//===--- ProBoundsAvoidUncheckedContainerAccess.cpp - clang-tidy ----------===//
//
// 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
//
//===----------------------------------------------------------------------===//

#include "ProBoundsAvoidUncheckedContainerAccess.h"
#include "../utils/Matchers.h"
#include "../utils/OptionsUtils.h"
#include "clang/ASTMatchers/ASTMatchFinder.h"
#include "llvm/ADT/StringRef.h"

using namespace clang::ast_matchers;

namespace clang::tidy::cppcoreguidelines {

static constexpr llvm::StringRef DefaultExclusionStr =
    "::std::map;::std::unordered_map;::std::flat_map";

ProBoundsAvoidUncheckedContainerAccess::ProBoundsAvoidUncheckedContainerAccess(
    StringRef Name, ClangTidyContext *Context)
    : ClangTidyCheck(Name, Context),
      ExcludedClasses(utils::options::parseStringList(
          Options.get("ExcludeClasses", DefaultExclusionStr))),
      FixMode(Options.get("FixMode", None)),
      FixFunction(Options.get("FixFunction", "gsl::at")),
      FixFunctionEmptyArgs(Options.get("FixFunctionEmptyArgs", FixFunction)) {}

void ProBoundsAvoidUncheckedContainerAccess::storeOptions(
    ClangTidyOptions::OptionMap &Opts) {
  Options.store(Opts, "ExcludeClasses",
                utils::options::serializeStringList(ExcludedClasses));
  Options.store(Opts, "FixMode", FixMode);
  Options.store(Opts, "FixFunction", FixFunction);
  Options.store(Opts, "FixFunctionEmptyArgs", FixFunctionEmptyArgs);
}

// TODO: if at() is defined in another class in the class hierarchy of the class
// that defines the operator[] we matched on, findAlternative() will not detect
// it.
static const CXXMethodDecl *
findAlternativeAt(const CXXMethodDecl *MatchedOperator) {
  const CXXRecordDecl *Parent = MatchedOperator->getParent();
  const QualType SubscriptThisObjType =
      MatchedOperator->getFunctionObjectParameterReferenceType();

  for (const CXXMethodDecl *Method : Parent->methods()) {
    // Require 'Method' to be as accessible as 'MatchedOperator' or more
    if (MatchedOperator->getAccess() < Method->getAccess())
      continue;

    if (MatchedOperator->isConst() != Method->isConst())
      continue;

    const QualType AtThisObjType =
        Method->getFunctionObjectParameterReferenceType();
    if (SubscriptThisObjType != AtThisObjType)
      continue;

    if (!Method->getNameInfo().getName().isIdentifier() ||
        Method->getName() != "at")
      continue;

    const bool SameReturnType =
        Method->getReturnType() == MatchedOperator->getReturnType();
    if (!SameReturnType)
      continue;

    const bool SameNumberOfArguments =
        Method->getNumParams() == MatchedOperator->getNumParams();
    if (!SameNumberOfArguments)
      continue;

    for (unsigned ArgInd = 0; ArgInd < Method->getNumParams(); ArgInd++) {
      const bool SameArgType =
          Method->parameters()[ArgInd]->getOriginalType() ==
          MatchedOperator->parameters()[ArgInd]->getOriginalType();
      if (!SameArgType)
        continue;
    }

    return Method;
  }
  return nullptr;
}

void ProBoundsAvoidUncheckedContainerAccess::registerMatchers(
    MatchFinder *Finder) {
  Finder->addMatcher(
      mapAnyOf(cxxOperatorCallExpr, cxxMemberCallExpr)
          .with(callee(
              cxxMethodDecl(
                  hasOverloadedOperatorName("[]"),
                  anyOf(parameterCountIs(0), parameterCountIs(1)),
                  unless(matchers::matchesAnyListedName(ExcludedClasses)))
                  .bind("operator")))
          .bind("caller"),
      this);
}

void ProBoundsAvoidUncheckedContainerAccess::check(
    const MatchFinder::MatchResult &Result) {

  const auto *MatchedExpr = Result.Nodes.getNodeAs<CallExpr>("caller");

  if (FixMode == None) {
    diag(MatchedExpr->getCallee()->getBeginLoc(),
         "possibly unsafe 'operator[]', consider bounds-safe alternatives")
        << MatchedExpr->getCallee()->getSourceRange();
    return;
  }

  if (const auto *OCE = dyn_cast<CXXOperatorCallExpr>(MatchedExpr)) {
    // Case: a[i]
    const auto LeftBracket = SourceRange(OCE->getCallee()->getBeginLoc(),
                                         OCE->getCallee()->getBeginLoc());
    const auto RightBracket =
        SourceRange(OCE->getOperatorLoc(), OCE->getOperatorLoc());

    if (FixMode == At) {
      // Case: a[i] => a.at(i)
      const auto *MatchedOperator =
          Result.Nodes.getNodeAs<CXXMethodDecl>("operator");
      const CXXMethodDecl *Alternative = findAlternativeAt(MatchedOperator);

      if (!Alternative) {
        diag(MatchedExpr->getCallee()->getBeginLoc(),
             "possibly unsafe 'operator[]', consider "
             "bounds-safe alternatives")
            << MatchedExpr->getCallee()->getSourceRange();
        return;
      }

      diag(MatchedExpr->getCallee()->getBeginLoc(),
           "possibly unsafe 'operator[]', consider "
           "bounds-safe alternative 'at()'")
          << MatchedExpr->getCallee()->getSourceRange()
          << FixItHint::CreateReplacement(LeftBracket, ".at(")
          << FixItHint::CreateReplacement(RightBracket, ")");

      diag(Alternative->getBeginLoc(), "viable 'at()' is defined here",
           DiagnosticIDs::Note)
          << Alternative->getNameInfo().getSourceRange();

    } else if (FixMode == Function) {
      // Case: a[i] => f(a, i)
      //
      // Since C++23, the subscript operator may also be called without an
      // argument, which makes the following distinction necessary
      const bool EmptySubscript =
          MatchedExpr->getDirectCallee()->getNumParams() == 0;

      if (EmptySubscript) {
        auto D = diag(MatchedExpr->getCallee()->getBeginLoc(),
                      "possibly unsafe 'operator[]'%select{, use safe "
                      "function '%1() instead|}0")
                 << FixFunctionEmptyArgs.empty() << FixFunctionEmptyArgs.str()
                 << MatchedExpr->getCallee()->getSourceRange();
        if (!FixFunctionEmptyArgs.empty()) {
          D << FixItHint::CreateInsertion(OCE->getArg(0)->getBeginLoc(),
                                          FixFunctionEmptyArgs.str() + "(")
            << FixItHint::CreateRemoval(LeftBracket)
            << FixItHint::CreateReplacement(RightBracket, ")");
        }
      } else {
        diag(MatchedExpr->getCallee()->getBeginLoc(),
             "possibly unsafe 'operator[]', use safe function '%0()' instead")
            << FixFunction.str() << MatchedExpr->getCallee()->getSourceRange()
            << FixItHint::CreateInsertion(OCE->getArg(0)->getBeginLoc(),
                                          FixFunction.str() + "(")
            << FixItHint::CreateReplacement(LeftBracket, ", ")
            << FixItHint::CreateReplacement(RightBracket, ")");
      }
    }
  } else if (const auto *MCE = dyn_cast<CXXMemberCallExpr>(MatchedExpr)) {
    // Case: a.operator[](i) or a->operator[](i)
    const auto *Callee = dyn_cast<MemberExpr>(MCE->getCallee());

    if (FixMode == At) {
      // Cases: a.operator[](i) => a.at(i) and a->operator[](i) => a->at(i)

      const auto *MatchedOperator =
          Result.Nodes.getNodeAs<CXXMethodDecl>("operator");

      const CXXMethodDecl *Alternative = findAlternativeAt(MatchedOperator);
      if (!Alternative) {
        diag(Callee->getBeginLoc(), "possibly unsafe 'operator[]', consider "
                                    "bounds-safe alternative 'at()'")
            << Callee->getSourceRange();
        return;
      }
      diag(MatchedExpr->getCallee()->getBeginLoc(),
           "possibly unsafe 'operator[]', consider "
           "bounds-safe alternative 'at()'")
          << FixItHint::CreateReplacement(
                 SourceRange(Callee->getMemberLoc(), Callee->getEndLoc()),
                 "at");

      diag(Alternative->getBeginLoc(), "viable 'at()' defined here",
           DiagnosticIDs::Note)
          << Alternative->getNameInfo().getSourceRange();

    } else if (FixMode == Function) {
      // Cases: a.operator[](i) => f(a, i) and a->operator[](i) => f(*a, i)
      const auto *Callee = dyn_cast<MemberExpr>(MCE->getCallee());

      const bool EmptySubscript =
          MCE->getMethodDecl()->getNumNonObjectParams() == 0;

      std::string BeginInsertion =
          (EmptySubscript ? FixFunctionEmptyArgs.str() : FixFunction.str()) +
          "(";

      if (Callee->isArrow())
        BeginInsertion += "*";

      // Since C++23, the subscript operator may also be called without an
      // argument, which makes the following distinction necessary
      if (EmptySubscript) {
        auto D = diag(MatchedExpr->getCallee()->getBeginLoc(),
                      "possibly unsafe 'operator[]'%select{, use safe "
                      "function '%1()' instead|}0")
                 << FixFunctionEmptyArgs.empty() << FixFunctionEmptyArgs.str()
                 << Callee->getSourceRange();

        if (!FixFunctionEmptyArgs.empty()) {
          D << FixItHint::CreateInsertion(MatchedExpr->getBeginLoc(),
                                          BeginInsertion)
            << FixItHint::CreateRemoval(
                   SourceRange(Callee->getOperatorLoc(),
                               MCE->getRParenLoc().getLocWithOffset(-1)));
        }
      } else {
        diag(Callee->getBeginLoc(),
             "possibly unsafe 'operator[]', use safe function '%0()' instead")
            << FixFunction.str() << Callee->getSourceRange()
            << FixItHint::CreateInsertion(MatchedExpr->getBeginLoc(),
                                          BeginInsertion)
            << FixItHint::CreateReplacement(
                   SourceRange(
                       Callee->getOperatorLoc(),
                       MCE->getArg(0)->getBeginLoc().getLocWithOffset(-1)),
                   ", ");
      }
    }
  }
}

} // namespace clang::tidy::cppcoreguidelines

namespace clang::tidy {
using P = cppcoreguidelines::ProBoundsAvoidUncheckedContainerAccess;

llvm::ArrayRef<std::pair<P::FixModes, StringRef>>
OptionEnumMapping<P::FixModes>::getEnumMapping() {
  static constexpr std::pair<P::FixModes, StringRef> Mapping[] = {
      {P::None, "none"}, {P::At, "at"}, {P::Function, "function"}};
  return {Mapping};
}
} // namespace clang::tidy