from machine import Pin, Timer

class Wiegand:
    def __init__(self, pin0, pin1, callback, buf_len=34):
        self.pin0 = Pin(pin0, Pin.IN, Pin.PULL_UP)
        self.pin1 = Pin(pin1, Pin.IN, Pin.PULL_UP)
        self.callback = callback
        self.buf = bytearray(buf_len)
        self.idx = 0
        self.timer = Timer(-1)

        self.pin0.irq(trigger=Pin.IRQ_FALLING, handler=self._irq)
        self.pin1.irq(trigger=Pin.IRQ_FALLING, handler=self._irq)

    def _irq(self, p):
        # 同时读取两根线，组合成 0b01 (bit=0) 或 0b10 (bit=1)
        state = (self.pin1.value() << 1) | self.pin0.value()
        if state not in (0b01, 0b10):
            return

        if self.idx < len(self.buf):
            self.buf[self.idx] = state
            self.idx += 1
            if self.idx == 1:
                # 只启动一次，80ms 后触发解析
                self.timer.init(period=80, mode=Timer.ONE_SHOT, callback=self._timeout)

    def _timeout(self, t):
        n = self.idx
        self.idx = 0
        data = bytes(self.buf[:n])       # 拷贝，防止中断覆盖
        self._parse(n, data)

    def _parse(self, n, data):
        if n == 26 and self._check_parity(data, 26):
            # 剔除首尾校验位，保留中间 24 位有效载荷
            payload = self._extract_bits(data, 1, 24)
            self.callback('wg26', payload)
        elif n == 34 and self._check_parity(data, 34):
            # 剔除首尾校验位，保留中间 32 位有效载荷
            payload = self._extract_bits(data, 1, 32)
            self.callback('wg34', payload)
        elif n == 8:
            # 键盘：低4位键值，高4位为低4位取反
            val = self._extract_bits(data, 0, 8)
            if ((val >> 4) ^ (val & 0x0F)) == 0x0F:
                self.callback('keypad', val & 0x0F)
        # 其余长度或校验失败直接丢弃

    def _check_parity(self, data, bits):
        """标准 Wiegand 奇偶校验：前一半偶数个1，后一半奇数个1"""
        half = bits // 2
        cnt_even = 0
        cnt_odd = 0
        for i in range(bits):
            if data[i] == 0b10:          # 该比特为 1
                if i < half:
                    cnt_even += 1
                else:
                    cnt_odd += 1
        return (cnt_even % 2 == 0) and (cnt_odd % 2 == 1)

    def _extract_bits(self, data, start, count):
        """从 data 中提取连续比特，MSB first，返回整数"""
        val = 0
        for i in range(start, start + count):
            val <<= 1
            if data[i] == 0b10:
                val |= 1
        return val