import hashlib

from typing import Optional
from .._payload import MqttPayload
from .._node import MqttModule, MqttNode

MODULE_NAME = 'MqttOtaModule'


class OtaResultPayload(MqttPayload):
    FORMAT = '=BB'
    result: int
    error_code: int


class OtaPayload(MqttPayload):
    secret: str
    filename: str

    # structure of returned data:
    #
    # uint8_t[len(secret)] secret;
    # uint8_t[16] md5;
    # *uint8_t data

    def pack(self):
        buf = bytearray(self.secret.encode())
        m = hashlib.md5()
        with open(self.filename, 'rb') as fd:
            content = fd.read()
            m.update(content)
            buf.extend(m.digest())
            buf.extend(content)
        return buf

    def unpack(cls, buf: bytes):
        raise RuntimeError(f'{cls.__class__.__name__}.unpack: not implemented')
        # secret = buf[:12].decode()
        # filename = buf[12:].decode()
        # return OTAPayload(secret=secret, filename=filename)


class MqttOtaModule(MqttModule):
    _ota_request: Optional[tuple[str, int]]

    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        self._ota_request = None

    def on_connect(self, mqtt: MqttNode):
        super().on_connect(mqtt)
        mqtt.subscribe_module("otares", self)

        if self._ota_request is not None:
            filename, qos = self._ota_request
            self._ota_request = None
            self.do_push_ota(self._mqtt_node_ref.secret, filename, qos)

    def handle_payload(self, mqtt: MqttNode, topic: str, payload: bytes) -> Optional[MqttPayload]:
        if topic == 'otares':
            message = OtaResultPayload.unpack(payload)
            self._logger.debug(message)
            return message

    def do_push_ota(self, secret: str, filename: str, qos: int):
        payload = OtaPayload(secret=secret, filename=filename)
        self._mqtt_node_ref.publish('ota',
                                    payload=payload.pack(),
                                    qos=qos)

    def push_ota(self,
                 filename: str,
                 qos: int):
        if not self._initialized:
            self._ota_request = (filename, qos)
        else:
            self.do_push_ota(self._mqtt_node_ref.secret, filename, qos)