-----------------------------------------------------------------------------
-- |
-- Module      :  Plugins.MBox
-- Copyright   :  (c) Jose A Ortega Ruiz
-- License     :  BSD-style (see LICENSE)
--
-- Maintainer  :  Jose A Ortega Ruiz <jao@gnu.org>
-- Stability   :  unstable
-- Portability :  unportable
--
-- A plugin for checking mail in mbox files.
--
-----------------------------------------------------------------------------

module Plugins.MBox (MBox(..)) where

import Prelude hiding (catch)
import Plugins
import Plugins.Utils (changeLoop, expandHome)

import Control.Monad (when)
import Control.Concurrent.STM
import Control.Exception (SomeException, handle, evaluate)

import System.Console.GetOpt
import System.Directory (doesDirectoryExist, doesFileExist)
import System.FilePath ((</>))
import System.INotify (Event(..), EventVariety(..), initINotify, addWatch)

import qualified Data.ByteString.Lazy.Char8 as B

data Options = Options
               { oAll :: Bool
               , oUniq :: Bool
               , oDir :: FilePath
               , oPrefix :: String
               , oSuffix :: String
               }

defaults :: Options
defaults = Options {
  oAll = False, oUniq = False, oDir = "", oPrefix = "", oSuffix = ""
  }

options :: [OptDescr (Options -> Options)]
options =
  [ Option "a" ["all"] (NoArg (\o -> o { oAll = True })) ""
  , Option "u" [] (NoArg (\o -> o { oUniq = True })) ""
  , Option "d" ["dir"] (ReqArg (\x o -> o { oDir = x }) "") ""
  , Option "p" ["prefix"] (ReqArg (\x o -> o { oPrefix = x }) "") ""
  , Option "s" ["suffix"] (ReqArg (\x o -> o { oSuffix = x }) "") ""
  ]

parseOptions :: [String] -> IO Options
parseOptions args =
  case getOpt Permute options args of
    (o, _, []) -> return $ foldr id defaults o
    (_, _, errs) -> ioError . userError $ concat errs

-- | A list of display names, paths to mbox files and display colours,
-- followed by a list of options.
data MBox = MBox [(String, FilePath, String)] [String] String
          deriving (Read, Show)

instance Exec MBox where
  alias (MBox _ _ a) = a
  start (MBox boxes args _) cb = do

    opts <- parseOptions args
    let dir = oDir opts
        allb = oAll opts
        pref = oPrefix opts
        suff = oSuffix opts
        uniq = oUniq opts
        names = map (\(t, _, _) -> t) boxes
        colors = map (\(_, _, c) -> c) boxes

    dirExists <- doesDirectoryExist dir

    let extractPath (_, f, _) = if dirExists then dir </> f else f
        events = [CloseWrite]

    i <- initINotify
    vs <- mapM (\m -> do
                   f <- expandHome $ extractPath m
                   exists <- doesFileExist f
                   n <- if exists then countMails f else return (-1)
                   v <- newTVarIO (f, n)
                   when exists $
                     addWatch i events f (handleNotification v) >> return ()
                   return v)
                boxes

    changeLoop (mapM (fmap snd . readTVar) vs) $ \ns ->
      let s = unwords [ showC uniq m n c | (m, n, c) <- zip3 names ns colors
                                         , allb || n > 0 ]
      in cb (if null s then "" else pref ++ s ++ suff)

showC :: Bool -> String -> Int -> String -> String
showC u m n c =
  if c == "" then msg else "<fc=" ++ c ++ ">" ++ msg ++ "</fc>"
    where msg = m ++ if not u || n > 1 then show n else ""

countMails :: FilePath -> IO Int
countMails f =
  handle ((\_ -> evaluate 0) :: SomeException -> IO Int)
         (do txt <- B.readFile f
             evaluate $! length . filter (B.isPrefixOf from) . B.lines $ txt)
  where from = B.pack "From "

handleNotification :: TVar (FilePath, Int) -> Event -> IO ()
handleNotification v _ =  do
  (p, _) <- atomically $ readTVar v
  n <- countMails p
  atomically $ writeTVar v (p, n)