import struct

class AFrame:
    def __init__(self, data: bytes):
        self.valid = False
        self.data_id = 0
        self.payload = b""
        self.values = []

        if len(data) < 24 + 8 + 2:
            return

        try:
            magic, dlen, dir_, data_id, ptype, sat = struct.unpack('>IIIIII', data[:24])
            payload = data[24:-2]
            tail = data[-2:]

            if magic != 0xEB90EB90 or tail != b'\x4C\x3A':
                return

            self.valid = True
            self.data_id = data_id
            self.payload = payload

            # 按8字节切分double
            vs = []
            buf = payload
            while len(buf) >= 8:
                v = struct.unpack('>d', buf[:8])[0]
                vs.append(v)
                buf = buf[8:]
            self.values = vs

        except:
            pass