//===--- GlobalSymbolBuilderMain.cpp -----------------------------*- C++-*-===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// GlobalSymbolBuilder is a tool to generate YAML-format symbols across the
// whole project. This tools is for **experimental** only. Don't use it in
// production code.
//
//===---------------------------------------------------------------------===//

#include "index/CanonicalIncludes.h"
#include "index/Index.h"
#include "index/Merge.h"
#include "index/SymbolCollector.h"
#include "index/SymbolYAML.h"
#include "clang/Frontend/CompilerInstance.h"
#include "clang/Frontend/FrontendActions.h"
#include "clang/Index/IndexDataConsumer.h"
#include "clang/Index/IndexingAction.h"
#include "clang/Tooling/CommonOptionsParser.h"
#include "clang/Tooling/Execution.h"
#include "clang/Tooling/Tooling.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/MemoryBuffer.h"
#include "llvm/Support/Path.h"
#include "llvm/Support/Signals.h"
#include "llvm/Support/ThreadPool.h"
#include "llvm/Support/YAMLTraits.h"

using namespace llvm;
using namespace clang::tooling;
using clang::clangd::SymbolSlab;

namespace clang {
namespace clangd {
namespace {

static llvm::cl::opt<std::string> AssumedHeaderDir(
    "assume-header-dir",
    llvm::cl::desc("The index includes header that a symbol is defined in. "
                   "If the absolute path cannot be determined (e.g. an "
                   "in-memory VFS) then the relative path is resolved against "
                   "this directory, which must be absolute. If this flag is "
                   "not given, such headers will have relative paths."),
    llvm::cl::init(""));

class SymbolIndexActionFactory : public tooling::FrontendActionFactory {
public:
  SymbolIndexActionFactory(tooling::ExecutionContext *Ctx) : Ctx(Ctx) {}

  clang::FrontendAction *create() override {
    // Wraps the index action and reports collected symbols to the execution
    // context at the end of each translation unit.
    class WrappedIndexAction : public WrapperFrontendAction {
    public:
      WrappedIndexAction(std::shared_ptr<SymbolCollector> C,
                         std::unique_ptr<CanonicalIncludes> Includes,
                         const index::IndexingOptions &Opts,
                         tooling::ExecutionContext *Ctx)
          : WrapperFrontendAction(
                index::createIndexingAction(C, Opts, nullptr)),
            Ctx(Ctx), Collector(C), Includes(std::move(Includes)),
            PragmaHandler(collectIWYUHeaderMaps(this->Includes.get())) {}

      std::unique_ptr<ASTConsumer>
      CreateASTConsumer(CompilerInstance &CI, StringRef InFile) override {
        CI.getPreprocessor().addCommentHandler(PragmaHandler.get());
        return WrapperFrontendAction::CreateASTConsumer(CI, InFile);
      }

      bool BeginInvocation(CompilerInstance &CI) override {
        // We want all comments, not just the doxygen ones.
        CI.getLangOpts().CommentOpts.ParseAllComments = true;
        return WrapperFrontendAction::BeginInvocation(CI);
      }

      void EndSourceFileAction() override {
        WrapperFrontendAction::EndSourceFileAction();

        const auto &CI = getCompilerInstance();
        if (CI.hasDiagnostics() &&
            CI.getDiagnostics().hasUncompilableErrorOccurred()) {
          llvm::errs()
              << "Found uncompilable errors in the translation unit. Igoring "
                 "collected symbols...\n";
          return;
        }

        auto Symbols = Collector->takeSymbols();
        for (const auto &Sym : Symbols) {
          Ctx->reportResult(Sym.ID.str(), SymbolToYAML(Sym));
        }
      }

    private:
      tooling::ExecutionContext *Ctx;
      std::shared_ptr<SymbolCollector> Collector;
      std::unique_ptr<CanonicalIncludes> Includes;
      std::unique_ptr<CommentHandler> PragmaHandler;
    };

    index::IndexingOptions IndexOpts;
    IndexOpts.SystemSymbolFilter =
        index::IndexingOptions::SystemSymbolFilterKind::All;
    IndexOpts.IndexFunctionLocals = false;
    auto CollectorOpts = SymbolCollector::Options();
    CollectorOpts.FallbackDir = AssumedHeaderDir;
    CollectorOpts.CollectIncludePath = true;
    CollectorOpts.CountReferences = true;
    CollectorOpts.Origin = SymbolOrigin::Static;
    auto Includes = llvm::make_unique<CanonicalIncludes>();
    addSystemHeadersMapping(Includes.get());
    CollectorOpts.Includes = Includes.get();
    return new WrappedIndexAction(
        std::make_shared<SymbolCollector>(std::move(CollectorOpts)),
        std::move(Includes), IndexOpts, Ctx);
  }

  tooling::ExecutionContext *Ctx;
};

// Combine occurrences of the same symbol across translation units.
SymbolSlab mergeSymbols(tooling::ToolResults *Results) {
  SymbolSlab::Builder UniqueSymbols;
  llvm::BumpPtrAllocator Arena;
  Symbol::Details Scratch;
  Results->forEachResult([&](llvm::StringRef Key, llvm::StringRef Value) {
    Arena.Reset();
    llvm::yaml::Input Yin(Value, &Arena);
    auto Sym = clang::clangd::SymbolFromYAML(Yin, Arena);
    clang::clangd::SymbolID ID;
    Key >> ID;
    if (const auto *Existing = UniqueSymbols.find(ID))
      UniqueSymbols.insert(mergeSymbol(*Existing, Sym, &Scratch));
    else
      UniqueSymbols.insert(Sym);
  });
  return std::move(UniqueSymbols).build();
}

} // namespace
} // namespace clangd
} // namespace clang

int main(int argc, const char **argv) {
  llvm::sys::PrintStackTraceOnErrorSignal(argv[0]);

  const char *Overview = R"(
  This is an **experimental** tool to generate YAML-format project-wide symbols
  for clangd (global code completion). It would be changed and deprecated
  eventually. Don't use it in production code!

  Example usage for building index for the whole project using CMake compile
  commands:

  $ global-symbol-builder --executor=all-TUs compile_commands.json > index.yaml

  Example usage for file sequence index without flags:

  $ global-symbol-builder File1.cpp File2.cpp ... FileN.cpp > index.yaml

  Note: only symbols from header files will be collected.
  )";

  auto Executor = clang::tooling::createExecutorFromCommandLineArgs(
      argc, argv, cl::GeneralCategory, Overview);

  if (!Executor) {
    llvm::errs() << llvm::toString(Executor.takeError()) << "\n";
    return 1;
  }

  if (!clang::clangd::AssumedHeaderDir.empty() &&
      !llvm::sys::path::is_absolute(clang::clangd::AssumedHeaderDir)) {
    llvm::errs() << "--assume-header-dir must be an absolute path.\n";
    return 1;
  }

  // Map phase: emit symbols found in each translation unit.
  auto Err = Executor->get()->execute(
      llvm::make_unique<clang::clangd::SymbolIndexActionFactory>(
          Executor->get()->getExecutionContext()));
  if (Err) {
    llvm::errs() << llvm::toString(std::move(Err)) << "\n";
  }

  // Reduce phase: combine symbols using the ID as a key.
  auto UniqueSymbols =
      clang::clangd::mergeSymbols(Executor->get()->getToolResults());

  // Output phase: emit YAML for result symbols.
  SymbolsToYAML(UniqueSymbols, llvm::outs());
  return 0;
}