/*
 * Copyright 2024 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
 *
 *     http://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 "audio_endpoint.h"
#include "audio_endpoint_private.h"

#include "comm/bt_lock.h"
#include "services/common/comm_session/session_send_buffer.h"
#include "services/common/new_timer/new_timer.h"
#include "system/logging.h"
#include "system/passert.h"
#include "util/circular_buffer.h"

#define AUDIO_ENDPOINT (10000)

#define ACTIVE_MODE_TIMEOUT      (10000)
#define ACTIVE_MODE_START_BUFFER (100)

_Static_assert(ACTIVE_MODE_TIMEOUT > ACTIVE_MODE_START_BUFFER,
  "ACTIVE_MODE_TIMEOUT must be greater than ACTIVE_MODE_START_BUFFER");

typedef struct {
  AudioEndpointSessionId id;
  AudioEndpointSetupCompleteCallback setup_completed;
  AudioEndpointStopTransferCallback stop_transfer;
  TimerID active_mode_trigger;
} AudioEndpointSession;

static AudioEndpointSessionId s_session_id = AUDIO_ENDPOINT_SESSION_INVALID_ID;
static AudioEndpointSession s_session;
static uint32_t s_dropped_frames;

static void prv_session_deinit(bool call_stop_handler) {
  bt_lock();
  if (call_stop_handler && s_session.stop_transfer) {
    s_session.stop_transfer(s_session.id);
  }

  if (s_session.active_mode_trigger != TIMER_INVALID_ID) {
    new_timer_delete(s_session.active_mode_trigger);
    s_session.active_mode_trigger = TIMER_INVALID_ID;
    CommSession *comm_session = comm_session_get_system_session();
    comm_session_set_responsiveness(
        comm_session, BtConsumerPpAudioEndpoint, ResponseTimeMax, 0);
  }

  s_session.id = AUDIO_ENDPOINT_SESSION_INVALID_ID;
  s_session.setup_completed = NULL;
  s_session.stop_transfer = NULL;
  bt_unlock();

  if (s_dropped_frames > 0) {
    PBL_LOG(LOG_LEVEL_INFO, "Dropped %"PRIu32" frames during audio transfer", s_dropped_frames);
  }
}

#ifndef PLATFORM_TINTIN
void audio_endpoint_protocol_msg_callback(CommSession *session, const uint8_t* data, size_t size) {
  MsgId msg_id = data[0];
  if (size >= sizeof(StopTransferMsg) && msg_id == MsgIdStopTransfer) {
    StopTransferMsg *msg = (StopTransferMsg *)data;

    if (msg->session_id == s_session.id) {
      prv_session_deinit(true /* call_stop_handler */);
    } else {
      PBL_LOG(LOG_LEVEL_WARNING, "Received mismatching session id: %u vs %u",
              msg->session_id, s_session.id);
    }
  }
}
#else
void audio_endpoint_protocol_msg_callback(CommSession *session, const uint8_t* data, size_t size) {
}
#endif

static void prv_responsiveness_granted_handler(void) {
  if (s_session.id == AUDIO_ENDPOINT_SESSION_INVALID_ID) {
    return;  // Party's over
  }

  AudioEndpointSetupCompleteCallback cb = NULL;
  AudioEndpointSessionId id = AUDIO_ENDPOINT_SESSION_INVALID_ID;

  bt_lock();
  // We're repeatedly calling comm_session_set_responsiveness_ext, but we only need to call the
  // completed handler the first time the requested responsiveness takes effect:
  if (s_session.setup_completed) {
    cb = s_session.setup_completed;
    id = s_session.id;
    s_session.setup_completed = NULL;
  }
  bt_unlock();

  if (cb) {
    cb(id);
  }
}

static void prv_start_active_mode(void *data) {
  CommSession *comm_session = comm_session_get_system_session();
  comm_session_set_responsiveness_ext(comm_session, BtConsumerPpAudioEndpoint, ResponseTimeMin,
                                      MIN_LATENCY_MODE_TIMEOUT_AUDIO_SECS,
                                      prv_responsiveness_granted_handler);
}

AudioEndpointSessionId audio_endpoint_setup_transfer(
    AudioEndpointSetupCompleteCallback setup_completed,
    AudioEndpointStopTransferCallback stop_transfer) {

  if (s_session.id != AUDIO_ENDPOINT_SESSION_INVALID_ID) {
    return AUDIO_ENDPOINT_SESSION_INVALID_ID;
  }

  bt_lock();

  s_session.id = ++s_session_id;
  s_session.setup_completed = setup_completed;
  s_session.stop_transfer = stop_transfer;
  s_session.active_mode_trigger = new_timer_create();
  s_dropped_frames = 0;

  // restart active mode before it expires, this way it will never be off during the transfer
  new_timer_start(s_session.active_mode_trigger, ACTIVE_MODE_TIMEOUT - ACTIVE_MODE_START_BUFFER,
      prv_start_active_mode, NULL, TIMER_START_FLAG_REPEATING);

  bt_unlock();

  prv_start_active_mode(NULL);

  return s_session.id;
}

void audio_endpoint_add_frame(AudioEndpointSessionId session_id, uint8_t *frame,
    uint8_t frame_size) {
  PBL_ASSERTN(session_id != AUDIO_ENDPOINT_SESSION_INVALID_ID);

  if (s_session.id != session_id) {
    return;
  }

  CommSession *comm_session = comm_session_get_system_session();
  SendBuffer *sb = comm_session_send_buffer_begin_write(comm_session, AUDIO_ENDPOINT,
                                                        sizeof(DataTransferMsg) + frame_size + 1,
                                                        0 /* timeout_ms, never block */);
  if (!sb) {
    s_dropped_frames++;
    PBL_LOG(LOG_LEVEL_DEBUG, "Dropping a frame...");
    return;
  }

  uint8_t header[sizeof(DataTransferMsg) + sizeof(uint8_t) /* frame_size */];
  DataTransferMsg *msg = (DataTransferMsg *) header;
  *msg = (const DataTransferMsg) {
    .msg_id = MsgIdDataTransfer,
    .session_id = session_id,
    .frame_count = 1,
  };
  msg->frames[0] = frame_size;

  comm_session_send_buffer_write(sb, header, sizeof(header));
  comm_session_send_buffer_write(sb, frame, frame_size);
  comm_session_send_buffer_end_write(sb);
}

void audio_endpoint_cancel_transfer(AudioEndpointSessionId session_id) {
  PBL_ASSERTN(session_id != AUDIO_ENDPOINT_SESSION_INVALID_ID);

  if (s_session.id != session_id) {
    return;
  }

  prv_session_deinit(false /* call_stop_handler */);
}

void audio_endpoint_stop_transfer(AudioEndpointSessionId session_id) {
  PBL_ASSERTN(session_id != AUDIO_ENDPOINT_SESSION_INVALID_ID);

  if (s_session.id != session_id) {
    return;
  }

  StopTransferMsg msg = (const StopTransferMsg) {
    .msg_id = MsgIdStopTransfer,
    .session_id = session_id,
  };

  prv_session_deinit(false /* call_stop_handler */);

  comm_session_send_data(comm_session_get_system_session(), AUDIO_ENDPOINT, (const uint8_t *) &msg,
                         sizeof(msg), COMM_SESSION_DEFAULT_TIMEOUT);
}