module Join where

import Control.Monad
import Data.List
import System.Environment (getArgs)

{-- nicht veraendern --}

data Field = A Int | B Int

readInt :: String -> Maybe Int
readInt s =  case [x | (x,t) <- reads s, ("","") <- lex t] of
               [x] -> Just x
               _   -> Nothing

{-- H10.2 --}

doJoin :: [String] -> [String] -> [String]
doJoin = undefined

doJoinFormat :: [Field] -> [String] -> [String] -> [String]
doJoinFormat = undefined

parseFormat :: String -> Maybe [Field]
parseFormat = undefined

{-- Vorbereitetes Gerüst --}

readLines :: String -> IO [String]
readLines path = liftM lines $ readFile path

main :: IO ()
main = do
    args <- getArgs
    case args of
      ["-f", fmtStr, file1, file2] | Just fmt <- parseFormat fmtStr ->
        mapM_ putStrLn =<< liftM2 (doJoinFormat fmt) (readLines file1) (readLines file2)
      [file1, file2] ->
        mapM_ putStrLn =<< liftM2 doJoin (readLines file1) (readLines file2)
      _ -> putStrLn "Syntax: Join [-f format] file1 file2"