X-OVH-SPAMCAUSE decoder

spam_decode.py

def decode(msg):
    text = ""
    for i in range(0, len(msg), 2):
        text += unrot(msg[i: i + 2], i // 2)                    # add position as extra parameter
    return text


def unrot(pair, pos, key=ord('x')):
    if pos % 2 == 0:                                            # "even" position => 2nd char is offset
        pair = pair[1] + pair[0]                                # swap letters in pair
    offset = (ord('g') - ord(pair[0])) * 16                     # treat 1st char as offset
    return chr(sum(ord(c) for c in pair) - key - offset)        # map to original character

  
if __name__ == '__main__':
    import sys
    print(decode(sys.argv[1]))

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