Network/MPD.hs

   1 {-
   2     libmpd for Haskell, an MPD client library.
   3     Copyright (C) 2005-2008  Ben Sinclair <bsinclai@turing.une.edu.au>
   4
   5     This library is free software; you can redistribute it and/or
   6     modify it under the terms of the GNU Lesser General Public
   7     License as published by the Free Software Foundation; either
   8     version 2.1 of the License, or (at your option) any later version.
   9
  10     This library is distributed in the hope that it will be useful,
  11     but WITHOUT ANY WARRANTY; without even the implied warranty of
  12     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13     Lesser General Public License for more details.
  14
  15     You should have received a copy of the GNU Lesser General Public
  16     License along with this library; if not, write to the Free Software
  17     Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
  18 -}
  19
  20 -- | Module    : Network.MPD
  21 -- Copyright   : (c) Ben Sinclair 2005-2008
  22 -- License     : LGPL
  23 -- Maintainer  : bsinclai@turing.une.edu.au
  24 -- Stability   : alpha
  25 -- Portability : Haskell 98
  26 --
  27 -- An MPD client library. MPD is a daemon for playing music that is
  28 -- controlled over a network socket. Its site is at <http://www.musicpd.org/>.
  29
  30 module Network.MPD (
  31     -- * Basic data types
  32     MPD, MPDError(..), ACKType(..), Response,
  33     -- * Connections
  34     withMPD, withMPDEx,
  35     module Network.MPD.Commands,
  36     ) where
  37
  38 import Network.MPD.Commands
  39 import Network.MPD.Core
  40 import Network.MPD.SocketConn
  41
  42 import Control.Monad (liftM)
  43 import Data.Maybe (listToMaybe)
  44 import Data.IORef (newIORef, atomicModifyIORef)
  45 import System.Environment (getEnv)
  46 import System.IO
  47 import System.IO.Error (isDoesNotExistError, ioError)
  48
  49 -- | A wrapper for 'withMPDEx' that uses localhost:6600 as the default
  50 -- host:port, or whatever is found in the environment variables MPD_HOST and
  51 -- MPD_PORT. If MPD_HOST is of the form \"password\@host\" the password
  52 -- will be supplied as well.
  53 --
  54 -- Examples:
  55 --
  56 -- > withMPD $ play Nothing
  57 -- > withMPD $ add_ Nothing "tool" >> play Nothing >> currentSong
  58 withMPD :: MPD a -> IO (Response a)
  59 withMPD m = do
  60     port <- liftM read (getEnvDefault "MPD_PORT" "6600")
  61     (pw,host) <- liftM (break (== '@')) (getEnvDefault "MPD_HOST" "localhost")
  62     let (host',pw') = if null host then (pw,host) else (drop 1 host,pw)
  63     pwGen <- mkPasswordGen [pw']
  64     withMPDEx host' port pwGen m
  65     where
  66         getEnvDefault x dflt =
  67             catch (getEnv x) (\e -> if isDoesNotExistError e
  68                                     then return dflt else ioError e)
  69
  70 -- | Create an action that produces passwords for a connection. You
  71 -- can pass these to 'withMPDEx' and it will use them to get passwords
  72 -- to send to the server until one works or it runs out of them.
  73 --
  74 -- > do gen <- mkPasswordGen ["password1", "password2"]
  75 -- >    withMPDEx "localhost" 6600 gen (update [])
  76 mkPasswordGen :: [String] -> IO (IO (Maybe String))
  77 mkPasswordGen = liftM f . newIORef
  78     where f = flip atomicModifyIORef $ \xs -> (drop 1 xs, listToMaybe xs)