+ Add naive selector detection.

1 files changed, 42 insertions, 14 deletions

diff --git a/src/Network/BitTorrent/PeerWire/Selection.hs b/src/Network/BitTorrent/PeerWire/Selection.hs
index 83ab8311..9d154613 100644
--- a/src/Network/BitTorrent/PeerWire/Selection.hs
+++ b/src/Network/BitTorrent/PeerWire/Selection.hs
@@ -10,7 +10,7 @@
 --   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.
+--     * Random first - at the start.
 --
 --     * Rarest first selection - performed to avoid situation when
 --     rarest piece is unaccessible.
@@ -19,28 +19,59 @@
 --     the subpieces of the content.
 --
 --   Note that BitTorrent applies the strict priority policy for
---   _subpiece_ or _blocks_ selection.
+--   /subpiece/ or /blocks/ selection.
 --
 module Network.BitTorrent.PeerWire.Selection
        ( Selector
+
+       -- * Construction
+       , selector, strategyClass
+
+       -- * Strategies
        , strictFirst, strictLast
        , rarestFirst, randomFirst, endGame
-
-       , autoSelector
        ) where
 
 import Data.Bitfield
 import Network.BitTorrent.PeerWire.Block
-import Network.BitTorrent.PeerWire.Message
 
 
-
-type Selector =  Bitfield      -- ^ Indices of client "have" pieces.
-             ->  Bitfield      -- ^ Indices of peer "have" pieces.
-             -> [Bitfield]     -- ^ Indices of other peers "have" pieces.
+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.
 
+type PieceThreshold = Int
+
+selector :: Selector       -- ^ Selector to use at the start.
+         -> PieceThreshold
+         -> Selector       -- ^ Selector to use after the client have the C pieces.
+         -> Selector       -- ^ Selector that changes behaviour based on completeness.
+selector start pt ready   h a xs =
+  case strategyClass pt h of
+    SCBeginning -> start h a xs
+    SCReady     -> ready h a xs
+    SCEnd       -> endGame h a xs
+
+data StartegyClass
+  = SCBeginning
+  | SCReady
+  | SCEnd
+    deriving (Show, Eq, Ord, Enum, Bounded)
+
+endThreshold :: PieceThreshold
+endThreshold = 1
+
+strategyClass :: PieceThreshold -> Bitfield -> StartegyClass
+strategyClass pt = classify . completeness
+  where
+    classify (have, total)
+      | have < pt                   = SCBeginning
+      | total - have > endThreshold = SCReady
+      | otherwise                   = SCEnd
+
+
 -- | Select the first available piece.
 strictFirst :: Selector
 strictFirst h a _ = findMin (difference a h)
@@ -56,15 +87,12 @@ rarestFirst h a xs = rarest (frequencies (map (intersection want) xs))
     want = difference h a
     rarest = Just . head
 
--- | In general random first is faster than rarest first strategy but
+-- | In average random first is faster than rarest first strategy but
 --    only if all pieces are available.
-randomFirst :: IO Selector
+randomFirst :: Selector
 randomFirst = do
 --  randomIO
   error "randomFirst"
 
 endGame :: Selector
 endGame = strictLast
-
-autoSelector :: Selector
-autoSelector = undefined