// 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.

#ifndef PLATFORM_IMPL_G3_BLUETOOTH_CLASSIC_H_
#define PLATFORM_IMPL_G3_BLUETOOTH_CLASSIC_H_

#include <memory>
#include <string>

#include "platform/api/bluetooth_classic.h"
#include "platform/base/byte_array.h"
#include "platform/base/exception.h"
#include "platform/base/input_stream.h"
#include "platform/base/listeners.h"
#include "platform/base/output_stream.h"
#include "platform/impl/g3/bluetooth_adapter.h"
#include "platform/impl/g3/pipe.h"
#include "absl/container/flat_hash_map.h"
#include "absl/container/flat_hash_set.h"
#include "absl/synchronization/mutex.h"

namespace location {
namespace nearby {
namespace g3 {

// https://developer.android.com/reference/android/bluetooth/BluetoothSocket.html.
class BluetoothSocket : public api::BluetoothSocket {
 public:
  BluetoothSocket() = default;
  explicit BluetoothSocket(BluetoothAdapter* adapter) : adapter_(adapter) {}
  ~BluetoothSocket() override;

  // Connects to another BluetoothSocket, to form a functional low-level
  // channel. From this point on, and until Close is called, connection exists.
  void Connect(BluetoothSocket& other);

  // NOTE:
  // It is an undefined behavior if GetInputStream() or GetOutputStream() is
  // called for a not-connected BluetoothSocket, i.e. any object that is not
  // returned by BluetoothClassicMedium::ConnectToService() for client side or
  // BluetoothServerSocket::Accept() for server side of connection.

  // Returns the InputStream of this connected BluetoothSocket.
  InputStream& GetInputStream() override;

  // Returns the OutputStream of this connected BluetoothSocket.
  // This stream is for local side to write.
  OutputStream& GetOutputStream() override;

  // Returns address of a remote BluetoothSocket or nullptr.
  BluetoothSocket* GetRemoteSocket() ABSL_LOCKS_EXCLUDED(mutex_);

  // Returns true if connection exists to the (possibly closed) remote socket.
  bool IsConnected() const ABSL_LOCKS_EXCLUDED(mutex_);

  // Returns true if socket is closed.
  bool IsClosed() const ABSL_LOCKS_EXCLUDED(mutex_);

  // Closes both input and output streams, marks Socket as closed.
  // After this call object should be treated as not connected.
  // Returns Exception::kIo on error, Exception::kSuccess otherwise.
  Exception Close() override ABSL_LOCKS_EXCLUDED(mutex_);

  // https://developer.android.com/reference/android/bluetooth/BluetoothSocket.html#getRemoteDevice()
  // Returns valid BluetoothDevice pointer if there is a connection, and
  // nullptr otherwise.
  BluetoothDevice* GetRemoteDevice() override ABSL_LOCKS_EXCLUDED(mutex_);

 private:
  void DoClose() ABSL_EXCLUSIVE_LOCKS_REQUIRED(mutex_);

  // Returns true if connection exists to the (possibly closed) remote socket.
  bool IsConnectedLocked() const ABSL_EXCLUSIVE_LOCKS_REQUIRED(mutex_);

  // Returns InputStream of our side of a connection.
  // This is what the remote side is supposed to read from.
  // This is a helper for GetInputStream() method.
  InputStream& GetLocalInputStream() ABSL_LOCKS_EXCLUDED(mutex_);

  // Returns OutputStream of our side of a connection.
  // This is what the local size is supposed to write to.
  // This is a helper for GetOutputStream() method.
  OutputStream& GetLocalOutputStream() ABSL_LOCKS_EXCLUDED(mutex_);

  // Output pipe is initialized by constructor, it remains always valid, until
  // it is closed. it represents output part of a local socket. Input part of a
  // local socket comes from the peer socket, after connection.
  std::shared_ptr<Pipe> output_{new Pipe};
  std::shared_ptr<Pipe> input_;
  mutable absl::Mutex mutex_;
  BluetoothAdapter* adapter_ = nullptr;  // Our Adapter. Read only.
  BluetoothSocket* remote_socket_ ABSL_GUARDED_BY(mutex_) = nullptr;
  bool closed_ ABSL_GUARDED_BY(mutex_) = false;
};

// https://developer.android.com/reference/android/bluetooth/BluetoothServerSocket.html.
class BluetoothServerSocket : public api::BluetoothServerSocket {
 public:
  explicit BluetoothServerSocket(BluetoothAdapter& adapter)
      : adapter_(&adapter) {}
  ~BluetoothServerSocket() override;

  // Blocks until either:
  // - at least one incoming connection request is available, or
  // - ServerSocket is closed.
  // On success, returns connected socket, ready to exchange data.
  // Returns nullptr on error.
  // Once error is reported, it is permanent, and ServerSocket has to be closed.
  //
  // Called by the server side of a connection.
  // Returns BluetoothSocket to the server side.
  // If not null, returned socket is connected to its remote (client-side) peer.
  std::unique_ptr<api::BluetoothSocket> Accept() override
      ABSL_LOCKS_EXCLUDED(mutex_);

  // Blocks until either:
  // - connection is available, or
  // - server socket is closed, or
  // - error happens.
  //
  // Called by the client side of a connection.
  // socket is an initialized BluetoothSocket, associated with a client
  // BluetoothAdapter.
  // Returns true, if socket is successfully connected.
  bool Connect(BluetoothSocket& socket) ABSL_LOCKS_EXCLUDED(mutex_);

  // Called by the server side of a connection before passing ownership of
  // BluetoothServerSocker to user, to track validity of a pointer to this
  // server socket,
  void SetCloseNotifier(std::function<void()> notifier)
      ABSL_LOCKS_EXCLUDED(mutex_);

  // Returns Exception::kIo on error, Exception::kSuccess otherwise.
  // Calls close_notifier if it was previously set, and marks socket as closed.
  Exception Close() override ABSL_LOCKS_EXCLUDED(mutex_);

 private:
  Exception DoClose() ABSL_EXCLUSIVE_LOCKS_REQUIRED(mutex_);

  absl::Mutex mutex_;
  absl::CondVar cond_;
  BluetoothAdapter* adapter_ = nullptr;  // Our Adapter. Read only.
  absl::flat_hash_set<BluetoothSocket*> pending_sockets_
      ABSL_GUARDED_BY(mutex_);
  std::function<void()> close_notifier_ ABSL_GUARDED_BY(mutex_);
  bool closed_ ABSL_GUARDED_BY(mutex_) = false;
};

// Container of operations that can be performed over the Bluetooth Classic
// medium.
class BluetoothClassicMedium : public api::BluetoothClassicMedium {
 public:
  explicit BluetoothClassicMedium(api::BluetoothAdapter& adapter);
  ~BluetoothClassicMedium() override;

  // NOTE(DiscoveryCallback):
  // BluetoothDevice is a proxy object created as a result of BT discovery.
  // Its lifetime spans between calls to device_discovered_cb and
  // device_lost_cb.
  // It is safe to use BluetoothDevice in device_discovered_cb() callback
  // and at any time afterwards, until device_lost_cb() is called.
  // It is not safe to use BluetoothDevice after returning from
  // device_lost_cb() callback.
  // https://developer.android.com/reference/android/bluetooth/BluetoothAdapter.html#startDiscovery()
  //
  // Returns true once the process of discovery has been initiated.
  bool StartDiscovery(DiscoveryCallback callback) override
      ABSL_LOCKS_EXCLUDED(mutex_);

  // https://developer.android.com/reference/android/bluetooth/BluetoothAdapter.html#cancelDiscovery()
  //
  // Returns true once discovery is well and truly stopped; after this returns,
  // there must be no more invocations of the DiscoveryCallback passed in to
  // StartDiscovery().
  bool StopDiscovery() override ABSL_LOCKS_EXCLUDED(mutex_);

  // Connects to existing remote BT service.
  //
  // A combination of
  // https://developer.android.com/reference/android/bluetooth/BluetoothDevice.html#createInsecureRfcommSocketToServiceRecord
  // followed by
  // https://developer.android.com/reference/android/bluetooth/BluetoothSocket.html#connect().
  //
  // service_uuid is the canonical textual representation
  // (https://en.wikipedia.org/wiki/Universally_unique_identifier#Format) of a
  // type 3 name-based
  // (https://en.wikipedia.org/wiki/Universally_unique_identifier#Versions_3_and_5_(namespace_name-based))
  // UUID.
  //
  // On success, returns a new BluetoothSocket.
  // On error, returns nullptr.
  std::unique_ptr<api::BluetoothSocket> ConnectToService(
      api::BluetoothDevice& remote_device,
      const std::string& service_uuid) override ABSL_LOCKS_EXCLUDED(mutex_);

  BluetoothAdapter& GetAdapter() { return *adapter_; }

  // Creates BT service, and begins listening for remote attempts to connect.
  //
  // https://developer.android.com/reference/android/bluetooth/BluetoothAdapter.html#listenUsingInsecureRfcommWithServiceRecord
  //
  // service_uuid is the canonical textual representation
  // (https://en.wikipedia.org/wiki/Universally_unique_identifier#Format) of a
  // type 3 name-based
  // (https://en.wikipedia.org/wiki/Universally_unique_identifier#Versions_3_and_5_(namespace_name-based))
  // UUID.
  //
  //  Returns nullptr on error.
  std::unique_ptr<api::BluetoothServerSocket> ListenForService(
      const std::string& service_name, const std::string& service_uuid) override
      ABSL_LOCKS_EXCLUDED(mutex_);

  api::BluetoothDevice* GetRemoteDevice(
      const std::string& mac_address) override;

 private:
  absl::Mutex mutex_;
  BluetoothAdapter* adapter_;  // Our device adapter; read-only.
  absl::flat_hash_map<std::string, BluetoothServerSocket*> sockets_
      ABSL_GUARDED_BY(mutex_);
};

}  // namespace g3
}  // namespace nearby
}  // namespace location

#endif  // PLATFORM_IMPL_G3_BLUETOOTH_CLASSIC_H_