bt_power.py

#!/usr/bin/env python3

import sys
import json
from subprocess import check_output, DEVNULL
from argparse import ArgumentParser, RawDescriptionHelpFormatter


def get_parser():
    parser = ArgumentParser(description=__doc__,  # Usage from docstring
                            formatter_class=RawDescriptionHelpFormatter)
    parser.add_argument('bt_device_name',
                        help='Bluetooth device name')
    return parser


def get_profile_dt(data_type):
    output = check_output(['system_profiler', data_type, '-json'],
                          encoding=sys.getdefaultencoding(),
                          stderr=DEVNULL)
    jdict = json.loads(output)
    return jdict.pop(data_type)


def extract_attr(dt_profile, device_name, attr='device_RSSI'):
    assert len(dt_profile) == 1   # More than one BT interface?
    devices = dt_profile[0]['device_title']
    found = [d for d in devices if list(d) == [device_name]]
    if not found:
        raise RuntimeError(f'Could not find device "{device_name}"')
    if len(found) > 1:
        raise RuntimeError(f'More than one device "{device_name}"')
    device = found[0][device_name]
    connected = device.get('device_isconnected')
    if connected is None:
        raise RuntimeError(f'No connection information for "{device_name}"')
    if connected == 'attrib_No':
        raise RuntimeError(f'Device "{device_name}" not connected')
    data = device.get(attr)
    if data is None:
        raise RuntimeError(f'No attribute "{attr}" for "{device_name}"')
    return data


def main():
    parser = get_parser()
    args = parser.parse_args()
    bt_p = get_profile_dt('SPBluetoothDataType')
    print(extract_attr(bt_p, args.bt_device_name, 'device_RSSI'))


if __name__ == '__main__':
    main()