Monitor a directory to rebuild pandoc files automatically.

monitor.hs

module Main where

import Filesystem (getWorkingDirectory)
import Filesystem.Path (extensions)
import System.FSNotify
import System.Exit
import System.Environment
import System.Cmd
import Control.Concurrent
import Control.Monad
import Data.String (fromString)

main = do
    cwd <- getWorkingDirectory
    args <- getArgs
    when (null args) $ do
        putStrLn "Please give at least one filename (with no extension, .pandoc is assumed)"
        exitFailure
    let files = map (\f -> (fromString $ f ++ ".pandoc", f)) args
    putStrLn "Watching current directory, press RETURN to exit."
    withManager $ \man -> do
        _ <- forkIO $ do
            watchTree man cwd (const True) $ \fp -> do
                case fp of
                    Removed _ _ -> return ()
                    Added file _ -> maybeCompile file files
                    Modified file _ -> maybeCompile file files
        _ <- getLine
        exitSuccess

maybeCompile file files = case lookup file files of
    Just f -> do
        let command = "pandoc " ++ f ++ ".pandoc -N --smart --webtex -c buttondown.css -o " ++ f ++ ".html"
        system command 
        return ()
    Nothing -> return ()