// Copyright 2017 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#pragma once

#include <memory>
#include <mutex>
#include <unordered_map>

#include <zircon/compiler.h>

#include "garnet/drivers/bluetooth/lib/common/cancelable_callback.h"
#include "garnet/drivers/bluetooth/lib/hci/acl_data_packet.h"
#include "garnet/drivers/bluetooth/lib/hci/connection.h"
#include "garnet/drivers/bluetooth/lib/hci/hci.h"
#include "garnet/drivers/bluetooth/lib/l2cap/channel.h"

#include "lib/fxl/macros.h"
#include "lib/fxl/memory/ref_ptr.h"
#include "lib/fxl/synchronization/thread_checker.h"
#include "lib/fxl/tasks/task_runner.h"

namespace bluetooth {

namespace hci {
class Transport;
}  // namespace hci

namespace l2cap {

namespace internal {
class LogicalLink;
}  // namespace internal

// ChannelManager implements the "Channel Manager" control block of L2CAP. In
// particular:
//
//   * It acts as a routing table for incoming ACL data by directing packets to
//     the appropriate internal logical link handler;
//
//   * Manages priority based scheduling.
//
//   * Provides an API surface for L2CAP channel creation and logical link
//     management bound to a single creation thread.
//
// There is a single instance of ChannelManager for each HCI transport.
class ChannelManager final {
 public:
  ChannelManager(fxl::RefPtr<hci::Transport> hci,
                 fxl::RefPtr<fxl::TaskRunner> task_runner);
  ~ChannelManager();

  // Registers the given connection with the L2CAP layer. L2CAP channels can be
  // opened on the logical link represented by |handle| after a call to this
  // method.
  //
  // It is an error to register the same |handle| value more than once without
  // first unregistering it (this is asserted in debug builds).
  void Register(hci::ConnectionHandle handle,
                hci::Connection::LinkType ll_type,
                hci::Connection::Role role);

  // Removes a previously registered connection. All corresponding Channels will
  // be closed and all incoming data packets on this link will be dropped.
  //
  // NOTE: It is recommended that a link entry be removed AFTER the controller
  // sends a HCI Disconnection Complete Event for the corresponding logical
  // link. This is to prevent incorrectly buffering data if the controller has
  // more packets to send after removing the link entry.
  void Unregister(hci::ConnectionHandle handle);

  // Opens the L2CAP fixed channel with |channel_id| over the logical link
  // identified by |connection_handle| and starts routing packets. Returns
  // nullptr if the channel is already open.
  //
  // See channel.h for documentation on |rx_callback| and |closed_callback|.
  // |rx_callback| is always posted on |rx_task_runner|. |closed_callback|
  // always runs on the thread that created this ChannelManager.
  std::unique_ptr<Channel> OpenFixedChannel(
      hci::ConnectionHandle connection_handle,
      ChannelId channel_id);

 private:
  // Called when an ACL data packet is received from the controller. This method
  // is responsible for routing the packet to the corresponding LogicalLink.
  void OnACLDataReceived(hci::ACLDataPacketPtr data_packet);

  fxl::RefPtr<hci::Transport> hci_;
  fxl::RefPtr<fxl::TaskRunner> task_runner_;

  std::mutex mtx_;
  std::unordered_map<hci::ConnectionHandle,
                     std::unique_ptr<internal::LogicalLink>>
      ll_map_ __TA_GUARDED(mtx_);

  // Stores packets received on a connection handle before a link for it has
  // been created.
  using PendingPacketMap =
      std::unordered_map<hci::ConnectionHandle,
                         fbl::DoublyLinkedList<hci::ACLDataPacketPtr>>;
  PendingPacketMap pending_packets_ __TA_GUARDED(mtx_);

  common::CancelableCallbackFactory<void()> cancelable_callback_factory_;
  fxl::ThreadChecker thread_checker_;

  FXL_DISALLOW_COPY_AND_ASSIGN(ChannelManager);
};

}  // namespace l2cap
}  // namespace bluetooth