import struct
import time


class BME280:
    DEFAULT_ADDR = 0x77

    def __init__(self, i2c, addr=DEFAULT_ADDR):
        self.i2c = i2c
        self.addr = addr

        # Reset sensor
        self.i2c.writeto_mem(self.addr, 0xE0, b"\xb6")
        time.sleep(0.1)

        self._read_calibration_data()

        # Humidity oversampling x1
        self.i2c.writeto_mem(self.addr, 0xF2, b"\x01")
        # Pressure oversampling x1, Temp oversampling x1, Normal mode
        self.i2c.writeto_mem(self.addr, 0xF4, b"\x27")
        # Standby 1000ms, filter off
        self.i2c.writeto_mem(self.addr, 0xF5, b"\xa0")

    def _read_calibration_data(self):
        calib = self.i2c.readfrom_mem(self.addr, 0x88, 24)
        c = struct.unpack("<HhhHhhhhhhhh", calib)
        self.dig_t1, self.dig_t2, self.dig_t3 = c[0], c[1], c[2]
        self.dig_p1, self.dig_p2, self.dig_p3 = c[3], c[4], c[5]
        self.dig_p4, self.dig_p5, self.dig_p6 = c[6], c[7], c[8]
        self.dig_p7, self.dig_p8, self.dig_p9 = c[9], c[10], c[11]

        self.dig_h1 = self.i2c.readfrom_mem(self.addr, 0xA1, 1)[0]
        h = struct.unpack("<hB", self.i2c.readfrom_mem(self.addr, 0xE1, 3)[:3])
        self.dig_h2, self.dig_h3 = h[0], h[1]

        e4 = self.i2c.readfrom_mem(self.addr, 0xE4, 2)
        self.dig_h4 = (e4[0] << 4) | (e4[1] & 0x0F)

        e5_e6 = self.i2c.readfrom_mem(self.addr, 0xE5, 2)
        self.dig_h5 = (e5_e6[0] >> 4) | (e5_e6[1] << 4)

        self.dig_h6 = struct.unpack("<b", self.i2c.readfrom_mem(self.addr, 0xE7, 1))[0]

    def read_values(self):
        raw = self.i2c.readfrom_mem(self.addr, 0xF7, 8)
        raw_p = ((raw[0] << 16) | (raw[1] << 8) | raw[2]) >> 4
        raw_t = ((raw[3] << 16) | (raw[4] << 8) | raw[5]) >> 4
        raw_h = (raw[6] << 8) | raw[7]

        # Temperature calculation (Celsius)
        var1 = (((raw_t >> 3) - (self.dig_t1 << 1)) * self.dig_t2) >> 11
        var2 = (
            (((raw_t >> 4) - self.dig_t1) * ((raw_t >> 4) - self.dig_t1)) >> 12
        ) * self.dig_t3 >> 14
        t_fine = var1 + var2
        temp = ((t_fine * 5 + 128) >> 8) / 100.0

        # Pressure calculation (hPa)
        p_var1 = t_fine - 128000
        p_var2 = (
            p_var1 * p_var1 * self.dig_p6 + ((p_var1 * self.dig_p5) << 17) + (self.dig_p4 << 35)
        )
        p_var1 = ((p_var1 * p_var1 * self.dig_p3) >> 8) + ((p_var1 * self.dig_p2) << 12)
        p_var1 = (((1 << 47) + p_var1) * self.dig_p1) >> 33

        if p_var1 == 0:
            pressure = 0.0
        else:
            p = 1048576 - raw_p
            p = (((p << 31) - p_var2) * 3125) // p_var1
            p_var1 = (self.dig_p9 * (p >> 13) * (p >> 13)) >> 25
            p_var2 = (self.dig_p8 * p) >> 19
            p = ((p + p_var1 + p_var2) >> 8) + (self.dig_p7 << 4)
            pressure = (p / 256.0) / 100.0

        # Humidity calculation (%)
        h_var = t_fine - 76800
        h_var = ((((raw_h << 14) - (self.dig_h4 << 20) - (self.dig_h5 * h_var)) + 16384) >> 15) * (
            (
                (
                    (
                        (((h_var * self.dig_h6) >> 10) * (((h_var * self.dig_h3) >> 11) + 32768))
                        >> 10
                    )
                    + 2097152
                )
                * self.dig_h2
                + 8192
            )
            >> 14
        )
        h_var = h_var - (((((h_var >> 15) * (h_var >> 15)) >> 7) * self.dig_h1) >> 4)
        h_var = max(0, min(h_var, 419430400))
        humidity = (h_var >> 12) / 1024.0

        return {
            "temperature": round(temp, 2),
            "pressure": round(pressure, 2),
            "humidity": round(humidity, 2),
        }