Network/MPD.hs

   1 {-
   2     libmpd for Haskell, an MPD client library.
   3     Copyright (C) 2005-2007  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 2005-2007
  22 -- License     : LGPL
  23 -- Maintainer  : bsinclai@turing.une.edu.au
  24 -- Stability   : alpha
  25 -- Portability : Haskell 98
  26 --
  27 -- MPD client library.
  28
  29 module Network.MPD (
  30     -- * Basic data types
  31     MPD, MPDError(..), ACKType(..), Response,
  32     -- * Connections
  33     withMPD, withMPDEx,
  34     module Network.MPD.Commands,
  35     ) where
  36
  37 import Network.MPD.Commands
  38 import Network.MPD.Prim
  39 import Network.MPD.SocketConn
  40
  41 import Control.Monad (liftM)
  42 import Data.Maybe (listToMaybe)
  43 import Data.IORef (newIORef, atomicModifyIORef)
  44 import System.Environment (getEnv)
  45 import System.IO
  46 import System.IO.Error (isDoesNotExistError, ioError)
  47
  48 -- | A wrapper for 'withMPDEx' that uses localhost:6600 as the default
  49 -- host:port, or whatever is found in the environment variables MPD_HOST and
  50 -- MPD_PORT. If MPD_HOST is of the form \"password\@host\" the password
  51 -- will be supplied as well.
  52 --
  53 -- Examples:
  54 --
  55 -- > withMPD $ play Nothing
  56 -- > withMPD $ add_ Nothing "tool" >> play Nothing >> currentSong
  57 withMPD :: MPD a -> IO (Response a)
  58 withMPD m = do
  59     port <- liftM read (getEnvDefault "MPD_PORT" "6600")
  60     (pw,host) <- liftM (break (== '@')) (getEnvDefault "MPD_HOST" "localhost")
  61     let (host',pw') = if null host then (pw,host) else (drop 1 host,pw)
  62     pwGen <- mkPasswordGen [pw']
  63     withMPDEx host' port pwGen m
  64     where
  65         getEnvDefault x dflt =
  66             catch (getEnv x) (\e -> if isDoesNotExistError e
  67                                     then return dflt else ioError e)
  68
  69 -- | Create an action that produces passwords for a connection. You
  70 -- can pass these to 'withMPDEx' and it will use them to get passwords
  71 -- to send to the server until one works or it runs out of them.
  72 --
  73 -- > do gen <- mkPasswordGen ["password1", "password2"]
  74 -- >    withMPDEx "localhost" 6600 gen (update [])
  75 mkPasswordGen :: [String] -> IO (IO (Maybe String))
  76 mkPasswordGen = liftM f . newIORef
  77     where f = flip atomicModifyIORef $ \xs -> (drop 1 xs, listToMaybe xs)