// Copyright 2020 Google LLC
//
// 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 "internal/platform/implementation/g3/bluetooth_classic.h"

#include <memory>
#include <optional>
#include <string>
#include <utility>

#include "absl/functional/any_invocable.h"
#include "absl/log/check.h"
#include "absl/strings/string_view.h"
#include "absl/synchronization/mutex.h"
#include "internal/platform/cancellation_flag.h"
#include "internal/platform/cancellation_flag_listener.h"
#include "internal/platform/exception.h"
#include "internal/platform/implementation/bluetooth_adapter.h"
#include "internal/platform/implementation/bluetooth_classic.h"
#include "internal/platform/implementation/g3/bluetooth_adapter.h"
#include "internal/platform/logging.h"
#include "internal/platform/mac_address.h"
#include "internal/platform/medium_environment.h"
#include "internal/platform/types.h"

namespace nearby {
namespace g3 {

BluetoothDevice* BluetoothSocket::GetRemoteDevice() {
  BluetoothSocket* remote_socket =
      static_cast<BluetoothSocket*>(GetRemoteSocket());
  if (remote_socket == nullptr || remote_socket->adapter_ == nullptr) {
    return nullptr;
  }
  return &remote_socket->adapter_->GetDevice();
}

std::unique_ptr<api::BluetoothSocket> BluetoothServerSocket::Accept() {
  absl::MutexLock lock(mutex_);
  while (!closed_ && pending_sockets_.empty()) {
    cond_.Wait(&mutex_);
  }
  // whether or not we were running in the wait loop, return early if closed.
  if (closed_) return {};
  auto* remote_socket =
      pending_sockets_.extract(pending_sockets_.begin()).value();
  CHECK(remote_socket);
  auto local_socket = std::make_unique<BluetoothSocket>(adapter_);
  local_socket->Connect(*remote_socket);
  remote_socket->Connect(*local_socket);
  cond_.SignalAll();
  return local_socket;
}

bool BluetoothServerSocket::Connect(BluetoothSocket& socket) {
  absl::MutexLock lock(mutex_);
  if (closed_) return false;
  if (socket.IsConnected()) {
    LOG(ERROR) << "Failed to connect to BT server socket: already connected";
    return true;  // already connected.
  }
  // add client socket to the pending list
  pending_sockets_.emplace(&socket);
  cond_.SignalAll();
  while (!socket.IsConnected()) {
    cond_.Wait(&mutex_);
    if (closed_) return false;
  }
  return true;
}

void BluetoothServerSocket::SetCloseNotifier(
    absl::AnyInvocable<void()> notifier) {
  absl::MutexLock lock(mutex_);
  close_notifier_ = std::move(notifier);
}

BluetoothServerSocket::~BluetoothServerSocket() {
  absl::MutexLock lock(mutex_);
  DoClose();
}

Exception BluetoothServerSocket::Close() {
  absl::MutexLock lock(mutex_);
  return DoClose();
}

Exception BluetoothServerSocket::DoClose() {
  bool should_notify = !closed_;
  closed_ = true;
  if (should_notify) {
    cond_.SignalAll();
    if (close_notifier_) {
      auto notifier = std::move(close_notifier_);
      mutex_.unlock();
      // Notifier may contain calls to public API, and may cause deadlock, if
      // mutex_ is held during the call.
      notifier();
      mutex_.lock();
    }
  }
  return {Exception::kSuccess};
}

BluetoothPairing::BluetoothPairing(api::BluetoothDevice& remote_device)
    : remote_device_(remote_device) {}

BluetoothPairing::~BluetoothPairing() {
  MediumEnvironment::Instance().ClearBluetoothDevicesForPairing();
}

bool BluetoothPairing::InitiatePairing(
    api::BluetoothPairingCallback pairing_cb) {
  return MediumEnvironment::Instance().InitiatePairing(&remote_device_,
                                                       std::move(pairing_cb));
}

bool BluetoothPairing::FinishPairing(
    std::optional<absl::string_view> pin_code) {
  return MediumEnvironment::Instance().FinishPairing(&remote_device_);
}

bool BluetoothPairing::CancelPairing() {
  return MediumEnvironment::Instance().CancelPairing(&remote_device_);
}

bool BluetoothPairing::Unpair() {
  return MediumEnvironment::Instance().SetPairingState(&remote_device_, false);
}

bool BluetoothPairing::IsPaired() {
  return MediumEnvironment::Instance().IsPaired(&remote_device_);
}

BluetoothClassicMedium::BluetoothClassicMedium(api::BluetoothAdapter& adapter)
    // TODO(apolyudov): implement and use downcast<> with static assertions.
    : adapter_(static_cast<BluetoothAdapter*>(&adapter)) {
  adapter_->SetBluetoothClassicMedium(this);
  auto& env = MediumEnvironment::Instance();
  env.RegisterBluetoothMedium(*this, GetAdapter());
}

BluetoothClassicMedium::~BluetoothClassicMedium() {
  adapter_->SetBluetoothClassicMedium(nullptr);
  auto& env = MediumEnvironment::Instance();
  env.UnregisterBluetoothMedium(*this);
}

bool BluetoothClassicMedium::StartDiscovery(DiscoveryCallback callback) {
  auto& env = MediumEnvironment::Instance();
  env.UpdateBluetoothMedium(*this, std::move(callback));
  return true;
}

bool BluetoothClassicMedium::StopDiscovery() {
  auto& env = MediumEnvironment::Instance();
  env.UpdateBluetoothMedium(*this, {});
  return true;
}

std::unique_ptr<api::BluetoothSocket> BluetoothClassicMedium::ConnectToService(
    api::BluetoothDevice& remote_device, const std::string& service_uuid,
    CancellationFlag* cancellation_flag) {
  LOG(INFO) << "G3 ConnectToService [self]: medium=" << this
            << ", adapter=" << &GetAdapter()
            << ", device=" << &GetAdapter().GetDevice();

  // Find the device in the MediumEnvironment, so that injected devices are
  // supported in tests.
  api::BluetoothDevice* device =
      MediumEnvironment::Instance().FindBluetoothDevice(
          remote_device.GetMacAddress());
  if (device == nullptr) {
    LOG(ERROR) << "G3 ConnectToService [peer]: device=" << &remote_device
               << " not found";
    return {};
  }

  auto& adapter = down_cast<BluetoothDevice*>(device)->GetAdapter();
  auto* medium =
      down_cast<BluetoothClassicMedium*>(adapter.GetBluetoothClassicMedium());

  if (!medium) return {};  // Adapter is not bound to medium. Bail out.

  BluetoothServerSocket* server_socket = nullptr;
  LOG(INFO) << "G3 ConnectToService [peer]: medium=" << medium
            << ", adapter=" << &adapter << ", device=" << &remote_device
            << ", uuid=" << service_uuid;
  // Then, find our server socket context in this medium.
  {
    absl::MutexLock medium_lock(medium->mutex_);
    auto item = medium->sockets_.find(service_uuid);
    server_socket = item != medium->sockets_.end() ? item->second : nullptr;
    if (server_socket == nullptr) {
      LOG(ERROR) << "Failed to find BT Server socket: uuid=" << service_uuid;
      return {};
    }
  }

  if (cancellation_flag->Cancelled()) {
    LOG(ERROR) << "G3 Bluetooth Connect: Has been cancelled: "
                  "service_uuid="
               << service_uuid;
    return {};
  }

  CancellationFlagListener listener(cancellation_flag, [&server_socket]() {
    LOG(INFO) << "G3 Bluetooth Cancel Connect.";
    if (server_socket != nullptr) server_socket->Close();
  });

  auto socket = std::make_unique<BluetoothSocket>(&GetAdapter());
  // Finally, Request to connect to this socket.
  if (!server_socket->Connect(*socket)) {
    LOG(ERROR) << "Failed to connect to existing BT Server socket: uuid="
               << service_uuid;
    return {};
  }

  if (cancellation_flag->Cancelled()) {
    LOG(ERROR) << "G3 Bluetooth Connect: Has been cancelled after connected: "
                  "service_uuid="
               << service_uuid;
    socket->Close();
    return {};
  }

  LOG(INFO) << "G3 ConnectToService: connected: socket=" << socket.get();
  return socket;
}

std::unique_ptr<api::BluetoothServerSocket>
BluetoothClassicMedium::ListenForService(const std::string& service_name,
                                         const std::string& service_uuid) {
  auto socket = std::make_unique<BluetoothServerSocket>(GetAdapter());
  socket->SetCloseNotifier([this, uuid = service_uuid]() {
    absl::MutexLock lock(mutex_);
    sockets_.erase(uuid);
  });
  LOG(INFO) << "Adding service: medium=" << this << ", uuid=" << service_uuid;
  absl::MutexLock lock(mutex_);
  sockets_.emplace(service_uuid, socket.get());
  return socket;
}

std::unique_ptr<api::BluetoothPairing> BluetoothClassicMedium::CreatePairing(
    api::BluetoothDevice& remote_device) {
  return std::make_unique<BluetoothPairing>(remote_device);
}

api::BluetoothDevice* BluetoothClassicMedium::GetRemoteDevice(
    MacAddress mac_address) {
  return MediumEnvironment::Instance().FindBluetoothDevice(mac_address);
}

void BluetoothClassicMedium::AddObserver(
    api::BluetoothClassicMedium::Observer* observer) {
  MediumEnvironment::Instance().AddObserver(observer);
}

void BluetoothClassicMedium::RemoveObserver(
    api::BluetoothClassicMedium::Observer* observer) {
  MediumEnvironment::Instance().RemoveObserver(observer);
}

}  // namespace g3
}  // namespace nearby