//===--- ScanDependencies.cpp -- Scans the dependencies of a module -------===//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2014 - 2020 Apple Inc. and the Swift project authors
// Licensed under Apache License v2.0 with Runtime Library Exception
//
// See https://swift.org/LICENSE.txt for license information
// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
//
//===----------------------------------------------------------------------===//

#include "swift-c/DependencyScan/DependencyScan.h"
#include "swift/Basic/PrettyStackTrace.h"

#include "swift/AST/ASTContext.h"
#include "swift/AST/Decl.h"
#include "swift/AST/DiagnosticEngine.h"
#include "swift/AST/DiagnosticsDriver.h"
#include "swift/AST/DiagnosticsFrontend.h"
#include "swift/AST/DiagnosticsSema.h"
#include "swift/AST/FileSystem.h"
#include "swift/AST/Module.h"
#include "swift/AST/ModuleDependencies.h"
#include "swift/AST/ModuleLoader.h"
#include "swift/AST/SourceFile.h"
#include "swift/Basic/Assertions.h"
#include "swift/Basic/Defer.h"
#include "swift/Basic/FileTypes.h"
#include "swift/Basic/LLVM.h"
#include "swift/Basic/STLExtras.h"
#include "swift/ClangImporter/ClangImporter.h"
#include "swift/DependencyScan/DependencyScanImpl.h"
#include "swift/DependencyScan/DependencyScanJSON.h"
#include "swift/DependencyScan/DependencyScanningTool.h"
#include "swift/DependencyScan/ModuleDependencyScanner.h"
#include "swift/DependencyScan/ScanDependencies.h"
#include "swift/DependencyScan/SerializedModuleDependencyCacheFormat.h"
#include "swift/DependencyScan/StringUtils.h"
#include "swift/Frontend/CachingUtils.h"
#include "swift/Frontend/CompileJobCacheKey.h"
#include "swift/Frontend/CompileJobCacheResult.h"
#include "swift/Frontend/Frontend.h"
#include "swift/Frontend/FrontendOptions.h"
#include "swift/Frontend/ModuleInterfaceLoader.h"
#include "swift/Strings.h"
#include "clang/Basic/Module.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SetOperations.h"
#include "llvm/ADT/SetVector.h"
#include "llvm/ADT/StringMap.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/ADT/StringSet.h"
#include "llvm/CAS/ActionCache.h"
#include "llvm/CAS/CASReference.h"
#include "llvm/CAS/ObjectStore.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Error.h"
#include "llvm/Support/FileSystem.h"
#include "llvm/Support/Path.h"
#include "llvm/Support/StringSaver.h"
#include "llvm/Support/VirtualOutputBackend.h"
#include "llvm/Support/YAMLParser.h"
#include "llvm/Support/YAMLTraits.h"
#include "llvm/Support/raw_ostream.h"
#include <algorithm>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <algorithm>

using namespace swift;
using namespace swift::dependencies;
using namespace swift::c_string_utils;
using namespace llvm::yaml;

namespace {

static std::string getScalaNodeText(Node *N) {
  SmallString<32> Buffer;
  return cast<ScalarNode>(N)->getValue(Buffer).str();
}

/// Parse an entry like this, where the "platforms" key-value pair is optional:
///  {
///     "swiftModuleName": "Foo",
///     "arguments": "-target 10.15",
///     "output": "../Foo.json"
///  },
static bool parseBatchInputEntries(ASTContext &Ctx, llvm::StringSaver &saver,
                                   Node *Node,
                                   std::vector<BatchScanInput> &result) {
  auto *SN = cast<SequenceNode>(Node);
  if (!SN)
    return true;
  for (auto It = SN->begin(); It != SN->end(); ++It) {
    auto *MN = cast<MappingNode>(&*It);
    BatchScanInput entry;
    std::optional<std::set<int8_t>> Platforms;
    for (auto &Pair : *MN) {
      auto Key = getScalaNodeText(Pair.getKey());
      auto *Value = Pair.getValue();
      if (Key == "clangModuleName") {
        entry.moduleName = saver.save(getScalaNodeText(Value));
        entry.isSwift = false;
      } else if (Key == "swiftModuleName") {
        entry.moduleName = saver.save(getScalaNodeText(Value));
        entry.isSwift = true;
      } else if (Key == "arguments") {
        entry.arguments = saver.save(getScalaNodeText(Value));
      } else if (Key == "output") {
        entry.outputPath = saver.save(getScalaNodeText(Value));
      } else {
        // Future proof.
        continue;
      }
    }
    if (entry.moduleName.empty())
      return true;
    if (entry.outputPath.empty())
      return true;
    result.emplace_back(std::move(entry));
  }
  return false;
}

static std::optional<std::vector<BatchScanInput>>
parseBatchScanInputFile(ASTContext &ctx, StringRef batchInputPath,
                        llvm::StringSaver &saver) {
  assert(!batchInputPath.empty());
  namespace yaml = llvm::yaml;
  std::vector<BatchScanInput> result;

  // Load the input file.
  llvm::ErrorOr<std::unique_ptr<llvm::MemoryBuffer>> FileBufOrErr =
      llvm::MemoryBuffer::getFile(batchInputPath);
  if (!FileBufOrErr) {
    ctx.Diags.diagnose(SourceLoc(), diag::batch_scan_input_file_missing,
                       batchInputPath);
    return std::nullopt;
  }
  StringRef Buffer = FileBufOrErr->get()->getBuffer();

  // Use a new source manager instead of the one from ASTContext because we
  // don't want the Json file to be persistent.
  SourceManager SM;
  yaml::Stream Stream(llvm::MemoryBufferRef(Buffer, batchInputPath),
                      SM.getLLVMSourceMgr());
  for (auto DI = Stream.begin(); DI != Stream.end(); ++DI) {
    assert(DI != Stream.end() && "Failed to read a document");
    yaml::Node *N = DI->getRoot();
    assert(N && "Failed to find a root");
    if (parseBatchInputEntries(ctx, saver, N, result)) {
      ctx.Diags.diagnose(SourceLoc(), diag::batch_scan_input_file_corrupted,
                         batchInputPath);
      return std::nullopt;
    }
  }
  return result;
}

class ExplicitModuleDependencyResolver {
public:
  ExplicitModuleDependencyResolver(
      ModuleDependencyID moduleID, ModuleDependenciesCache &cache,
      CompilerInstance &instance, std::optional<SwiftDependencyTracker> tracker)
      : moduleID(moduleID), cache(cache), instance(instance),
        resolvingDepInfo(cache.findKnownDependency(moduleID)),
        tracker(std::move(tracker)) {
    // Copy commandline.
    commandline = resolvingDepInfo.getCommandline();
  }

  llvm::Error
  resolve(const std::set<ModuleDependencyID> &dependencies,
          std::optional<std::set<ModuleDependencyID>> bridgingHeaderDeps) {
    // No need to resolve dependency for placeholder.
    if (moduleID.Kind == ModuleDependencyKind::SwiftPlaceholder)
      return llvm::Error::success();

    // If the dependency is already finalized, nothing needs to be done.
    if (resolvingDepInfo.isFinalized())
      return llvm::Error::success();

    if (auto ID = resolvingDepInfo.getClangIncludeTree())
      includeTrees.push_back(*ID);

    for (const auto &depModuleID : dependencies) {
      const auto &depInfo = cache.findKnownDependency(depModuleID);
      switch (depModuleID.Kind) {
      case swift::ModuleDependencyKind::SwiftInterface: {
        auto interfaceDepDetails = depInfo.getAsSwiftInterfaceModule();
        assert(interfaceDepDetails && "Expected Swift Interface dependency.");
        if (auto err = handleSwiftInterfaceModuleDependency(
                depModuleID, *interfaceDepDetails))
          return err;
      } break;
      case swift::ModuleDependencyKind::SwiftBinary: {
        auto binaryDepDetails = depInfo.getAsSwiftBinaryModule();
        assert(binaryDepDetails && "Expected Swift Binary Module dependency.");
        if (auto err = handleSwiftBinaryModuleDependency(depModuleID,
                                                         *binaryDepDetails))
          return err;
      } break;
      case swift::ModuleDependencyKind::SwiftPlaceholder: {
        auto placeholderDetails = depInfo.getAsPlaceholderDependencyModule();
        assert(placeholderDetails && "Expected Swift Placeholder dependency.");
        if (auto err = handleSwiftPlaceholderModuleDependency(
                depModuleID, *placeholderDetails))
          return err;
      } break;
      case swift::ModuleDependencyKind::Clang: {
        auto clangDepDetails = depInfo.getAsClangModule();
        assert(clangDepDetails && "Expected Clang Module dependency.");
        if (auto err =
                handleClangModuleDependency(depModuleID, *clangDepDetails))
          return err;
      } break;
      case swift::ModuleDependencyKind::SwiftSource: {
        auto sourceDepDetails = depInfo.getAsSwiftSourceModule();
        assert(sourceDepDetails && "Expected Swift Source Module dependency.");
        if (auto err = handleSwiftSourceModuleDependency(depModuleID,
                                                         *sourceDepDetails))
          return err;
      } break;
      default:
        llvm_unreachable("Unhandled dependency kind.");
      }
    }

    // Update bridging header build command if there is a bridging header
    // dependency.
    if (auto E = addBridgingHeaderDeps(resolvingDepInfo))
      return E;
    if (bridgingHeaderDeps) {
      bridgingHeaderBuildCmd =
          resolvingDepInfo.getBridgingHeaderCommandline();
      for (auto bridgingDep : *bridgingHeaderDeps) {
        auto &dep = cache.findKnownDependency(bridgingDep);
        auto *clangDep = dep.getAsClangModule();
        assert(clangDep && "wrong module dependency kind");
        if (!clangDep->moduleCacheKey.empty()) {
          bridgingHeaderBuildCmd.push_back("-Xcc");
          bridgingHeaderBuildCmd.push_back("-fmodule-file-cache-key");
          bridgingHeaderBuildCmd.push_back("-Xcc");
          bridgingHeaderBuildCmd.push_back(clangDep->mappedPCMPath);
          bridgingHeaderBuildCmd.push_back("-Xcc");
          bridgingHeaderBuildCmd.push_back(clangDep->moduleCacheKey);
        }
      }
    }

    pruneUnusedVFSOverlay();

    // Update the dependency in the cache with the modified command-line.
    if (resolvingDepInfo.isSwiftInterfaceModule() ||
        resolvingDepInfo.isClangModule()) {
      if (cache.getScanService().hasPathMapping())
        commandline =
            remapPathsFromCommandLine(commandline, [&](StringRef path) {
              return cache.getScanService().remapPath(path);
            });
    }

    auto dependencyInfoCopy = resolvingDepInfo;
    if (auto err = finalize(dependencyInfoCopy))
      return err;

    dependencyInfoCopy.setIsFinalized(true);
    cache.updateDependency(moduleID, dependencyInfoCopy);
    return llvm::Error::success();
  }

private:
  // Finalize the resolving dependency info.
  llvm::Error finalize(ModuleDependencyInfo &depInfo) {
    if (resolvingDepInfo.isSwiftPlaceholderModule())
      return llvm::Error::success();

    // Add macros.
    for (auto &macro : macros)
      depInfo.addMacroDependency(
          macro.first(), macro.second.LibraryPath, macro.second.ExecutablePath);

    for (auto &macro : depInfo.getMacroDependencies()) {
      std::string arg = macro.second.LibraryPath + "#" +
                        macro.second.ExecutablePath + "#" + macro.first;
      commandline.push_back("-load-resolved-plugin");
      commandline.push_back(arg);
    }

    // Update CAS dependencies.
    if (auto err = collectCASDependencies(depInfo))
      return err;

    if (!bridgingHeaderBuildCmd.empty())
      depInfo.updateBridgingHeaderCommandLine(
          bridgingHeaderBuildCmd);
    if (!resolvingDepInfo.isSwiftBinaryModule()) {
      depInfo.updateCommandLine(commandline);
      if (auto err = updateModuleCacheKey(depInfo))
        return err;
    }

    return llvm::Error::success();
  }

  llvm::Error handleSwiftInterfaceModuleDependency(
      ModuleDependencyID depModuleID,
      const SwiftInterfaceModuleDependenciesStorage &interfaceDepDetails) {
    if (!resolvingDepInfo.isSwiftSourceModule()) {
      auto &path = interfaceDepDetails.moduleCacheKey.empty()
                       ? interfaceDepDetails.moduleOutputPath
                       : interfaceDepDetails.moduleCacheKey;
      commandline.push_back("-swift-module-file=" + depModuleID.ModuleName +
                            "=" + path);
    }
    addMacroDependencies(depModuleID, interfaceDepDetails);
    return llvm::Error::success();
  }

  llvm::Error handleSwiftBinaryModuleDependency(
      ModuleDependencyID depModuleID,
      const SwiftBinaryModuleDependencyStorage &binaryDepDetails) {
    if (!resolvingDepInfo.isSwiftSourceModule()) {
      auto &path = binaryDepDetails.moduleCacheKey.empty()
                       ? binaryDepDetails.compiledModulePath
                       : binaryDepDetails.moduleCacheKey;
      commandline.push_back("-swift-module-file=" + depModuleID.ModuleName +
                            "=" + path);
      // If this binary module was built with a header, the header's module
      // dependencies must also specify a .modulemap to the compilation, in
      // order to resolve the header's own header include directives.
      for (const auto &bridgingHeaderDepID :
           binaryDepDetails.headerModuleDependencies) {
        auto optionalBridgingHeaderDepModuleInfo =
            cache.findKnownDependency(bridgingHeaderDepID);
        const auto bridgingHeaderDepModuleDetails =
            optionalBridgingHeaderDepModuleInfo.getAsClangModule();
        commandline.push_back("-Xcc");
        commandline.push_back(
            "-fmodule-map-file=" +
            cache.getScanService().remapPath(
                bridgingHeaderDepModuleDetails->moduleMapFile));
      }
    }
    addMacroDependencies(depModuleID, binaryDepDetails);
    return llvm::Error::success();
  }

  llvm::Error handleSwiftPlaceholderModuleDependency(
      ModuleDependencyID depModuleID,
      const SwiftPlaceholderModuleDependencyStorage &placeholderDetails) {
    if (!resolvingDepInfo.isSwiftSourceModule())
      commandline.push_back("-swift-module-file=" + depModuleID.ModuleName +
                            "=" + placeholderDetails.compiledModulePath);
    return llvm::Error::success();
  }

  llvm::Error handleClangModuleDependency(
      ModuleDependencyID depModuleID,
      const ClangModuleDependencyStorage &clangDepDetails) {
    if (!resolvingDepInfo.isSwiftSourceModule()) {
      if (!resolvingDepInfo.isClangModule()) {
        commandline.push_back("-Xcc");
        commandline.push_back("-fmodule-file=" + depModuleID.ModuleName + "=" +
                              clangDepDetails.mappedPCMPath);
      }
      if (!clangDepDetails.moduleCacheKey.empty()) {
        commandline.push_back("-Xcc");
        commandline.push_back("-fmodule-file-cache-key");
        commandline.push_back("-Xcc");
        commandline.push_back(clangDepDetails.mappedPCMPath);
        commandline.push_back("-Xcc");
        commandline.push_back(clangDepDetails.moduleCacheKey);
      }
    }

    // Collect CAS deppendencies from clang modules.
    if (!clangDepDetails.CASFileSystemRootID.empty())
      rootIDs.push_back(clangDepDetails.CASFileSystemRootID);
    if (!clangDepDetails.CASClangIncludeTreeRootID.empty())
      includeTrees.push_back(clangDepDetails.CASClangIncludeTreeRootID);

    collectUsedVFSOverlay(clangDepDetails);

    return llvm::Error::success();
  }

  llvm::Error handleSwiftSourceModuleDependency(
      ModuleDependencyID depModuleID,
      const SwiftSourceModuleDependenciesStorage &sourceDepDetails) {
    addMacroDependencies(depModuleID, sourceDepDetails);
    return addBridgingHeaderDeps(sourceDepDetails);
  }

  llvm::Error addBridgingHeaderDeps(const ModuleDependencyInfo &depInfo) {
    auto sourceDepDetails = depInfo.getAsSwiftSourceModule();
    if (!sourceDepDetails)
      return llvm::Error::success();

    return addBridgingHeaderDeps(*sourceDepDetails);
  }

  llvm::Error addBridgingHeaderDeps(
      const SwiftSourceModuleDependenciesStorage &sourceDepDetails) {
    if (sourceDepDetails.textualModuleDetails.CASBridgingHeaderIncludeTreeRootID
            .empty()) {
      if (!sourceDepDetails.textualModuleDetails.bridgingSourceFiles.empty()) {
        if (tracker) {
          tracker->startTracking(/*includeCommonDeps*/ false);
          for (auto &file :
               sourceDepDetails.textualModuleDetails.bridgingSourceFiles)
            tracker->trackFile(file);
          auto bridgeRoot = tracker->createTreeFromDependencies();
          if (!bridgeRoot)
            return bridgeRoot.takeError();
          fileListIDs.push_back(bridgeRoot->getID().toString());
        }
      }
    } else
      includeTrees.push_back(sourceDepDetails.textualModuleDetails
                                 .CASBridgingHeaderIncludeTreeRootID);
    return llvm::Error::success();
  };

  void addMacroDependencies(ModuleDependencyID moduleID,
                            const ModuleDependencyInfoStorageBase &dep) {
    auto directDeps = cache.getAllDependencies(this->moduleID);
    if (llvm::find(directDeps, moduleID) == directDeps.end())
      return;

    for (auto &entry : dep.macroDependencies)
      macros.insert({entry.first,
                     {entry.second.LibraryPath, entry.second.ExecutablePath}});
  }

  static bool isVFSOverlayFlag(StringRef arg) {
    return arg == "-ivfsoverlay" || arg == "-vfsoverlay";
  };
  static bool isXCCArg(StringRef arg) { return arg == "-Xcc"; };


  void
  collectUsedVFSOverlay(const ClangModuleDependencyStorage &clangDepDetails) {
    // true if the previous argument was the dash-option of an option pair
    bool getNext = false;
    for (const auto &A : clangDepDetails.buildCommandLine) {
      StringRef arg(A);
      if (isXCCArg(arg))
        continue;
      if (getNext) {
        getNext = false;
        usedVFSOverlayPaths.insert(arg);
      } else if (isVFSOverlayFlag(arg))
        getNext = true;
    }
  }

  void pruneUnusedVFSOverlay() {
    // Pruning of unused VFS overlay options for Clang dependencies is performed
    // by the Clang dependency scanner.
    if (moduleID.Kind == ModuleDependencyKind::Clang)
      return;

    std::vector<std::string> resolvedCommandLine;
    size_t skip = 0;
    for (auto it = commandline.begin(), end = commandline.end();
         it != end; it++) {
      if (skip) {
        skip--;
        continue;
      }
      // If this VFS overlay was not used across any of the dependencies, skip
      // it.
      if ((it + 1) != end && isXCCArg(*it) && isVFSOverlayFlag(*(it + 1))) {
        assert(it + 2 != end); // Extra -Xcc
        assert(it + 3 != end); // Actual VFS overlay path argument
        if (!usedVFSOverlayPaths.contains(*(it + 3))) {
          skip = 3;
          continue;
        }
      }
      resolvedCommandLine.push_back(*it);
    }
    commandline = std::move(resolvedCommandLine);
  }

  llvm::Error collectCASDependencies(ModuleDependencyInfo &dependencyInfoCopy) {
    if (!instance.getInvocation().getCASOptions().EnableCaching)
      return llvm::Error::success();

    // Collect CAS info from current resolving module.
    if (auto *sourceDep = resolvingDepInfo.getAsSwiftSourceModule()) {
      tracker->startTracking();
      llvm::for_each(
          sourceDep->sourceFiles,
          [this](const std::string &file) { tracker->trackFile(file); });
      llvm::for_each(
          sourceDep->auxiliaryFiles,
          [this](const std::string &file) { tracker->trackFile(file); });
      llvm::for_each(sourceDep->macroDependencies, [this](const auto &entry) {
        tracker->trackFile(entry.second.LibraryPath);
      });
      auto root = tracker->createTreeFromDependencies();
      if (!root)
        return root.takeError();
      auto rootID = root->getID().toString();
      dependencyInfoCopy.updateCASFileSystemRootID(rootID);
      fileListIDs.push_back(rootID);
    } else if (auto *textualDep =
                   resolvingDepInfo.getAsSwiftInterfaceModule()) {
      tracker->startTracking();
      tracker->trackFile(textualDep->swiftInterfaceFile);
      llvm::for_each(
          textualDep->auxiliaryFiles,
          [this](const std::string &file) { tracker->trackFile(file); });
      llvm::for_each(textualDep->macroDependencies,
                     [this](const auto &entry) {
                       tracker->trackFile(entry.second.LibraryPath);
                     });
      auto root = tracker->createTreeFromDependencies();
      if (!root)
        return root.takeError();
      auto rootID = root->getID().toString();
      dependencyInfoCopy.updateCASFileSystemRootID(rootID);
      fileListIDs.push_back(rootID);
    }

    // Update build command line.
    if (resolvingDepInfo.isSwiftInterfaceModule() ||
        resolvingDepInfo.isSwiftSourceModule()) {
      // Update with casfs option.
      for (auto rootID : rootIDs) {
        commandline.push_back("-cas-fs");
        commandline.push_back(rootID);
      }

      for (auto tree : includeTrees) {
        commandline.push_back("-clang-include-tree-root");
        commandline.push_back(tree);
      }

      for (auto list : fileListIDs) {
        commandline.push_back("-clang-include-tree-filelist");
        commandline.push_back(list);
      }
    }

    // Compute and update module cache key.
    if (auto *binaryDep = dependencyInfoCopy.getAsSwiftBinaryModule()) {
      if (auto E = setupBinaryCacheKey(binaryDep->compiledModulePath,
                                       dependencyInfoCopy))
        return E;
    }
    return llvm::Error::success();
  }

  llvm::Error updateModuleCacheKey(ModuleDependencyInfo &depInfo) {
    if (!instance.getInvocation().getCASOptions().EnableCaching)
      return llvm::Error::success();

    auto &CAS = cache.getScanService().getCAS();
    auto commandLine = depInfo.getCommandline();
    std::vector<const char *> Args;
    if (commandLine.size() > 1)
      for (auto &c : ArrayRef<std::string>(commandLine).drop_front(1))
        Args.push_back(c.c_str());

    auto base = createCompileJobBaseCacheKey(CAS, Args);
    if (!base)
      return base.takeError();

    // Module compilation commands always have only one input and the input
    // index is always 0.
    auto key = createCompileJobCacheKeyForOutput(CAS, *base, /*InputIndex=*/0);
    if (!key)
      return key.takeError();

    depInfo.updateModuleCacheKey(CAS.getID(*key).toString());
    return llvm::Error::success();
  }

  llvm::Error setupBinaryCacheKey(StringRef path,
                                  ModuleDependencyInfo &depInfo) {
    auto &CASFS = cache.getScanService().getSharedCachingFS();
    auto &CAS = cache.getScanService().getCAS();
    // For binary module, we need to make sure the lookup key is setup here in
    // action cache. We just use the CASID of the binary module itself as key.
    auto Ref = CASFS.getObjectRefForFileContent(path);
    if (!Ref)
      return llvm::errorCodeToError(Ref.getError());
    assert(*Ref && "Binary module should be loaded into CASFS already");
    depInfo.updateModuleCacheKey(CAS.getID(**Ref).toString());

    swift::cas::CompileJobCacheResult::Builder Builder;
    Builder.addOutput(file_types::ID::TY_SwiftModuleFile, **Ref);
    auto Result = Builder.build(CAS);
    if (!Result)
      return Result.takeError();
    if (auto E =
            instance.getActionCache().put(CAS.getID(**Ref), CAS.getID(*Result)))
      return E;
    return llvm::Error::success();
  }

private:
  ModuleDependencyID moduleID;
  ModuleDependenciesCache &cache;
  CompilerInstance &instance;
  const ModuleDependencyInfo &resolvingDepInfo;

  std::optional<SwiftDependencyTracker> tracker;
  std::vector<std::string> rootIDs;
  std::vector<std::string> includeTrees;
  std::vector<std::string> fileListIDs;
  std::vector<std::string> commandline;
  std::vector<std::string> bridgingHeaderBuildCmd;
  llvm::StringMap<MacroPluginDependency> macros;
  llvm::StringSet<> usedVFSOverlayPaths;
};

static llvm::Error resolveExplicitModuleInputs(
    ModuleDependencyID moduleID,
    const std::set<ModuleDependencyID> &dependencies,
    ModuleDependenciesCache &cache, CompilerInstance &instance,
    std::optional<std::set<ModuleDependencyID>> bridgingHeaderDeps,
    std::optional<SwiftDependencyTracker> tracker) {
  ExplicitModuleDependencyResolver resolver(moduleID, cache, instance,
                                            std::move(tracker));
  return resolver.resolve(dependencies, bridgingHeaderDeps);
}

static bool writePrescanJSONToOutput(DiagnosticEngine &diags,
                                     llvm::vfs::OutputBackend &backend,
                                     StringRef path,
                                     swiftscan_import_set_t importSet) {
  return withOutputPath(diags, backend, path, [&](llvm::raw_pwrite_stream &os) {
    writePrescanJSON(os, importSet);
    return false;
  });
}

static bool writeJSONToOutput(DiagnosticEngine &diags,
                              llvm::vfs::OutputBackend &backend, StringRef path,
                              swiftscan_dependency_graph_t dependencies) {
  return withOutputPath(diags, backend, path, [&](llvm::raw_pwrite_stream &os) {
    writeJSON(os, dependencies);
    return false;
  });
}

static void bridgeDependencyIDs(const ArrayRef<ModuleDependencyID> dependencies,
                                std::vector<std::string> &bridgedDependencyNames) {
  for (const auto &dep : dependencies) {
    std::string dependencyKindAndName;
    switch (dep.Kind) {
    case ModuleDependencyKind::SwiftInterface:
    case ModuleDependencyKind::SwiftSource:
      dependencyKindAndName = "swiftTextual";
      break;
    case ModuleDependencyKind::SwiftBinary:
      dependencyKindAndName = "swiftBinary";
      break;
    case ModuleDependencyKind::SwiftPlaceholder:
      dependencyKindAndName = "swiftPlaceholder";
      break;
    case ModuleDependencyKind::Clang:
      dependencyKindAndName = "clang";
      break;
    default:
      llvm_unreachable("Unhandled dependency kind.");
    }
    dependencyKindAndName += ":";
    dependencyKindAndName += dep.ModuleName;
    bridgedDependencyNames.push_back(dependencyKindAndName);
  }
}

static swiftscan_macro_dependency_set_t *createMacroDependencySet(
    const std::map<std::string, MacroPluginDependency> &macroDeps) {
  if (macroDeps.empty())
    return nullptr;

  swiftscan_macro_dependency_set_t *set = new swiftscan_macro_dependency_set_t;
  set->count = macroDeps.size();
  set->macro_dependencies = new swiftscan_macro_dependency_t[set->count];
  unsigned SI = 0;
  for (auto &entry : macroDeps) {
    set->macro_dependencies[SI] = new swiftscan_macro_dependency_s;
    set->macro_dependencies[SI]->moduleName = create_clone(entry.first.c_str());
    set->macro_dependencies[SI]->libraryPath =
        create_clone(entry.second.LibraryPath.c_str());
    set->macro_dependencies[SI]->executablePath =
        create_clone(entry.second.ExecutablePath.c_str());
    ++ SI;
  }
  return set;
}

static swiftscan_dependency_graph_t
generateFullDependencyGraph(const CompilerInstance &instance,
                            const DependencyScanDiagnosticCollector *diagnosticCollector,
                            const ModuleDependenciesCache &cache,
                            const ArrayRef<ModuleDependencyID> allModules) {
  if (allModules.empty()) {
    return nullptr;
  }

  std::string mainModuleName = allModules.front().ModuleName;
  swiftscan_dependency_set_t *dependencySet = new swiftscan_dependency_set_t;
  dependencySet->count = allModules.size();
  dependencySet->modules =
      new swiftscan_dependency_info_t[dependencySet->count];

  for (size_t i = 0; i < allModules.size(); ++i) {
    const auto &moduleID = allModules[i];
    auto &moduleDependencyInfo = cache.findKnownDependency(moduleID);
    // Collect all the required pieces to build a ModuleInfo
    auto swiftPlaceholderDeps = moduleDependencyInfo.getAsPlaceholderDependencyModule();
    auto swiftTextualDeps = moduleDependencyInfo.getAsSwiftInterfaceModule();
    auto swiftSourceDeps = moduleDependencyInfo.getAsSwiftSourceModule();
    auto swiftBinaryDeps = moduleDependencyInfo.getAsSwiftBinaryModule();
    auto clangDeps = moduleDependencyInfo.getAsClangModule();

    // ModulePath
    const char *modulePathSuffix =
        moduleDependencyInfo.isSwiftModule() ? ".swiftmodule" : ".pcm";
    std::string modulePath;
    if (swiftTextualDeps)
      modulePath = swiftTextualDeps->moduleOutputPath;
    else if (swiftPlaceholderDeps)
      modulePath = swiftPlaceholderDeps->compiledModulePath;
    else if (swiftBinaryDeps)
      modulePath = swiftBinaryDeps->compiledModulePath;
    else if (clangDeps)
      modulePath = clangDeps->pcmOutputPath;
    else
      modulePath = moduleID.ModuleName + modulePathSuffix;

    // SourceFiles
    std::vector<std::string> sourceFiles;
    if (swiftSourceDeps) {
      sourceFiles = swiftSourceDeps->sourceFiles;
    } else if (clangDeps) {
      sourceFiles = clangDeps->fileDependencies;
    }

    auto directDependencies = cache.getAllDependencies(moduleID);
    std::vector<std::string> clangHeaderDependencyNames;
    for (const auto &headerDepID : moduleDependencyInfo.getHeaderClangDependencies())
      clangHeaderDependencyNames.push_back(headerDepID.ModuleName);

    // Generate a swiftscan_clang_details_t object based on the dependency kind
    auto getModuleDetails = [&]() -> swiftscan_module_details_t {
      swiftscan_module_details_s *details = new swiftscan_module_details_s;
      if (swiftTextualDeps) {
        swiftscan_string_ref_t moduleInterfacePath =
            create_clone(swiftTextualDeps->swiftInterfaceFile.c_str());
        swiftscan_string_ref_t bridgingHeaderPath =
            swiftTextualDeps->textualModuleDetails.bridgingHeaderFile
                    .has_value()
                ? create_clone(
                      swiftTextualDeps->textualModuleDetails.bridgingHeaderFile
                          .value()
                          .c_str())
                : create_null();
        details->kind = SWIFTSCAN_DEPENDENCY_INFO_SWIFT_TEXTUAL;
        // Create an overlay dependencies set according to the output format
        std::vector<std::string> bridgedOverlayDependencyNames;
        bridgeDependencyIDs(swiftTextualDeps->swiftOverlayDependencies,
                            bridgedOverlayDependencyNames);

        details->swift_textual_details = {
            moduleInterfacePath,
            create_set(swiftTextualDeps->compiledModuleCandidates),
            bridgingHeaderPath,
            create_set(
                swiftTextualDeps->textualModuleDetails.bridgingSourceFiles),
            create_set(clangHeaderDependencyNames),
            create_set(bridgedOverlayDependencyNames),
            create_set(swiftTextualDeps->textualModuleDetails.buildCommandLine),
            /*bridgingHeaderBuildCommand*/ create_set({}),
            create_set(swiftTextualDeps->textualModuleDetails.extraPCMArgs),
            create_clone(swiftTextualDeps->contextHash.c_str()),
            swiftTextualDeps->isFramework,
            swiftTextualDeps->isStatic,
            create_clone(swiftTextualDeps->textualModuleDetails
                             .CASFileSystemRootID.c_str()),
            create_clone(swiftTextualDeps->textualModuleDetails
                             .CASBridgingHeaderIncludeTreeRootID.c_str()),
            create_clone(swiftTextualDeps->moduleCacheKey.c_str()),
            createMacroDependencySet(
                swiftTextualDeps->macroDependencies),
            create_clone(swiftTextualDeps->userModuleVersion.c_str())};
      } else if (swiftSourceDeps) {
        swiftscan_string_ref_t moduleInterfacePath = create_null();
        swiftscan_string_ref_t bridgingHeaderPath =
          swiftSourceDeps->textualModuleDetails.bridgingHeaderFile.has_value()
                ? create_clone(
                           swiftSourceDeps->textualModuleDetails.bridgingHeaderFile.value().c_str())
                : create_null();
        details->kind = SWIFTSCAN_DEPENDENCY_INFO_SWIFT_TEXTUAL;
        // Create an overlay dependencies set according to the output format
        std::vector<std::string> bridgedOverlayDependencyNames;
        bridgeDependencyIDs(swiftSourceDeps->swiftOverlayDependencies,
                            bridgedOverlayDependencyNames);

        details->swift_textual_details = {
            moduleInterfacePath, create_empty_set(), bridgingHeaderPath,
            create_set(
                swiftSourceDeps->textualModuleDetails.bridgingSourceFiles),
            create_set(clangHeaderDependencyNames),
            create_set(bridgedOverlayDependencyNames),
            create_set(swiftSourceDeps->textualModuleDetails.buildCommandLine),
            create_set(swiftSourceDeps->bridgingHeaderBuildCommandLine),
            create_set(swiftSourceDeps->textualModuleDetails.extraPCMArgs),
            /*contextHash*/
            create_clone(
                instance.getInvocation().getModuleScanningHash().c_str()),
            /*isFramework*/ false,
            /*isStatic*/ false,
            /*CASFS*/
            create_clone(swiftSourceDeps->textualModuleDetails
                             .CASFileSystemRootID.c_str()),
            /*IncludeTree*/
            create_clone(swiftSourceDeps->textualModuleDetails
                             .CASBridgingHeaderIncludeTreeRootID.c_str()),
            /*CacheKey*/ create_clone(""),
            createMacroDependencySet(
                swiftSourceDeps->macroDependencies),
            /*userModuleVersion*/ create_clone("")};
      } else if (swiftPlaceholderDeps) {
        details->kind = SWIFTSCAN_DEPENDENCY_INFO_SWIFT_PLACEHOLDER;
        details->swift_placeholder_details = {
            create_clone(swiftPlaceholderDeps->compiledModulePath.c_str()),
            create_clone(swiftPlaceholderDeps->moduleDocPath.c_str()),
            create_clone(swiftPlaceholderDeps->sourceInfoPath.c_str())};
      } else if (swiftBinaryDeps) {
        details->kind = SWIFTSCAN_DEPENDENCY_INFO_SWIFT_BINARY;
        // Create an overlay dependencies set according to the output format
        std::vector<std::string> bridgedOverlayDependencyNames;
        bridgeDependencyIDs(swiftBinaryDeps->swiftOverlayDependencies,
                            bridgedOverlayDependencyNames);
        details->swift_binary_details = {
            create_clone(swiftBinaryDeps->compiledModulePath.c_str()),
            create_clone(swiftBinaryDeps->moduleDocPath.c_str()),
            create_clone(swiftBinaryDeps->sourceInfoPath.c_str()),
            create_set(bridgedOverlayDependencyNames),
            create_clone(swiftBinaryDeps->headerImport.c_str()),
            create_set(clangHeaderDependencyNames),
            create_set(swiftBinaryDeps->headerSourceFiles),
            swiftBinaryDeps->isFramework,
            swiftBinaryDeps->isStatic,
            createMacroDependencySet(swiftBinaryDeps->macroDependencies),
            create_clone(swiftBinaryDeps->moduleCacheKey.c_str()),
            create_clone(swiftBinaryDeps->userModuleVersion.c_str())};
      } else {
        // Clang module details
        details->kind = SWIFTSCAN_DEPENDENCY_INFO_CLANG;
        details->clang_details = {
            create_clone(clangDeps->moduleMapFile.c_str()),
            create_clone(clangDeps->contextHash.c_str()),
            create_set(clangDeps->buildCommandLine),
            create_set(clangDeps->capturedPCMArgs),
            create_clone(clangDeps->CASFileSystemRootID.c_str()),
            create_clone(clangDeps->CASClangIncludeTreeRootID.c_str()),
            create_clone(clangDeps->moduleCacheKey.c_str())};
      }
      return details;
    };

    swiftscan_dependency_info_s *moduleInfo = new swiftscan_dependency_info_s;
    dependencySet->modules[i] = moduleInfo;

    std::string encodedModuleName = createEncodedModuleKindAndName(moduleID);
    auto ttt = create_clone(encodedModuleName.c_str());
    moduleInfo->module_name = ttt;
    moduleInfo->module_path = create_clone(modulePath.c_str());
    moduleInfo->source_files = create_set(sourceFiles);

    // Create a direct dependencies set according to the output format
    std::vector<std::string> bridgedDependencyNames;
    bridgeDependencyIDs(directDependencies.getArrayRef(),
                        bridgedDependencyNames);
    moduleInfo->direct_dependencies = create_set(bridgedDependencyNames);
    moduleInfo->details = getModuleDetails();

    // Create a link libraries set for this module
    auto &linkLibraries = moduleDependencyInfo.getLinkLibraries();
    swiftscan_link_library_set_t *linkLibrarySet =
        new swiftscan_link_library_set_t;
    linkLibrarySet->count = linkLibraries.size();
    linkLibrarySet->link_libraries =
        new swiftscan_link_library_info_t[linkLibrarySet->count];
    for (size_t i = 0; i < linkLibraries.size(); ++i) {
      const auto &ll = linkLibraries[i];
      swiftscan_link_library_info_s *llInfo = new swiftscan_link_library_info_s;
      llInfo->name = create_clone(ll.getName().str().c_str());
      llInfo->isFramework = ll.getKind() == LibraryKind::Framework;
      llInfo->forceLoad = ll.shouldForceLoad();
      linkLibrarySet->link_libraries[i] = llInfo;
    }
    moduleInfo->link_libraries = linkLibrarySet;
  }

  swiftscan_dependency_graph_t result = new swiftscan_dependency_graph_s;
  result->main_module_name = create_clone(mainModuleName.c_str());
  result->dependencies = dependencySet;
  result->diagnostics =
              diagnosticCollector
              ? mapCollectedDiagnosticsForOutput(diagnosticCollector)
              : nullptr;
  return result;
}

/// Implements a topological sort via recursion and reverse postorder DFS.
/// Does not bother handling cycles, relying on a DAG guarantee by the client.
static std::vector<ModuleDependencyID>
computeTopologicalSortOfExplicitDependencies(
    const std::vector<ModuleDependencyID> &allModules,
    const ModuleDependenciesCache &cache) {
  std::unordered_set<ModuleDependencyID> visited;
  std::vector<ModuleDependencyID> result;
  std::stack<ModuleDependencyID> stack;

  // Must be explicitly-typed to allow recursion
  std::function<void(const ModuleDependencyID &)> visit;
  visit = [&visit, &cache, &visited, &result,
           &stack](const ModuleDependencyID &moduleID) {
    // Mark this node as visited -- we are done if it already was.
    if (!visited.insert(moduleID).second)
      return;

    // Otherwise, visit each adjacent node.
    for (const auto &succID : cache.getAllDependencies(moduleID)) {
      // We don't worry if successor is already in this current stack,
      // since that would mean we have found a cycle, which should not
      // be possible because we checked for cycles earlier.
      stack.push(succID);
      visit(succID);
      auto top = stack.top();
      stack.pop();
      assert(top == succID);
    }

    // Add to the result.
    result.push_back(moduleID);
  };

  for (const auto &modID : allModules) {
    assert(stack.empty());
    stack.push(modID);
    visit(modID);
    auto top = stack.top();
    stack.pop();
    assert(top == modID);
  }

  std::reverse(result.begin(), result.end());
  return result;
}

/// For each module in the graph, compute a set of all its dependencies,
/// direct *and* transitive.
static std::unordered_map<ModuleDependencyID, std::set<ModuleDependencyID>>
computeTransitiveClosureOfExplicitDependencies(
    const std::vector<ModuleDependencyID> &topologicallySortedModuleList,
    const ModuleDependenciesCache &cache) {
  // The usage of an ordered ::set is important to ensure the
  // dependencies are listed in a deterministic order.
  std::unordered_map<ModuleDependencyID, std::set<ModuleDependencyID>> result;
  for (const auto &modID : topologicallySortedModuleList)
    result[modID] = {modID};

  // Traverse the set of modules in reverse topological order, assimilating
  // transitive closures
  for (auto it = topologicallySortedModuleList.rbegin(),
            end = topologicallySortedModuleList.rend();
       it != end; ++it) {
    const auto &modID = *it;
    auto &modReachableSet = result[modID];
    for (const auto &succID : cache.getAllDependencies(modID)) {
      const auto &succReachableSet = result[succID];
      llvm::set_union(modReachableSet, succReachableSet);
    }
  }
  // For ease of use down-the-line, remove the node's self from its set of
  // reachable nodes
  for (const auto &modID : topologicallySortedModuleList)
    result[modID].erase(modID);

  return result;
}

static std::set<ModuleDependencyID> computeBridgingHeaderTransitiveDependencies(
    const ModuleDependencyInfo &dep,
    const std::unordered_map<ModuleDependencyID, std::set<ModuleDependencyID>>
        &transitiveClosures,
    const ModuleDependenciesCache &cache) {
  std::set<ModuleDependencyID> result;
  if (!dep.isSwiftSourceModule())
    return result;

  for (auto &depID : dep.getHeaderClangDependencies()) {
    result.insert(depID);
    auto succDeps = transitiveClosures.find(depID);
    assert(succDeps != transitiveClosures.end() && "unknown dependency");
    llvm::set_union(result, succDeps->second);
  }

  return result;
}

static std::vector<ModuleDependencyID>
findClangDepPath(const ModuleDependencyID &from, const ModuleDependencyID &to,
                 const ModuleDependenciesCache &cache) {
  std::unordered_set<ModuleDependencyID> visited;
  std::vector<ModuleDependencyID> result;
  std::stack<ModuleDependencyID, std::vector<ModuleDependencyID>> stack;

  // Must be explicitly-typed to allow recursion
  std::function<void(const ModuleDependencyID &)> visit;

  visit = [&visit, &cache, &visited, &result, &stack,
           to](const ModuleDependencyID &moduleID) {
    if (!visited.insert(moduleID).second)
      return;

    if (moduleID == to) {
      // Copy stack contents to the result
      auto end = &stack.top() + 1;
      auto begin = end - stack.size();
      result.assign(begin, end);
      return;
    }

    // Otherwise, visit each child node.
    for (const auto &succID : cache.getAllDependencies(moduleID)) {
      stack.push(succID);
      visit(succID);
      stack.pop();
    }
  };

  stack.push(from);
  visit(from);
  return result;
}

static bool diagnoseCycle(const CompilerInstance &instance,
                          const ModuleDependenciesCache &cache,
                          ModuleDependencyID mainId) {
  ModuleDependencyIDSetVector openSet;
  ModuleDependencyIDSetVector closeSet;

  auto kindIsSwiftDependency = [&](const ModuleDependencyID &ID) {
    return ID.Kind == swift::ModuleDependencyKind::SwiftInterface ||
           ID.Kind == swift::ModuleDependencyKind::SwiftBinary ||
           ID.Kind == swift::ModuleDependencyKind::SwiftSource;
  };

  auto emitModulePath = [&](const std::vector<ModuleDependencyID> path,
                            llvm::SmallString<64> &buffer) {
    llvm::interleave(
        path,
        [&buffer](const ModuleDependencyID &id) {
          buffer.append(id.ModuleName);
          switch (id.Kind) {
          case swift::ModuleDependencyKind::SwiftSource:
            buffer.append(" (Source Target)");
            break;
          case swift::ModuleDependencyKind::SwiftInterface:
            buffer.append(".swiftinterface");
            break;
          case swift::ModuleDependencyKind::SwiftBinary:
            buffer.append(".swiftmodule");
            break;
          case swift::ModuleDependencyKind::Clang:
            buffer.append(".pcm");
            break;
          default:
            llvm::report_fatal_error(
                Twine("Invalid Module Dependency Kind in cycle: ") +
                id.ModuleName);
            break;
          }
        },
        [&buffer] { buffer.append(" -> "); });
  };

  auto emitCycleDiagnostic = [&](const ModuleDependencyID &sourceId,
				 const ModuleDependencyID &sinkId) {
    auto startIt = std::find(openSet.begin(), openSet.end(), sourceId);
    assert(startIt != openSet.end());
    std::vector<ModuleDependencyID> cycleNodes(startIt, openSet.end());
    cycleNodes.push_back(sinkId);
    llvm::SmallString<64> errorBuffer;
    emitModulePath(cycleNodes, errorBuffer);
    instance.getASTContext().Diags.diagnose(
        SourceLoc(), diag::scanner_find_cycle, errorBuffer.str());

    // TODO: for (std::tuple<const ModuleDependencyID&, const
    // ModuleDependencyID&> v : cycleNodes | std::views::adjacent<2>)
    for (auto it = cycleNodes.begin(), end = cycleNodes.end(); it != end;
         it++) {
      if (it + 1 == cycleNodes.end())
        continue;

      const auto &thisID = *it;
      const auto &nextID = *(it + 1);
      if (kindIsSwiftDependency(thisID) && kindIsSwiftDependency(nextID) &&
          llvm::any_of(
              cache.getSwiftOverlayDependencies(thisID),
              [&](const ModuleDependencyID id) { return id == nextID; })) {
        llvm::SmallString<64> noteBuffer;
        auto clangDepPath = findClangDepPath(
            thisID,
            ModuleDependencyID{nextID.ModuleName, ModuleDependencyKind::Clang},
            cache);
        emitModulePath(clangDepPath, noteBuffer);
        instance.getASTContext().Diags.diagnose(
            SourceLoc(), diag::scanner_find_cycle_swift_overlay_path,
            thisID.ModuleName, nextID.ModuleName, noteBuffer.str());
      }
    }
  };

  // Start from the main module and check direct and overlay dependencies
  openSet.insert(mainId);
  while (!openSet.empty()) {
    auto lastOpen = openSet.back();
    auto beforeSize = openSet.size();
    assert(cache.findDependency(lastOpen).has_value() &&
           "Missing dependency info during cycle diagnosis.");
    for (const auto &depId : cache.getAllDependencies(lastOpen)) {
      if (closeSet.count(depId))
        continue;
      // Ensure we detect dependency of the Source target
      // on an existing Swift module with the same name
      if (kindIsSwiftDependency(depId) &&
          depId.ModuleName == mainId.ModuleName && openSet.contains(mainId)) {
        emitCycleDiagnostic(mainId, depId);
        return true;
      }
      if (openSet.insert(depId)) {
        break;
      } else {
        emitCycleDiagnostic(depId, depId);
        return true;
      }
    }
    // No new node added. We can close this node
    if (openSet.size() == beforeSize) {
      closeSet.insert(openSet.back());
      openSet.pop_back();
    } else {
      assert(openSet.size() == beforeSize + 1);
    }
  }
  assert(openSet.empty());
  closeSet.clear();
  return false;
}

static void updateCachedInstanceOpts(CompilerInstance &cachedInstance,
                                     const CompilerInstance &invocationInstance,
                                     llvm::StringRef entryArguments) {
  cachedInstance.getASTContext().SearchPathOpts =
      invocationInstance.getASTContext().SearchPathOpts;

  // The Clang Importer arguments must consist of a combination of
  // Clang Importer arguments of the current invocation to inherit its Clang-specific
  // search path options, followed by the options specific to the given batch-entry,
  // which may overload some of the invocation's options (e.g. target)
  cachedInstance.getASTContext().ClangImporterOpts =
      invocationInstance.getASTContext().ClangImporterOpts;
  std::istringstream iss(entryArguments.str());
  std::vector<std::string> splitArguments(
      std::istream_iterator<std::string>{iss},
      std::istream_iterator<std::string>());
  for (auto it = splitArguments.begin(), end = splitArguments.end(); it != end;
       ++it) {
    if ((*it) == "-Xcc") {
      assert((it + 1 != end) && "Expected option following '-Xcc'");
      cachedInstance.getASTContext().ClangImporterOpts.ExtraArgs.push_back(
          *(it + 1));
    }
  }
}

static bool
forEachBatchEntry(CompilerInstance &invocationInstance,
                  ModuleDependenciesCache &invocationCache,
                  CompilerArgInstanceCacheMap *versionedPCMInstanceCache,
                  llvm::StringSaver &saver,
                  const std::vector<BatchScanInput> &batchInput,
                  llvm::function_ref<void(BatchScanInput, CompilerInstance &,
                                          ModuleDependenciesCache &)>
                      scanningAction) {
  const CompilerInvocation &invoke = invocationInstance.getInvocation();
  bool localSubInstanceMap = false;
  CompilerArgInstanceCacheMap *subInstanceMap;
  if (versionedPCMInstanceCache)
    subInstanceMap = versionedPCMInstanceCache;
  else {
    subInstanceMap = new CompilerArgInstanceCacheMap;
    localSubInstanceMap = true;
  }
  SWIFT_DEFER {
    if (localSubInstanceMap)
      delete subInstanceMap;
  };

  auto &diags = invocationInstance.getDiags();
  ForwardingDiagnosticConsumer FDC(invocationInstance.getDiags());

  for (auto &entry : batchInput) {
    CompilerInstance *pInstance = nullptr;
    ModuleDependenciesCache *pCache = nullptr;
    if (entry.arguments.empty()) {
      // Use the compiler's instance if no arguments are specified.
      pInstance = &invocationInstance;
      pCache = &invocationCache;
    } else if (subInstanceMap->count(entry.arguments)) {
      // Use the previously created instance if we've seen the arguments
      // before.
      pInstance = std::get<0>((*subInstanceMap)[entry.arguments]).get();
      pCache = std::get<2>((*subInstanceMap)[entry.arguments]).get();
      // We must update the search paths of this instance to instead reflect
      // those of the current scanner invocation.
      updateCachedInstanceOpts(*pInstance, invocationInstance, entry.arguments);
    } else {
      // Create a new instance by the arguments and save it in the map.
      auto newService = std::make_unique<SwiftDependencyScanningService>();
      auto newInstance = std::make_unique<CompilerInstance>();

      SmallVector<const char *, 4> args;
      llvm::cl::TokenizeGNUCommandLine(entry.arguments, saver, args);
      CompilerInvocation subInvoke = invoke;
      newInstance->addDiagnosticConsumer(&FDC);
      if (subInvoke.parseArgs(args, diags)) {
        invocationInstance.getDiags().diagnose(
            SourceLoc(), diag::scanner_arguments_invalid, entry.arguments);
        return true;
      }
      std::string InstanceSetupError;
      if (newInstance->setup(subInvoke, InstanceSetupError)) {
        invocationInstance.getDiags().diagnose(
            SourceLoc(), diag::scanner_arguments_invalid, entry.arguments);
        return true;
      }
      auto mainModuleName = newInstance->getMainModule()->getNameStr();
      auto scanContextHash =
          newInstance->getInvocation().getModuleScanningHash();
      auto moduleOutputPath = newInstance->getInvocation()
                                  .getFrontendOptions()
                                  .ExplicitModulesOutputPath;
      auto newLocalCache = std::make_unique<ModuleDependenciesCache>(
          *newService, mainModuleName.str(), moduleOutputPath, scanContextHash);
      pInstance = newInstance.get();
      pCache = newLocalCache.get();
      subInstanceMap->insert(
          {entry.arguments,
           std::make_tuple(std::move(newInstance), std::move(newService),
                           std::move(newLocalCache))});
    }
    assert(pInstance);
    assert(pCache);
    scanningAction(entry, *pInstance, *pCache);
  }

  return false;
}
} // namespace

bool swift::dependencies::scanDependencies(CompilerInstance &CI) {
  ASTContext &ctx = CI.getASTContext();
  const FrontendOptions &opts = CI.getInvocation().getFrontendOptions();
  std::string depGraphOutputPath = opts.InputsAndOutputs.getSingleOutputFilename();
  // `-scan-dependencies` invocations use a single new instance
  // of a module cache
  SwiftDependencyScanningService *service = ctx.Allocate<SwiftDependencyScanningService>();
  ModuleDependenciesCache cache(
      *service, CI.getMainModule()->getNameStr().str(),
      CI.getInvocation().getFrontendOptions().ExplicitModulesOutputPath,
      CI.getInvocation().getModuleScanningHash());

  // Load the dependency cache if -reuse-dependency-scan-cache
  // is specified
  if (opts.ReuseDependencyScannerCache) {
    auto cachePath = opts.SerializedDependencyScannerCachePath;
    module_dependency_cache_serialization::readInterModuleDependenciesCache(cachePath, cache);
    if (opts.EmitDependencyScannerCacheRemarks)
      ctx.Diags.diagnose(SourceLoc(), diag::remark_reuse_cache, cachePath);
  }
  
  if (service->setupCachingDependencyScanningService(CI))
    return true;

  // Execute scan
  llvm::ErrorOr<swiftscan_dependency_graph_t> dependenciesOrErr =
      performModuleScan(CI, nullptr, cache);

  // Serialize the dependency cache if -serialize-dependency-scan-cache
  // is specified
  if (opts.SerializeDependencyScannerCache) {
    auto savePath = opts.SerializedDependencyScannerCachePath;
    module_dependency_cache_serialization::writeInterModuleDependenciesCache(
          ctx.Diags, CI.getOutputBackend(), savePath, cache);
    if (opts.EmitDependencyScannerCacheRemarks)
      ctx.Diags.diagnose(SourceLoc(), diag::remark_save_cache, savePath);
  }

  if (dependenciesOrErr.getError())
    return true;
  auto dependencies = std::move(*dependenciesOrErr);

  if (writeJSONToOutput(ctx.Diags, CI.getOutputBackend(), depGraphOutputPath,
                        dependencies))
    return true;

  // This process succeeds regardless of whether any errors occurred.
  // FIXME: We shouldn't need this, but it's masking bugs in our scanning
  // logic where we don't create a fresh context when scanning Swift interfaces
  // that includes their own command-line flags.
  ctx.Diags.resetHadAnyError();
  return false;
}

bool swift::dependencies::prescanDependencies(CompilerInstance &instance) {
  ASTContext &Context = instance.getASTContext();
  const FrontendOptions &opts = instance.getInvocation().getFrontendOptions();
  std::string path = opts.InputsAndOutputs.getSingleOutputFilename();
  // `-scan-dependencies` invocations use a single new instance
  // of a module cache
  SwiftDependencyScanningService *singleUseService = Context.Allocate<SwiftDependencyScanningService>();
  ModuleDependenciesCache cache(
      *singleUseService, instance.getMainModule()->getNameStr().str(),
      instance.getInvocation().getFrontendOptions().ExplicitModulesOutputPath,
      instance.getInvocation().getModuleScanningHash());

  // Execute import prescan, and write JSON output to the output stream
  auto importSetOrErr = performModulePrescan(instance, nullptr, cache);
  if (importSetOrErr.getError())
    return true;
  auto importSet = std::move(*importSetOrErr);

  // Serialize and output main module dependencies only and exit.
  if (writePrescanJSONToOutput(Context.Diags, instance.getOutputBackend(), path,
                               importSet))
    return true;

  // This process succeeds regardless of whether any errors occurred.
  // FIXME: We shouldn't need this, but it's masking bugs in our scanning
  // logic where we don't create a fresh context when scanning Swift interfaces
  // that includes their own command-line flags.
  Context.Diags.resetHadAnyError();
  return false;
}

bool swift::dependencies::batchScanDependencies(
    CompilerInstance &instance, llvm::StringRef batchInputFile) {
  // The primary cache used for scans carried out with the compiler instance
  // we have created

  SwiftDependencyScanningService singleUseService;
  if (singleUseService.setupCachingDependencyScanningService(instance))
    return true;

  ModuleDependenciesCache cache(
      singleUseService, instance.getMainModule()->getNameStr().str(),
      instance.getInvocation().getFrontendOptions().ExplicitModulesOutputPath,
      instance.getInvocation().getModuleScanningHash());
  (void)instance.getMainModule();
  llvm::BumpPtrAllocator alloc;
  llvm::StringSaver saver(alloc);
  auto batchInput =
      parseBatchScanInputFile(instance.getASTContext(), batchInputFile, saver);
  if (!batchInput.has_value())
    return true;

  auto batchScanResults = performBatchModuleScan(
      instance, /*DependencyScanDiagnosticCollector*/ nullptr,
      cache, /*versionedPCMInstanceCache*/ nullptr, saver,
      *batchInput);

  // Write the result JSON to the specified output path, for each entry
  auto ientries = batchInput->cbegin();
  auto iresults = batchScanResults.cbegin();
  for (; ientries != batchInput->end() and iresults != batchScanResults.end();
       ++ientries, ++iresults) {
    if ((*iresults).getError())
      return true;

    if (writeJSONToOutput(instance.getASTContext().Diags,
                          instance.getOutputBackend(), (*ientries).outputPath,
                          **iresults))
      return true;
  }
  return false;
}

std::string
swift::dependencies::createEncodedModuleKindAndName(ModuleDependencyID id) {
  switch (id.Kind) {
  case ModuleDependencyKind::SwiftInterface:
  case ModuleDependencyKind::SwiftSource:
    return "swiftTextual:" + id.ModuleName;
  case ModuleDependencyKind::SwiftBinary:
    return "swiftBinary:" + id.ModuleName;
  case ModuleDependencyKind::SwiftPlaceholder:
    return "swiftPlaceholder:" + id.ModuleName;
  case ModuleDependencyKind::Clang:
    return "clang:" + id.ModuleName;
  default:
    llvm_unreachable("Unhandled dependency kind.");
  }
}

static void resolveDependencyCommandLineArguments(
    CompilerInstance &instance, ModuleDependenciesCache &cache,
    const std::vector<ModuleDependencyID> &topoSortedModuleList) {
  auto moduleTransitiveClosures =
      computeTransitiveClosureOfExplicitDependencies(topoSortedModuleList,
                                                     cache);
  auto tracker = cache.getScanService().createSwiftDependencyTracker(
      instance.getInvocation());
  for (const auto &modID : llvm::reverse(topoSortedModuleList)) {
    auto dependencyClosure = moduleTransitiveClosures[modID];
    // For main module or binary modules, no command-line to resolve.
    // For Clang modules, their dependencies are resolved by the clang Scanner
    // itself for us.
    auto &deps = cache.findKnownDependency(modID);
    std::optional<std::set<ModuleDependencyID>> bridgingHeaderDeps;
    if (modID.Kind == ModuleDependencyKind::SwiftSource)
      bridgingHeaderDeps = computeBridgingHeaderTransitiveDependencies(
          deps, moduleTransitiveClosures, cache);

    if (auto E =
            resolveExplicitModuleInputs(modID, dependencyClosure, cache,
                                        instance, bridgingHeaderDeps, tracker))
      instance.getDiags().diagnose(SourceLoc(), diag::error_cas,
                                   toString(std::move(E)));
  }
}

static void
updateDependencyTracker(CompilerInstance &instance,
                        ModuleDependenciesCache &cache,
                        const std::vector<ModuleDependencyID> &allModules) {
  if (auto depTracker = instance.getDependencyTracker()) {
    for (auto module : allModules) {
      auto optionalDeps = cache.findDependency(module);
      if (!optionalDeps.has_value())
        continue;
      auto deps = optionalDeps.value();

      if (auto swiftDeps = deps->getAsSwiftInterfaceModule()) {
        depTracker->addDependency(swiftDeps->swiftInterfaceFile,
                                  /*IsSystem=*/false);
        for (const auto &bridgingSourceFile :
             swiftDeps->textualModuleDetails.bridgingSourceFiles)
          depTracker->addDependency(bridgingSourceFile, /*IsSystem=*/false);
      } else if (auto swiftSourceDeps = deps->getAsSwiftSourceModule()) {
        for (const auto &sourceFile : swiftSourceDeps->sourceFiles)
          depTracker->addDependency(sourceFile, /*IsSystem=*/false);
        for (const auto &bridgingSourceFile :
             swiftSourceDeps->textualModuleDetails.bridgingSourceFiles)
          depTracker->addDependency(bridgingSourceFile, /*IsSystem=*/false);
      } else if (auto clangDeps = deps->getAsClangModule()) {
        if (!clangDeps->moduleMapFile.empty())
          depTracker->addDependency(clangDeps->moduleMapFile,
                                    /*IsSystem=*/false);
        for (const auto &sourceFile : clangDeps->fileDependencies)
          depTracker->addDependency(sourceFile, /*IsSystem=*/false);
      }
    }
  }
}

static void resolveImplicitLinkLibraries(const CompilerInstance &instance,
                                         ModuleDependenciesCache &cache) {
  auto langOpts = instance.getInvocation().getLangOptions();
  auto irGenOpts = instance.getInvocation().getIRGenOptions();
  auto mainModuleName = instance.getMainModule()->getNameStr();
  auto mainModuleID = ModuleDependencyID{mainModuleName.str(),
                                         ModuleDependencyKind::SwiftSource};
  auto mainModuleDepInfo = cache.findKnownDependency(mainModuleID);

  std::vector<LinkLibrary> linkLibraries;
  auto addLinkLibrary = [&linkLibraries](const LinkLibrary &ll) {
    linkLibraries.push_back(ll);
  };

  if (langOpts.EnableObjCInterop)
    addLinkLibrary({"objc", LibraryKind::Library});

  if (langOpts.EnableCXXInterop) {
    auto OptionalCxxDep = cache.findDependency(CXX_MODULE_NAME);
    auto OptionalCxxStdLibDep = cache.findDependency("CxxStdlib");
    bool hasStaticCxx =
        OptionalCxxDep.has_value() && OptionalCxxDep.value()->isStaticLibrary();
    bool hasStaticCxxStdlib = OptionalCxxStdLibDep.has_value() &&
                              OptionalCxxStdLibDep.value()->isStaticLibrary();
    registerCxxInteropLibraries(langOpts.Target, mainModuleName, hasStaticCxx,
                                hasStaticCxxStdlib, langOpts.CXXStdlib,
                                addLinkLibrary);
  }

  if (!irGenOpts.UseJIT && !langOpts.hasFeature(Feature::Embedded))
    registerBackDeployLibraries(irGenOpts, addLinkLibrary);

  mainModuleDepInfo.setLinkLibraries(linkLibraries);
  cache.updateDependency(mainModuleID, mainModuleDepInfo);
}

llvm::ErrorOr<swiftscan_dependency_graph_t>
swift::dependencies::performModuleScan(
    CompilerInstance &instance,
    DependencyScanDiagnosticCollector *diagnosticCollector,
    ModuleDependenciesCache &cache) {
  auto scanner = ModuleDependencyScanner(
      cache.getScanService(), instance.getInvocation(),
      instance.getSILOptions(), instance.getASTContext(),
      *instance.getDependencyTracker(), instance.getDiags(),
      instance.getInvocation().getFrontendOptions().ParallelDependencyScan);

  // Identify imports of the main module and add an entry for it
  // to the dependency graph.
  auto mainModuleName = instance.getMainModule()->getNameStr();
  auto mainModuleID = ModuleDependencyID{mainModuleName.str(),
                                         ModuleDependencyKind::SwiftSource};
  if (!cache.hasDependency(mainModuleID))
    cache.recordDependency(mainModuleName,
                           *scanner.getMainModuleDependencyInfo(instance.getMainModule()));

  // Perform the full module scan starting at the main module.
  auto allModules = scanner.performDependencyScan(mainModuleID, cache);
  if (diagnoseCycle(instance, cache, mainModuleID))
    return std::make_error_code(std::errc::not_supported);

  auto topologicallySortedModuleList =
      computeTopologicalSortOfExplicitDependencies(allModules, cache);
  resolveDependencyCommandLineArguments(instance, cache,
                                        topologicallySortedModuleList);
  resolveImplicitLinkLibraries(instance, cache);
  updateDependencyTracker(instance, cache, allModules);

  if (instance.getInvocation().getFrontendOptions().EmitDependencyScannerCacheRemarks)
    instance.getASTContext().Diags.diagnose(SourceLoc(), diag::remark_scanner_uncached_lookups, scanner.getNumLookups());

  return generateFullDependencyGraph(instance, diagnosticCollector, cache,
                                     topologicallySortedModuleList);
}

llvm::ErrorOr<swiftscan_import_set_t>
swift::dependencies::performModulePrescan(CompilerInstance &instance,
                                          DependencyScanDiagnosticCollector *diagnosticCollector,
                                          ModuleDependenciesCache &cache) {
  // Setup the scanner
  auto scanner = ModuleDependencyScanner(
      cache.getScanService(), instance.getInvocation(),
      instance.getSILOptions(), instance.getASTContext(),
      *instance.getDependencyTracker(), instance.getDiags(),
      instance.getInvocation().getFrontendOptions().ParallelDependencyScan);
  // Execute import prescan, and write JSON output to the output stream
  auto mainDependencies =
      scanner.getMainModuleDependencyInfo(instance.getMainModule());
  if (!mainDependencies)
    return mainDependencies.getError();
  auto *importSet = new swiftscan_import_set_s;

  std::vector<std::string> importIdentifiers;
  importIdentifiers.reserve(mainDependencies->getModuleImports().size());
  llvm::transform(mainDependencies->getModuleImports(),
                  std::back_inserter(importIdentifiers),
                  [](const auto &importInfo) -> std::string {
                    return importInfo.importIdentifier;
                  });
  importSet->imports = create_set(importIdentifiers);
  importSet->diagnostics =
      diagnosticCollector
          ? mapCollectedDiagnosticsForOutput(diagnosticCollector)
          : nullptr;
  importSet->diagnostics =
      diagnosticCollector
          ? mapCollectedDiagnosticsForOutput(diagnosticCollector)
          : nullptr;
  return importSet;
}

std::vector<llvm::ErrorOr<swiftscan_dependency_graph_t>>
swift::dependencies::performBatchModuleScan(
    CompilerInstance &invocationInstance,
    DependencyScanDiagnosticCollector *diagnosticCollector,
    ModuleDependenciesCache &invocationCache,
    CompilerArgInstanceCacheMap *versionedPCMInstanceCache,
    llvm::StringSaver &saver, const std::vector<BatchScanInput> &batchInput) {
  std::vector<llvm::ErrorOr<swiftscan_dependency_graph_t>> batchScanResult;
  batchScanResult.reserve(batchInput.size());

  // Perform a full dependency scan for each batch entry module
  forEachBatchEntry(
      invocationInstance, invocationCache, versionedPCMInstanceCache, saver,
      batchInput,
      [&batchScanResult, &diagnosticCollector](BatchScanInput entry,
                         CompilerInstance &instance,
                         ModuleDependenciesCache &cache) {
        auto scanner = ModuleDependencyScanner(
            cache.getScanService(), instance.getInvocation(),
            instance.getSILOptions(), instance.getASTContext(),
            *instance.getDependencyTracker(), instance.getDiags(),
            instance.getInvocation().getFrontendOptions().ParallelDependencyScan);

        StringRef moduleName = entry.moduleName;
        bool isClang = !entry.isSwift;
        ModuleDependencyID moduleID{
           moduleName.str(), isClang ? ModuleDependencyKind::Clang
                                     : ModuleDependencyKind::SwiftInterface};
        std::optional<const ModuleDependencyInfo *> rootDeps;
        std::vector<ModuleDependencyID> allDependencies;
        if (isClang) {
          // Loading the clang module using Clang importer.
          // This action will populate the cache with the main module's
          // dependencies.
          ModuleDependencyIDSetVector allClangModules;
          rootDeps = scanner.getNamedClangModuleDependencyInfo(moduleName, cache, allClangModules);
          if (!rootDeps.has_value()) {
            batchScanResult.push_back(
                std::make_error_code(std::errc::invalid_argument));
            return;
          }
          allDependencies = allClangModules.takeVector();
        } else {
          rootDeps = scanner.getNamedSwiftModuleDependencyInfo(moduleName, cache);
          if (!rootDeps.has_value()) {
            batchScanResult.push_back(
                std::make_error_code(std::errc::invalid_argument));
            return;
          }
          allDependencies = scanner.performDependencyScan(moduleID, cache);
        }

        batchScanResult.push_back(
            generateFullDependencyGraph(instance, diagnosticCollector, cache,
                                        allDependencies));
        if (diagnosticCollector)
          diagnosticCollector->reset();
      });

  return batchScanResult;
}