module Network.BitTorrent.Client.Handle
       ( -- * Handle
         Handle

         -- * Initialization
       , openTorrent
       , openMagnet
       , closeHandle

         -- * Control
       , start
       , pause
       , stop

         -- * Query
       , getHandle
       , HandleState
       , getState
       ) where

import Control.Applicative
import Control.Concurrent
import Control.Monad
import Control.Monad.Trans
import Data.HashMap.Strict as HM

import Data.Torrent
import Data.Torrent.InfoHash
import Data.Torrent.Magnet
import Network.BitTorrent.Client.Types
import Network.BitTorrent.DHT      as DHT
import Network.BitTorrent.Exchange as Exchange
import Network.BitTorrent.Tracker  as Tracker

{-----------------------------------------------------------------------
--  Safe handle set manupulation
-----------------------------------------------------------------------}

-- | Guarantees that we newer allocate the same handle twice.
allocHandle :: InfoHash -> BitTorrent Handle -> BitTorrent Handle
allocHandle ih m = do
  c @ Client {..} <- getClient
  liftIO $ modifyMVar clientTorrents $ \ handles -> do
    case HM.lookup ih handles of
      Just h  -> return (handles, h)
      Nothing -> do
        h <- runBitTorrent c m
        return (HM.insert ih h handles, h)

-- |
freeHandle :: InfoHash -> BitTorrent () -> BitTorrent ()
freeHandle ih finalizer = do
  c @ Client {..} <- getClient
  liftIO $ modifyMVar_ clientTorrents $ \ handles -> do
    case HM.lookup ih handles of
      Nothing -> return handles
      Just _  -> do
        runBitTorrent c finalizer
        return (HM.delete ih handles)

-- |
lookupHandle :: InfoHash -> BitTorrent (Maybe Handle)
lookupHandle ih = do
  Client {..} <- getClient
  handles     <- liftIO $ readMVar clientTorrents
  return (HM.lookup ih handles)

{-----------------------------------------------------------------------
--  Initialization
-----------------------------------------------------------------------}

-- | Open a torrent in 'stop'ed state. Use 'nullTorrent' to open
-- handle from 'InfoDict'. This operation do not block.
openTorrent :: FilePath -> Torrent -> BitTorrent Handle
openTorrent rootPath t @ Torrent {..} = do
  let ih = idInfoHash tInfoDict
  allocHandle ih $ do
    c @ Client {..} <- getClient
    tses <- liftIO $ Tracker.newSession ih (trackerList t)
    eses <- liftIO $ Exchange.newSession (externalAddr c) rootPath tInfoDict
    return $ Handle ih (idPrivate tInfoDict) tses eses

-- | Use 'nullMagnet' to open handle from 'InfoHash'.
openMagnet :: Magnet -> BitTorrent Handle
openMagnet = undefined

-- | Stop torrent and destroy all sessions. You don't need to close
-- handles at application exit, all handles will be automatically
-- closed at 'Network.BitTorrent.Client.closeClient'. This operation
-- may block.
closeHandle :: Handle -> BitTorrent ()
closeHandle h @ Handle {..} = do
  freeHandle topic $ do
    stop h
    liftIO $ Exchange.closeSession exchange
    liftIO $ Tracker.closeSession trackers

{-----------------------------------------------------------------------
--  Control
-----------------------------------------------------------------------}

-- | Start downloading, uploading and announcing this torrent.
--
-- This operation is blocking, use
-- 'Control.Concurrent.Async.Lifted.async' if needed.
start :: Handle -> BitTorrent ()
start Handle {..} = do
  Client {..} <- getClient
  liftIO $ Tracker.notify trackerManager trackers Tracker.Started
  unless private $ do
    liftDHT $ DHT.insert topic undefined
  peers <- liftIO $ askPeers trackerManager trackers
  forM_ peers $ \ peer -> do
    liftIO $ Exchange.insert peer exchange

-- | Stop downloading this torrent.
pause :: Handle -> BitTorrent ()
pause _ = return ()

-- | Stop downloading, uploading and announcing this torrent.
stop :: Handle -> BitTorrent ()
stop Handle {..} = do
  Client {..} <- getClient
  unless private $ do
    liftDHT $ DHT.delete topic undefined
  liftIO  $ Tracker.notify trackerManager trackers Tracker.Stopped

{-----------------------------------------------------------------------
--  Query
-----------------------------------------------------------------------}

data HandleState
  = Running
  | Paused
  | Stopped

getHandle :: InfoHash -> BitTorrent Handle
getHandle ih = do
  mhandle <- lookupHandle ih
  case mhandle of
    Nothing -> error "should we throw some exception?"
    Just h  -> return h

getState :: Handle -> IO HandleState
getState = undefined