import string

class B40:
    cset = "".join(sorted("\0" + string.digits + string.ascii_uppercase + " .,"))
    assert len(cset) == 40

    def dec(self, bytes):
        i = 0
        j = 0
        while True:
            if j == 0:
                d = bytes[i] * 256
                if i + 1 < len(bytes):
                    d += bytes[i+1]
                print(f"[DEC] {d: 5}")
                i += 2
                j = 3
            print(d, end=" ")
            d = d * 40 # 24 bit temporary result
            top = d >> 16
            d = d & 0xffff
            print(d, top, end=" ")
            if top == 0:
                break
            c = self.cset[top]
            print(repr(c))
            yield c
            j -= 1
        print()

    def enc(self, message):
        message = [self.cset.find(c) for c in message.upper()]
        assert not any(i==-1 for i in message)

        print(len(message))
        while len(message) % 3:
            message.append(0)

        for i in range(0, len(message), 3):
            trio = message[i:i+3][::-1]
            d = 0
            for c in trio:
                d = (d + (c << 16) + 39) // 40
                print(f"{c:2} {repr(self.cset[c]):5}", f"{d:5d}", end=" ")
            print(f" {d: 5}")
            assert 0 <= d < 65536
            yield d >> 8
            yield d & 0xff
        yield 0


b40 = B40()
encoded = list(b40.enc("hello world 12,345.67"))
print(encoded)
decoded = list(b40.dec(encoded))
print(decoded)
print(repr(b40.cset))