from app.qingping.models import QingpingState


def parse_cgdn1(data: bytes, rssi: int | None = None) -> QingpingState | None:

    # Восемь первых байт — заголовок CGDN1.
    if len(data) < 8:
        return None

    temperature = None
    humidity = None
    pm25 = None
    pm10 = None
    co2 = None

    pos = 8

    while pos + 2 <= len(data):
        field_type = data[pos]
        length = data[pos + 1]

        pos += 2

        if pos + length > len(data):
            return None

        value = data[pos:pos + length]
        pos += length

        # Temperature + Humidity
        if field_type == 0x01 and length == 4:
            temperature = (
                int.from_bytes(
                    value[0:2],
                    byteorder="little",
                    signed=True,
                )
                / 10
            )

            humidity = (
                int.from_bytes(
                    value[2:4],
                    byteorder="little",
                    signed=False,
                )
                / 10
            )

        # PM2.5 + PM10
        elif field_type == 0x12 and length == 4:
            pm25 = int.from_bytes(
                value[0:2],
                byteorder="little",
            )

            pm10 = int.from_bytes(
                value[2:4],
                byteorder="little",
            )

        # CO2
        elif field_type == 0x13 and length == 2:
            co2 = int.from_bytes(
                value,
                byteorder="little",
            )

    if any(
        value is None
        for value in (
            temperature,
            humidity,
            pm25,
            pm10,
            co2,
        )
    ):
        return None

    return QingpingState(
        temperature=temperature,
        humidity=humidity,
        co2=co2,
        pm25=pm25,
        pm10=pm10,
        rssi=rssi,
    )