import collections
import time

from micropython import const
from adafruit_bus_device.i2c_device import I2CDevice

_CONTROL0 = const(0)
_IRQ_STATUS = const(2)
_STATUS0 = const(3)
_YEAR = const(4)
_DST = const(0xa)
_ID = const(0xd)

class RxComplete:
    pass
RX_COMPLETE = RxComplete()

class CycleComplete:
    pass
CYCLE_COMPLETE = CycleComplete()

class _ROBits:
    def __init__(self, count, reg, shift):
        self.reg = reg
        self.shift = shift
        self.mask = (1<<count) - 1

    def __get__(self, obj, objtype=None):
        buf = obj._buffer
        with obj._i2c_device as i2c:
            buf[0] = self.reg
            i2c.write(buf, end=1)
            i2c.readinto(buf, start=1, end=2)
        return (buf[1] >> self.shift) & self.mask

class _RWBits(_ROBits):
    def __set__(self, obj, value):
        if value & ~self.mask:
            raise ValueError(
                f"Value 0x{value:02x} does not fit in mask 0x{self.mask:02x}"
            )
        reg_value = self.__get__(obj)
        reg_value &= ~(self.mask << self.shift)
        reg_value |= value << self.shift
        
        buf = obj._buffer
        buf[1] = reg_value
        with obj._i2c_device as i2c:
            i2c.write(buf, end=2)

def _ROBit(reg, shift):
    return _ROBits(1, reg, shift)

def _RWBit(reg, shift):
    return _RWBits(1, reg, shift)

def _bcd2bin(value):
    """Convert binary coded decimal to Binary
    :param value: the BCD value to convert to binary (required, no default)
    """
    return value - 6 * (value >> 4)

DSTInfo = collections.namedtuple('DSTInfo', (
    'month', 'day', 'hour', 'special'))

class ES100:
    device_id = _ROBits(8, _ID, 0)

    cycle_start = _ROBit(_CONTROL0, 0)
    antenna_1_off = _ROBit(_CONTROL0, 1)
    antenna_2_off = _ROBit(_CONTROL0, 2)
    start_antenna_2 = _ROBit(_CONTROL0, 3)
    tracking_enable = _ROBit(_CONTROL0, 4)

    irq_status_raw = _ROBits(3, _IRQ_STATUS, 0)
    status0_raw = _ROBits(8, _STATUS0, 0)

    rx_ok = _ROBit(_STATUS0, 0)
    antenna = _ROBit(_STATUS0, 1)
    lsw = _ROBits(2, _STATUS0, 3)
    dst = _ROBits(2, _STATUS0, 5)
    tracking = _ROBit(_STATUS0, 7)

    @property
    def utcnow(self):
        buf = self._buffer
        buf[0] = _YEAR
        with self._i2c_device as i2c:
            i2c.write(buf, end=1)
            i2c.readinto(buf, end=6)
        return time.struct_time(
            _bcd2bin(buf[0]),
            _bcd2bin(buf[1]),
            _bcd2bin(buf[2]),
            _bcd2bin(buf[3]),
            _bcd2bin(buf[4]),
            _bcd2bin(buf[5]),
            -1, -1, -1)
     
    @property
    def dstinfo(self):
        buf = self._buffer
        buf[0] = _DST
        with self._i2c_device as i2c:
            i2c.write(buf, end=1)
            i2c.readinto(buf, end=3)
        return DSTInfo(
            _bcd2bin(buf[0]),
            _bcd2bin(buf[1]),
            buf[2] & 0xf,
            buf[2] >> 4)
        
    def __init__(self, bus, address=0x32):
        self._buffer = bytearray(6)
        self._i2c_device = I2CDevice(bus, address)

    def start_reception(self):
        with self._i2c_device as dev:
            dev.write(b'\00\01')

    @property
    def irq_status(self):
        i = self.irq_status_raw
        result = []
        if i & 1:
            result.append(RX_COMPLETE)
        if i & 4:
            result.append(CYCLE_COMPLETE)
        return result