From 2749007675a6ff28979fa793b48ffe910635c708 Mon Sep 17 00:00:00 2001
From: Sam Truzjan <pxqr.sta@gmail.com>
Date: Sun, 1 Dec 2013 14:32:05 +0400
Subject: Add a few thoughts about piece management

---
 src/Network/BitTorrent/Exchange/Assembler.hs | 82 ++++++++++++++++++++++++++++
 1 file changed, 82 insertions(+)
 create mode 100644 src/Network/BitTorrent/Exchange/Assembler.hs

diff --git a/src/Network/BitTorrent/Exchange/Assembler.hs b/src/Network/BitTorrent/Exchange/Assembler.hs
new file mode 100644
index 00000000..a490d2dc
--- /dev/null
+++ b/src/Network/BitTorrent/Exchange/Assembler.hs
@@ -0,0 +1,82 @@
+module Network.BitTorrent.Exchange.Assembler
+       ( Assembler
+       , insert
+
+         -- * Query
+       , pendingPieces
+       , completeBlocks
+       , incompleteBlocks
+       ) where
+
+import Data.IntMap.Strict as IM
+import Data.Maybe
+import Data.Torrent.Piece
+import Data.Torrent.Block
+
+type PieceMap = IntMap
+
+-- TODO move to Data.Torrent.Piece ?
+-- assembler is also a block selector?
+data Assembler a = Assembler
+  { piecePending :: PieceMap [Block a]
+  , pieceInfo    :: PieceInfo
+  }
+
+
+data Result a
+  = Assembled (Piece a)
+  | Failed     PieceIx
+
+-- | You should check if a returned by peer block is actually have
+-- been requested and in-flight. This is needed to avoid "I send
+-- random corrupted block" attacks.
+insert :: Block a -> Assembler a -> (Assembler a, Maybe (Result a))
+insert Block {..} Assembler {..} = undefined
+--  updateWithKey bixPiece
+
+pendingPieces :: Assembler a -> [PieceIx]
+pendingPieces Assembler {..} = keys piecePending
+
+completeBlocks :: Assembler a -> PieceIx -> [Block a]
+completeBlocks Assembler {..} pix = fromMaybe [] $ IM.lookup pix piecePending
+
+incompleteBlocks :: Assembler a -> PieceIx -> [BlockIx]
+incompleteBlocks = undefined
+
+-- TODO merge BlockSelector with Assembler?
+data BlockSelector a = BlockSelector
+  { assembler   :: Assembler a -- we do not select already transfered blocks
+  , inflightSet :: Set BlockIx -- we do not select blocks in flight
+  }
+
+insert :: BlockSelector -> (BlockSelector a, Maybe (Result a))
+insert = undefined
+
+
+data StorageAdapter = StorageAdapter
+  { bitfield :: Bitfield
+  , requestQ :: Queue PieceIx
+  }
+-- we do select 'incompleteBlocks' that is not in flight
+
+--assembler :: Assembler -> Conduit (Block a) (Result a)
+--assembler = undefined
+
+-- by priority
+--   foreign request queue (max queue size)
+--   assembler block information (max queue size)
+--   selection strategies (bitfields)
+
+-- when in flight queue is full we do not use selector
+--   in flight queue information (max queue size)
+
+-- piece select is used when
+data PieceSelector = Selector
+  { forceQueue        :: TVar (Queue PieceIx)
+  , forcePendingQueue :: TVar (Queue PieceIx)
+  , assembler :: TVar Assembler
+  , strategy  :: Bool
+  }
+
+select :: Selector -> (Selector, PieceIx)
+select = undefined
\ No newline at end of file
-- 
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