custom/notify-user.nix


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{ stdenv, writeTextFile
, ghcWithPackages
, user ? "gkleen"
, libnotify
}:

stdenv.mkDerivation {
  name = ''notify-${user}'';
  src = writeTextFile { name = ''notify-${user}.hs''; text = ''
    {-# LANGUAGE ViewPatterns #-}
  
    import System.FilePath.Glob (glob)
    import System.Environment (setEnv, getArgs)
    import System.Process (spawnProcess, waitForProcess)
    import System.Exit (exitWith, ExitCode(..))

    import Data.List (isPrefixOf, dropWhile, dropWhileEnd)
    import Data.Char (isSpace)

    import Control.Monad (forM_, void)

    main = do
      envFiles <- glob "/home/${user}/.dbus/session-bus/*"
      forM_ envFiles $ \envFile -> do
        sessionAddr <- tail . snd . break (== '=') . head . filter ("DBUS_SESSION_BUS_ADDRESS=" `isPrefixOf`) . lines <$> readFile envFile
        setEnv "DBUS_SESSION_BUS_ADDRESS" sessionAddr
        lines <- lines <$> getContents
        case lines of
          [] -> exitWith ExitSuccess
          ((trim -> summary):(trim . unlines -> contents)) -> do
            ph <- spawnProcess "${libnotify}/bin/notify-send" =<< (++ [summary, contents]) <$> getArgs
            void $ waitForProcess ph
      where
        trim = dropWhileEnd isSpace . dropWhile isSpace
  ''; };
  phases = [ "buildPhase" "installPhase" ];
  buildPhase = ''
    ${ghcWithPackages (p: with p; [ Glob process ])}/bin/ghc -odir . -hidir . $src -o notify-${user}
  '';
  installPhase = ''
    mkdir -p $out/bin
    cp notify-${user} $out/bin
    chmod +x $out/bin/notify-${user}
  '';
}