module Main where

import System
import List
import Char
import System.Directory
import Monad


main = do x <- getArgs
          Just hatPath <- findExecutable "hat-make"
          let hatFolder = dropFilename hatPath
          let y = case x of
                    [x] -> x
                    _ -> error "Please give the name of the file to hat-make on the command line"
          system $ "ghc -M " ++ y
          mak <- readFile "Makefile"
          let (files,depends) = parseMakefile mak
          translate hatFolder files depends
          compileAll hatFolder y

dropFilename x = reverse $ dropWhile (\x -> not $ x `elem` "\\/") $ reverse x


parseMakefile :: String -> ([String], [(String, String)])
parseMakefile src =
        (
            nub $ concat [[a,b] | (a,b) <- res]
            ,
            nub $ [(a,b) | (a,b) <- res, a /= b]
        )
    where
        res = concatMap f $ lines src
    
        f :: String -> [(String, String)]
        f ('#':_) = []
        f x = [(filename a, filename b)]
            where (a,_:b) = break (== ':') x

filename x = reverse $ tail $ dropWhile (/= '.') $ reverse $ filter (not . isSpace) x


translate :: String -> [String] -> [(String, String)] -> IO ()
translate hatFolder files deps =
        if null files then return ()
        else if null yes then error "Circular dependancies"
        else mapM_ (translateFile hatFolder) yes >> translate hatFolder no newdeps
    where
        newdeps = [(a,b) | (a,b) <- deps, not (b `elem` yes)]
        (yes,no) = partition isDoable files
        isDoable x = not $ any ((==) x . fst) deps


translateFile :: String -> FilePath -> IO ()
translateFile hatFolder file = do
    fil <- pickFile file
    putStrLn $ "Converting with Hat, " ++ fil
    systemTry $ hatFolder ++ "/hat-trans.exe " ++ fil ++ " -I" ++ hatFolder ++ "/hx"


pickFile :: FilePath -> IO FilePath
pickFile x = do hs  <- doesFileExist (x++".hs")
                lhs <- doesFileExist (x++".lhs")
                return $ if lhs then x ++ ".lhs" else x ++ ".hs"

compileAll :: String -> String -> IO ()
compileAll hatFolder file = do
    putStrLn "Compiling with GHC..."
    systemTry $ "ghc --make Hat/" ++ file ++ " -ffi -fglasgow-exts -cpp -i.;" ++
                    hatFolder ++ "/hs " ++
                    hatFolder ++ "/c/hat-c.o"

systemTry :: String -> IO ()
systemTry x = do y <- system x
                 when (y /= ExitSuccess) exitFailure