions) that accept the given number of arguments.

class FunctionCallFilterCCC : public CorrectionCandidateCallback {

public:

  FunctionCallFilterCCC(Sema &SemaRef, unsigned NumArgs,

                        bool HasExplicitTemplateArgs,

                        MemberExpr *ME = nullptr);

  bool ValidateCandidate(const TypoCorrection &candidate) override;

  std::unique_ptr<CorrectionCandidateCallback> clone() override {

    return std::make_unique<FunctionCallFilterCCC>(*this);

  }

private:

  unsigned NumArgs;

  bool HasExplicitTemplateArgs;

  DeclContext *CurContext;

  MemberExpr *MemberFn;

};

// Callback class that effectively disabled typo correction

class NoTypoCorrectionCCC final : public CorrectionCandidateCallback {

public:

  NoTypoCorrectionCCC() {

    WantTypeSpecifiers = false;

    WantExpressionKeywords = false;

    WantCXXNamedCasts = false;

    WantFunctionLikeCasts = false;

    WantRemainingKeywords = false;

  }

  bool ValidateCandidate(const TypoCorrection &candidate) override {

    return false;

  }

  std::unique_ptr<CorrectionCandidateCallback> clone() override {

    return std::make_unique<NoTypoCorrectionCCC>(*this);

  }

};

} // namespace clang

#endif // LLVM_CLANG_SEMA_TYPOCORRECTION_H