1 files changed, 106 insertions, 9 deletions

diff --git a/src/Network/BitTorrent/Tracker.hs b/src/Network/BitTorrent/Tracker.hs
index 04a7b43e..275b5422 100644
--- a/src/Network/BitTorrent/Tracker.hs
+++ b/src/Network/BitTorrent/Tracker.hs
@@ -6,16 +6,18 @@
 --   Portability :  non-portable
 --
 --   This module provides high level API for peer->tracker
---   communication.
+--   communication. Tracker is used to discover other peers in the
+--   network.
 --
+--   By convention most trackers support another form of request,
+--   which queries the state of a given torrent (or all torrents) that
+--   the tracker is managing. This module also provides a way to
+--   easily request scrape info for a particular torrent list.
+--
+{-# LANGUAGE OverloadedStrings #-}
 {-# LANGUAGE RecordWildCards #-}
 module Network.BitTorrent.Tracker
-       ( module Network.BitTorrent.Tracker.Scrape
-
-       , withTracker, completedReq
-
-         -- * Progress
-       , Progress(..), startProgress
+       ( withTracker, completedReq
 
          -- * Connection
        , TConnection(..), tconnection
@@ -27,6 +29,11 @@ module Network.BitTorrent.Tracker
 
          -- * Re-export
        , defaultPorts
+
+         -- * Scrape
+       , ScrapeInfo(..), Scrape
+       , scrapeURL
+       , scrape, scrapeOne
        ) where
 
 import Control.Applicative
@@ -34,15 +41,23 @@ import Control.Concurrent
 import Control.Concurrent.STM
 import Control.Exception
 import Control.Monad
+import Data.BEncode
+import           Data.ByteString (ByteString)
+import qualified Data.ByteString as B
+import qualified Data.ByteString.Char8 as BC
+import           Data.Map (Map)
+import qualified Data.Map as M
+import Data.Monoid
 import Data.IORef
-import Data.Torrent
+
 import Network
+import Network.HTTP
 import Network.URI
 
+import Data.Torrent
 import Network.BitTorrent.Internal
 import Network.BitTorrent.Peer
 import Network.BitTorrent.Tracker.Protocol
-import Network.BitTorrent.Tracker.Scrape
 
 
 -- | 'TConnection' (shorthand for Tracker session) combines tracker request
@@ -179,3 +194,85 @@ withTracker initProgress conn action = bracket start end (action . fst)
       killThread tid
       pr <- getProgress se
       askTracker $ stoppedReq conn pr
+
+
+
+-- | Information about particular torrent.
+data ScrapeInfo = ScrapeInfo {
+    siComplete   :: Int
+    -- ^ Number of seeders - peers with the entire file.
+  , siDownloaded :: Int
+    -- ^ Total number of times the tracker has registered a completion.
+  , siIncomplete :: Int
+    -- ^ Number of leechers.
+  , siName       :: Maybe ByteString
+    -- ^ Name of the torrent file, as specified by the "name"
+    --   file in the info section of the .torrent file.
+  } deriving (Show, Eq)
+
+-- | Scrape info about a set of torrents.
+type Scrape = Map InfoHash ScrapeInfo
+
+instance BEncodable ScrapeInfo where
+  toBEncode si = fromAssocs
+    [ "complete"   -->  siComplete si
+    , "downloaded" -->  siDownloaded si
+    , "incomplete" -->  siIncomplete si
+    , "name"       -->? siName si
+    ]
+
+  fromBEncode (BDict d) =
+    ScrapeInfo <$> d >--  "complete"
+               <*> d >--  "downloaded"
+               <*> d >--  "incomplete"
+               <*> d >--? "name"
+  fromBEncode _ = decodingError "ScrapeInfo"
+
+-- | Trying to convert /announce/ URL to /scrape/ URL. If 'scrapeURL'
+--   gives 'Nothing' then tracker do not support scraping. The info hash
+--   list is used to restrict the tracker's report to that particular
+--   torrents. Note that scrapping of multiple torrents may not be
+--   supported. (Even if scrapping convention is supported)
+--
+scrapeURL :: URI -> [InfoHash] -> Maybe URI
+scrapeURL uri ihs = do
+  newPath <- replace (BC.pack (uriPath uri))
+  let newURI = uri { uriPath = BC.unpack newPath }
+  return (foldl addHashToURI newURI ihs)
+ where
+    replace :: ByteString -> Maybe ByteString
+    replace p
+      | ps <- BC.splitWith (== '/') p
+      , "announce" `B.isPrefixOf` last ps
+      = let newSuff = "scrape" <> B.drop (B.length "announce") (last ps)
+        in Just (B.intercalate "/" (init ps ++ [newSuff]))
+      | otherwise = Nothing
+
+
+-- | For each 'InfoHash' of torrents request scrape info from the tracker.
+--   However if the info hash list is 'null', the tracker should list
+--   all available torrents.
+--   Note that the 'URI' should be /announce/ URI, not /scrape/ URI.
+--
+scrape :: URI                -- ^ Announce 'URI'.
+       -> [InfoHash]         -- ^ Torrents to be scrapped.
+       -> IO (Result Scrape) -- ^ 'ScrapeInfo' for each torrent.
+scrape announce ihs
+  | Just uri<- scrapeURL announce ihs = do
+    rawResp  <- simpleHTTP (Request uri GET [] "")
+    respBody <- getResponseBody rawResp
+    return (decoded (BC.pack respBody))
+
+  | otherwise = return (Left "Tracker do not support scraping")
+
+-- | More particular version of 'scrape', just for one torrent.
+--
+scrapeOne :: URI                     -- ^ Announce 'URI'
+          -> InfoHash                -- ^ Hash of the torrent info.
+          -> IO (Result ScrapeInfo)  -- ^ 'ScrapeInfo' for the torrent.
+scrapeOne uri ih = extract <$> scrape uri [ih]
+  where
+    extract (Right m)
+      | Just s <- M.lookup ih m = Right s
+      | otherwise = Left "unable to find info hash in response dict"
+    extract (Left e) = Left e