miscale.py

import time
from interruptingcow import timeout

from exceptions import DeviceTimeoutError
from mqtt import MqttMessage
from workers.base import BaseWorker

REQUIREMENTS = ["bluepy"]


# Bluepy might need special settings
# sudo setcap 'cap_net_raw,cap_net_admin+eip' /usr/local/lib/python3.6/dist-packages/bluepy/bluepy-helper


class MiscaleWorker(BaseWorker):

    SCAN_TIMEOUT = 5

    def status_update(self):
        return [
            MqttMessage(
                topic=self.format_topic("weight/kg"), payload=self._get_weight()
            )
        ]

    def _get_weight(self):
        from bluepy import btle

        scan_processor = ScanProcessor(self.mac)
        scanner = btle.Scanner().withDelegate(scan_processor)
        scanner.scan(self.SCAN_TIMEOUT, passive=True)

        with timeout(
            self.SCAN_TIMEOUT,
            exception=DeviceTimeoutError(
                "Retrieving the weight from {} device {} timed out after {} seconds".format(
                    repr(self), self.mac, self.SCAN_TIMEOUT
                )
            ),
        ):
            while scan_processor.weight is None:
                time.sleep(1)
            return scan_processor.weight

        return -1


class ScanProcessor:
    def __init__(self, mac):
        self._mac = mac
        self._weight = None

    def handleDiscovery(self, dev, isNewDev, _):
        if dev.addr == self.mac.lower() and isNewDev:
            for (sdid, desc, data) in dev.getScanData():
                if data.startswith("1d18") and sdid == 22:
                    measured = int((data[8:10] + data[6:8]), 16) * 0.01

                    self._weight = round(measured / 2, 2)

    @property
    def mac(self):
        return self._mac

    @property
    def weight(self):
        return self._weight