module PascalPreprocessor where

import Text.Parsec

import Control.Monad.IO.Class

import System.IO

import qualified Data.Map as Map

preprocess :: String -> IO String

preprocess fn = do

    r <- runParserT (preprocessFile fn) Map.empty "" ""

    case r of

         (Left a) -> do

             hPutStrLn stderr (show a)

             return ""

         (Right a) -> return a

    where

    preprocessFile :: String -> ParsecT String (Map.Map String String) IO String

    preprocessFile fn = do

        f <- liftIO (readFile fn)

        setInput f

        preprocessor

    preprocessor, codeBlock, switch :: ParsecT String (Map.Map String String) IO String

    preprocessor = chainl codeBlock (return (++)) ""

    codeBlock = choice [

            switch

            , char '\'' >> many (noneOf "'") >>= \s -> char '\'' >> return ('\'' : s ++ "'")

            ]

    switch = do

        try $ string "{$"

        s <- choice [

            include

            , unknown

            ]

        return s

    include = do

        try $ string "INCLUDE"

        spaces

        (char '"')

        fn <- many1 $ noneOf "\"\n"

        char '"'

        spaces

        char '}'

        f <- liftIO (readFile fn)

        c <- getInput

        setInput $ f ++ c

        return ""

    unknown = do

        fn <- many1 $ noneOf "}\n"

        char '}'

        return ""