//===- IndexingAction.cpp - Frontend index action -------------------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//

#include "clang/Index/IndexingAction.h"
#include "clang/Index/IndexDataConsumer.h"
#include "FileIndexRecord.h"
#include "IndexingContext.h"
#include "ClangIndexRecordWriter.h"
#include "IndexDataStoreUtils.h"
#include "clang/Index/IndexUnitWriter.h"
#include "clang/Frontend/CompilerInstance.h"
#include "clang/Frontend/FrontendAction.h"
#include "clang/Frontend/FrontendDiagnostic.h"
#include "clang/Frontend/MultiplexConsumer.h"
#include "clang/Frontend/Utils.h"
#include "clang/Lex/Preprocessor.h"
#include "clang/Serialization/ASTReader.h"

using namespace clang;
using namespace clang::index;

void IndexDataConsumer::_anchor() {}

bool IndexDataConsumer::handleDeclOccurence(const Decl *D, SymbolRoleSet Roles,
                                            ArrayRef<SymbolRelation> Relations,
                                            FileID FID, unsigned Offset,
                                            ASTNodeInfo ASTNode) {
  return true;
}

bool IndexDataConsumer::handleMacroOccurence(const IdentifierInfo *Name,
                                             const MacroInfo *MI, SymbolRoleSet Roles,
                                             FileID FID, unsigned Offset) {
  return true;
}

bool IndexDataConsumer::handleModuleOccurence(const ImportDecl *ImportD,
                                              SymbolRoleSet Roles,
                                              FileID FID, unsigned Offset) {
  return true;
}

namespace {

class IndexASTConsumer : public ASTConsumer {
  IndexingContext &IndexCtx;

public:
  IndexASTConsumer(IndexingContext &IndexCtx)
    : IndexCtx(IndexCtx) {}

protected:
  void Initialize(ASTContext &Context) override {
    IndexCtx.setASTContext(Context);
    IndexCtx.getDataConsumer().initialize(Context);
  }

  bool HandleTopLevelDecl(DeclGroupRef DG) override {
    return IndexCtx.indexDeclGroupRef(DG);
  }

  void HandleInterestingDecl(DeclGroupRef DG) override {
    // Ignore deserialized decls.
  }

  void HandleTopLevelDeclInObjCContainer(DeclGroupRef DG) override {
    IndexCtx.indexDeclGroupRef(DG);
  }

  void HandleTranslationUnit(ASTContext &Ctx) override {
  }
};

class IndexActionBase {
protected:
  std::shared_ptr<IndexDataConsumer> DataConsumer;
  IndexingContext IndexCtx;

  IndexActionBase(std::shared_ptr<IndexDataConsumer> dataConsumer,
                  IndexingOptions Opts)
    : DataConsumer(std::move(dataConsumer)),
      IndexCtx(Opts, *DataConsumer) {}

  std::unique_ptr<IndexASTConsumer> createIndexASTConsumer(CompilerInstance &CI) {
    IndexCtx.setSysrootPath(CI.getHeaderSearchOpts().Sysroot);
    return llvm::make_unique<IndexASTConsumer>(IndexCtx);
  }

  void finish() {
    DataConsumer->finish();
  }
};

class IndexAction : public ASTFrontendAction, IndexActionBase {
public:
  IndexAction(std::shared_ptr<IndexDataConsumer> DataConsumer,
              IndexingOptions Opts)
    : IndexActionBase(std::move(DataConsumer), Opts) {}

protected:
  std::unique_ptr<ASTConsumer> CreateASTConsumer(CompilerInstance &CI,
                                                 StringRef InFile) override {
    return createIndexASTConsumer(CI);
  }

  void EndSourceFileAction() override {
    FrontendAction::EndSourceFileAction();
    finish();
  }
};

class WrappingIndexAction : public WrapperFrontendAction, IndexActionBase {
  bool CreatedASTConsumer = false;

public:
  WrappingIndexAction(std::unique_ptr<FrontendAction> WrappedAction,
                      std::shared_ptr<IndexDataConsumer> DataConsumer,
                      IndexingOptions Opts)
    : WrapperFrontendAction(std::move(WrappedAction)),
      IndexActionBase(std::move(DataConsumer), Opts) {}

protected:
  std::unique_ptr<ASTConsumer> CreateASTConsumer(CompilerInstance &CI,
                                                 StringRef InFile) override;
  void EndSourceFileAction() override;
};

} // anonymous namespace

void WrappingIndexAction::EndSourceFileAction() {
  // Invoke wrapped action's method.
  WrapperFrontendAction::EndSourceFileAction();
  if (CreatedASTConsumer)
    finish();
}

std::unique_ptr<ASTConsumer>
WrappingIndexAction::CreateASTConsumer(CompilerInstance &CI, StringRef InFile) {
  auto OtherConsumer = WrapperFrontendAction::CreateASTConsumer(CI, InFile);
  if (!OtherConsumer)
    return nullptr;

  CreatedASTConsumer = true;
  std::vector<std::unique_ptr<ASTConsumer>> Consumers;
  Consumers.push_back(std::move(OtherConsumer));
  Consumers.push_back(createIndexASTConsumer(CI));
  return llvm::make_unique<MultiplexConsumer>(std::move(Consumers));
}

std::unique_ptr<FrontendAction>
index::createIndexingAction(std::shared_ptr<IndexDataConsumer> DataConsumer,
                            IndexingOptions Opts,
                            std::unique_ptr<FrontendAction> WrappedAction) {
  if (WrappedAction)
    return llvm::make_unique<WrappingIndexAction>(std::move(WrappedAction),
                                                  std::move(DataConsumer),
                                                  Opts);
  return llvm::make_unique<IndexAction>(std::move(DataConsumer), Opts);
}


static bool topLevelDeclVisitor(void *context, const Decl *D) {
  IndexingContext &IndexCtx = *static_cast<IndexingContext*>(context);
  return IndexCtx.indexTopLevelDecl(D);
}

static void indexTranslationUnit(ASTUnit &Unit, IndexingContext &IndexCtx) {
  Unit.visitLocalTopLevelDecls(&IndexCtx, topLevelDeclVisitor);
}

void index::indexASTUnit(ASTUnit &Unit,
                         std::shared_ptr<IndexDataConsumer> DataConsumer,
                         IndexingOptions Opts) {
  IndexingContext IndexCtx(Opts, *DataConsumer);
  IndexCtx.setASTContext(Unit.getASTContext());
  DataConsumer->initialize(Unit.getASTContext());
  indexTranslationUnit(Unit, IndexCtx);
  DataConsumer->finish();
}

void index::indexModuleFile(serialization::ModuleFile &Mod,
                            ASTReader &Reader,
                            std::shared_ptr<IndexDataConsumer> DataConsumer,
                            IndexingOptions Opts) {
  ASTContext &Ctx = Reader.getContext();
  IndexingContext IndexCtx(Opts, *DataConsumer);
  IndexCtx.setASTContext(Ctx);
  DataConsumer->initialize(Ctx);

  for (const Decl *D :Reader.getModuleFileLevelDecls(Mod)) {
    IndexCtx.indexTopLevelDecl(D);
  }
  DataConsumer->finish();
}

//===----------------------------------------------------------------------===//
// Index Data Recording
//===----------------------------------------------------------------------===//

namespace {

class IndexDataRecorder : public IndexDataConsumer {
  IndexingContext *IndexCtx = nullptr;
  const Preprocessor *PP = nullptr;
  typedef llvm::DenseMap<FileID, std::unique_ptr<FileIndexRecord>> RecordByFileTy;
  RecordByFileTy RecordByFile;

public:
  void init(IndexingContext *idxCtx, const CompilerInstance &CI) {
    IndexCtx = idxCtx;
    PP = &CI.getPreprocessor();
    initialize(CI.getASTContext());
  }

  RecordByFileTy::const_iterator record_begin() const { return RecordByFile.begin(); }
  RecordByFileTy::const_iterator record_end() const { return RecordByFile.end(); }
  bool record_empty() const { return RecordByFile.empty(); }

private:
  bool handleDeclOccurence(const Decl *D, SymbolRoleSet Roles,
                           ArrayRef<SymbolRelation> Relations,
                           FileID FID, unsigned Offset,
                           ASTNodeInfo ASTNode) override {
    // Ignore the predefines buffer.
    if (FID == PP->getPredefinesFileID())
      return true;

    FileIndexRecord &Rec = getFileIndexRecord(FID);
    Rec.addDeclOccurence(Roles, Offset, D, Relations);
    return true;
  }

  FileIndexRecord &getFileIndexRecord(FileID FID) {
    auto &Entry = RecordByFile[FID];
    if (!Entry) {
      Entry.reset(new FileIndexRecord(FID, IndexCtx->isSystemFile(FID)));
    }
    return *Entry;
  }
};

struct IncludeLocation {
  const FileEntry *Source;
  const FileEntry *Target;
  unsigned Line;
};

class IncludePPCallbacks : public PPCallbacks {
  IndexingContext &IndexCtx;
  RecordingOptions RecordOpts;
  std::vector<IncludeLocation> &Includes;
  SourceManager &SourceMgr;

public:
  IncludePPCallbacks(IndexingContext &indexCtx, RecordingOptions recordOpts,
                     std::vector<IncludeLocation> &IncludesForFile,
                     SourceManager &SourceMgr) :
    IndexCtx(indexCtx), RecordOpts(recordOpts),
    Includes(IncludesForFile), SourceMgr(SourceMgr) {}

private:
  void addInclude(SourceLocation From, const FileEntry *To) {
    assert(To);
    if (RecordOpts.RecordIncludes == RecordingOptions::IncludesRecordingKind::None)
      return;

    std::pair<FileID, unsigned> LocInfo = SourceMgr.getDecomposedExpansionLoc(From);
    switch (RecordOpts.RecordIncludes) {
      case RecordingOptions::IncludesRecordingKind::None:
        llvm_unreachable("should have already checked in the beginning");
      case RecordingOptions::IncludesRecordingKind::UserOnly:
        if (IndexCtx.isSystemFile(LocInfo.first))
          return; // Ignore includes of system headers.
        break;
      case RecordingOptions::IncludesRecordingKind::All:
        break;
    }
    auto *FE = SourceMgr.getFileEntryForID(LocInfo.first);
    if (!FE)
      return;
    auto lineNo = SourceMgr.getLineNumber(LocInfo.first, LocInfo.second);
    Includes.push_back({FE, To, lineNo});
  }

  virtual void InclusionDirective(SourceLocation HashLoc,
                                  const Token &IncludeTok,
                                  StringRef FileName,
                                  bool IsAngled,
                                  CharSourceRange FilenameRange,
                                  const FileEntry *File,
                                  StringRef SearchPath,
                                  StringRef RelativePath,
                                  const Module *Imported) override {
    if (HashLoc.isFileID() && File && File->isValid())
      addInclude(HashLoc, File);
  }
};

class IndexDependencyProvider {
public:
  virtual ~IndexDependencyProvider() {}

  virtual void visitFileDependencies(const CompilerInstance &CI,
      llvm::function_ref<void(const FileEntry *FE, bool isSystem)> visitor) = 0;
  virtual void visitIncludes(
                 llvm::function_ref<void(const FileEntry *Source, unsigned Line,
                                         const FileEntry *Target)> visitor) = 0;
  virtual void visitModuleImports(const CompilerInstance &CI,
                 llvm::function_ref<void(serialization::ModuleFile &Mod,
                                         bool isSystem)> visitor) = 0;
};

class SourceFilesIndexDependencyCollector : public DependencyCollector, public IndexDependencyProvider {
  IndexingContext &IndexCtx;
  RecordingOptions RecordOpts;
  llvm::SetVector<const FileEntry *> Entries;
  llvm::BitVector IsSystemByUID;
  std::vector<IncludeLocation> Includes;
  SourceManager *SourceMgr = nullptr;
  std::string SysrootPath;

public:
  SourceFilesIndexDependencyCollector(IndexingContext &indexCtx, RecordingOptions recordOpts)
    : IndexCtx(indexCtx), RecordOpts(recordOpts) {}

  virtual void attachToPreprocessor(Preprocessor &PP) override {
    DependencyCollector::attachToPreprocessor(PP);
    PP.addPPCallbacks(llvm::make_unique<IncludePPCallbacks>(IndexCtx,
                                                            RecordOpts,
                                                            Includes,
                                                            PP.getSourceManager()));
  }

  void setSourceManager(SourceManager *SourceMgr) {
    this->SourceMgr = SourceMgr;
  }
  void setSysrootPath(StringRef sysroot) { SysrootPath = sysroot; }

  void visitFileDependencies(const CompilerInstance &CI,
      llvm::function_ref<void(const FileEntry *FE, bool isSystem)> visitor) override {
    for (auto *FE : getEntries()) {
      visitor(FE, isSystemFile(FE));
    }
  }

  void visitIncludes(
                 llvm::function_ref<void(const FileEntry *Source, unsigned Line,
                                         const FileEntry *Target)> visitor) override {
    for (auto &Include : Includes) {
      visitor(Include.Source, Include.Line, Include.Target);
    }
  }

  void visitModuleImports(const CompilerInstance &CI,
                 llvm::function_ref<void(serialization::ModuleFile &Mod,
                                         bool isSystem)> visitor) override {
    HeaderSearch &HS = CI.getPreprocessor().getHeaderSearchInfo();

    if (auto Reader = CI.getModuleManager()) {
      Reader->getModuleManager().visit([&](serialization::ModuleFile &Mod) -> bool {
        bool isSystemMod = false;
        if (Mod.isModule()) {
          if (auto *M = HS.lookupModule(Mod.ModuleName, /*AllowSearch=*/false))
            isSystemMod = M->IsSystem;
        }
        if (!isSystemMod || needSystemDependencies())
          visitor(Mod, isSystemMod);
        return true; // skip module dependencies.
      });
    }
  }

private:
  bool isSystemFile(const FileEntry *FE) {
    auto UID = FE->getUID();
    return IsSystemByUID.size() > UID && IsSystemByUID[UID];
  }

  ArrayRef<const FileEntry *> getEntries() const {
    return Entries.getArrayRef();
  }

  bool needSystemDependencies() override {
    return RecordOpts.RecordSystemDependencies;
  }

  bool sawDependency(StringRef Filename, bool FromModule,
                     bool IsSystem, bool IsModuleFile, bool IsMissing) override {
    bool sawIt = DependencyCollector::sawDependency(Filename, FromModule,
                                                    IsSystem, IsModuleFile,
                                                    IsMissing);
    if (auto *FE = SourceMgr->getFileManager().getFile(Filename)) {
      if (sawIt)
        Entries.insert(FE);
      // Record system-ness for all files that we pass through.
      if (IsSystemByUID.size() < FE->getUID()+1)
        IsSystemByUID.resize(FE->getUID()+1);
        IsSystemByUID[FE->getUID()] = IsSystem || isInSysroot(Filename);
    }
    return sawIt;
  }

  bool isInSysroot(StringRef Filename) {
    return !SysrootPath.empty() && Filename.startswith(SysrootPath);
  }
};

class IndexRecordActionBase {
protected:
  RecordingOptions RecordOpts;
  IndexDataRecorder Recorder;
  IndexingContext IndexCtx;
  SourceFilesIndexDependencyCollector DepCollector;

  IndexRecordActionBase(IndexingOptions IndexOpts, RecordingOptions recordOpts)
    : RecordOpts(std::move(recordOpts)),
      IndexCtx(IndexOpts, Recorder),
      DepCollector(IndexCtx, RecordOpts) {
  }

  std::unique_ptr<IndexASTConsumer>
  createIndexASTConsumer(CompilerInstance &CI) {
    IndexCtx.setSysrootPath(CI.getHeaderSearchOpts().Sysroot);
    Recorder.init(&IndexCtx, CI);

    Preprocessor &PP = CI.getPreprocessor();
    DepCollector.setSourceManager(&CI.getSourceManager());
    DepCollector.setSysrootPath(IndexCtx.getSysrootPath());
    DepCollector.attachToPreprocessor(PP);

    return llvm::make_unique<IndexASTConsumer>(IndexCtx);
  }

  void finish(CompilerInstance &CI);
};

class IndexRecordAction : public ASTFrontendAction, IndexRecordActionBase {
public:
  IndexRecordAction(IndexingOptions IndexOpts, RecordingOptions RecordOpts)
    : IndexRecordActionBase(std::move(IndexOpts), std::move(RecordOpts)) {}

protected:
  std::unique_ptr<ASTConsumer> CreateASTConsumer(CompilerInstance &CI,
                                                 StringRef InFile) override {
    return createIndexASTConsumer(CI);
  }

  void EndSourceFileAction() override {
    FrontendAction::EndSourceFileAction();
    finish(getCompilerInstance());
  }
};

class WrappingIndexRecordAction : public WrapperFrontendAction, IndexRecordActionBase {
  bool CreatedASTConsumer = false;

public:
  WrappingIndexRecordAction(std::unique_ptr<FrontendAction> WrappedAction,
                            IndexingOptions IndexOpts,
                            RecordingOptions RecordOpts)
    : WrapperFrontendAction(std::move(WrappedAction)),
      IndexRecordActionBase(std::move(IndexOpts), std::move(RecordOpts)) {}

protected:
  std::unique_ptr<ASTConsumer> CreateASTConsumer(CompilerInstance &CI,
                                                 StringRef InFile) override {
    auto OtherConsumer = WrapperFrontendAction::CreateASTConsumer(CI, InFile);
    if (!OtherConsumer)
      return nullptr;

    CreatedASTConsumer = true;
    std::vector<std::unique_ptr<ASTConsumer>> Consumers;
    Consumers.push_back(std::move(OtherConsumer));
    Consumers.push_back(createIndexASTConsumer(CI));
    return llvm::make_unique<MultiplexConsumer>(std::move(Consumers));
  }

  void EndSourceFileAction() override {
    // Invoke wrapped action's method.
    WrapperFrontendAction::EndSourceFileAction();
    if (CreatedASTConsumer)
      finish(getCompilerInstance());
  }
};

} // anonymous namespace

static std::string getClangVersion() {
  // Try picking the version from an Apple Clang tag.
  std::string RepositoryPath = getClangRepositoryPath();
  StringRef BuildNumber = StringRef(RepositoryPath);
  size_t DashOffset = BuildNumber.find('-');
  if (BuildNumber.startswith("clang") && DashOffset != StringRef::npos) {
    BuildNumber = BuildNumber.substr(DashOffset + 1);
    return BuildNumber;
  }
  // Fallback to the generic version.
  return CLANG_VERSION_STRING;
}

static void writeUnitData(const CompilerInstance &CI,
                          IndexDataRecorder &Recorder,
                          IndexDependencyProvider &DepProvider,
                          IndexingOptions IndexOpts,
                          RecordingOptions RecordOpts,
                          StringRef OutputFile,
                          const FileEntry *RootFile,
                          Module *UnitModule,
                          StringRef SysrootPath);

void IndexRecordActionBase::finish(CompilerInstance &CI) {
  // We may emit more diagnostics so do the begin/end source file invocations
  // on the diagnostic client.
  // FIXME: FrontendAction::EndSourceFile() should probably not call
  // CI.getDiagnosticClient().EndSourceFile()' until after it has called
  // 'EndSourceFileAction()', so that code executing during EndSourceFileAction()
  // can emit diagnostics. If this is fixed, DiagClientBeginEndRAII can go away.
  struct DiagClientBeginEndRAII {
    CompilerInstance &CI;
    DiagClientBeginEndRAII(CompilerInstance &CI) : CI(CI) {
      CI.getDiagnosticClient().BeginSourceFile(CI.getLangOpts());
    }
    ~DiagClientBeginEndRAII() {
      CI.getDiagnosticClient().EndSourceFile();
    }
  } diagClientBeginEndRAII(CI);

  SourceManager &SM = CI.getSourceManager();
  DiagnosticsEngine &Diag = CI.getDiagnostics();
  HeaderSearch &HS = CI.getPreprocessor().getHeaderSearchInfo();
  StringRef DataPath = RecordOpts.DataDirPath;

  std::string Error;
  if (IndexUnitWriter::initIndexDirectory(DataPath, Error)) {
    unsigned DiagID = Diag.getCustomDiagID(
        DiagnosticsEngine::Error, "failed creating index directory %0");
    Diag.Report(DiagID) << Error;
    return;
  }

  std::string OutputFile = CI.getFrontendOpts().OutputFile;
  if (OutputFile.empty()) {
    OutputFile = CI.getFrontendOpts().Inputs[0].getFile();
    OutputFile += ".o";
  }

  const FileEntry *RootFile = nullptr;
  Module *UnitMod = nullptr;
  bool isModuleGeneration = CI.getLangOpts().isCompilingModule();
  if (!isModuleGeneration &&
      CI.getFrontendOpts().ProgramAction != frontend::GeneratePCH) {
    RootFile = SM.getFileEntryForID(SM.getMainFileID());
  }
  if (isModuleGeneration) {
    UnitMod = HS.lookupModule(CI.getLangOpts().CurrentModule,
                              /*AllowSearch=*/false);
  }

  writeUnitData(CI, Recorder, DepCollector, IndexCtx.getIndexOpts(), RecordOpts,
                OutputFile, RootFile, UnitMod,
                IndexCtx.getSysrootPath());
}

/// Checks if the unit file exists for module file, if it doesn't it generates
/// index data for it.
static bool produceIndexDataForModuleFile(
                                      serialization::ModuleFile &Mod,
                                      const CompilerInstance &CI,
                                      IndexingOptions IndexOpts,
                                      RecordingOptions RecordOpts,
                                      IndexUnitWriter &ParentUnitWriter);

static void writeUnitData(const CompilerInstance &CI,
                          IndexDataRecorder &Recorder,
                          IndexDependencyProvider &DepProvider,
                          IndexingOptions IndexOpts,
                          RecordingOptions RecordOpts,
                          StringRef OutputFile,
                          const FileEntry *RootFile,
                          Module *UnitModule,
                          StringRef SysrootPath) {

  SourceManager &SM = CI.getSourceManager();
  DiagnosticsEngine &Diag = CI.getDiagnostics();
  HeaderSearch &HS = CI.getPreprocessor().getHeaderSearchInfo();
  StringRef DataPath = RecordOpts.DataDirPath;
  bool IsSystemUnit = UnitModule ? UnitModule->IsSystem : false;
  bool IsModuleUnit = UnitModule != nullptr;
  bool IsDebugCompilation = CI.getCodeGenOpts().OptimizationLevel == 0;
  std::string ModuleName = UnitModule ? UnitModule->getFullModuleName() : std::string();

  auto getModuleInfo = [](writer::OpaqueModule mod, SmallVectorImpl<char> &Scratch) -> writer::ModuleInfo {
    assert(mod);
    writer::ModuleInfo info;
    std::string fullName = static_cast<const Module*>(mod)->getFullModuleName();
    unsigned offset = Scratch.size();
    Scratch.append(fullName.begin(), fullName.end());
    info.Name = StringRef(Scratch.data()+offset, fullName.size());
    return info;
  };

  auto findModuleForHeader = [&](const FileEntry *FE) -> Module * {
    if (!UnitModule)
      return nullptr;
    if (auto Mod = HS.findModuleForHeader(FE).getModule())
      if (Mod->isSubModuleOf(UnitModule))
        return Mod;
    return nullptr;
  };

  IndexUnitWriter UnitWriter(CI.getFileManager(),
                             DataPath,
                             "clang", getClangVersion(),
                             OutputFile,
                             ModuleName,
                             RootFile,
                             IsSystemUnit,
                             IsModuleUnit,
                             IsDebugCompilation,
                             CI.getTargetOpts().Triple,
                             SysrootPath,
                             getModuleInfo);

  DepProvider.visitFileDependencies(CI, [&](const FileEntry *FE, bool isSystemFile) {
    UnitWriter.addFileDependency(FE, isSystemFile, findModuleForHeader(FE));
  });
  DepProvider.visitIncludes([&](const FileEntry *Source, unsigned Line, const FileEntry *Target) {
    UnitWriter.addInclude(Source, Line, Target);
  });
  DepProvider.visitModuleImports(CI, [&](serialization::ModuleFile &Mod, bool isSystemMod) {
    Module *UnitMod = HS.lookupModule(Mod.ModuleName, /*AllowSearch=*/false);
    UnitWriter.addASTFileDependency(Mod.File, isSystemMod, UnitMod);
    if (Mod.isModule()) {
      produceIndexDataForModuleFile(Mod, CI, IndexOpts, RecordOpts, UnitWriter);
    }
  });

  ClangIndexRecordWriter RecordWriter(CI.getASTContext(), RecordOpts);
  for (auto I = Recorder.record_begin(), E = Recorder.record_end(); I != E; ++I) {
    FileID FID = I->first;
    const FileIndexRecord &Rec = *I->second;
    const FileEntry *FE = SM.getFileEntryForID(FID);
    std::string RecordFile;
    std::string Error;

    if (RecordWriter.writeRecord(FE->getName(), Rec, Error, &RecordFile)) {
      unsigned DiagID = Diag.getCustomDiagID(DiagnosticsEngine::Error,
                                             "failed writing record '%0': %1");
      Diag.Report(DiagID) << RecordFile << Error;
      return;
    }
    UnitWriter.addRecordFile(RecordFile, FE, Rec.isSystem(),
                             findModuleForHeader(FE));
  }

  std::string Error;
  if (UnitWriter.write(Error)) {
    unsigned DiagID = Diag.getCustomDiagID(DiagnosticsEngine::Error,
                                           "failed writing unit data: %0");
    Diag.Report(DiagID) << Error;
    return;
  }
}

namespace {
class ModuleFileIndexDependencyCollector : public IndexDependencyProvider {
  serialization::ModuleFile &ModFile;
  RecordingOptions RecordOpts;

public:
  ModuleFileIndexDependencyCollector(serialization::ModuleFile &Mod,
                                     RecordingOptions recordOpts)
  : ModFile(Mod), RecordOpts(recordOpts) {}

  void visitFileDependencies(const CompilerInstance &CI,
      llvm::function_ref<void(const FileEntry *FE, bool isSystem)> visitor) override {
    auto Reader = CI.getModuleManager();
    Reader->visitInputFiles(ModFile, RecordOpts.RecordSystemDependencies,
                            /*Complain=*/false,
                        [&](const serialization::InputFile &IF, bool isSystem) {
      auto *FE = IF.getFile();
      if (!FE)
        return;
      // Ignore module map files, they are not as important to track as source
      // files and they may be auto-generated which would create an undesirable
      // dependency on an intermediate build byproduct.
      if (FE->getName().endswith("module.modulemap"))
        return;

      visitor(FE, isSystem);
    });
  }

  void visitIncludes(
           llvm::function_ref<void(const FileEntry *Source, unsigned Line,
                                   const FileEntry *Target)> visitor) override {
   // FIXME: Module files without a preprocessing record do not have info about
   // include locations. Serialize enough data to be able to retrieve such info.
  }

  void visitModuleImports(const CompilerInstance &CI,
                 llvm::function_ref<void(serialization::ModuleFile &Mod,
                                         bool isSystem)> visitor) override {
    HeaderSearch &HS = CI.getPreprocessor().getHeaderSearchInfo();
    for (auto *Mod : ModFile.Imports) {
      bool isSystemMod = false;
      if (auto *M = HS.lookupModule(Mod->ModuleName, /*AllowSearch=*/false))
        isSystemMod = M->IsSystem;
      if (!isSystemMod || RecordOpts.RecordSystemDependencies)
        visitor(*Mod, isSystemMod);
    }
  }
};
} // anonymous namespace.

static void indexModule(serialization::ModuleFile &Mod,
                        const CompilerInstance &CI,
                        IndexingOptions IndexOpts,
                        RecordingOptions RecordOpts) {
  DiagnosticsEngine &Diag = CI.getDiagnostics();
  Diag.Report(Mod.ImportLoc, diag::remark_index_producing_module_file_data)
    << Mod.FileName;

  StringRef SysrootPath = CI.getHeaderSearchOpts().Sysroot;
  HeaderSearch &HS = CI.getPreprocessor().getHeaderSearchInfo();
  Module *UnitMod = HS.lookupModule(Mod.ModuleName, /*AllowSearch=*/false);

  IndexDataRecorder Recorder;
  IndexingContext IndexCtx(IndexOpts, Recorder);

  IndexCtx.setASTContext(CI.getASTContext());
  IndexCtx.setSysrootPath(SysrootPath);
  Recorder.init(&IndexCtx, CI);

  for (const Decl *D : CI.getModuleManager()->getModuleFileLevelDecls(Mod)) {
    IndexCtx.indexTopLevelDecl(D);
  }
  Recorder.finish();

  ModuleFileIndexDependencyCollector DepCollector(Mod, RecordOpts);
  writeUnitData(CI, Recorder, DepCollector, IndexOpts, RecordOpts,
                Mod.FileName, /*RootFile=*/nullptr, UnitMod, SysrootPath);

}

static bool produceIndexDataForModuleFile(
                                      serialization::ModuleFile &Mod,
                                      const CompilerInstance &CI,
                                      IndexingOptions IndexOpts,
                                      RecordingOptions RecordOpts,
                                      IndexUnitWriter &ParentUnitWriter) {
  DiagnosticsEngine &Diag = CI.getDiagnostics();
  std::string Error;
  // We don't do timestamp check with the PCM file, on purpose. The PCM may get
  // touched for various reasons which would cause unnecessary work to emit
  // index data. User modules normally will get rebuilt and their index data
  // re-emitted, and system modules are generally stable (and they can also can
  // get rebuilt along with their index data).
  auto IsUptodateOpt = ParentUnitWriter.isUnitUpToDateForOutputFile(Mod.FileName, None, Error);
  if (!IsUptodateOpt.hasValue()) {
    unsigned DiagID = Diag.getCustomDiagID(DiagnosticsEngine::Error,
                                           "failed file status check: %0");
    Diag.Report(DiagID) << Error;
    return false;
  }
  if (*IsUptodateOpt)
    return false;

  indexModule(Mod, CI, IndexOpts, RecordOpts);
  return true;
}

static std::unique_ptr<FrontendAction>
createIndexDataRecordingAction(IndexingOptions IndexOpts,
                               RecordingOptions RecordOpts,
                               std::unique_ptr<FrontendAction> WrappedAction) {
  if (WrappedAction)
    return llvm::make_unique<WrappingIndexRecordAction>(std::move(WrappedAction),
                                                        std::move(IndexOpts),
                                                        std::move(RecordOpts));
  return llvm::make_unique<IndexRecordAction>(std::move(IndexOpts),
                                              std::move(RecordOpts));
}

static std::pair<IndexingOptions, RecordingOptions>
getIndexOptionsFromFrontendOptions(const FrontendOptions &FEOpts) {
  index::IndexingOptions IndexOpts;
  index::RecordingOptions RecordOpts;
  RecordOpts.DataDirPath = FEOpts.IndexStorePath;
  if (FEOpts.IndexIgnoreSystemSymbols) {
    IndexOpts.SystemSymbolFilter =
    index::IndexingOptions::SystemSymbolFilterKind::None;
  }
  RecordOpts.RecordSymbolCodeGenName = FEOpts.IndexRecordCodegenName;
  return { IndexOpts, RecordOpts };
}

std::unique_ptr<FrontendAction>
index::createIndexDataRecordingAction(const FrontendOptions &FEOpts,
                                std::unique_ptr<FrontendAction> WrappedAction) {
  index::IndexingOptions IndexOpts;
  index::RecordingOptions RecordOpts;
  std::tie(IndexOpts, RecordOpts) = getIndexOptionsFromFrontendOptions(FEOpts);
  return ::createIndexDataRecordingAction(IndexOpts, RecordOpts,
                                          std::move(WrappedAction));
}

bool index::emitIndexDataForModuleFile(const Module *Mod,
                                       const CompilerInstance &CI,
                                       IndexUnitWriter &ParentUnitWriter) {
  index::IndexingOptions IndexOpts;
  index::RecordingOptions RecordOpts;
  std::tie(IndexOpts, RecordOpts) = getIndexOptionsFromFrontendOptions(CI.getFrontendOpts());

  auto astReader = CI.getModuleManager();
  serialization::ModuleFile *ModFile = astReader->getModuleManager().lookup(Mod->getASTFile());
  assert(ModFile && "no module file loaded for module ?");
  return produceIndexDataForModuleFile(*ModFile, CI, IndexOpts, RecordOpts, ParentUnitWriter);
}