import json
import logging
import threading
import fibre
from fibre.utils import Logger

logger = logging.getLogger(__name__)
logger.setLevel(logging.DEBUG)
fibre_logger = Logger(verbose=logger.getEffectiveLevel() == logging.DEBUG)


class OdriveManager:
    _CONFIG_KEY = 'config'
    _CRC_KEY = 'crc16'

    def __init__(self, serial_number, cache_file=None):
        self.channel = None
        self.serial_number = serial_number
        self.cache_file = cache_file or 'odrive-cache-{serial_number}.json' \
            .format(serial_number=serial_number)

    def setup_odrive(self, config, crc):
        """
        Set up fibre remote object using given configuration.
        """

        json_data = {"name": "fibre_node", "members": config}
        self.channel._interface_definition_crc = crc

        # Just some black magic
        # Nothing to see here
        logger.debug('Making fibre remote object connection.')
        obj = fibre.remote_object.RemoteObject(
            json_data,
            None,
            self.channel,
            fibre_logger,
        )
        obj.__dict__['_json_data'] = json_data['members']
        obj.__dict__['_json_crc'] = crc

        return obj

    def read_config_from_device(self):
        """
        Read fibre connection configuration from odrive device directly, then
        cache it in a JSON file.
        """

        json_bytes = self.channel.remote_endpoint_read_buffer(0)

        try:
            json_string = json_bytes.decode('ascii')
        except UnicodeDecodeError as e:
            logger.warning('Loaded JSON bytes not valid ascii: %s.', str(e))
            return None

        logger.debug('Calculating crc for JSON string.')
        crc = fibre.protocol.calc_crc16(
            fibre.protocol.PROTOCOL_VERSION,
            json_bytes,
        )

        try:
            config = json.loads(json_string)
        except json.decoder.JSONDecodeError as e:
            logger.warning(
                'Loaded JSON string from odrive invalid: %s.',
                str(e),
            )
            return None

        od = self.setup_odrive(config=config, crc=crc)

        logger.info('Caching JSON data in file.')
        with open(self.cache_file, 'w') as f:
            json.dump({self._CONFIG_KEY: config, self._CRC_KEY: crc}, f)

        return od

    def find_odrive(self):
        """
        Find odrive device and set up fibre connection.
        """

        cancellation_token = threading.Event()

        def callback(channel):
            self.channel = channel
            cancellation_token.set()

        fibre.usbbulk_transport.discover_channels(
            path=None,
            callback=callback,
            logger=fibre_logger,
            serial_number=self.serial_number,
            cancellation_token=cancellation_token,
            channel_termination_token=None,
        )

        try:
            with open(self.cache_file, 'r') as f:
                data = json.load(f)
                config = data[self._CONFIG_KEY]
                crc = data[self._CRC_KEY]

                # TODO: Handle bad checksum
                od = self.setup_odrive(config=config, crc=crc)
                return od

        except (FileNotFoundError, KeyError, json.decoder.JSONDecodeError) as e:
            logger.warning('Could not read cached odrive configuration (%s). '
                           'Reading from device.', str(e))

            od = self.read_config_from_device()
            return od


if __name__ == '__main__':
    od = OdriveManager(serial_number='20763382304B').find_odrive()

    print(od)