-- -*-haskell-*-
--  Vision (for the Voice): an XMMS2 client.
--
--  Author:  Oleg Belozeorov
--  Created: 18 Jun. 2010
--
--  Copyright (C) 2010 Oleg Belozeorov
--
--  This program is free software; you can redistribute it and/or
--  modify it under the terms of the GNU General Public License as
--  published by the Free Software Foundation; either version 3 of
--  the License, or (at your option) any later version.
--
--  This program is distributed in the hope that it will be useful,
--  but WITHOUT ANY WARRANTY; without even the implied warranty of
--  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
--  General Public License for more details.
--

module Medialib
  ( Stamp
  , MediaInfo
  , initMedialib
  , requestInfo
  , onMediaInfo
  , getInfo
  , retrieveProperties
  ) where

import Control.Concurrent.MVar
import Control.Monad
import Control.Monad.Trans

import Data.Map (Map)
import Data.IntMap (IntMap)
import qualified Data.IntMap as IntMap
import Data.Maybe
import Data.List
import Data.IORef

import Graphics.UI.Gtk hiding (add, remove)

import XMMS2.Client
import XMMS2.Client.Bindings (propdictToDict)

import Utils
import Context
import XMMS
import Handler


type Stamp = Int
type MediaInfo = Map String Property


data CacheEntry
  = CEReady Stamp MediaInfo
  | CERetrieving

data Cache
  = Cache { cEntries   :: IntMap CacheEntry
          , cNextStamp :: Stamp
          }

emptyCache =
  Cache { cEntries   = IntMap.empty
        , cNextStamp = 1
        }


data MLib
  = MLib { mCache       :: MVar Cache
         , mOnMediaInfo :: HandlerMVar (MediaId, Stamp, MediaInfo)
         }

cache = mCache context


onMediaInfo = onHandler $ mOnMediaInfo context

initMedialib = do
  context <- initContext
  let ?context = context

  onServerConnectionAdd . ever $ \conn ->
    if conn
    then broadcastMedialibEntryChanged xmms >>* do
      id <- result
      let id' = fromIntegral id
      liftIO $ withMVar cache $ \cache ->
        when (isJust . IntMap.lookup id' $ cEntries cache) $
          medialibGetInfo xmms id >>* handleInfo id'
      persist
    else
      modifyMVar_ cache $ \cache ->
        return cache { cEntries = IntMap.empty }

  return ?context

requestInfo id =
  modifyMVar_ cache $ \cache ->
    let id'     = fromIntegral id
        entries = cEntries cache in
    case IntMap.lookup id' entries of
      Nothing -> do
        medialibGetInfo xmms id >>* handleInfo id'
        return cache { cEntries = IntMap.insert id' CERetrieving $ cEntries cache }
      Just (CEReady s i) -> do
        idleAdd (onMediaInfo (invoke (id, s, i)) >> return False) priorityHighIdle
        return cache
      _ ->
        return cache


initContext = do
  cache       <- newMVar emptyCache
  onMediaInfo <- makeHandlerMVar
  return $ augmentContext
    MLib { mCache       = cache
         , mOnMediaInfo = onMediaInfo }

handleInfo id = do
  rawv <- resultRawValue
  liftIO $ do
    info  <- valueGet =<< propdictToDict rawv []
    stamp <- modifyMVar cache $ \cache ->
      let stamp   = cNextStamp cache
          entries = cEntries cache
          entry   = CEReady stamp info in
      return (Cache { cEntries   = IntMap.insert id entry entries
                    , cNextStamp = succ stamp }, stamp)
    onMediaInfo $ invoke (fromIntegral id, stamp, info)

getInfo id =
  withMVar cache $ \cache ->
    return $ case IntMap.lookup (fromIntegral id) $ cEntries cache of
      Just (CEReady _ info) -> Just info
      _                     -> Nothing

retrieveProperties ids f = do
  let ids'       = nub ids
      len        = length ids'
      step       = len `div` 100

  ref <- newIORef (0, ids', [])
  hid <- onMediaInfo . add $ \(id, _, info) -> do
    (ctr, todo, ready) <- readIORef ref
    case todo of
      (i:is) | i == id ->
        if null is
        then do
          f . Right $ reverse ((id, info) : ready)
          return False
        else do
          let ctr' = ctr + 1
          when (step == 0 || ctr' `mod` step == 0) $
            f . Left $ fromIntegral ctr' / fromIntegral len
          requestInfo $ head is
          writeIORef ref (ctr', is, (id, info) : ready)
          return True
      _ ->
        return True

  requestInfo $ head ids
  return . onMediaInfo $ remove hid