{-# LANGUAGE RecordWildCards #-}

import Foreign.C.Types (CFloat(..))
import qualified Sound.JACK as Jack
import qualified Sound.JACK.Audio as Audio

import Options.Applicative

import Data.Maybe

import System.Directory
import System.FilePath
import System.Posix.Files
import System.Posix.IO
import System.Environment

import Control.Concurrent
import Control.Concurrent.MVar

import qualified Control.Monad.Trans.Class as Trans
import qualified Control.Monad.Exception.Synchronous as Sync

import Control.Exception
import System.IO.Error

import System.INotify

data Options = Options
               { input :: String
               , output :: String
               , client :: String
               , connFrom :: Maybe String
               , connTo :: Maybe String
               , initialLevel :: Float
               , stateDir :: FilePath
               }

optionParser :: Parser Options
optionParser = Options <$>
               strOption ( long "input"
                           <> metavar "STRING"
                         )
               <*> strOption ( long "output"
                               <> metavar "STRING"
                             )
               <*> strOption ( long "client"
                               <> metavar "STRING"
                             )
               <*> optional (strOption ( long "input-from"
                                         <> metavar "STRING"
                                       ))
               <*> optional (strOption ( long "output-to"
                                         <> metavar "STRING"
                                       ))
               <*> (fromMaybe 0 <$> optional (option auto ( long "level"
                                                            <> metavar "FLOAT"
                                                          )
                                             )
                   )
               <*> strOption ( long "dir"
                               <> metavar "DIRECTORY"
                             )

main :: IO ()
main = execParser opts >>= trivmix
  where
    opts = info (helper <*> optionParser)
           ( fullDesc
             <> progDesc "Setup a JACK mixing input/output pair controlled by fifos in a state directory"
             <> header "Trivmix - A trivial mixer"
           )

trivmix :: Options -> IO ()
trivmix Options{..} = do
  createDirectoryIfMissing True stateDir
  level <- newMVar initialLevel
  let levelFile = stateDir </> "level"
  onLevelFile levelFile initialLevel $ withINotify $ \n -> do
    addWatch n [Modify] levelFile (const $ handleLevel level levelFile)
    Jack.handleExceptions $
      Jack.withClientDefault client $ \client ->
      Jack.withPort client input $ \input' ->
      Jack.withPort client output $ \output' -> do
        case connFrom of
          Nothing -> return ()
          Just f -> Jack.connect client input f
        case connTo of
          Nothing -> return ()
          Just t -> Jack.connect client t output
        Audio.withProcessMono client input' (mix level) output' $
          Jack.withActivation client $ Trans.lift $ do
            Jack.waitForBreak
  
mix :: MVar Float -> CFloat -> IO CFloat
mix level input = do
  level' <- readMVar level
  return $ (CFloat level') * input

onLevelFile :: FilePath -> Float -> IO a -> IO a
onLevelFile file initial action = do
  exists <- doesFileExist file
  let acquire = case exists of
        True -> return ()
        False -> createFile file mode >>= closeFd
      mode = foldl unionFileModes nullFileMode [ ownerReadMode
                                               , ownerWriteMode
                                               , groupReadMode
                                               , groupWriteMode
                                               ]
      release = case exists of
        True -> return ()
        False -> removeFile file
  bracket_ acquire release action

handleLevel :: MVar Float -> FilePath -> IO ()
handleLevel level file = catch action handler
  where
    action = readFile file >>= readIO >>= swapMVar level >>= const (return ())
    handler e = if isUserError e
                then readMVar level >>= \l -> writeFile file (show l)
                else throw e