-- |
--   Module      :  Network.BitTorrent.Core.PeerAddr
--   Copyright   :  (c) Sam Truzjan 2013
--                  (c) Daniel Gröber 2013
--   License     :  BSD3
--   Maintainer  :  pxqr.sta@gmail.com
--   Stability   :  provisional
--   Portability :  portable
--
--   'PeerAddr' is used to represent peer address. Currently it's
--   just peer IP and peer port but this might change in future.
--
{-# LANGUAGE TemplateHaskell            #-}
{-# LANGUAGE StandaloneDeriving         #-}
{-# LANGUAGE GeneralizedNewtypeDeriving #-}
{-# LANGUAGE DeriveDataTypeable         #-}
{-# LANGUAGE FlexibleInstances          #-}
{-# LANGUAGE DeriveFunctor              #-}
{-# LANGUAGE ViewPatterns               #-}
{-# OPTIONS -fno-warn-orphans           #-} -- for PortNumber instances
module Network.BitTorrent.Core.PeerAddr
       ( -- * Peer address
         PeerAddr(..)
       , defaultPorts
       , peerSockAddr
       , peerSocket

         -- * Peer storage
       , PeerStore
       , Network.BitTorrent.Core.PeerAddr.lookup
       , Network.BitTorrent.Core.PeerAddr.insert
       ) where

import Control.Applicative
import Control.Monad
import Data.Aeson (ToJSON, FromJSON)
import Data.Aeson.TH
import Data.BEncode   as BS
import Data.BEncode.BDict (BKey)
import Data.ByteString.Char8 as BS8
import Data.Char
import Data.Default
import Data.Hashable
import Data.HashMap.Strict as HM
import Data.IP
import Data.List      as L
import Data.List.Split
import Data.Maybe
import Data.Monoid
import Data.Serialize as S
import Data.String
import Data.Typeable
import Data.Word
import Network.Socket
import Text.PrettyPrint as PP hiding ((<>))
import Text.PrettyPrint.Class
import Text.Read (readMaybe)
import qualified Text.ParserCombinators.ReadP as RP

import Data.Torrent.InfoHash
import Data.Torrent.JSON
import Network.BitTorrent.Core.PeerId


{-----------------------------------------------------------------------
--  Port number
-----------------------------------------------------------------------}

deriving instance ToJSON PortNumber
deriving instance FromJSON PortNumber

instance BEncode PortNumber where
  toBEncode   = toBEncode    .  fromEnum
  fromBEncode = fromBEncode >=> portNumber
    where
      portNumber :: Integer -> BS.Result PortNumber
      portNumber n
        | 0 <= n && n <= fromIntegral (maxBound :: Word16)
        = pure $ fromIntegral n
        | otherwise = decodingError $ "PortNumber: " ++ show n

instance Serialize PortNumber where
  get = fromIntegral <$> getWord16be
  {-# INLINE get #-}
  put = putWord16be . fromIntegral
  {-# INLINE put #-}

instance Hashable PortNumber where
  hashWithSalt s = hashWithSalt s . fromEnum
  {-# INLINE hashWithSalt #-}

instance Pretty PortNumber where
  pretty = PP.int . fromEnum
  {-# INLINE pretty #-}

{-----------------------------------------------------------------------
--  IP addr
-----------------------------------------------------------------------}

class IPAddress i where
  toHostAddr :: i -> Either HostAddress HostAddress6

instance IPAddress IPv4 where
  toHostAddr = Left . toHostAddress
  {-# INLINE toHostAddr #-}

instance IPAddress IPv6 where
  toHostAddr = Right . toHostAddress6
  {-# INLINE toHostAddr #-}

instance IPAddress IP where
  toHostAddr (IPv4 ip) = toHostAddr ip
  toHostAddr (IPv6 ip) = toHostAddr ip
  {-# INLINE toHostAddr #-}

deriving instance Typeable IP
deriving instance Typeable IPv4
deriving instance Typeable IPv6

ipToBEncode :: Show i => i -> BValue
ipToBEncode ip = BString $ BS8.pack $ show ip
{-# INLINE ipToBEncode #-}

ipFromBEncode :: Read a => BValue -> BS.Result a
ipFromBEncode (BString (BS8.unpack -> ipStr))
  | Just ip <- readMaybe (ipStr) = pure ip
  |         otherwise            = decodingError $ "IP: " ++ ipStr
ipFromBEncode _    = decodingError $ "IP: addr should be a bstring"

instance BEncode IP where
  toBEncode   = ipToBEncode
  {-# INLINE toBEncode #-}
  fromBEncode = ipFromBEncode
  {-# INLINE fromBEncode #-}

instance BEncode IPv4 where
  toBEncode   = ipToBEncode
  {-# INLINE toBEncode #-}
  fromBEncode = ipFromBEncode
  {-# INLINE fromBEncode #-}

instance BEncode IPv6 where
  toBEncode   = ipToBEncode
  {-# INLINE toBEncode #-}
  fromBEncode = ipFromBEncode
  {-# INLINE fromBEncode #-}

-- | When 'get'ing an IP it must be 'isolate'd to the appropriate
-- number of bytes since we have no other way of telling which
-- address type we are trying to parse
instance Serialize IP where
    put (IPv4 ip) = put ip
    put (IPv6 ip) = put ip

    get = do
      n <- remaining
      case n of
        4  -> IPv4 <$> get
        16 -> IPv6 <$> get
        _ -> fail "Wrong number of bytes remaining to parse IP"

instance Serialize IPv4 where
    put = putWord32host    .  toHostAddress
    get = fromHostAddress <$> getWord32host

instance Serialize IPv6 where
    put ip = put $ toHostAddress6 ip
    get = fromHostAddress6 <$> get

instance Pretty IPv4 where
  pretty = PP.text . show
  {-# INLINE pretty #-}

instance Pretty IPv6 where
  pretty = PP.text . show
  {-# INLINE pretty #-}

instance Pretty IP where
  pretty = PP.text . show
  {-# INLINE pretty #-}

instance Hashable IPv4 where
  hashWithSalt = hashUsing toHostAddress
  {-# INLINE hashWithSalt #-}

instance Hashable IPv6 where
  hashWithSalt s a = hashWithSalt s (toHostAddress6 a)

instance Hashable IP where
  hashWithSalt s (IPv4 h) = hashWithSalt s h
  hashWithSalt s (IPv6 h) = hashWithSalt s h

{-----------------------------------------------------------------------
--  Peer addr
-----------------------------------------------------------------------}
-- TODO check semantic of ord and eq instances

-- | Peer address info normally extracted from peer list or peer
-- compact list encoding.
data PeerAddr a = PeerAddr
  { peerId   :: !(Maybe PeerId)

    -- | This is usually 'IPv4', 'IPv6', 'IP' or unresolved
    -- 'HostName'.
  , peerHost :: !a

    -- | The port the peer listenning for incoming P2P sessions.
  , peerPort :: {-# UNPACK #-} !PortNumber
  } deriving (Show, Eq, Ord, Typeable, Functor)

$(deriveJSON omitRecordPrefix ''PeerAddr)

peer_ip_key, peer_id_key, peer_port_key :: BKey
peer_ip_key   = "ip"
peer_id_key   = "peer id"
peer_port_key = "port"

-- | The tracker's 'announce response' compatible encoding.
instance (Typeable a, BEncode a) => BEncode (PeerAddr a) where
  toBEncode PeerAddr {..} = toDict $
       peer_ip_key   .=! peerHost
    .: peer_id_key   .=? peerId
    .: peer_port_key .=! peerPort
    .: endDict

  fromBEncode = fromDict $ do
    peerAddr <$>! peer_ip_key
             <*>? peer_id_key
             <*>! peer_port_key
    where
      peerAddr = flip PeerAddr

-- | The tracker's 'compact peer list' compatible encoding. The
-- 'peerId' is always 'Nothing'.
--
--   For more info see: <http://www.bittorrent.org/beps/bep_0023.html>
--
-- TODO: test byte order
instance (Serialize a) => Serialize (PeerAddr a) where
  put PeerAddr {..} = put peerHost >> put peerPort
  get = PeerAddr Nothing <$> get <*> get

-- | @127.0.0.1:6881@
instance Default (PeerAddr IPv4) where
  def = "127.0.0.1:6881"

-- | @127.0.0.1:6881@
instance Default (PeerAddr IP) where
  def = IPv4 <$> def

-- | Example:
--
--   @peerPort \"127.0.0.1:6881\" == 6881@
--
instance IsString (PeerAddr IPv4) where
  fromString str
    | [hostAddrStr, portStr] <- splitWhen (== ':') str
    , Just hostAddr <- readMaybe hostAddrStr
    , Just portNum  <- toEnum <$> readMaybe portStr
                = PeerAddr Nothing hostAddr portNum
    | otherwise = error $ "fromString: unable to parse (PeerAddr IPv4): " ++ str

instance Read (PeerAddr IPv4) where
  readsPrec i = RP.readP_to_S $ do
    ipv4 <- RP.readS_to_P (readsPrec i)
    _    <- RP.char ':'
    port <- toEnum <$> RP.readS_to_P (readsPrec i)
    return $ PeerAddr Nothing ipv4 port

readsIPv6_port :: String -> [((IPv6, PortNumber), String)]
readsIPv6_port = RP.readP_to_S $ do
  ip <- RP.char '[' *> (RP.readS_to_P reads) <* RP.char ']'
  _ <- RP.char ':'
  port <- toEnum <$> read <$> (RP.many1 $ RP.satisfy isDigit) <* RP.eof
  return (ip,port)

instance IsString (PeerAddr IPv6) where
  fromString str
    | [((ip,port),"")] <- readsIPv6_port str =
        PeerAddr Nothing ip port
    | otherwise = error $ "fromString: unable to parse (PeerAddr IPv6): " ++ str

instance IsString (PeerAddr IP) where
  fromString str
    | '[' `L.elem` str = IPv6 <$> fromString str
    |      otherwise   = IPv4 <$> fromString str

-- | fingerprint + "at" + dotted.host.inet.addr:port
-- TODO: instances for IPv6, HostName
instance Pretty a => Pretty (PeerAddr a) where
  pretty PeerAddr {..}
    | Just pid <- peerId = pretty (fingerprint pid) <+> "at" <+> paddr
    |     otherwise      = paddr
    where
      paddr = pretty peerHost <> ":" <> text (show peerPort)

instance Hashable a => Hashable (PeerAddr a) where
  hashWithSalt s PeerAddr {..} =
    s `hashWithSalt` peerId `hashWithSalt` peerHost `hashWithSalt` peerPort

-- | Ports typically reserved for bittorrent P2P listener.
defaultPorts :: [PortNumber]
defaultPorts =  [6881..6889]

_resolvePeerAddr :: (IPAddress i) => PeerAddr HostName -> PeerAddr i
_resolvePeerAddr = undefined

_peerSockAddr :: PeerAddr IP -> (Family, SockAddr)
_peerSockAddr PeerAddr {..} =
    case peerHost of
          IPv4 ipv4 ->
              (AF_INET, SockAddrInet peerPort (toHostAddress  ipv4))
          IPv6 ipv6 ->
              (AF_INET6, SockAddrInet6 peerPort 0 (toHostAddress6 ipv6) 0)

peerSockAddr :: PeerAddr IP -> SockAddr
peerSockAddr = snd . _peerSockAddr

-- | Create a socket connected to the address specified in a peerAddr
peerSocket :: SocketType -> PeerAddr IP -> IO Socket
peerSocket socketType pa = do
    let (family, addr) = _peerSockAddr pa
    sock <- socket family socketType defaultProtocol
    connect sock addr
    return sock

{-----------------------------------------------------------------------
--  Peer storage
-----------------------------------------------------------------------}
-- TODO use more memory efficient representation

-- | Storage used to keep track a set of known peers in client,
-- tracker or DHT sessions.
newtype PeerStore ip = PeerStore (HashMap InfoHash [PeerAddr ip])

-- | Empty store.
instance Default (PeerStore a) where
  def = PeerStore HM.empty
  {-# INLINE def #-}

-- | Monoid under union operation.
instance Eq a => Monoid (PeerStore a) where
  mempty  = def
  {-# INLINE mempty #-}

  mappend (PeerStore a) (PeerStore b) =
    PeerStore (HM.unionWith L.union a b)
  {-# INLINE mappend #-}

-- | Can be used to store peers between invocations of the client
-- software.
instance Serialize (PeerStore a) where
  get = undefined
  put = undefined

-- | Used in 'get_peers' DHT queries.
lookup :: InfoHash -> PeerStore a -> [PeerAddr a]
lookup ih (PeerStore m) = fromMaybe [] $ HM.lookup ih m

-- | Used in 'announce_peer' DHT queries.
insert :: Eq a => InfoHash -> PeerAddr a -> PeerStore a -> PeerStore a
insert ih a (PeerStore m) = PeerStore (HM.insertWith L.union ih [a] m)