-- |
--   Copyright   :  (c) Sam T. 2013
--   License     :  MIT
--   Maintainer  :  pxqr.sta@gmail.com
--   Stability   :  experimental
--   Portability :  portable
--
--   This module implement opaque broadcast message passing. It
--   provides sessions needed by Network.BitTorrent and
--   Network.BitTorrent.Exchange and modules. To hide some internals
--   of this module we detach it from Exchange.
--
--   Note: expose only static data in data field lists, all dynamic
--   data should be modified through standalone functions.
--
{-# LANGUAGE OverloadedStrings     #-}
{-# LANGUAGE RecordWildCards       #-}
{-# LANGUAGE TemplateHaskell       #-}
{-# LANGUAGE FlexibleInstances     #-}
{-# LANGUAGE FlexibleContexts      #-}
{-# LANGUAGE MultiParamTypeClasses #-}
{-# LANGUAGE UndecidableInstances  #-}
module Network.BitTorrent.Internal
       ( Progress(..), startProgress

       , ClientSession (clientPeerID, allowedExtensions)
       , newClient, getCurrentProgress

       , SwarmSession(SwarmSession, torrentMeta, clientSession)
       , newLeacher, newSeeder

       , PeerSession(PeerSession, connectedPeerAddr
                    , swarmSession, enabledExtensions
                    )
       , SessionState
       , bitfield, status
       , emptyBF, fullBF, singletonBF
       , getPieceCount, getPeerBF
       , sessionError, withPeerSession

         -- * Timeouts
       , updateIncoming, updateOutcoming
       ) where

import Control.Applicative
import Control.Concurrent
import Control.Concurrent.STM
import Control.Lens
import Control.Monad.State
import Control.Monad.Reader
import Control.Exception

import Data.IORef
import Data.Default
import Data.Function
import Data.Ord
import Data.Set as S

import Data.Serialize hiding (get)
import Text.PrettyPrint

import Network
import Network.Socket
import Network.Socket.ByteString

import GHC.Event as Ev

import Data.Bitfield as BF
import Data.Torrent
import Network.BitTorrent.Extension
import Network.BitTorrent.Peer
import Network.BitTorrent.Exchange.Protocol as BT



-- | 'Progress' contains upload/download/left stats about
--   current client state.
--
--   This data is considered as dynamic within one session.
--
data Progress = Progress {
    prUploaded   :: Integer -- ^ Total amount of bytes uploaded.
  , prDownloaded :: Integer -- ^ Total amount of bytes downloaded.
  , prLeft       :: Integer -- ^ Total amount of bytes left.
  } deriving Show

startProgress :: Integer -> Progress
startProgress = Progress 0 0


{-----------------------------------------------------------------------
    Client session
-----------------------------------------------------------------------}

-- | In one application we could have many clients with difference
-- ID's and enabled extensions.
data ClientSession = ClientSession {
    -- | Our peer ID used in handshaked and discovery mechanism.
    clientPeerID      :: PeerID

    -- | Extensions we should try to use. Hovewer some particular peer
    -- might not support some extension, so we keep enableExtension in
    -- 'PeerSession'.
  , allowedExtensions :: [Extension]

  , swarmSessions     :: TVar (Set SwarmSession)
  , eventManager      :: EventManager
  , currentProgress   :: TVar  Progress
  }

instance Eq ClientSession where
  (==) = (==) `on` clientPeerID

instance Ord ClientSession where
  compare = comparing clientPeerID

getCurrentProgress :: MonadIO m => ClientSession -> m Progress
getCurrentProgress = liftIO . readTVarIO . currentProgress

newClient :: [Extension] -> IO ClientSession
newClient exts = do
  mgr <- Ev.new
  forkIO $ loop mgr

  ClientSession
    <$> newPeerID
    <*> pure exts
    <*> newTVarIO S.empty
    <*> pure mgr
    <*> newTVarIO (startProgress 0)

{-----------------------------------------------------------------------
    Swarm session
-----------------------------------------------------------------------}

-- | Extensions are set globally by
--   Swarm session are un
data SwarmSession = SwarmSession {
    torrentMeta       :: Torrent
  , clientSession     :: ClientSession

    -- | Modify this carefully updating global progress.
  , clientBitfield    :: TVar  Bitfield
  , connectedPeers    :: TVar (Set PeerSession)
  }

instance Eq SwarmSession where
  (==) = (==) `on` (tInfoHash . torrentMeta)

instance Ord SwarmSession where
  compare = comparing (tInfoHash . torrentMeta)

newSwarmSession :: Bitfield -> ClientSession -> Torrent -> IO SwarmSession
newSwarmSession bf cs @ ClientSession {..} t @ Torrent {..}
  = SwarmSession <$> pure t
                 <*> pure cs
                 <*> newTVarIO bf
                 <*> newTVarIO S.empty

newSeeder :: ClientSession -> Torrent -> IO SwarmSession
newSeeder cs t @ Torrent {..}
  = newSwarmSession (haveAll (pieceCount tInfo)) cs t

newLeacher :: ClientSession -> Torrent -> IO SwarmSession
newLeacher cs t @ Torrent {..}
  = newSwarmSession (haveNone (pieceCount tInfo)) cs t

isLeacher :: SwarmSession -> IO Bool
isLeacher = undefined

getClientBitfield :: MonadIO m => SwarmSession -> m Bitfield
getClientBitfield = liftIO . readTVarIO .  clientBitfield

{-
haveDone :: MonadIO m => PieceIx -> SwarmSession -> m ()
haveDone ix =
  liftIO $ atomically $ do
    bf <- readTVar clientBitfield
    writeTVar (have ix bf)
    currentProgress
-}
{-----------------------------------------------------------------------
    Peer session
-----------------------------------------------------------------------}

data PeerSession = PeerSession {
    -- | Used as unique 'PeerSession' identifier within one
    -- 'SwarmSession'.
    connectedPeerAddr :: PeerAddr

  , swarmSession      :: SwarmSession

    -- | Extensions such that both peer and client support.
  , enabledExtensions :: [Extension]

    -- | To dissconnect from died peers appropriately we should check
    -- if a peer do not sent the KA message within given interval. If
    -- yes, we should throw an exception in 'TimeoutCallback' and
    -- close session between peers.
    --
    -- We should update timeout if we /receive/ any message within
    -- timeout interval to keep connection up.
  , incomingTimeout     :: TimeoutKey

    -- | To send KA message appropriately we should know when was last
    -- time we sent a message to a peer. To do that we keep registered
    -- timeout in event manager and if we do not sent any message to
    -- the peer within given interval then we send KA message in
    -- 'TimeoutCallback'.
    --
    -- We should update timeout if we /send/ any message within timeout
    -- to avoid reduntant KA messages.
  , outcomingTimeout   :: TimeoutKey

  , broadcastMessages :: Chan   [Message]
  , sessionState      :: IORef   SessionState
  }

data SessionState = SessionState {
    _bitfield :: Bitfield
  , _status   :: SessionStatus
  }

$(makeLenses ''SessionState)

instance Eq PeerSession where
  (==) = (==) `on` connectedPeerAddr

instance Ord PeerSession where
  compare = comparing connectedPeerAddr

instance (MonadIO m, MonadReader PeerSession m)
      => MonadState SessionState m where
  get   = asks sessionState >>= liftIO . readIORef
  put s = asks sessionState >>= \ref -> liftIO $ writeIORef ref s

sessionError :: MonadIO m => Doc -> m ()
sessionError msg
  = liftIO $ throwIO $ userError $ render $ msg <+> "in session"

-- TODO check if it connected yet peer
withPeerSession :: SwarmSession -> PeerAddr
                -> ((Socket, PeerSession) -> IO a)
                -> IO a

withPeerSession ss @ SwarmSession {..} addr
    = bracket openSession closeSession
  where
    openSession = do
      let caps = encodeExts $ allowedExtensions $ clientSession
      let pid  = clientPeerID $ clientSession
      let chs  = Handshake defaultBTProtocol caps (tInfoHash torrentMeta) pid

      sock <- connectToPeer addr
      phs  <- handshake sock chs `onException` close sock

      let enabled = decodeExts (enabledCaps caps (handshakeCaps phs))
      ps <- PeerSession addr ss enabled
         <$> registerTimeout (eventManager clientSession)
                maxIncomingTime abortSession
         <*> registerTimeout (eventManager clientSession)
                maxOutcomingTime (sendKA sock)
         <*> newChan
         <*> do {
           ; tc <- totalCount <$> readTVarIO clientBitfield
           ; newIORef (SessionState (haveNone tc) def)
           }
      return (sock, ps)

    closeSession = close . fst

getPieceCount :: (MonadReader PeerSession m) => m PieceCount
getPieceCount = asks (pieceCount . tInfo . torrentMeta . swarmSession)

emptyBF :: (MonadReader PeerSession m) => m Bitfield
emptyBF = liftM haveNone getPieceCount

fullBF ::  (MonadReader PeerSession m) => m Bitfield
fullBF = liftM haveAll getPieceCount

singletonBF :: (MonadReader PeerSession m) => PieceIx -> m Bitfield
singletonBF ix = liftM (BF.singleton ix) getPieceCount

getPeerBF :: (MonadIO m, MonadReader PeerSession m) => m Bitfield
getPeerBF = asks swarmSession >>= liftIO . readTVarIO . clientBitfield

--data Signal =
--nextBroadcast :: P2P (Maybe Signal)
--nextBroadcast =


{-----------------------------------------------------------------------
    Timeouts
-----------------------------------------------------------------------}

sec :: Int
sec = 1000 * 1000

maxIncomingTime :: Int
maxIncomingTime = 120 * sec

maxOutcomingTime :: Int
maxOutcomingTime = 1 * sec

-- | Should be called after we have received any message from a peer.
updateIncoming :: PeerSession -> IO ()
updateIncoming PeerSession {..} = do
  updateTimeout (eventManager (clientSession swarmSession))
    incomingTimeout maxIncomingTime

-- | Should be called before we have send any message to a peer.
updateOutcoming :: PeerSession -> IO ()
updateOutcoming PeerSession {..}  =
  updateTimeout (eventManager (clientSession swarmSession))
    outcomingTimeout maxOutcomingTime

sendKA :: Socket -> IO ()
sendKA sock {- SwarmSession {..} -} = do
  print "I'm sending keep alive."
  sendAll sock (encode BT.KeepAlive)
--  let mgr = eventManager clientSession
--  updateTimeout mgr
  print "Done.."

abortSession :: IO ()
abortSession = error "abortSession: not implemented"