//===--- UseRangesCheck.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 "UseRangesCheck.h"
#include "Matchers.h"
#include "clang/AST/ASTContext.h"
#include "clang/AST/Decl.h"
#include "clang/AST/Expr.h"
#include "clang/ASTMatchers/ASTMatchFinder.h"
#include "clang/ASTMatchers/ASTMatchers.h"
#include "clang/ASTMatchers/ASTMatchersInternal.h"
#include "clang/Basic/Diagnostic.h"
#include "clang/Basic/LLVM.h"
#include "clang/Basic/SourceLocation.h"
#include "clang/Basic/SourceManager.h"
#include "clang/Lex/Lexer.h"
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SmallBitVector.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/ADT/Twine.h"
#include "llvm/Support/raw_ostream.h"
#include <cassert>
#include <optional>
#include <string>

using namespace clang::ast_matchers;

static constexpr const char BoundCall[] = "CallExpr";
static constexpr const char FuncDecl[] = "FuncDecl";
static constexpr const char ArgName[] = "ArgName";

namespace clang::tidy::utils {

static std::string getFullPrefix(ArrayRef<UseRangesCheck::Indexes> Signature) {
  std::string Output;
  llvm::raw_string_ostream OS(Output);
  for (const UseRangesCheck::Indexes &Item : Signature)
    OS << Item.BeginArg << ":" << Item.EndArg << ":"
       << (Item.ReplaceArg == UseRangesCheck::Indexes::First ? '0' : '1');
  return Output;
}

namespace {

AST_MATCHER(Expr, hasSideEffects) {
  return Node.HasSideEffects(Finder->getASTContext());
}
} // namespace

static auto
makeExprMatcher(ast_matchers::internal::Matcher<Expr> ArgumentMatcher,
                ArrayRef<StringRef> MethodNames,
                ArrayRef<StringRef> FreeNames) {
  return expr(
      anyOf(cxxMemberCallExpr(argumentCountIs(0),
                              callee(cxxMethodDecl(hasAnyName(MethodNames))),
                              on(ArgumentMatcher)),
            callExpr(argumentCountIs(1), hasArgument(0, ArgumentMatcher),
                     hasDeclaration(functionDecl(hasAnyName(FreeNames))))));
}

static ast_matchers::internal::Matcher<CallExpr>
makeMatcherPair(StringRef State, const UseRangesCheck::Indexes &Indexes,
                ArrayRef<StringRef> BeginFreeNames,
                ArrayRef<StringRef> EndFreeNames,
                const std::optional<UseRangesCheck::ReverseIteratorDescriptor>
                    &ReverseDescriptor) {
  std::string ArgBound = (ArgName + llvm::Twine(Indexes.BeginArg)).str();
  SmallString<64> ID = {BoundCall, State};
  ast_matchers::internal::Matcher<CallExpr> ArgumentMatcher = allOf(
      hasArgument(Indexes.BeginArg,
                  makeExprMatcher(expr(unless(hasSideEffects())).bind(ArgBound),
                                  {"begin", "cbegin"}, BeginFreeNames)),
      hasArgument(Indexes.EndArg,
                  makeExprMatcher(
                      expr(matchers::isStatementIdenticalToBoundNode(ArgBound)),
                      {"end", "cend"}, EndFreeNames)));
  if (ReverseDescriptor) {
    ArgBound.push_back('R');
    SmallVector<StringRef> RBegin{
        llvm::make_first_range(ReverseDescriptor->FreeReverseNames)};
    SmallVector<StringRef> REnd{
        llvm::make_second_range(ReverseDescriptor->FreeReverseNames)};
    ArgumentMatcher = anyOf(
        ArgumentMatcher,
        allOf(hasArgument(
                  Indexes.BeginArg,
                  makeExprMatcher(expr(unless(hasSideEffects())).bind(ArgBound),
                                  {"rbegin", "crbegin"}, RBegin)),
              hasArgument(
                  Indexes.EndArg,
                  makeExprMatcher(
                      expr(matchers::isStatementIdenticalToBoundNode(ArgBound)),
                      {"rend", "crend"}, REnd))));
  }
  return callExpr(argumentCountAtLeast(
                      std::max(Indexes.BeginArg, Indexes.EndArg) + 1),
                  ArgumentMatcher)
      .bind(ID);
}

void UseRangesCheck::registerMatchers(MatchFinder *Finder) {
  auto Replaces = getReplacerMap();
  ReverseDescriptor = getReverseDescriptor();
  auto BeginEndNames = getFreeBeginEndMethods();
  llvm::SmallVector<StringRef, 4> BeginNames{
      llvm::make_first_range(BeginEndNames)};
  llvm::SmallVector<StringRef, 4> EndNames{
      llvm::make_second_range(BeginEndNames)};
  Replacers.clear();
  llvm::DenseSet<Replacer *> SeenRepl;
  for (auto I = Replaces.begin(), E = Replaces.end(); I != E; ++I) {
    auto Replacer = I->getValue();
    if (!SeenRepl.insert(Replacer.get()).second)
      continue;
    Replacers.push_back(Replacer);
    assert(!Replacer->getReplacementSignatures().empty() &&
           llvm::all_of(Replacer->getReplacementSignatures(),
                        [](auto Index) { return !Index.empty(); }));
    std::vector<StringRef> Names(1, I->getKey());
    for (auto J = std::next(I); J != E; ++J)
      if (J->getValue() == Replacer)
        Names.push_back(J->getKey());

    std::vector<ast_matchers::internal::DynTypedMatcher> TotalMatchers;
    // As we match on the first matched signature, we need to sort the
    // signatures in order of length(longest to shortest). This way any
    // signature that is a subset of another signature will be matched after the
    // other.
    SmallVector<Signature> SigVec(Replacer->getReplacementSignatures());
    llvm::sort(SigVec, [](auto &L, auto &R) { return R.size() < L.size(); });
    for (const auto &Signature : SigVec) {
      std::vector<ast_matchers::internal::DynTypedMatcher> Matchers;
      for (const auto &ArgPair : Signature)
        Matchers.push_back(makeMatcherPair(getFullPrefix(Signature), ArgPair,
                                           BeginNames, EndNames,
                                           ReverseDescriptor));
      TotalMatchers.push_back(
          ast_matchers::internal::DynTypedMatcher::constructVariadic(
              ast_matchers::internal::DynTypedMatcher::VO_AllOf,
              ASTNodeKind::getFromNodeKind<CallExpr>(), std::move(Matchers)));
    }
    Finder->addMatcher(
        callExpr(
            callee(functionDecl(hasAnyName(std::move(Names)))
                       .bind((FuncDecl + Twine(Replacers.size() - 1).str()))),
            ast_matchers::internal::DynTypedMatcher::constructVariadic(
                ast_matchers::internal::DynTypedMatcher::VO_AnyOf,
                ASTNodeKind::getFromNodeKind<CallExpr>(),
                std::move(TotalMatchers))
                .convertTo<CallExpr>()),
        this);
  }
}

static void removeFunctionArgs(DiagnosticBuilder &Diag, const CallExpr &Call,
                               ArrayRef<unsigned> Indexes,
                               const ASTContext &Ctx) {
  llvm::SmallVector<unsigned> Sorted(Indexes);
  llvm::sort(Sorted);
  // Keep track of commas removed
  llvm::SmallBitVector Commas(Call.getNumArgs());
  // The first comma is actually the '(' which we can't remove
  Commas[0] = true;
  for (unsigned Index : Sorted) {
    const Expr *Arg = Call.getArg(Index);
    if (Commas[Index]) {
      if (Index >= Commas.size()) {
        Diag << FixItHint::CreateRemoval(Arg->getSourceRange());
      } else {
        // Remove the next comma
        Commas[Index + 1] = true;
        Diag << FixItHint::CreateRemoval(CharSourceRange::getTokenRange(
            {Arg->getBeginLoc(),
             Lexer::getLocForEndOfToken(
                 Arg->getEndLoc(), 0, Ctx.getSourceManager(), Ctx.getLangOpts())
                 .getLocWithOffset(1)}));
      }
    } else {
      Diag << FixItHint::CreateRemoval(CharSourceRange::getTokenRange(
          Arg->getBeginLoc().getLocWithOffset(-1), Arg->getEndLoc()));
      Commas[Index] = true;
    }
  }
}

void UseRangesCheck::check(const MatchFinder::MatchResult &Result) {
  Replacer *Replacer = nullptr;
  const FunctionDecl *Function = nullptr;
  for (const auto &[Node, Value] : Result.Nodes.getMap()) {
    StringRef NodeStr(Node);
    if (!NodeStr.consume_front(FuncDecl))
      continue;
    Function = Value.get<FunctionDecl>();
    size_t Index;
    if (NodeStr.getAsInteger(10, Index)) {
      llvm_unreachable("Unable to extract replacer index");
    }
    assert(Index < Replacers.size());
    Replacer = Replacers[Index].get();
    break;
  }
  assert(Replacer && Function);
  SmallString<64> Buffer;
  for (const Signature &Sig : Replacer->getReplacementSignatures()) {
    Buffer.assign({BoundCall, getFullPrefix(Sig)});
    const auto *Call = Result.Nodes.getNodeAs<CallExpr>(Buffer);
    if (!Call)
      continue;

    // FIXME: This check specifically handles `CXXNullPtrLiteralExpr`, but
    // a more general solution might be needed.
    if (Function->getName() == "find") {
      const unsigned ValueArgIndex = 2;
      if (Call->getNumArgs() <= ValueArgIndex)
        continue;
      const Expr *ValueExpr =
          Call->getArg(ValueArgIndex)->IgnoreParenImpCasts();
      if (isa<CXXNullPtrLiteralExpr>(ValueExpr))
        return;
    }

    auto Diag = createDiag(*Call);
    if (auto ReplaceName = Replacer->getReplaceName(*Function))
      Diag << FixItHint::CreateReplacement(Call->getCallee()->getSourceRange(),
                                           *ReplaceName);
    if (auto Include = Replacer->getHeaderInclusion(*Function))
      Diag << Inserter.createIncludeInsertion(
          Result.SourceManager->getFileID(Call->getBeginLoc()), *Include);
    llvm::SmallVector<unsigned, 3> ToRemove;
    for (const auto &[First, Second, Replace] : Sig) {
      auto ArgNode = ArgName + std::to_string(First);
      if (const auto *ArgExpr = Result.Nodes.getNodeAs<Expr>(ArgNode)) {
        Diag << FixItHint::CreateReplacement(
            Call->getArg(Replace == Indexes::Second ? Second : First)
                ->getSourceRange(),
            Lexer::getSourceText(
                CharSourceRange::getTokenRange(ArgExpr->getSourceRange()),
                Result.Context->getSourceManager(),
                Result.Context->getLangOpts()));
      } else {
        assert(ReverseDescriptor && "Couldn't find forward argument");
        ArgNode.push_back('R');
        ArgExpr = Result.Nodes.getNodeAs<Expr>(ArgNode);
        assert(ArgExpr && "Couldn't find forward or reverse argument");
        if (ReverseDescriptor->ReverseHeader)
          Diag << Inserter.createIncludeInsertion(
              Result.SourceManager->getFileID(Call->getBeginLoc()),
              *ReverseDescriptor->ReverseHeader);
        StringRef ArgText = Lexer::getSourceText(
            CharSourceRange::getTokenRange(ArgExpr->getSourceRange()),
            Result.Context->getSourceManager(), Result.Context->getLangOpts());
        SmallString<128> ReplaceText;
        if (ReverseDescriptor->IsPipeSyntax)
          ReplaceText.assign(
              {ArgText, " | ", ReverseDescriptor->ReverseAdaptorName});
        else
          ReplaceText.assign(
              {ReverseDescriptor->ReverseAdaptorName, "(", ArgText, ")"});
        Diag << FixItHint::CreateReplacement(
            Call->getArg(Replace == Indexes::Second ? Second : First)
                ->getSourceRange(),
            ReplaceText);
      }
      ToRemove.push_back(Replace == Indexes::Second ? First : Second);
    }
    removeFunctionArgs(Diag, *Call, ToRemove, *Result.Context);
    return;
  }
  llvm_unreachable("No valid signature found");
}

bool UseRangesCheck::isLanguageVersionSupported(
    const LangOptions &LangOpts) const {
  return LangOpts.CPlusPlus11;
}

UseRangesCheck::UseRangesCheck(StringRef Name, ClangTidyContext *Context)
    : ClangTidyCheck(Name, Context),
      Inserter(Options.getLocalOrGlobal("IncludeStyle",
                                        utils::IncludeSorter::IS_LLVM),
               areDiagsSelfContained()) {}

void UseRangesCheck::registerPPCallbacks(const SourceManager &,
                                         Preprocessor *PP, Preprocessor *) {
  Inserter.registerPreprocessor(PP);
}

void UseRangesCheck::storeOptions(ClangTidyOptions::OptionMap &Opts) {
  Options.store(Opts, "IncludeStyle", Inserter.getStyle());
}

std::optional<std::string>
UseRangesCheck::Replacer::getHeaderInclusion(const NamedDecl &) const {
  return std::nullopt;
}

DiagnosticBuilder UseRangesCheck::createDiag(const CallExpr &Call) {
  return diag(Call.getBeginLoc(), "use a ranges version of this algorithm");
}

std::optional<UseRangesCheck::ReverseIteratorDescriptor>
UseRangesCheck::getReverseDescriptor() const {
  return std::nullopt;
}

ArrayRef<std::pair<StringRef, StringRef>>
UseRangesCheck::getFreeBeginEndMethods() const {
  return {};
}

std::optional<TraversalKind> UseRangesCheck::getCheckTraversalKind() const {
  return TK_IgnoreUnlessSpelledInSource;
}
} // namespace clang::tidy::utils
