xref: /btstack/src/classic/avrcp_target.c (revision 12b7c8ec5c3729fa7a7046391fe2e35c562eb400)

/*
 * Copyright (C) 2016 BlueKitchen GmbH
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the copyright holders nor the names of
 *    contributors may be used to endorse or promote products derived
 *    from this software without specific prior written permission.
 * 4. Any redistribution, use, or modification is done solely for
 *    personal benefit and not for any commercial purpose or for
 *    monetary gain.
 *
 * THIS SOFTWARE IS PROVIDED BY BLUEKITCHEN GMBH AND CONTRIBUTORS
 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL MATTHIAS
 * RINGWALD OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
 * THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 * Please inquire about commercial licensing options at
 * [email protected]
 *
 */

#define __BTSTACK_FILE__ "avrcp_target.c"

#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <inttypes.h>

#include "btstack.h"
#include "classic/avrcp.h"

#define AVRCP_ATTR_HEADER_LEN  8

static const uint8_t AVRCP_NOTIFICATION_TRACK_SELECTED[] = {0,0,0,0,0,0,0,0};
static const uint8_t AVRCP_NOTIFICATION_TRACK_NOT_SELECTED[] = {0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF};

static avrcp_context_t avrcp_target_context;

void avrcp_target_create_sdp_record(uint8_t * service, uint32_t service_record_handle, uint8_t browsing, uint16_t supported_features, const char * service_name, const char * service_provider_name){
    avrcp_create_sdp_record(0, service, service_record_handle, browsing, supported_features, service_name, service_provider_name);
}

static void avrcp_target_emit_operation(btstack_packet_handler_t callback, uint16_t avrcp_cid, avrcp_operation_id_t operation_id, uint8_t operands_length, uint8_t operand){
    if (!callback) return;
    uint8_t event[8];
    int pos = 0;
    event[pos++] = HCI_EVENT_AVRCP_META;
    event[pos++] = sizeof(event) - 2;
    event[pos++] = AVRCP_SUBEVENT_OPERATION;
    little_endian_store_16(event, pos, avrcp_cid);
    pos += 2;
    event[pos++] = operation_id;
    event[pos++] = operands_length;
    event[pos++] = operand;
    (*callback)(HCI_EVENT_PACKET, 0, event, sizeof(event));
}

static void avrcp_target_emit_respond_vendor_dependent_query(btstack_packet_handler_t callback, uint16_t avrcp_cid, uint8_t subevent_id){
    if (!callback) return;
    uint8_t event[5];
    int pos = 0;
    event[pos++] = HCI_EVENT_AVRCP_META;
    event[pos++] = sizeof(event) - 2;
    event[pos++] = subevent_id;
    little_endian_store_16(event, pos, avrcp_cid);
    (*callback)(HCI_EVENT_PACKET, 0, event, sizeof(event));
}

static uint16_t avrcp_target_pack_single_element_attribute_number(uint8_t * packet, uint16_t pos, avrcp_media_attribute_id_t attr_id, uint32_t value){
    if ((attr_id < 1) || (attr_id > AVRCP_MEDIA_ATTR_COUNT)) return 0;
    uint16_t attr_value_length = sprintf((char *)(packet+pos+8), "%0" PRIu32, value);
    big_endian_store_32(packet, pos, attr_id);
    pos += 4;
    big_endian_store_16(packet, pos, RFC2978_CHARSET_MIB_UTF8);
    pos += 2;
    big_endian_store_16(packet, pos, attr_value_length);
    pos += 2;
    return 8 + attr_value_length;
}

static uint16_t avrcp_target_pack_single_element_attribute_string(uint8_t * packet, uint16_t pos, rfc2978_charset_mib_enumid_t mib_enumid, avrcp_media_attribute_id_t attr_id, uint8_t * attr_value, uint16_t attr_value_to_copy, uint16_t attr_value_size, uint8_t header){
    if (attr_value_size == 0) return 0;
    if ((attr_id < 1) || (attr_id > AVRCP_MEDIA_ATTR_COUNT)) return 0;
    if (header){
        big_endian_store_32(packet, pos, attr_id);
        pos += 4;
        big_endian_store_16(packet, pos, mib_enumid);
        pos += 2;
        big_endian_store_16(packet, pos, attr_value_size);
        pos += 2;
    }
    memcpy(packet+pos, attr_value, attr_value_to_copy);
    pos += attr_value_size;
    return header * 8 + attr_value_size;
}

static int avrcp_target_abort_continue_response(uint16_t cid, avrcp_connection_t * connection){
    uint16_t pos = 0;
    l2cap_reserve_packet_buffer();
    uint8_t * packet = l2cap_get_outgoing_buffer();

    connection->command_opcode  = AVRCP_CMD_OPCODE_VENDOR_DEPENDENT;
    connection->command_type    = AVRCP_CTYPE_RESPONSE_ACCEPTED;
    connection->subunit_type    = AVRCP_SUBUNIT_TYPE_PANEL;
    connection->subunit_id      = AVRCP_SUBUNIT_ID;

    packet[pos++] = (connection->transaction_label << 4) | (AVRCP_SINGLE_PACKET << 2) | (AVRCP_RESPONSE_FRAME << 1) | 0;
    // Profile IDentifier (PID)
    packet[pos++] = BLUETOOTH_SERVICE_CLASS_AV_REMOTE_CONTROL >> 8;
    packet[pos++] = BLUETOOTH_SERVICE_CLASS_AV_REMOTE_CONTROL & 0x00FF;

    // command_type
    packet[pos++] = connection->command_type;
    // subunit_type | subunit ID
    packet[pos++] = (connection->subunit_type << 3) | connection->subunit_id;
    // opcode
    packet[pos++] = (uint8_t)connection->command_opcode;

    // company id is 3 bytes long
    big_endian_store_24(packet, pos, BT_SIG_COMPANY_ID);
    pos += 3;

    packet[pos++] = AVRCP_PDU_ID_REQUEST_ABORT_CONTINUING_RESPONSE;

    // reserve byte for packet type
    packet[pos++] = AVRCP_SINGLE_PACKET;
    big_endian_store_16(packet, pos, 0);
    pos += 2;
    return l2cap_send_prepared(cid, pos);
}

static int avrcp_target_send_now_playing_info(uint16_t cid, avrcp_connection_t * connection){
    uint16_t pos = 0;
    l2cap_reserve_packet_buffer();
    uint8_t * packet = l2cap_get_outgoing_buffer();
    uint16_t  size   = l2cap_get_remote_mtu_for_local_cid(connection->l2cap_signaling_cid);

    packet[pos++] = (connection->transaction_label << 4) | (AVRCP_SINGLE_PACKET << 2) | (AVRCP_RESPONSE_FRAME << 1) | 0;
    // Profile IDentifier (PID)
    packet[pos++] = BLUETOOTH_SERVICE_CLASS_AV_REMOTE_CONTROL >> 8;
    packet[pos++] = BLUETOOTH_SERVICE_CLASS_AV_REMOTE_CONTROL & 0x00FF;

    // command_type
    packet[pos++] = connection->command_type;
    // subunit_type | subunit ID
    packet[pos++] = (connection->subunit_type << 3) | connection->subunit_id;
    // opcode
    packet[pos++] = (uint8_t)connection->command_opcode;

    // company id is 3 bytes long
    big_endian_store_24(packet, pos, BT_SIG_COMPANY_ID);
    pos += 3;

    packet[pos++] = AVRCP_PDU_ID_GET_ELEMENT_ATTRIBUTES;

    // reserve byte for packet type
    uint8_t pos_packet_type = pos;
    pos++;

    uint16_t playing_info_buffer_len_position = pos;
    pos += 2;
    // printf("connection->next_attr_id %d \n", connection->next_attr_id);
    if (connection->next_attr_id == AVRCP_MEDIA_ATTR_NONE){
        packet[pos_packet_type] = AVRCP_SINGLE_PACKET;
        connection->packet_type = AVRCP_SINGLE_PACKET;
        packet[pos++] = count_set_bits_uint32(connection->now_playing_info_attr_bitmap);
        connection->next_attr_id++;
    }
    // printf("updated connection->next_attr_id %d, connection->attribute_value_offset %d \n", connection->next_attr_id, connection->attribute_value_offset);

    uint8_t fragmented = 0;
    int num_free_bytes = size - pos - 2;
    uint8_t MAX_NUMBER_ATTR_LEN = 10;

    while (!fragmented && num_free_bytes > 0 && connection->next_attr_id <= AVRCP_MEDIA_ATTR_SONG_LENGTH_MS){
        avrcp_media_attribute_id_t attr_id = connection->next_attr_id;
        int attr_index = attr_id - 1;

        if (connection->now_playing_info_attr_bitmap & (1 << attr_id)){
            int num_written_bytes = 0;
            int num_bytes_to_write = 0;
            switch (attr_id){
                case AVRCP_MEDIA_ATTR_ALL:
                case AVRCP_MEDIA_ATTR_NONE:
                    break;
                case AVRCP_MEDIA_ATTR_TRACK:
                    num_bytes_to_write = AVRCP_ATTR_HEADER_LEN + MAX_NUMBER_ATTR_LEN;
                    if (num_free_bytes >= num_bytes_to_write){
                        num_written_bytes = avrcp_target_pack_single_element_attribute_number(packet, pos, attr_id, connection->track_nr);
                        break;
                    }
                    fragmented = 1;
                    connection->attribute_value_offset = 0;
                    break;
                case AVRCP_MEDIA_ATTR_TOTAL_NUM_ITEMS:
                    num_bytes_to_write = AVRCP_ATTR_HEADER_LEN + MAX_NUMBER_ATTR_LEN;
                    if (num_free_bytes >= num_bytes_to_write){
                        num_written_bytes = avrcp_target_pack_single_element_attribute_number(packet, pos, attr_id, connection->total_tracks);
                        break;
                    }
                    fragmented = 1;
                    connection->attribute_value_offset = 0;
                    break;
                case AVRCP_MEDIA_ATTR_SONG_LENGTH_MS:
                    num_bytes_to_write = AVRCP_ATTR_HEADER_LEN + MAX_NUMBER_ATTR_LEN;
                    if (num_free_bytes >= num_bytes_to_write){
                        num_written_bytes = avrcp_target_pack_single_element_attribute_number(packet, pos, attr_id, connection->song_length_ms);
                        break;
                    }
                    fragmented = 1;
                    connection->attribute_value_offset = 0;
                    break;
                default:{
                    uint8_t   header = (connection->attribute_value_offset == 0);
                    uint8_t * attr_value =     (uint8_t *) (connection->now_playing_info[attr_index].value + connection->attribute_value_offset);
                    uint16_t  attr_value_len = connection->now_playing_info[attr_index].len - connection->attribute_value_offset;

                    num_bytes_to_write = attr_value_len + header * AVRCP_ATTR_HEADER_LEN;
                    if (num_bytes_to_write <= num_free_bytes){
                        connection->attribute_value_offset = 0;
                        num_written_bytes = num_bytes_to_write;
                        avrcp_target_pack_single_element_attribute_string(packet, pos, RFC2978_CHARSET_MIB_UTF8, attr_id, attr_value, attr_value_len, connection->now_playing_info[attr_index].len, header);
                        break;
                    }
                    fragmented = 1;
                    num_written_bytes = num_free_bytes;
                    attr_value_len = num_free_bytes - header * AVRCP_ATTR_HEADER_LEN;
                    avrcp_target_pack_single_element_attribute_string(packet, pos, RFC2978_CHARSET_MIB_UTF8, attr_id, attr_value, attr_value_len, connection->now_playing_info[attr_index].len, header);
                    connection->attribute_value_offset += attr_value_len;
                    break;
                }
            }
            pos += num_written_bytes;
            num_free_bytes -= num_written_bytes;
        }
        if (!fragmented){
            connection->next_attr_id++;
        }
    }

    if (fragmented){
        switch (connection->packet_type){
            case AVRCP_SINGLE_PACKET:
                connection->packet_type = AVRCP_START_PACKET;
                break;
            default:
                connection->packet_type = AVRCP_CONTINUE_PACKET;
                break;
        }
    } else {
        if (connection->next_attr_id >= AVRCP_MEDIA_ATTR_SONG_LENGTH_MS){ // DONE
            if (connection->packet_type != AVRCP_SINGLE_PACKET){
                connection->packet_type = AVRCP_END_PACKET;
            }
        }
    }
    packet[pos_packet_type] = connection->packet_type;
    // store attr value length
    big_endian_store_16(packet, playing_info_buffer_len_position, pos - playing_info_buffer_len_position - 2);
    return l2cap_send_prepared(cid, size);
}



static int avrcp_target_send_response(uint16_t cid, avrcp_connection_t * connection){
    int pos = 0;
    l2cap_reserve_packet_buffer();
    uint8_t * packet = l2cap_get_outgoing_buffer();

    // transport header
    // Transaction label | Packet_type | C/R | IPID (1 == invalid profile identifier)

    // TODO: check for fragmentation
    connection->packet_type = AVRCP_SINGLE_PACKET;

    packet[pos++] = (connection->transaction_label << 4) | (connection->packet_type << 2) | (AVRCP_RESPONSE_FRAME << 1) | 0;
    // Profile IDentifier (PID)
    packet[pos++] = BLUETOOTH_SERVICE_CLASS_AV_REMOTE_CONTROL >> 8;
    packet[pos++] = BLUETOOTH_SERVICE_CLASS_AV_REMOTE_CONTROL & 0x00FF;
    // command_type
    packet[pos++] = connection->command_type;
    // subunit_type | subunit ID
    packet[pos++] = (connection->subunit_type << 3) | connection->subunit_id;
    // opcode
    packet[pos++] = (uint8_t)connection->command_opcode;
    // operands
    memcpy(packet+pos, connection->cmd_operands, connection->cmd_operands_length);
    // printf_hexdump(packet+pos, connection->cmd_operands_length);

    pos += connection->cmd_operands_length;
    connection->wait_to_send = 0;
    return l2cap_send_prepared(cid, pos);
}

static uint8_t avrcp_target_response_accept(avrcp_connection_t * connection, avrcp_subunit_type_t subunit_type, avrcp_subunit_id_t subunit_id, avrcp_command_opcode_t opcode, avrcp_pdu_id_t pdu_id, avrcp_status_code_t status){
    // AVRCP_CTYPE_RESPONSE_REJECTED
    connection->command_type = AVRCP_CTYPE_RESPONSE_ACCEPTED;
    connection->subunit_type = subunit_type;
    connection->subunit_id =   subunit_id;
    connection->command_opcode = opcode;
    // company id is 3 bytes long
    int pos = connection->cmd_operands_length;
    connection->cmd_operands[pos++] = pdu_id;
    connection->cmd_operands[pos++] = 0;
    // param length
    big_endian_store_16(connection->cmd_operands, pos, 1);
    pos += 2;
    connection->cmd_operands[pos++] = status;
    connection->cmd_operands_length = pos;
    connection->state = AVCTP_W2_SEND_RESPONSE;
    avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
    return ERROR_CODE_SUCCESS;
}

static uint8_t avrcp_target_response_reject(avrcp_connection_t * connection, avrcp_subunit_type_t subunit_type, avrcp_subunit_id_t subunit_id, avrcp_command_opcode_t opcode, avrcp_pdu_id_t pdu_id, avrcp_status_code_t status){
    // AVRCP_CTYPE_RESPONSE_REJECTED
    connection->command_type = AVRCP_CTYPE_RESPONSE_REJECTED;
    connection->subunit_type = subunit_type;
    connection->subunit_id =   subunit_id;
    connection->command_opcode = opcode;
    // company id is 3 bytes long
    int pos = connection->cmd_operands_length;
    connection->cmd_operands[pos++] = pdu_id;
    connection->cmd_operands[pos++] = 0;
    // param length
    big_endian_store_16(connection->cmd_operands, pos, 1);
    pos += 2;
    connection->cmd_operands[pos++] = status;
    connection->cmd_operands_length = pos;
    connection->state = AVCTP_W2_SEND_RESPONSE;
    avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
    return ERROR_CODE_SUCCESS;
}

static uint8_t avrcp_target_response_not_implemented(avrcp_connection_t * connection, avrcp_subunit_type_t subunit_type, avrcp_subunit_id_t subunit_id, avrcp_command_opcode_t opcode, avrcp_pdu_id_t pdu_id, uint8_t event_id){
    connection->command_type = AVRCP_CTYPE_RESPONSE_NOT_IMPLEMENTED;
    connection->subunit_type = subunit_type;
    connection->subunit_id =   subunit_id;
    connection->command_opcode = opcode;

    // company id is 3 bytes long
    int pos = connection->cmd_operands_length;
    connection->cmd_operands[pos++] = pdu_id;
    connection->cmd_operands[pos++] = 0;
    // param length
    big_endian_store_16(connection->cmd_operands, pos, 1);
    pos += 2;
    connection->cmd_operands[pos++] = event_id;
    connection->cmd_operands_length = pos;

    connection->state = AVCTP_W2_SEND_RESPONSE;
    avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
    return ERROR_CODE_SUCCESS;
}

static uint8_t avrcp_target_response_vendor_dependent_interim(avrcp_connection_t * connection, avrcp_subunit_type_t subunit_type, avrcp_subunit_id_t subunit_id, avrcp_command_opcode_t opcode, avrcp_pdu_id_t pdu_id, uint8_t event_id, const uint8_t * value, uint16_t value_len){
    connection->command_type = AVRCP_CTYPE_RESPONSE_INTERIM;
    connection->subunit_type = subunit_type;
    connection->subunit_id =   subunit_id;
    connection->command_opcode = opcode;

    // company id is 3 bytes long
    int pos = connection->cmd_operands_length;
    connection->cmd_operands[pos++] = pdu_id;
    connection->cmd_operands[pos++] = 0;
    // param length
    big_endian_store_16(connection->cmd_operands, pos, 1 + value_len);
    pos += 2;
    connection->cmd_operands[pos++] = event_id;
    if (value && value_len > 0){
        memcpy(connection->cmd_operands + pos, value, value_len);
        pos += value_len;
    }
    connection->cmd_operands_length = pos;

    connection->state = AVCTP_W2_SEND_RESPONSE;
    avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
    return ERROR_CODE_SUCCESS;
}

// static uint8_t avrcp_target_response_vendor_dependent_changed(avrcp_connection_t * connection, avrcp_pdu_id_t pdu_id, uint8_t event_id){
//     connection->command_opcode = AVRCP_CMD_OPCODE_VENDOR_DEPENDENT;
//     connection->command_type = AVRCP_CTYPE_RESPONSE_CHANGED_STABLE;
//     connection->subunit_type = AVRCP_SUBUNIT_TYPE_PANEL;
//     connection->subunit_id = AVRCP_SUBUNIT_ID;

//     // company id is 3 bytes long
//     int pos = connection->cmd_operands_length;
//     connection->cmd_operands[pos++] = pdu_id;
//     connection->cmd_operands[pos++] = 0;
//     // param length
//     big_endian_store_16(connection->cmd_operands, pos, 1);
//     pos += 2;
//     connection->cmd_operands[pos++] = event_id;
//     connection->cmd_operands_length = pos;

//     connection->state = AVCTP_W2_SEND_RESPONSE;
//     avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
//     return ERROR_CODE_SUCCESS;
// }

static uint8_t avrcp_target_pass_through_response(uint16_t avrcp_cid, avrcp_command_type_t cmd_type, avrcp_operation_id_t opid, uint8_t operands_length, uint8_t operand){
    avrcp_connection_t * connection = get_avrcp_connection_for_avrcp_cid(avrcp_cid, &avrcp_target_context);
    if (!connection){
        log_error("Could not find a connection.");
        return ERROR_CODE_UNKNOWN_CONNECTION_IDENTIFIER;
    }
    connection->command_type = cmd_type;
    connection->subunit_type = AVRCP_SUBUNIT_TYPE_PANEL;
    connection->subunit_id =   AVRCP_SUBUNIT_ID;
    connection->command_opcode = AVRCP_CMD_OPCODE_PASS_THROUGH;

    int pos = 0;
    connection->cmd_operands[pos++] = opid;
    connection->cmd_operands[pos++] = operands_length;
    if (operands_length == 1){
        connection->cmd_operands[pos++] = operand;
    }
    connection->cmd_operands_length = pos;

    connection->state = AVCTP_W2_SEND_RESPONSE;
    avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
    return ERROR_CODE_SUCCESS;
}

uint8_t avrcp_target_operation_rejected(uint16_t avrcp_cid, avrcp_operation_id_t opid, uint8_t operands_length, uint8_t operand){
    return avrcp_target_pass_through_response(avrcp_cid, AVRCP_CTYPE_RESPONSE_REJECTED, opid, operands_length, operand);
}

uint8_t avrcp_target_operation_accepted(uint16_t avrcp_cid, avrcp_operation_id_t opid, uint8_t operands_length, uint8_t operand){
    return avrcp_target_pass_through_response(avrcp_cid, AVRCP_CTYPE_RESPONSE_ACCEPTED, opid, operands_length, operand);
}

uint8_t avrcp_target_operation_not_implemented(uint16_t avrcp_cid, avrcp_operation_id_t opid, uint8_t operands_length, uint8_t operand){
    return avrcp_target_pass_through_response(avrcp_cid, AVRCP_CTYPE_RESPONSE_ACCEPTED, opid, operands_length, operand);
}

void avrcp_target_set_unit_info(uint16_t avrcp_cid, avrcp_subunit_type_t unit_type, uint32_t company_id){
    avrcp_connection_t * connection = get_avrcp_connection_for_avrcp_cid(avrcp_cid, &avrcp_target_context);
    if (!connection){
        log_error("avrcp_target_operation_reject: could not find a connection.");
        return;
    }
    connection->unit_type = unit_type;
    connection->company_id = company_id;
}

void avrcp_target_set_subunit_info(uint16_t avrcp_cid, avrcp_subunit_type_t subunit_type, const uint8_t * subunit_info_data, uint16_t subunit_info_data_size){
    avrcp_connection_t * connection = get_avrcp_connection_for_avrcp_cid(avrcp_cid, &avrcp_target_context);
    if (!connection){
        log_error("avrcp_target_operation_reject: could not find a connection.");
        return;
    }
    connection->subunit_info_type = subunit_type;
    connection->subunit_info_data = subunit_info_data;
    connection->subunit_info_data_size = subunit_info_data_size;
}

static uint8_t avrcp_target_unit_info(avrcp_connection_t * connection){
    if (connection->state != AVCTP_CONNECTION_OPENED) return ERROR_CODE_COMMAND_DISALLOWED;

    uint8_t unit = 0;
    connection->command_type = AVRCP_CTYPE_RESPONSE_IMPLEMENTED_STABLE;
    connection->subunit_type = AVRCP_SUBUNIT_TYPE_UNIT; //vendor unique
    connection->subunit_id =   AVRCP_SUBUNIT_ID_IGNORE;
    connection->command_opcode = AVRCP_CMD_OPCODE_UNIT_INFO;

    connection->cmd_operands_length = 5;
    connection->cmd_operands[0] = 0x07;
    connection->cmd_operands[1] = (connection->unit_type << 4) | unit;
    // company id is 3 bytes long
    big_endian_store_32(connection->cmd_operands, 2, connection->company_id);

    connection->state = AVCTP_W2_SEND_RESPONSE;
    avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
    return ERROR_CODE_SUCCESS;
}

static uint8_t avrcp_target_subunit_info(avrcp_connection_t * connection, uint8_t offset){
    if (connection->state != AVCTP_CONNECTION_OPENED) return ERROR_CODE_COMMAND_DISALLOWED;
    if (offset - 4 > connection->subunit_info_data_size) return AVRCP_STATUS_INVALID_PARAMETER;

    connection->command_opcode = AVRCP_CMD_OPCODE_SUBUNIT_INFO;
    connection->command_type = AVRCP_CTYPE_RESPONSE_IMPLEMENTED_STABLE;
    connection->subunit_type = AVRCP_SUBUNIT_TYPE_UNIT; //vendor unique
    connection->subunit_id =   AVRCP_SUBUNIT_ID_IGNORE;
    // printf("avrcp_target_subunit_info  subunit_type %d\n", connection->subunit_type);

    uint8_t page = offset / 4;
    uint8_t extension_code = 7;
    connection->cmd_operands_length = 5;
    connection->cmd_operands[0] = (page << 4) | extension_code;

    memcpy(connection->cmd_operands+1, connection->subunit_info_data + offset, 4);

    connection->state = AVCTP_W2_SEND_RESPONSE;
    avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
    return ERROR_CODE_SUCCESS;
}

static inline uint8_t avrcp_prepare_vendor_dependent_response(uint16_t avrcp_cid, avrcp_connection_t ** out_connection, avrcp_pdu_id_t pdu_id, uint16_t param_length){
    *out_connection = get_avrcp_connection_for_avrcp_cid(avrcp_cid, &avrcp_target_context);
    if (!*out_connection){
        log_error("avrcp tartget: could not find a connection.");
        return ERROR_CODE_UNKNOWN_CONNECTION_IDENTIFIER;
    }

    if ((*out_connection)->state != AVCTP_CONNECTION_OPENED) return ERROR_CODE_COMMAND_DISALLOWED;
    (*out_connection)->command_opcode  = AVRCP_CMD_OPCODE_VENDOR_DEPENDENT;
    (*out_connection)->command_type    = AVRCP_CTYPE_RESPONSE_IMPLEMENTED_STABLE;
    (*out_connection)->subunit_type    = AVRCP_SUBUNIT_TYPE_PANEL;
    (*out_connection)->subunit_id      = AVRCP_SUBUNIT_ID;

    (*out_connection)->cmd_operands[(*out_connection)->cmd_operands_length++] = pdu_id;
    // reserved
    (*out_connection)->cmd_operands[(*out_connection)->cmd_operands_length++] = 0;
    // param length
    big_endian_store_16((*out_connection)->cmd_operands, (*out_connection)->cmd_operands_length, param_length);
    (*out_connection)->cmd_operands_length += 2;
    return ERROR_CODE_SUCCESS;
}

static uint8_t avrcp_target_capability(uint16_t avrcp_cid, avrcp_capability_id_t capability_id, uint8_t capabilities_num, uint8_t * capabilities, uint8_t size){
    avrcp_connection_t * connection = NULL;
    uint8_t status = avrcp_prepare_vendor_dependent_response(avrcp_cid, &connection, AVRCP_PDU_ID_GET_CAPABILITIES, 2+size);
    if (status != ERROR_CODE_SUCCESS) return status;

    connection->cmd_operands[connection->cmd_operands_length++] = capability_id;
    connection->cmd_operands[connection->cmd_operands_length++] = capabilities_num;
    memcpy(connection->cmd_operands+connection->cmd_operands_length, capabilities, size);
    connection->cmd_operands_length += size;

    connection->state = AVCTP_W2_SEND_RESPONSE;
    avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
    return ERROR_CODE_SUCCESS;
}

uint8_t avrcp_target_supported_events(uint16_t avrcp_cid, uint8_t capabilities_num, uint8_t * capabilities, uint8_t size){
    return avrcp_target_capability(avrcp_cid, AVRCP_CAPABILITY_ID_EVENT, capabilities_num, capabilities, size);
}

uint8_t avrcp_target_supported_companies(uint16_t avrcp_cid, uint8_t capabilities_num, uint8_t * capabilities, uint8_t size ){
    return avrcp_target_capability(avrcp_cid, AVRCP_CAPABILITY_ID_COMPANY, capabilities_num, capabilities, size);
}

uint8_t avrcp_target_play_status(uint16_t avrcp_cid, uint32_t song_length_ms, uint32_t song_position_ms, avrcp_playback_status_t play_status){
    avrcp_connection_t * connection = NULL;
    uint8_t status = avrcp_prepare_vendor_dependent_response(avrcp_cid, &connection, AVRCP_PDU_ID_GET_PLAY_STATUS, 11);
    if (status != ERROR_CODE_SUCCESS) return status;

    big_endian_store_32(connection->cmd_operands, connection->cmd_operands_length, song_length_ms);
    connection->cmd_operands_length += 4;
    big_endian_store_32(connection->cmd_operands, connection->cmd_operands_length, song_position_ms);
    connection->cmd_operands_length += 4;
    connection->cmd_operands[connection->cmd_operands_length++] = play_status;

    connection->state = AVCTP_W2_SEND_RESPONSE;
    avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
    return ERROR_CODE_SUCCESS;
}

static uint8_t avrcp_target_now_playing_info(avrcp_connection_t * connection){
    connection->now_playing_info_response = 1;
    if (connection->state != AVCTP_CONNECTION_OPENED) return ERROR_CODE_COMMAND_DISALLOWED;
    connection->command_opcode  = AVRCP_CMD_OPCODE_VENDOR_DEPENDENT;
    connection->command_type    = AVRCP_CTYPE_RESPONSE_IMPLEMENTED_STABLE;
    connection->subunit_type    = AVRCP_SUBUNIT_TYPE_PANEL;
    connection->subunit_id      = AVRCP_SUBUNIT_ID;

    connection->state = AVCTP_W2_SEND_RESPONSE;
    avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
    return ERROR_CODE_SUCCESS;
}

static uint8_t avrcp_target_store_media_attr(avrcp_connection_t * connection, avrcp_media_attribute_id_t attr_id, const char * value){
    int index = attr_id - 1;
    if (!value) return AVRCP_STATUS_INVALID_PARAMETER;
    connection->now_playing_info[index].value = (uint8_t*)value;
    connection->now_playing_info[index].len   = strlen(value);
    // printf("store %lu bytes, %s\n",  strlen(value), value);
    return ERROR_CODE_SUCCESS;
}

uint8_t avrcp_target_set_playback_status(uint16_t avrcp_cid, avrcp_playback_status_t playback_status){
    avrcp_connection_t * connection = get_avrcp_connection_for_avrcp_cid(avrcp_cid, &avrcp_target_context);
    if (!connection){
        log_error("avrcp_unit_info: could not find a connection.");
        return ERROR_CODE_UNKNOWN_CONNECTION_IDENTIFIER;
    }
    if (connection->playback_status == playback_status) return ERROR_CODE_SUCCESS;

    connection->playback_status = playback_status;
    connection->playback_status_changed = 1;
    avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
    return ERROR_CODE_SUCCESS;
}

void avrcp_target_set_now_playing_info(uint16_t avrcp_cid, const avrcp_track_t * current_track, uint16_t total_tracks){
    avrcp_connection_t * connection = get_avrcp_connection_for_avrcp_cid(avrcp_cid, &avrcp_target_context);
    if (!connection){
        log_error("avrcp_unit_info: could not find a connection. cid 0x%02x\n", avrcp_cid);
        return;
    }
    if (!current_track){
        connection->track_selected = 0;
        connection->playback_status = AVRCP_PLAYBACK_STATUS_ERROR;
        return;
    }
    memcpy(connection->track_id, current_track->track_id, 8);
    connection->song_length_ms = current_track->song_length_ms;
    connection->track_nr = current_track->track_nr;
    connection->total_tracks = total_tracks;
    avrcp_target_store_media_attr(connection, AVRCP_MEDIA_ATTR_TITLE, current_track->title);
    avrcp_target_store_media_attr(connection, AVRCP_MEDIA_ATTR_ARTIST, current_track->artist);
    avrcp_target_store_media_attr(connection, AVRCP_MEDIA_ATTR_ALBUM, current_track->album);
    avrcp_target_store_media_attr(connection, AVRCP_MEDIA_ATTR_GENRE, current_track->genre);
    connection->track_selected = 1;

    if (connection->notifications_enabled & (1 << AVRCP_NOTIFICATION_EVENT_TRACK_CHANGED)) {
        connection->track_changed = 1;
        avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
    }
    return;
}

uint8_t avrcp_target_track_changed(uint16_t avrcp_cid, uint8_t * track_id){
    avrcp_connection_t * connection = get_avrcp_connection_for_avrcp_cid(avrcp_cid, &avrcp_target_context);
    if (!connection){
        log_error("avrcp_target_track_changed: could not find connection.");
        return ERROR_CODE_UNKNOWN_CONNECTION_IDENTIFIER;
    }
    if (!track_id) return ERROR_CODE_UNKNOWN_CONNECTION_IDENTIFIER;

    if (connection->notifications_enabled & (1 << AVRCP_NOTIFICATION_EVENT_TRACK_CHANGED)) {
        connection->track_changed = 1;
        memcpy(connection->track_id, track_id, 8);
        avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
    }
    return ERROR_CODE_SUCCESS;
}

uint8_t avrcp_target_playing_content_changed(uint16_t avrcp_cid){
    avrcp_connection_t * connection = get_avrcp_connection_for_avrcp_cid(avrcp_cid, &avrcp_target_context);
    if (!connection){
        log_error("avrcp_unit_info: could not find a connection.");
        return ERROR_CODE_UNKNOWN_CONNECTION_IDENTIFIER;
    }
    if (connection->notifications_enabled & (1 << AVRCP_NOTIFICATION_EVENT_NOW_PLAYING_CONTENT_CHANGED)) {
        connection->playing_content_changed = 1;
        avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
    }
    return ERROR_CODE_SUCCESS;
}

uint8_t avrcp_target_battery_status_changed(uint16_t avrcp_cid, avrcp_battery_status_t battery_status){
    avrcp_connection_t * connection = get_avrcp_connection_for_avrcp_cid(avrcp_cid, &avrcp_target_context);
    if (!connection){
        log_error("avrcp_unit_info: could not find a connection.");
        return ERROR_CODE_UNKNOWN_CONNECTION_IDENTIFIER;
    }
    if (connection->battery_status == battery_status) return ERROR_CODE_SUCCESS;
    if (connection->notifications_enabled & (1 << AVRCP_NOTIFICATION_EVENT_BATT_STATUS_CHANGED)) {
        connection->battery_status = battery_status;
        connection->battery_status_changed = 1;
        avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
    }
    return ERROR_CODE_SUCCESS;
}

uint8_t avrcp_target_volume_changed(uint16_t avrcp_cid, uint8_t volume_percentage){
    avrcp_connection_t * connection = get_avrcp_connection_for_avrcp_cid(avrcp_cid, &avrcp_target_context);
    if (!connection){
        log_error("avrcp_unit_info: could not find a connection.");
        return ERROR_CODE_UNKNOWN_CONNECTION_IDENTIFIER;
    }
    if (connection->volume_percentage == volume_percentage) return ERROR_CODE_SUCCESS;
    if (connection->notifications_enabled & (1 << AVRCP_NOTIFICATION_EVENT_VOLUME_CHANGED )) {
        connection->volume_percentage = volume_percentage;
        connection->volume_percentage_changed = 1;
        avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
    }
    return ERROR_CODE_SUCCESS;
}


static uint8_t * avrcp_get_company_id(uint8_t *packet, uint16_t size){
    UNUSED(size);
    return packet + 6;
}

static uint8_t * avrcp_get_pdu(uint8_t *packet, uint16_t size){
    UNUSED(size);
    return packet + 9;
}

static uint8_t avrcp_is_receive_pass_through_cmd(uint8_t operation_id){
    return operation_id & 0x80;
}

static void avrcp_handle_l2cap_data_packet_for_signaling_connection(avrcp_connection_t * connection, uint8_t *packet, uint16_t size){
    UNUSED(connection);
    UNUSED(packet);
    UNUSED(size);

    // uint8_t opcode;

    uint8_t transport_header = packet[0];
    connection->transaction_label = transport_header >> 4;
    // uint8_t packet_type = (transport_header & 0x0F) >> 2;
    // uint8_t frame_type = (transport_header & 0x03) >> 1;
    // uint8_t ipid = transport_header & 0x01;
    // uint8_t byte_value = packet[2];
    // uint16_t pid = (byte_value << 8) | packet[2];

    // avrcp_command_type_t ctype = (avrcp_command_type_t) packet[3];
    // uint8_t byte_value = packet[4];
    avrcp_subunit_type_t subunit_type = (avrcp_subunit_type_t) (packet[4] >> 3);
    avrcp_subunit_id_t   subunit_id   = (avrcp_subunit_id_t) (packet[4] & 0x07);
    // opcode = packet[pos++];

    // printf("    Transport header 0x%02x (transaction_label %d, packet_type %d, frame_type %d, ipid %d), pid 0x%4x\n",
    //     transport_header, transaction_label, packet_type, frame_type, ipid, pid);
    // printf_hexdump(packet+pos, size-pos);

    avrcp_command_opcode_t opcode = avrcp_cmd_opcode(packet,size);
    uint8_t * company_id = avrcp_get_company_id(packet, size);
    uint8_t * pdu = avrcp_get_pdu(packet, size);
    // uint16_t param_length = big_endian_read_16(pdu, 2);

    int pos = 4;
    uint8_t   pdu_id;
    connection->cmd_operands_length = 0;

    switch (opcode){
        case AVRCP_CMD_OPCODE_UNIT_INFO:
            avrcp_target_unit_info(connection);
            break;
        case AVRCP_CMD_OPCODE_SUBUNIT_INFO:{
            uint8_t offset =  4 * (packet[pos+2]>>4);
            avrcp_target_subunit_info(connection, offset);
            break;
        }
        case AVRCP_CMD_OPCODE_PASS_THROUGH:{
            log_info("AVRCP_OPERATION_ID 0x%02x, operands length %d, operand %d", packet[6], packet[7], packet[8]);
            avrcp_operation_id_t operation_id = packet[6];

            if (avrcp_is_receive_pass_through_cmd(operation_id)){
                operation_id = packet[6] & 0x7F;
                avrcp_target_operation_accepted(connection->avrcp_cid, packet[6], packet[7], packet[8]);
                break;
            }

            switch (operation_id){
                case AVRCP_OPERATION_ID_PLAY:
                case AVRCP_OPERATION_ID_PAUSE:
                case AVRCP_OPERATION_ID_STOP:
                case AVRCP_OPERATION_ID_VOLUME_UP:
                case AVRCP_OPERATION_ID_VOLUME_DOWN:
                case AVRCP_OPERATION_ID_REWIND:
                case AVRCP_OPERATION_ID_FAST_FORWARD:
                case AVRCP_OPERATION_ID_FORWARD:
                case AVRCP_OPERATION_ID_BACKWARD:
                case AVRCP_OPERATION_ID_SKIP:
                case AVRCP_OPERATION_ID_MUTE:
                case AVRCP_OPERATION_ID_CHANNEL_UP:
                case AVRCP_OPERATION_ID_CHANNEL_DOWN:
                case AVRCP_OPERATION_ID_SELECT:
                case AVRCP_OPERATION_ID_UP:
                case AVRCP_OPERATION_ID_DOWN:
                case AVRCP_OPERATION_ID_LEFT:
                case AVRCP_OPERATION_ID_RIGHT:
                case AVRCP_OPERATION_ID_ROOT_MENU:
                    printf("received op 0x%02x\n", operation_id);
                    avrcp_target_operation_accepted(connection->avrcp_cid, packet[6], packet[7], packet[8]);
                    avrcp_target_emit_operation(avrcp_target_context.avrcp_callback, connection->avrcp_cid, operation_id, packet[7], packet[8]);
                    break;
                case AVRCP_OPERATION_ID_UNDEFINED:
                    avrcp_target_operation_not_implemented(connection->avrcp_cid, packet[6], packet[7], packet[8]);
                    return;
                default:
                    avrcp_target_operation_not_implemented(connection->avrcp_cid, packet[6], packet[7], packet[8]);
                    return;
            }
            break;
        }

        case AVRCP_CMD_OPCODE_VENDOR_DEPENDENT:
            pdu_id = pdu[0];
            // 1 - reserved
            // 2-3 param length,
            memcpy(connection->cmd_operands, company_id, 3);
            connection->cmd_operands_length = 3;
            switch (pdu_id){
                case AVRCP_PDU_ID_GET_CAPABILITIES:{
                    avrcp_capability_id_t capability_id = (avrcp_capability_id_t) pdu[pos];
                    switch (capability_id){
                        case AVRCP_CAPABILITY_ID_EVENT:
                            avrcp_target_emit_respond_vendor_dependent_query(avrcp_target_context.avrcp_callback, connection->avrcp_cid, AVRCP_SUBEVENT_EVENT_IDS_QUERY);
                            break;
                        case AVRCP_CAPABILITY_ID_COMPANY:
                            avrcp_target_emit_respond_vendor_dependent_query(avrcp_target_context.avrcp_callback, connection->avrcp_cid, AVRCP_SUBEVENT_COMPANY_IDS_QUERY);
                            break;
                        default:
                            avrcp_target_response_reject(connection, subunit_type, subunit_id, opcode, pdu_id, AVRCP_STATUS_INVALID_PARAMETER);
                            break;
                    }
                    break;
                }
                case AVRCP_PDU_ID_GET_PLAY_STATUS:
                    avrcp_target_emit_respond_vendor_dependent_query(avrcp_target_context.avrcp_callback, connection->avrcp_cid, AVRCP_SUBEVENT_PLAY_STATUS_QUERY);
                    break;
                case AVRCP_PDU_ID_REQUEST_ABORT_CONTINUING_RESPONSE:
                    connection->cmd_operands[0] = pdu[4];
                    connection->abort_continue_response = 1;
                    avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
                    break;
                case AVRCP_PDU_ID_REQUEST_CONTINUING_RESPONSE:
                    if (pdu[4] != AVRCP_PDU_ID_GET_ELEMENT_ATTRIBUTES){
                        avrcp_target_response_reject(connection, subunit_type, subunit_id, opcode, pdu_id, AVRCP_STATUS_INVALID_COMMAND);
                        return;
                    }
                    connection->now_playing_info_response = 1;
                    avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
                    break;
                case AVRCP_PDU_ID_GET_ELEMENT_ATTRIBUTES:{
                    uint8_t play_identifier[8];
                    memset(play_identifier, 0, 8);
                    if (memcmp(pdu+pos, play_identifier, 8) != 0) {
                        avrcp_target_response_reject(connection, subunit_type, subunit_id, opcode, pdu_id, AVRCP_STATUS_INVALID_PARAMETER);
                        return;
                    }
                    pos += 8;
                    uint8_t attribute_count = pdu[pos++];
                    // printf("AVRCP_PDU_ID_GET_ELEMENT_ATTRIBUTES attribute count %d\n", attribute_count);
                    connection->next_attr_id = AVRCP_MEDIA_ATTR_NONE;
                    if (!attribute_count){
                        connection->now_playing_info_attr_bitmap = 0xFE;
                    } else {
                        int i;
                        connection->now_playing_info_attr_bitmap = 0;
                        for (i=0; i < attribute_count; i++){
                            uint16_t attr_id = big_endian_read_16(pdu, pos);
                            pos += 2;
                            connection->now_playing_info_attr_bitmap |= (1 << attr_id);
                        }
                    }
                    log_info("now_playing_info_attr_bitmap 0x%02x", connection->now_playing_info_attr_bitmap);
                    avrcp_target_now_playing_info(connection);
                    break;
                }
                case AVRCP_PDU_ID_REGISTER_NOTIFICATION:{
                    // 0 - pdu id
                    // 1 - reserved
                    // 2-3 param length
                    avrcp_notification_event_id_t event_id = (avrcp_notification_event_id_t) pdu[4];
                    uint16_t event_mask = (1 << event_id);

                    switch (event_id){
                        case AVRCP_NOTIFICATION_EVENT_TRACK_CHANGED:
                            connection->notifications_enabled |= event_mask;
                            if (connection->track_selected){
                                avrcp_target_response_vendor_dependent_interim(connection, subunit_type, subunit_id, opcode, pdu_id, event_id, AVRCP_NOTIFICATION_TRACK_SELECTED, 8);
                            } else {
                                avrcp_target_response_vendor_dependent_interim(connection, subunit_type, subunit_id, opcode, pdu_id, event_id, AVRCP_NOTIFICATION_TRACK_NOT_SELECTED, 8);
                            }
                            break;
                        case AVRCP_NOTIFICATION_EVENT_PLAYBACK_STATUS_CHANGED:
                            connection->notifications_enabled |= event_mask;
                            avrcp_target_response_vendor_dependent_interim(connection, subunit_type, subunit_id, opcode, pdu_id, event_id, (const uint8_t *)&connection->playback_status, 1);
                            break;
                        case AVRCP_NOTIFICATION_EVENT_NOW_PLAYING_CONTENT_CHANGED:
                            connection->notifications_enabled |= event_mask;
                            avrcp_target_response_vendor_dependent_interim(connection, subunit_type, subunit_id, opcode, pdu_id, event_id, NULL, 0);
                            break;
                        case AVRCP_NOTIFICATION_EVENT_VOLUME_CHANGED:
                            connection->notifications_enabled |= event_mask;
                            avrcp_target_response_vendor_dependent_interim(connection, subunit_type, subunit_id, opcode, pdu_id, event_id, (const uint8_t *)&connection->volume_percentage, 1);
                            break;
                        case AVRCP_NOTIFICATION_EVENT_BATT_STATUS_CHANGED:
                            connection->notifications_enabled |= event_mask;
                            avrcp_target_response_vendor_dependent_interim(connection, subunit_type, subunit_id, opcode, pdu_id, event_id, (const uint8_t *)&connection->battery_status, 1);
                            break;
                        case AVRCP_NOTIFICATION_EVENT_AVAILABLE_PLAYERS_CHANGED:
                        case AVRCP_NOTIFICATION_EVENT_PLAYER_APPLICATION_SETTING_CHANGED:
                        case AVRCP_NOTIFICATION_EVENT_ADDRESSED_PLAYER_CHANGED:
                        case AVRCP_NOTIFICATION_EVENT_UIDS_CHANGED:
                            avrcp_target_response_not_implemented(connection, subunit_type, subunit_id, opcode, pdu_id, event_id);
                            return;
                        default:
                            avrcp_target_response_reject(connection, subunit_type, subunit_id, opcode, pdu_id, AVRCP_STATUS_INVALID_PARAMETER);
                            return;
                    }
                    break;
                }
                case AVRCP_PDU_ID_SET_ABSOLUTE_VOLUME: {
                    uint16_t param_length = big_endian_read_16(pdu,2);
                    if (param_length != 1){
                        avrcp_target_response_reject(connection, subunit_type, subunit_id, opcode, pdu_id, AVRCP_STATUS_INVALID_COMMAND);
                        printf("param_length is %d != 1 \n", param_length);
                        break;
                    }

                    uint8_t absolute_volume = pdu[4];
                    if (absolute_volume > 0x7F){
                        avrcp_target_response_reject(connection, subunit_type, subunit_id, opcode, pdu_id, AVRCP_STATUS_INVALID_COMMAND);
                        printf("absolute_volume %d  > 127 \n", absolute_volume);
                        break;
                    }
                    connection->volume_percentage = absolute_volume;
                    avrcp_target_response_accept(connection, subunit_type, subunit_id, opcode, pdu_id, absolute_volume);
                    break;
                }
                default:
                    log_info("AVRCP target: unhandled pdu id 0x%02x", pdu_id);
                    avrcp_target_response_reject(connection, subunit_type, subunit_id, opcode, pdu_id, AVRCP_STATUS_INVALID_COMMAND);
                    break;
            }
            break;
        default:
            log_info("AVRCP target: opcode 0x%02x not implemented", avrcp_cmd_opcode(packet,size));
            break;
    }
}

static int avrcp_target_send_notification(uint16_t cid, avrcp_connection_t * connection, uint8_t notification_id, uint8_t * value, uint16_t value_len){
    if (!connection){
        log_error("avrcp tartget: could not find a connection.");
        return ERROR_CODE_UNKNOWN_CONNECTION_IDENTIFIER;
    }

    connection->command_opcode  = AVRCP_CMD_OPCODE_VENDOR_DEPENDENT;
    connection->command_type    = AVRCP_CTYPE_RESPONSE_CHANGED_STABLE;
    connection->subunit_type    = AVRCP_SUBUNIT_TYPE_PANEL;
    connection->subunit_id      = AVRCP_SUBUNIT_ID;

    uint16_t pos = 0;
    l2cap_reserve_packet_buffer();
    uint8_t * packet = l2cap_get_outgoing_buffer();
    uint16_t  size   = l2cap_get_remote_mtu_for_local_cid(connection->l2cap_signaling_cid);

    connection->packet_type = AVRCP_SINGLE_PACKET;
    packet[pos++] = (connection->transaction_label << 4) | (connection->packet_type << 2) | (AVRCP_RESPONSE_FRAME << 1) | 0;
    // Profile IDentifier (PID)
    packet[pos++] = BLUETOOTH_SERVICE_CLASS_AV_REMOTE_CONTROL >> 8;
    packet[pos++] = BLUETOOTH_SERVICE_CLASS_AV_REMOTE_CONTROL & 0x00FF;

    // command_type
    packet[pos++] = connection->command_type;
    // subunit_type | subunit ID
    packet[pos++] = (connection->subunit_type << 3) | connection->subunit_id;
    // opcode
    packet[pos++] = (uint8_t)connection->command_opcode;

    // company id is 3 bytes long
    big_endian_store_24(packet, pos, BT_SIG_COMPANY_ID);
    pos += 3;

    packet[pos++] = AVRCP_PDU_ID_REGISTER_NOTIFICATION;
    packet[pos++] = 0;
    uint16_t remainig_outgoing_buffer_size = size > (value_len + 2 + 1) ? size - (value_len + 2 + 1): 0;
    uint16_t caped_value_len = value_len > remainig_outgoing_buffer_size ? remainig_outgoing_buffer_size : value_len;
    big_endian_store_16(packet, pos, caped_value_len);
    pos += 2;
    packet[pos++] = notification_id;

    memcpy(packet+pos, value, caped_value_len);
    pos += caped_value_len;
    connection->wait_to_send = 0;
    return l2cap_send_prepared(cid, pos);
}

static void avrcp_target_reset_notification(avrcp_connection_t * connection, uint8_t notification_id){
    if (!connection){
        log_error("avrcp tartget: could not find a connection.");
        return;
    }
    connection->notifications_enabled &= ~(1 << notification_id);
    connection->command_opcode  = AVRCP_CMD_OPCODE_VENDOR_DEPENDENT;

}

static void avrcp_controller_packet_handler(uint8_t packet_type, uint16_t channel, uint8_t *packet, uint16_t size){
    avrcp_connection_t * connection;
    switch (packet_type) {
        case L2CAP_DATA_PACKET:
            connection = get_avrcp_connection_for_l2cap_signaling_cid(channel, &avrcp_target_context);
            if (!connection) break;
            avrcp_handle_l2cap_data_packet_for_signaling_connection(connection, packet, size);
            break;
        case HCI_EVENT_PACKET:
            switch (hci_event_packet_get_type(packet)){
                case L2CAP_EVENT_CAN_SEND_NOW:{
                    connection = get_avrcp_connection_for_l2cap_signaling_cid(channel, &avrcp_target_context);
                    if (!connection) {
                        log_error("Connection not found\n");
                        break;
                    }

                    if (connection->abort_continue_response){
                        connection->abort_continue_response = 0;
                        connection->now_playing_info_response = 0;
                        avrcp_target_abort_continue_response(connection->l2cap_signaling_cid, connection);
                        break;
                    }

                    if (connection->now_playing_info_response){
                        connection->now_playing_info_response = 0;
                        avrcp_target_send_now_playing_info(connection->l2cap_signaling_cid, connection);
                        break;
                    }

                    if (connection->track_changed){
                        connection->track_changed = 0;
                        avrcp_target_send_notification(connection->l2cap_signaling_cid, connection, AVRCP_NOTIFICATION_EVENT_TRACK_CHANGED, connection->track_id, 8);
                        avrcp_target_reset_notification(connection, AVRCP_NOTIFICATION_EVENT_TRACK_CHANGED);
                        avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
                        break;
                    }

                    if (connection->playback_status_changed){
                        connection->playback_status_changed = 0;
                        avrcp_target_send_notification(connection->l2cap_signaling_cid, connection, AVRCP_NOTIFICATION_EVENT_PLAYBACK_STATUS_CHANGED, &connection->playback_status_changed, 1);
                        avrcp_target_reset_notification(connection, AVRCP_NOTIFICATION_EVENT_PLAYBACK_STATUS_CHANGED);
                        avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
                        break;
                    }

                    if (connection->playing_content_changed){
                        connection->playing_content_changed = 0;
                        avrcp_target_send_notification(connection->l2cap_signaling_cid, connection, AVRCP_NOTIFICATION_EVENT_NOW_PLAYING_CONTENT_CHANGED, NULL, 0);
                        avrcp_target_reset_notification(connection, AVRCP_NOTIFICATION_EVENT_NOW_PLAYING_CONTENT_CHANGED);
                        avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
                        break;
                    }

                    if (connection->battery_status_changed){
                        connection->battery_status_changed = 0;
                        avrcp_target_send_notification(connection->l2cap_signaling_cid, connection, AVRCP_NOTIFICATION_EVENT_BATT_STATUS_CHANGED, (uint8_t *)&connection->battery_status, 1);
                        avrcp_target_reset_notification(connection, AVRCP_NOTIFICATION_EVENT_BATT_STATUS_CHANGED);
                        avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
                        break;
                    }

                    if (connection->volume_percentage_changed){
                        connection->volume_percentage_changed = 0;
                        avrcp_target_send_notification(connection->l2cap_signaling_cid, connection, AVRCP_NOTIFICATION_EVENT_VOLUME_CHANGED, &connection->volume_percentage, 1);
                        avrcp_target_reset_notification(connection, AVRCP_NOTIFICATION_EVENT_VOLUME_CHANGED);
                        avrcp_request_can_send_now(connection, connection->l2cap_signaling_cid);
                        break;
                    }

                    switch (connection->state){
                        case AVCTP_W2_SEND_RESPONSE:
                            connection->state = AVCTP_CONNECTION_OPENED;
                            // if (connection->now_playing_info_response){
                            //     connection->now_playing_info_response = 0;
                            //     avrcp_target_send_now_playing_info(connection->l2cap_signaling_cid, connection);
                            //     break;
                            // }
                            avrcp_target_send_response(connection->l2cap_signaling_cid, connection);
                            break;
                        default:
                            return;
                    }
                    break;
            }
            default:
                avrcp_packet_handler(packet_type, channel, packet, size, &avrcp_target_context);
                break;
        }
        default:
            break;
    }
}

void avrcp_target_init(void){
    avrcp_target_context.role = AVRCP_TARGET;
    avrcp_target_context.connections = NULL;
    avrcp_target_context.packet_handler = avrcp_controller_packet_handler;
    l2cap_register_service(&avrcp_controller_packet_handler, BLUETOOTH_PROTOCOL_AVCTP, 0xffff, LEVEL_0);
}

void avrcp_target_register_packet_handler(btstack_packet_handler_t callback){
    if (callback == NULL){
        log_error("avrcp_register_packet_handler called with NULL callback");
        return;
    }
    avrcp_target_context.avrcp_callback = callback;
}

uint8_t avrcp_target_connect(bd_addr_t bd_addr, uint16_t * avrcp_cid){
    return avrcp_connect(bd_addr, &avrcp_target_context, avrcp_cid);
}

uint8_t avrcp_target_disconnect(uint16_t avrcp_cid){
    avrcp_connection_t * connection = get_avrcp_connection_for_avrcp_cid(avrcp_cid, &avrcp_target_context);
    if (!connection){
        log_error("avrcp_get_capabilities: could not find a connection.");
        return ERROR_CODE_UNKNOWN_CONNECTION_IDENTIFIER;
    }
    if (connection->state != AVCTP_CONNECTION_OPENED) return ERROR_CODE_COMMAND_DISALLOWED;
    l2cap_disconnect(connection->l2cap_signaling_cid, 0);
    return ERROR_CODE_SUCCESS;
}