-- |
--   Copyright   :  (c) Sam Truzjan 2013
--   License     :  BSD3
--   Maintainer  :  pxqr.sta@gmail.com
--   Stability   :  experimental
--   Portability :  portable
--
--   Every tracker should support announce query. This query is used
--   to discover peers within a swarm and have two-fold effect:
--
--     * peer doing announce discover other peers using peer list from
--     the response to the announce query.
--
--     * tracker store peer information and use it in the succeeding
--     requests made by other peers, until the peer info expires.
--
--   By convention most trackers support another form of request —
--   scrape query — which queries the state of a given torrent (or
--   a list of torrents) that the tracker is managing.
--
{-# LANGUAGE FlexibleInstances          #-}
{-# LANGUAGE GeneralizedNewtypeDeriving #-}
{-# LANGUAGE TemplateHaskell            #-}
{-# LANGUAGE DeriveDataTypeable         #-}
{-# OPTIONS -fno-warn-orphans           #-}
module Network.BitTorrent.Tracker.Message
       ( -- * Announce
         -- ** Request
         Event(..)
       , AnnounceQuery(..)
       , renderAnnounceQuery
       , ParamParseFailure
       , parseAnnounceQuery

         -- ** Response
       , PeerList (..)
       , AnnounceInfo(..)
       , defaultNumWant
       , parseFailureStatus

         -- * Scrape
       , ScrapeQuery
       , ScrapeInfo(..)
       , Scrape
       )
       where

import Control.Applicative
import Control.Monad
import Data.Aeson (ToJSON(..), FromJSON(..))
import Data.Aeson.TH
import Data.BEncode as BE hiding (Result)
import Data.BEncode.BDict as BE
import Data.ByteString as BS
import Data.ByteString.Char8 as BC
import Data.Char as Char
import Data.Convertible
import Data.List as L
import Data.Map  as M
import Data.Maybe
import Data.Serialize as S hiding (Result)
import Data.Text (Text)
import Data.Text.Encoding
import Data.Typeable
import Data.Word
import Network
import Network.HTTP.Types.QueryLike
import Network.HTTP.Types.URI hiding (urlEncode)
import Network.HTTP.Types.Status
import Network.Socket
import Text.Read (readMaybe)

import Data.Torrent.InfoHash
import Data.Torrent.Progress
import Network.BitTorrent.Core.PeerId
import Network.BitTorrent.Core.PeerAddr


{-----------------------------------------------------------------------
--  Events
-----------------------------------------------------------------------}

-- | Events used to specify which kind of announce query is performed.
data Event = Started
             -- ^ For the first request: when a peer join the swarm.
           | Stopped
             -- ^ Sent when the peer is shutting down.
           | Completed
             -- ^ To be sent when the peer completes a download.
             deriving (Show, Read, Eq, Ord, Enum, Bounded, Typeable)

$(deriveJSON (L.map toLower . L.dropWhile isLower) ''Event)

-- | HTTP tracker protocol compatible encoding.
instance QueryValueLike Event where
  toQueryValue e = toQueryValue (Char.toLower x : xs)
    where
      (x : xs) = show e -- INVARIANT: this is always nonempty list

type EventId = Word32

-- | UDP tracker encoding event codes.
eventId :: Event -> EventId
eventId Completed = 1
eventId Started   = 2
eventId Stopped   = 3

-- TODO add Regular event
putEvent :: Putter (Maybe Event)
putEvent Nothing  = putWord32be 0
putEvent (Just e) = putWord32be (eventId e)

getEvent :: S.Get (Maybe Event)
getEvent = do
  eid <- getWord32be
  case eid of
    0 -> return Nothing
    1 -> return $ Just Completed
    2 -> return $ Just Started
    3 -> return $ Just Stopped
    _ -> fail "unknown event id"

{-----------------------------------------------------------------------
  Announce query
-----------------------------------------------------------------------}

-- | A tracker request is HTTP GET request; used to include metrics
--   from clients that help the tracker keep overall statistics about
--   the torrent. The most important, requests are used by the tracker
--   to keep track lists of active peer for a particular torrent.
--
data AnnounceQuery = AnnounceQuery
   {
     -- | Hash of info part of the torrent usually obtained from
     -- 'Torrent'.
     reqInfoHash   :: !InfoHash

     -- | ID of the peer doing request.
   , reqPeerId     :: !PeerId

     -- | Port to listen to for connections from other
     -- peers. Tracker should respond with this port when
     -- some /other/ peer request the tracker with the same info hash.
     -- Normally, this port is choosed from 'defaultPorts'.
   , reqPort       :: !PortNumber

     -- | Current progress of peer doing request.
   , reqProgress   :: !Progress

     -- | The peer IP. Needed only when client communicated with
     -- tracker throught a proxy.
   , reqIP         :: Maybe HostAddress

     -- | Number of peers that the peers wants to receive from. See
     -- note for 'defaultNumWant'.
   , reqNumWant    :: Maybe Int

     -- | If not specified, the request is regular periodic request.
   , reqEvent      :: Maybe Event
   } deriving (Show, Eq, Typeable)

$(deriveJSON (L.map toLower . L.dropWhile isLower) ''AnnounceQuery)

instance QueryValueLike PortNumber where
  toQueryValue = toQueryValue . show . fromEnum

instance QueryValueLike Word32 where
  toQueryValue = toQueryValue . show

instance QueryValueLike Int where
  toQueryValue = toQueryValue . show

-- | HTTP tracker protocol compatible encoding.
instance QueryLike AnnounceQuery where
  toQuery AnnounceQuery {..} =
      toQuery reqProgress ++
      [ ("info_hash", toQueryValue reqInfoHash)
      , ("peer_id"  , toQueryValue reqPeerId)
      , ("port"     , toQueryValue reqPort)
      , ("ip"       , toQueryValue reqIP)
      , ("numwant"  , toQueryValue reqNumWant)
      , ("event"    , toQueryValue reqEvent)
      ]

-- | UDP tracker protocol compatible encoding.
instance Serialize AnnounceQuery where
  put AnnounceQuery {..} = do
    put           reqInfoHash
    put           reqPeerId
    put           reqProgress
    putEvent      reqEvent
    putWord32be $ fromMaybe 0 reqIP
    putWord32be $ 0 -- TODO what the fuck is "key"?
    putWord32be $ fromIntegral $ fromMaybe (-1) reqNumWant

    put           reqPort

  get = do
    ih   <- get
    pid  <- get

    progress <- get

    ev   <- getEvent
    ip   <- getWord32be
--    key  <- getWord32be -- TODO
    want <- getWord32be

    port <- get

    return $ AnnounceQuery {
        reqInfoHash   = ih
      , reqPeerId     = pid
      , reqPort       = port
      , reqProgress   = progress
      , reqIP         = if ip == 0 then Nothing else Just ip
      , reqNumWant    = if want == -1 then Nothing
                        else Just (fromIntegral want)
      , reqEvent      = ev
      }

--renderAnnounceQueryBuilder :: AnnounceQuery -> BS.Builder
--renderAnnounceQueryBuilder = undefined

-- | Encode announce query and add it to the base tracker URL.
renderAnnounceQuery :: AnnounceQuery -> SimpleQuery
renderAnnounceQuery = filterMaybes . toQuery
  where
    filterMaybes :: [(a, Maybe b)] -> [(a, b)]
    filterMaybes = catMaybes . L.map f
      where
        f (_, Nothing) = Nothing
        f (a, Just b ) = Just (a, b)

data QueryParam
  = ParamInfoHash
  | ParamPeerId
  | ParamPort
  | ParamUploaded
  | ParamLeft
  | ParamDownloaded
  | ParamIP
  | ParamNumWant
  | ParamEvent
    deriving (Show, Eq, Ord, Enum)

data ParamParseFailure
  = Missing QueryParam               -- ^ param not found in query string;
  | Invalid QueryParam BS.ByteString -- ^ param present but not valid.
    deriving (Show, Eq)

paramName :: QueryParam -> BS.ByteString
paramName ParamInfoHash   = "info_hash"
paramName ParamPeerId     = "peer_id"
paramName ParamPort       = "port"
paramName ParamUploaded   = "uploaded"
paramName ParamLeft       = "left"
paramName ParamDownloaded = "downloaded"
paramName ParamIP         = "ip"
paramName ParamNumWant    = "numwant"
paramName ParamEvent      = "event"

class FromParam a where
  fromParam :: BS.ByteString -> Maybe a

instance FromParam InfoHash where
  fromParam = either (const Nothing) pure . safeConvert

instance FromParam PeerId where
  fromParam = either (const Nothing) pure . safeConvert

instance FromParam Word32 where
  fromParam = readMaybe . BC.unpack

instance FromParam Word64 where
  fromParam = readMaybe . BC.unpack

instance FromParam Int where
  fromParam = readMaybe . BC.unpack

instance FromParam PortNumber where
  fromParam bs = fromIntegral <$> (fromParam bs :: Maybe Word32)

instance FromParam Event where
  fromParam bs = do
    (x, xs) <- BC.uncons bs
    readMaybe $ BC.unpack $ BC.cons (Char.toUpper x) xs

type Result = Either ParamParseFailure

withError :: ParamParseFailure -> Maybe a -> Result a
withError e = maybe (Left e) Right

reqParam :: FromParam a => QueryParam -> SimpleQuery -> Result a
reqParam param xs = do
  val <- withError (Missing param) $ L.lookup (paramName param) xs
  withError (Invalid param val) (fromParam val)

optParam :: FromParam a => QueryParam -> SimpleQuery -> Result (Maybe a)
optParam param ps
  | Just x <- L.lookup (paramName param) ps
  = pure <$> withError (Invalid param x) (fromParam x)
  | otherwise = pure Nothing

parseProgress :: SimpleQuery -> Result Progress
parseProgress params = Progress
  <$> reqParam ParamDownloaded params
  <*> reqParam ParamLeft       params
  <*> reqParam ParamUploaded   params

-- | Parse announce request from a query string.
parseAnnounceQuery :: SimpleQuery -> Either ParamParseFailure AnnounceQuery
parseAnnounceQuery params = AnnounceQuery
  <$> reqParam ParamInfoHash params
  <*> reqParam ParamPeerId   params
  <*> reqParam ParamPort     params
  <*> parseProgress params
  <*> optParam ParamIP       params
  <*> optParam ParamNumWant  params
  <*> optParam ParamEvent    params

-- TODO add extension datatype
--type AnnounceRequest = ()

{-----------------------------------------------------------------------
--  Announce response
-----------------------------------------------------------------------}

-- | Tracker can return peer list in either compact(BEP23) or not
-- compact form.
--
--   For more info see: <http://www.bittorrent.org/beps/bep_0023.html>
--
data PeerList
  =        PeerList { getPeerList :: [PeerAddr] }
  | CompactPeerList { getPeerList :: [PeerAddr] }
    deriving (Show, Eq, Typeable)

instance ToJSON PeerList where
  toJSON      = toJSON . getPeerList

instance FromJSON PeerList where
  parseJSON v = PeerList <$> parseJSON v

putCompactPeerList :: S.Putter [PeerAddr]
putCompactPeerList = mapM_ put

getCompactPeerList :: S.Get [PeerAddr]
getCompactPeerList = many get

instance BEncode PeerList where
  toBEncode (PeerList        xs) = toBEncode xs
  toBEncode (CompactPeerList xs) = toBEncode $ runPut (putCompactPeerList xs)

  fromBEncode (BList    l ) = PeerList        <$> fromBEncode (BList l)
  fromBEncode (BString  s ) = CompactPeerList <$> runGet getCompactPeerList s
  fromBEncode  _            = decodingError "Peer list"

-- | The tracker response includes a peer list that helps the client
--   participate in the torrent. The most important is 'respPeer' list
--   used to join the swarm.
--
data AnnounceInfo =
     Failure !Text -- ^ Failure reason in human readable form.
   | AnnounceInfo {
       -- | Number of peers completed the torrent. (seeders)
       respComplete    :: !(Maybe Int)

       -- | Number of peers downloading the torrent. (leechers)
     , respIncomplete  :: !(Maybe Int)

       -- | Recommended interval to wait between requests, in seconds.
     , respInterval    :: !Int

       -- | Minimal amount of time between requests, in seconds. A
       -- peer /should/ make timeout with at least 'respMinInterval'
       -- value, otherwise tracker might not respond. If not specified
       -- the same applies to 'respInterval'.
     , respMinInterval :: !(Maybe Int)

       -- | Peers that must be contacted.
     , respPeers       :: !PeerList

       -- | Human readable warning.
     , respWarning     :: !(Maybe Text)
     } deriving (Show, Typeable)

$(deriveJSON (L.map toLower . L.dropWhile isLower) ''AnnounceInfo)

-- | HTTP tracker protocol compatible encoding.
instance BEncode AnnounceInfo where
  toBEncode (Failure t)        = toDict $
       "failure reason" .=! t
    .: endDict

  toBEncode  AnnounceInfo {..} = toDict $
       "complete"        .=? respComplete
    .: "incomplete"      .=? respIncomplete
    .: "interval"        .=! respInterval
    .: "min interval"    .=? respMinInterval
    .: "peers"           .=! respPeers
    .: "warning message" .=? respWarning
    .: endDict

  fromBEncode (BDict d)
    | Just t <- BE.lookup "failure reason" d = Failure <$> fromBEncode t
    | otherwise = (`fromDict` (BDict d)) $ do
      AnnounceInfo
        <$>? "complete"
        <*>? "incomplete"
        <*>! "interval"
        <*>? "min interval"
        <*>! "peers"
        <*>? "warning message"
  fromBEncode _ = decodingError "Announce info"

-- | UDP tracker protocol compatible encoding.
instance Serialize AnnounceInfo where
  put (Failure msg) = put $ encodeUtf8 msg
  put  AnnounceInfo {..} = do
    putWord32be $ fromIntegral respInterval
    putWord32be $ fromIntegral $ fromMaybe 0 respIncomplete
    putWord32be $ fromIntegral $ fromMaybe 0 respComplete
    forM_ (getPeerList respPeers) put

  get = do
    interval <- getWord32be
    leechers <- getWord32be
    seeders  <- getWord32be
    peers    <- many get

    return $ AnnounceInfo {
        respWarning     = Nothing
      , respInterval    = fromIntegral interval
      , respMinInterval = Nothing
      , respIncomplete  = Just $ fromIntegral leechers
      , respComplete    = Just $ fromIntegral seeders
      , respPeers       = PeerList peers
      }

-- | Above 25, new peers are highly unlikely to increase download
--   speed.  Even 30 peers is /plenty/, the official client version 3
--   in fact only actively forms new connections if it has less than
--   30 peers and will refuse connections if it has 55.
--
--   <https://wiki.theory.org/BitTorrent_Tracker_Protocol#Basic_Tracker_Announce_Request>
--
defaultNumWant :: Int
defaultNumWant = 50

missingOffset :: Int
missingOffset = 101

invalidOffset :: Int
invalidOffset = 150

-- | Get HTTP response error code from a announce params parse
-- failure.
--
--   For more info see:
--   <https://wiki.theory.org/BitTorrent_Tracker_Protocol#Response_Codes>
--
parseFailureCode :: ParamParseFailure -> Int
parseFailureCode (Missing param  ) = missingOffset + fromEnum param
parseFailureCode (Invalid param _) = invalidOffset + fromEnum param

-- | Human readable message
parseFailureMessage :: ParamParseFailure -> BS.ByteString
parseFailureMessage e = BS.concat $ case e of
  Missing p   -> ["Missing parameter: ", paramName p]
  Invalid p v -> ["Invalid parameter: ", paramName p, " = ", v]

parseFailureStatus :: ParamParseFailure -> Status
parseFailureStatus = mkStatus <$> parseFailureCode <*> parseFailureMessage

--type AnnounceResponse = Either Status AnnounceInfo -- TODO
--type TrackerResponse = () -- TODO

{-----------------------------------------------------------------------
  Scrape message
-----------------------------------------------------------------------}

type ScrapeQuery = [InfoHash]

-- | Overall information about particular torrent.
data ScrapeInfo = ScrapeInfo {
    -- | Number of seeders - peers with the entire file.
    siComplete   :: {-# UNPACK #-} !Int

    -- | Total number of times the tracker has registered a completion.
  , siDownloaded :: {-# UNPACK #-} !Int

    -- | Number of leechers.
  , siIncomplete :: {-# UNPACK #-} !Int

    -- | Name of the torrent file, as specified by the "name"
    --   file in the info section of the .torrent file.
  , siName       :: !(Maybe Text)
  } deriving (Show, Eq, Typeable)

$(deriveJSON (L.map toLower . L.dropWhile isLower) ''ScrapeInfo)

-- TODO hash map
-- | Scrape info about a set of torrents.
type Scrape = Map InfoHash ScrapeInfo

-- | HTTP tracker protocol compatible encoding.
instance BEncode ScrapeInfo where
  toBEncode ScrapeInfo {..} = toDict $
       "complete"   .=! siComplete
    .: "downloaded" .=! siDownloaded
    .: "incomplete" .=! siIncomplete
    .: "name"       .=? siName
    .: endDict

  fromBEncode = fromDict $ do
    ScrapeInfo <$>! "complete"
               <*>! "downloaded"
               <*>! "incomplete"
               <*>? "name"

-- | UDP tracker protocol compatible encoding.
instance Serialize ScrapeInfo where
  put ScrapeInfo {..} = do
    putWord32be $ fromIntegral siComplete
    putWord32be $ fromIntegral siDownloaded
    putWord32be $ fromIntegral siIncomplete

  get = do
    seeders   <- getWord32be
    downTimes <- getWord32be
    leechers  <- getWord32be

    return $ ScrapeInfo {
        siComplete   = fromIntegral seeders
      , siDownloaded = fromIntegral downTimes
      , siIncomplete = fromIntegral leechers
      , siName       = Nothing
      }