from ciphers.poly import PolyCipher

def crack_poly_secret(plaintext, ciphertext): 
    if len(plaintext) != len(ciphertext): 
        print("Must be same length")
        return None 
    
    shift_values = []

    for i in range(len(plaintext)): 
        plain_char = plaintext[i]
        cipher_char = ciphertext[i]
        shift = (ord(cipher_char) - ord(plain_char)) % 128
        shift_values.append(shift)

    
    secret_candidate = ''.join(chr(s) for s in shift_values)

    
    for size in range(1, len(secret_candidate)):
        pattern = secret_candidate[:size]
        repeated = (pattern * ((len(secret_candidate) // size) + 1))[:len(secret_candidate)]
        if repeated == secret_candidate:
            return pattern
    
    return secret_candidate