4 files changed, 79 insertions, 7 deletions

diff --git a/bench/Main.hs b/bench/Main.hs
index 94341c84..e4f756a3 100644
--- a/bench/Main.hs
+++ b/bench/Main.hs
@@ -48,19 +48,25 @@ bitfieldInter n = BT.empty n `intersection` BT.empty n
 bitfieldUnion :: Int -> Bitfield
 bitfieldUnion n = BT.empty n `union` BT.empty n
 
+selectionStrictFirst :: Int -> Maybe Int
+selectionStrictFirst n = strictFirst (BT.empty n) (BT.empty n) []
 
 main :: IO ()
 main = do
   let datas = replicate 10000 (Request (BlockIx 0 0 0))
+  let m = 1024 * 1024
 
   defaultMain
     [ datas `deepseq` bench "message/encode"   $ nf encodeMessages datas
     , let binary = encodeMessages datas in
       binary `deepseq` bench "message/decode"  $ nf decodeMessages binary
 
-    , bench "bitfield/min"          $ nf bitfieldMin   10000000
-    , bench "bitfield/max"          $ nf bitfieldMax   10000000
-    , bench "bitfield/difference"   $ nf bitfieldDiff  10000000
-    , bench "bitfield/intersection" $ nf bitfieldInter 10000000
-    , bench "bitfield/union"        $ nf bitfieldUnion 10000000
+      -- ~ 256KiB * 10M = 2.5TiB
+    , bench "bitfield/min"          $ nf bitfieldMin   (10 * m)
+    , bench "bitfield/max"          $ nf bitfieldMax   (10 * m)
+    , bench "bitfield/difference"   $ nf bitfieldDiff  (10 * m)
+    , bench "bitfield/intersection" $ nf bitfieldInter (10 * m)
+    , bench "bitfield/union"        $ nf bitfieldUnion (10 * m)
+
+    , bench "selection/strictFirst" $ nf selectionStrictFirst  (10 * m)
     ]
\ No newline at end of file
diff --git a/network-bittorrent.cabal b/network-bittorrent.cabal
index 02074287..e3f60869 100644
--- a/network-bittorrent.cabal
+++ b/network-bittorrent.cabal
@@ -36,8 +36,9 @@ library
                      , Network.BitTorrent.Tracker.Scrape
 
                      , Network.BitTorrent.PeerWire
-                     , Network.BitTorrent.PeerWire.Bitfield
                      , Network.BitTorrent.PeerWire.Block
+                     , Network.BitTorrent.PeerWire.Bitfield
+                     , Network.BitTorrent.PeerWire.Selection
                      , Network.BitTorrent.PeerWire.Message
                      , Network.BitTorrent.PeerWire.Handshake
 
diff --git a/src/Network/BitTorrent/PeerWire.hs b/src/Network/BitTorrent/PeerWire.hs
index db9287d8..6d8ff156 100644
--- a/src/Network/BitTorrent/PeerWire.hs
+++ b/src/Network/BitTorrent/PeerWire.hs
@@ -8,7 +8,8 @@
 {-# LANGUAGE DoAndIfThenElse #-}
 module Network.BitTorrent.PeerWire (module PW) where
 
-import Network.BitTorrent.PeerWire.Bitfield as PW
 import Network.BitTorrent.PeerWire.Block as PW
+import Network.BitTorrent.PeerWire.Bitfield as PW
+import Network.BitTorrent.PeerWire.Selection as PW
 import Network.BitTorrent.PeerWire.Message as PW
 import Network.BitTorrent.PeerWire.Handshake as PW
diff --git a/src/Network/BitTorrent/PeerWire/Selection.hs b/src/Network/BitTorrent/PeerWire/Selection.hs
new file mode 100644
index 00000000..04049812
--- /dev/null
+++ b/src/Network/BitTorrent/PeerWire/Selection.hs
@@ -0,0 +1,64 @@
+-- TODO tests
+-- |
+--   Copyright   :  (c) Sam T. 2013
+--   License     :  MIT
+--   Maintainer  :  pxqr.sta@gmail.com
+--   Stability   :  experimental
+--   Portability :  portable
+--
+--   This module provides commonly used piece seletion algorithms
+--   which used to find out which one next piece to download.
+--   Selectors considered to be used in the following order:
+--
+--     * Random first or rarest first selection - at the start.
+--
+--     * Rarest first selection - performed to avoid situation when
+--     rarest piece is unaccessible.
+--
+--     * _End game_ seletion - performed after a peer has requested all
+--     the subpieces of the content.
+--
+--   Note that BitTorrent applies the strict priority policy for
+--   _subpiece_ or _blocks_ selection.
+--
+module Network.BitTorrent.PeerWire.Selection
+       ( Selector
+       , strictFirst, rarestFirst, randomFirst, endGame, autoSelector
+       ) where
+
+import Network.BitTorrent.PeerWire.Block
+import Network.BitTorrent.PeerWire.Message
+import Network.BitTorrent.PeerWire.Bitfield
+
+
+type Selector =  Bitfield      -- ^ Indices of client "have" pieces.
+             ->  Bitfield      -- ^ Indices of peer "have" pieces.
+             -> [Bitfield]     -- ^ Indices of other peers "have" pieces.
+             -> Maybe PieceIx  -- ^ Zero-based index of piece to request
+                               --   to, if any.
+
+-- | Select the first available piece.
+strictFirst :: Selector
+strictFirst h a _ = findMin (difference a h)
+
+
+-- |
+rarestFirst :: Selector
+rarestFirst h a xs = error "rarestFirst"
+    -- rarest (frequencies (map (intersection want) xs))
+  where
+    want = difference h a
+    rarest = undefined
+
+-- | In general random first is faster than rarest first strategy but
+--    only if all pieces are available.
+randomFirst :: IO Selector
+randomFirst = do
+--  randomIO
+  error "randomFirst"
+
+endGame :: Selector
+endGame = undefined
+
+autoSelector :: Selector
+autoSelector = undefined