"""
AGS10

Micropython library for the AGS10(TVOC)
=======================================================
@dahanzimin From the Mixly Team
"""
import time
from micropython import const

_AGS10_ADC         = const(0x00)
_AGS10_CAL         = const(0x01)
_AGS10_RES         = const(0x20)
_AGS10_ADD         = const(0x21)

class AGS10:
    def __init__(self, i2c_bus, address=0x1A, delay=1000):
        self._i2c = i2c_bus
        self._addr = address
        self._voc = 0
        self._delay = delay
        self._star = 0
        self.ready = 0

    def _crc8(self, buf, is_byte=False):
        '''Perform CRC check on the data'''
        crc = 0xff
        for byte in buf:
            crc ^= byte
            for _ in range(8):
                if crc & 0x80:
                    crc = (crc << 1) ^ 0x31
                else:
                    crc = crc << 1
        return  crc.to_bytes(1, 'little') if is_byte else crc & 0xff

    def _wreg(self, reg, buf):
        '''Write memory address'''
        self._i2c.writeto_mem(self._addr, reg, buf)
        time.sleep_ms(20)

    def _rreg(self, reg, nbytes=5):
        '''Read memory address'''
        _buf = self._i2c.readfrom_mem(self._addr, reg, nbytes)
        time.sleep_ms(20)
        return _buf[:4] if self._crc8(_buf[:4]) == _buf[4] else None

    def address(self, addr=None):
        _scan = self._i2c.scan()
        if addr is None:
            if self._addr in _scan:
                return self._addr
            elif len(_scan) == 1:
                self._addr = _scan[0]
                return self._addr
            else:
                return None
        else:
            if self.address():
                if 8<= addr <=119:
                    _buf = bytes([addr, (~ addr) & 0xff] * 2)
                    self._wreg(_AGS10_ADD, _buf + self._crc8(_buf, True))
                    if addr in self._i2c.scan():
                        self._addr = addr
                        return True
                else:
                    raise ValueError("Not within the valid range of 8-119")

    def calibration(self, zero=1):
        '''0: Factory restoration 1:Sensor resistance'''
        _buf = b'\x00\x0c'
        _buf += b'\x00\x00' if zero else b'\xff\xff' 
        self._wreg(_AGS10_ADD,  _buf + self._crc8(_buf, True))

    @property
    def getdata(self):
        if time.ticks_diff(time.ticks_ms(), self._star) >= self._delay: 
            self._star = time.ticks_ms() 
            _buf = self._rreg(_AGS10_ADC)
            self._voc = int.from_bytes(_buf[1:4], 'big')
            self.ready = not (_buf[0] & 0x01)
        return self._voc / 1000

    def read(self, hcho_mw=30.033 , co2_mv=0.853, co2_base=400):
        '''unit ppm'''
        self.getdata
        _voc = self._voc / 1000 #ppm
        return round( _voc, 2), round( _voc / hcho_mw, 2), co2_base + round( _voc / co2_mv, 2)

    def tvoc(self):
        return self.read()[0]

    def hcho(self, tvoc_mw=30.053):
        return self.read(hcho_mw=hcho_mw)[1]

    def eco2(self, co2_mv=0.853):
        return self.read(co2_mv=co2_mv)[2]