add scrapeURL implementation

1 files changed, 57 insertions, 3 deletions

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