input_file = "/tmp/cocacola"

type Code = String

read_codes :: IO [Code]
read_codes = do
    ls <- readFile input_file
    return $ lines ls

possible_codes :: [Code]
possible_codes = gen_word 8 ['A'..'Z']
    where 
        gen_word :: Int -> [Char] -> [Code]
        gen_word 0 _ = [""]
        gen_word len alphabet = concat $ map (\c -> map (\rest -> c:rest) rests) alphabet 
            where rests = gen_word (len - 1) alphabet


checks :: [Code -> Bool]
checks = [(\c -> head c == 'B') ]

generate_codes :: [Code] -> [Code]
generate_codes init_codes =
    filter passes_checks codes
    where
        passes_checks code = all (\test -> test code) checks
        codes = possible_codes

--main :: IO ()
main = do 
    known_codes <- read_codes
    mapM putStrLn $ generate_codes known_codes