3 files changed, 84 insertions, 20 deletions

diff --git a/src/Data/Torrent/InfoHash.hs b/src/Data/Torrent/InfoHash.hs
index 448e9a5a..b2ca44ee 100644
--- a/src/Data/Torrent/InfoHash.hs
+++ b/src/Data/Torrent/InfoHash.hs
@@ -1,5 +1,6 @@
 module Data.Torrent.InfoHash
        ( InfoHash (getInfoHash)
+       , addHashToURI
 
          -- ^ Construction
        , hash, hashlazy
@@ -10,6 +11,8 @@ module Data.Torrent.InfoHash
 
 import Control.Applicative
 import Data.Foldable
+import Data.List as L
+import Data.Char
 import           Data.ByteString (ByteString)
 import qualified Data.ByteString as B
 import qualified Data.ByteString.Char8 as BC
@@ -18,6 +21,9 @@ import qualified Data.ByteString.Builder.Prim as B
 import qualified Data.ByteString.Lazy as Lazy
 import Data.Serialize
 import qualified Crypto.Hash.SHA1 as C
+import Network.URI
+import Numeric
+
 
 -- | Exactly 20 bytes long SHA1 hash.
 newtype InfoHash = InfoHash { getInfoHash :: ByteString }
@@ -39,3 +45,21 @@ hashlazy = InfoHash . C.hashlazy
 ppHex :: InfoHash -> ByteString
 ppHex = Lazy.toStrict . B.toLazyByteString .
         foldMap (B.primFixed B.word8HexFixed) . B.unpack . getInfoHash
+
+addHashToURI :: URI -> InfoHash -> URI
+addHashToURI uri s = uri {
+    uriQuery = uriQuery uri ++ mkPref (uriQuery uri) ++
+               "info_hash=" ++ rfc1738Encode (BC.unpack (getInfoHash s))
+  }
+  where
+    mkPref [] = "?"
+    mkPref ('?' : _) = "&"
+    mkPref _ = error "addHashToURI"
+
+    rfc1738Encode = L.concatMap (\c -> if unreservedS c then [c] else encodeHex c)
+      where
+        unreservedS = (`L.elem` chars)
+        chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_./"
+        encodeHex c = '%' : pHex c
+        pHex c = let p = (showHex . ord $ c) ""
+                 in if L.length p == 1 then '0' : p else p
diff --git a/src/Network/Torrent/Tracker.hs b/src/Network/Torrent/Tracker.hs
index 5faa1dd9..ef2413f6 100644
--- a/src/Network/Torrent/Tracker.hs
+++ b/src/Network/Torrent/Tracker.hs
@@ -30,7 +30,6 @@ import Network.HTTP
 import Network.URI
 import Network.Torrent.PeerID
 
-import Numeric
 
 data Peer = Peer {
       peerID   :: Maybe PeerID
@@ -150,22 +149,9 @@ instance URLEncode TRequest where
     where s :: String -> String;  s = id; {-# INLINE s #-}
 
 encodeRequest :: TRequest -> URI
-encodeRequest req = URL.urlEncode req `addToURI` reqAnnounce req
-                    `addHash` BC.unpack (getInfoHash (reqInfoHash req))
-  where
-    addHash :: URI -> String -> URI
-    addHash uri s = uri { uriQuery = uriQuery uri ++  "&info_hash=" ++ rfc1738Encode s }
-
-    rfc1738Encode :: String -> String
-    rfc1738Encode = L.concatMap (\c -> if unreserved c then [c] else encode c)
-            where
-              unreserved = (`L.elem` chars)
-              chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_./"
-              encode :: Char -> String
-              encode c = '%' : pHex c
-              pHex c =
-                let p = (showHex . ord $ c) ""
-                in if L.length p == 1 then '0' : p else p
+encodeRequest req = URL.urlEncode req
+                    `addToURI`      reqAnnounce req
+                    `addHashToURI`  reqInfoHash req
 
 
 -- | Ports typically reserved for bittorrent.
diff --git a/src/Network/Torrent/Tracker/Scrape.hs b/src/Network/Torrent/Tracker/Scrape.hs
index 2d1dec07..6bfb488f 100644
--- a/src/Network/Torrent/Tracker/Scrape.hs
+++ b/src/Network/Torrent/Tracker/Scrape.hs
@@ -1,8 +1,62 @@
+{-# LANGUAGE OverloadedStrings #-}
 module Network.Torrent.Tracker.Scrape
-       (
+       ( ScrapeInfo(..), Scrape
+       , scrapeURL
        ) where
 
+import Control.Applicative
+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.Torrent.InfoHash
 import Network.URI
 
-scrapeURL :: URI -> Maybe URI
-scrapeURL = undefined
+data ScrapeInfo = ScrapeInfo {
+    siComplete   :: Int              -- ^ Number of seeders.
+  , siDownloaded :: Int
+    -- ^ Total number of times the tracker has registered a completion.
+  , siIncomplete :: Int              -- ^ Number of leechers
+  , siName       :: Maybe ByteString -- ^
+  } deriving (Show, Eq)
+
+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"
+
+-- TODO: encode info hash
+-- | 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