//

//  Copyright 2020 The Abseil Authors.

//

// Licensed under the Apache License, Version 2.0 (the "License");

// you may not use this file except in compliance with the License.

// You may obtain a copy of the License at

//

//      https://www.apache.org/licenses/LICENSE-2.0

//

// Unless required by applicable law or agreed to in writing, software

// distributed under the License is distributed on an "AS IS" BASIS,

// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

// See the License for the specific language governing permissions and

// limitations under the License.

#include "absl/flags/reflection.h"

#include <assert.h>

#include <atomic>

#include <string>

#include "absl/base/config.h"

#include "absl/base/no_destructor.h"

#include "absl/base/thread_annotations.h"

#include "absl/container/flat_hash_map.h"

#include "absl/flags/commandlineflag.h"

#include "absl/flags/internal/private_handle_accessor.h"

#include "absl/flags/internal/registry.h"

#include "absl/flags/usage_config.h"

#include "absl/strings/str_cat.h"

#include "absl/strings/string_view.h"

#include "absl/synchronization/mutex.h"

namespace absl {

ABSL_NAMESPACE_BEGIN

namespace flags_internal {

// --------------------------------------------------------------------

// FlagRegistry

//    A FlagRegistry singleton object holds all flag objects indexed by their

//    names so that if you know a flag's name, you can access or set it. If the

//    function is named FooLocked(), you must own the registry lock before

//    calling the function; otherwise, you should *not* hold the lock, and the

//    function will acquire it itself if needed.

// --------------------------------------------------------------------

class FlagRegistry {

 public:

  FlagRegistry() = default;

  ~FlagRegistry() = default;

  // Store a flag in this registry. Takes ownership of *flag.

  void RegisterFlag(CommandLineFlag& flag, const char* filename);

  void Lock() ABSL_EXCLUSIVE_LOCK_FUNCTION(lock_) { lock_.Lock(); }

  void Unlock() ABSL_UNLOCK_FUNCTION(lock_) { lock_.Unlock(); }

  // Returns the flag object for the specified name, or nullptr if not found.

  // Will emit a warning if a 'retired' flag is specified.

  CommandLineFlag* FindFlag(absl::string_view name);

  static FlagRegistry& GlobalRegistry();  // returns a singleton registry

 private:

  friend class flags_internal::FlagSaverImpl;  // reads all the flags in order

                                               // to copy them

  friend void ForEachFlag(std::function<void(CommandLineFlag&)> visitor);

  friend void FinalizeRegistry();

  // The map from name to flag, for FindFlag().

  using FlagMap = absl::flat_hash_map<absl::string_view, CommandLineFlag*>;

  using FlagIterator = FlagMap::iterator;

  using FlagConstIterator = FlagMap::const_iterator;

  FlagMap flags_;

  std::vector<CommandLineFlag*> flat_flags_;

  std::atomic<bool> finalized_flags_{false};

  absl::Mutex lock_;

  // Disallow

  FlagRegistry(const FlagRegistry&);

  FlagRegistry& operator=(const FlagRegistry&);

};

namespace {

class FlagRegistryLock {

 public:

  explicit FlagRegistryLock(FlagRegistry& fr) : fr_(fr) { fr_.Lock(); }

  ~FlagRegistryLock() { fr_.Unlock(); }

 private:

  FlagRegistry& fr_;

};

}  // namespace

CommandLineFlag* FlagRegistry::FindFlag(absl::string_view name) {

  if (finalized_flags_.load(std::memory_order_acquire)) {

    // We could save some gcus here if we make `Name()` be non-virtual.

    // We could move the `const char*` name to the base class.

    auto it = std::partition_point(

        flat_flags_.begin(), flat_flags_.end(),

        [=](CommandLineFlag* f) { return f->Name() < name; });

    if (it != flat_flags_.end() && (*it)->Name() == name) return *it;

  }

  FlagRegistryLock frl(*this);

  auto it = flags_.find(name);

  return it != flags_.end() ? it->second : nullptr;

}

void FlagRegistry::RegisterFlag(CommandLineFlag& flag, const char* filename) {

  if (filename != nullptr &&

      flag.Filename() != GetUsageConfig().normalize_filename(filename)) {

    flags_internal::ReportUsageError(

        absl::StrCat(

            "Inconsistency between flag object and registration for flag '",

            flag.Name(),

            "', likely due to duplicate flags or an ODR violation. Relevant "

            "files: ",

            flag.Filename(), " and ", filename),

        true);

    std::exit(1);

  }

  FlagRegistryLock registry_lock(*this);

  std::pair<FlagIterator, bool> ins =

      flags_.insert(FlagMap::value_type(flag.Name(), &flag));

  if (ins.second == false) {  // means the name was already in the map

    CommandLineFlag& old_flag = *ins.first->second;

    if (flag.IsRetired() != old_flag.IsRetired()) {

      // All registrations must agree on the 'retired' flag.

      flags_internal::ReportUsageError(

          absl::StrCat(

              "Retired flag '", flag.Name(), "' was defined normally in file '",

              (flag.IsRetired() ? old_flag.Filename() : flag.Filename()), "'."),

          true);

    } else if (flags_internal::PrivateHandleAccessor::TypeId(flag) !=

               flags_internal::PrivateHandleAccessor::TypeId(old_flag)) {

      flags_internal::ReportUsageError(

          absl::StrCat("Flag '", flag.Name(),

                       "' was defined more than once but with "

                       "differing types. Defined in files '",

                       old_flag.Filename(), "' and '", flag.Filename(), "'."),

          true);

    } else if (old_flag.IsRetired()) {

      return;

    } else if (old_flag.Filename() != flag.Filename()) {

      flags_internal::ReportUsageError(

          absl::StrCat("Flag '", flag.Name(),

                       "' was defined more than once (in files '",

                       old_flag.Filename(), "' and '", flag.Filename(), "')."),

          true);

    } else {

      flags_internal::ReportUsageError(

          absl::StrCat(

              "Something is wrong with flag '", flag.Name(), "' in file '",

              flag.Filename(), "'. One possibility: file '", flag.Filename(),

              "' is being linked both statically and dynamically into this "

              "executable. e.g. some files listed as srcs to a test and also "

              "listed as srcs of some shared lib deps of the same test."),

          true);

    }

    // All cases above are fatal, except for the retired flags.

    std::exit(1);

  }

}

FlagRegistry& FlagRegistry::GlobalRegistry() {

  static absl::NoDestructor<FlagRegistry> global_registry;

  return *global_registry;

}

// --------------------------------------------------------------------

void ForEachFlag(std::function<void(CommandLineFlag&)> visitor) {

  FlagRegistry& registry = FlagRegistry::GlobalRegistry();

  if (registry.finalized_flags_.load(std::memory_order_acquire)) {

    for (const auto& i : registry.flat_flags_) visitor(*i);

  }

  FlagRegistryLock frl(registry);

  for (const auto& i : registry.flags_) visitor(*i.second);

}

// --------------------------------------------------------------------

bool RegisterCommandLineFlag(CommandLineFlag& flag, const char* filename) {

  FlagRegistry::GlobalRegistry().RegisterFlag(flag, filename);

  return true;

}

void FinalizeRegistry() {

  auto& registry = FlagRegistry::GlobalRegistry();

  FlagRegistryLock frl(registry);

  if (registry.finalized_flags_.load(std::memory_order_relaxed)) {

    // Was already finalized. Ignore the second time.

    return;

  }

  registry.flat_flags_.reserve(registry.flags_.size());

  for (const auto& f : registry.flags_) {

    registry.flat_flags_.push_back(f.second);

  }

  std::sort(std::begin(registry.flat_flags_), std::end(registry.flat_flags_),

            [](const CommandLineFlag* lhs, const CommandLineFlag* rhs) {

              return lhs->Name() < rhs->Name();

            });

  registry.flags_.clear();

  registry.finalized_flags_.store(true, std::memory_order_release);

}

// --------------------------------------------------------------------

namespace {

// These are only used as constexpr global objects.

// They do not use a virtual destructor to simplify their implementation.

// They are not destroyed except at program exit, so leaks do not matter.

#if defined(__GNUC__) && !defined(__clang__)

#pragma GCC diagnostic push

#pragma GCC diagnostic ignored "-Wnon-virtual-dtor"

#endif

class RetiredFlagObj final : public CommandLineFlag {

 public:

  constexpr RetiredFlagObj(const char* name, FlagFastTypeId type_id)

      : name_(name), type_id_(type_id) {}

 private:

  absl::string_view Name() const override { return name_; }

  std::string Filename() const override {

    OnAccess();

    return "RETIRED";

  }

  FlagFastTypeId TypeId() const override { return type_id_; }

  std::string Help() const override {

    OnAccess();

    return "";

  }

  bool IsRetired() const override { return true; }

  bool IsSpecifiedOnCommandLine() const override {

    OnAccess();

    return false;

  }

  std::string DefaultValue() const override {

    OnAccess();

    return "";

  }

  std::string CurrentValue() const override {

    OnAccess();

    return "";

  }

  // Any input is valid

  bool ValidateInputValue(absl::string_view) const override {

    OnAccess();

    return true;

  }

  std::unique_ptr<flags_internal::FlagStateInterface> SaveState() override {

    return nullptr;

  }

  bool ParseFrom(absl::string_view, flags_internal::FlagSettingMode,

                 flags_internal::ValueSource, std::string&) override {

    OnAccess();

    return false;

  }

  void CheckDefaultValueParsingRoundtrip() const override { OnAccess(); }

  void Read(void*) const override { OnAccess(); }

  void OnAccess() const {

    flags_internal::ReportUsageError(

        absl::StrCat("Accessing retired flag '", name_, "'"), false);

  }

  // Data members

  const char* const name_;

  const FlagFastTypeId type_id_;

};

#if defined(__GNUC__) && !defined(__clang__)

#pragma GCC diagnostic pop

#endif

}  // namespace

void Retire(const char* name, FlagFastTypeId type_id, char* buf) {

  static_assert(sizeof(RetiredFlagObj) == kRetiredFlagObjSize, "");

  static_assert(alignof(RetiredFlagObj) == kRetiredFlagObjAlignment, "");

  auto* flag = ::new (static_cast<void*>(buf))

      flags_internal::RetiredFlagObj(name, type_id);

  FlagRegistry::GlobalRegistry().RegisterFlag(*flag, nullptr);

}

// --------------------------------------------------------------------

class FlagSaverImpl {

 public:

  FlagSaverImpl() = default;

  FlagSaverImpl(const FlagSaverImpl&) = delete;

  void operator=(const FlagSaverImpl&) = delete;

  // Saves the flag states from the flag registry into this object.

  // It's an error to call this more than once.

  void SaveFromRegistry() {

    assert(backup_registry_.empty());  // call only once!

    flags_internal::ForEachFlag([&](CommandLineFlag& flag) {

      if (auto flag_state =

              flags_internal::PrivateHandleAccessor::SaveState(flag)) {

        backup_registry_.emplace_back(std::move(flag_state));

      }

    });

  }

  // Restores the saved flag states into the flag registry.

  void RestoreToRegistry() {

    for (const auto& flag_state : backup_registry_) {

      flag_state->Restore();

    }

  }

 private:

  std::vector<std::unique_ptr<flags_internal::FlagStateInterface>>

      backup_registry_;

};

}  // namespace flags_internal

FlagSaver::FlagSaver() : impl_(new flags_internal::FlagSaverImpl) {

  impl_->SaveFromRegistry();

}

FlagSaver::~FlagSaver() {

  if (!impl_) return;

  impl_->RestoreToRegistry();

  delete impl_;

}

// --------------------------------------------------------------------

CommandLineFlag* FindCommandLineFlag(absl::string_view name) {

  if (name.empty()) return nullptr;

  flags_internal::FlagRegistry& registry =

      flags_internal::FlagRegistry::GlobalRegistry();

  return registry.FindFlag(name);

}

// --------------------------------------------------------------------

absl::flat_hash_map<absl::string_view, absl::CommandLineFlag*> GetAllFlags() {

  absl::flat_hash_map<absl::string_view, absl::CommandLineFlag*> res;

  flags_internal::ForEachFlag([&](CommandLineFlag& flag) {

    if (!flag.IsRetired()) res.insert({flag.Name(), &flag});

  });

  return res;

}

ABSL_NAMESPACE_END

}  // namespace absl