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path: root/src/Network/BitTorrent/DHT/Search.hs
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{-# LANGUAGE CPP #-}
{-# LANGUAGE PatternSynonyms #-}
{-# LANGUAGE RecordWildCards #-}
{-# LANGUAGE ScopedTypeVariables #-}
{-# LANGUAGE FlexibleContexts #-}
{-# LANGUAGE LambdaCase #-}
module Network.BitTorrent.DHT.Search where

import Control.Concurrent.Tasks
import Control.Concurrent.STM
import Control.Exception
import Control.Monad
import Data.Bool
import Data.Function
import Data.List
import qualified Data.Map.Strict     as Map
         ;import Data.Map.Strict     (Map)
import Data.Maybe
import qualified Data.Set            as Set
         ;import Data.Set            (Set)
import System.IO
import System.IO.Error

import qualified Data.MinMaxPSQ   as MM
         ;import Data.MinMaxPSQ   (MinMaxPSQ, MinMaxPSQ')
import qualified Data.Wrapper.PSQ as PSQ
         ;import Data.Wrapper.PSQ (pattern (:->), Binding, PSQ, PSQKey)
import Network.Address hiding (NodeId)
import Network.DHT.Routing as R
#ifdef THREAD_DEBUG
import Control.Concurrent.Lifted.Instrument
#else
import Control.Concurrent.Lifted
import GHC.Conc                  (labelThread)
#endif

data Search nid addr tok ni r = Search
    { searchSpace        :: KademliaSpace nid ni
    , searchNodeAddress  :: ni -> addr
    , searchQuery        :: nid -> ni -> IO (Maybe ([ni], [r], tok))
    }

data SearchState nid addr tok ni r = SearchState
    {-
    { searchParams :: Search nid addr ni r

    , searchTarget       :: nid
      -- | This action will be performed at least once on each search result.
      -- It may be invoked multiple times since different nodes may report the
      -- same result.  If the action returns 'False', the search will be
      -- aborted, otherwise it will continue until it is decided that we've
      -- asked the closest K nodes to the target.
    , searchResult      :: r -> STM Bool

    -}

    { -- | The number of pending queries.  Incremented before any query is sent
      -- and decremented when we get a reply.
      searchPendingCount :: TVar Int
      -- | Nodes scheduled to be queried.
    , searchQueued       :: TVar (MinMaxPSQ ni nid)
      -- | The nearest K nodes that issued a reply.
    , searchInformant    :: TVar (MinMaxPSQ' ni nid tok)
      -- | This tracks already-queried addresses so we avoid bothering them
      -- again. XXX: We could probably keep only the pending queries in this
      -- set.  It also can be a bounded 'MinMaxPSQ', although searchAlpha
      -- should limit the number of outstanding queries.
    , searchVisited      :: TVar (Set addr)
    }

newSearch :: ( Ord addr
             , PSQKey nid
             , PSQKey ni
             ) =>
             {-
             KademliaSpace nid ni
             -> (ni -> addr)
             -> (ni -> IO ([ni], [r])) -- the query action.
             -> (r -> STM Bool)        -- receives search results.
             -> nid                    -- target of search
             -}
             Search nid addr tok ni r
             -> nid
             -> [ni]                   -- Initial nodes to query.
             -> STM (SearchState nid addr tok ni r)
newSearch (Search space nAddr qry) target ns = do
    c <- newTVar 0
    q <- newTVar $ MM.fromList
                 $ map (\n -> n :-> kademliaXor space target (kademliaLocation space n))
                 $ ns
    i <- newTVar MM.empty
    v <- newTVar Set.empty
    return -- (Search space nAddr qry) , r , target
           ( SearchState c q i v )

searchAlpha :: Int
searchAlpha = 8

searchK :: Int
searchK = 8

sendQuery :: forall addr nid tok ni r.
            ( Ord addr
            , PSQKey nid
            , PSQKey ni
            , Show nid
            ) =>
            Search nid addr tok ni r
            -> nid
            -> (r -> STM Bool)
            -> SearchState nid addr tok ni r
            -> Binding ni nid
            -> IO ()
sendQuery Search{..} searchTarget searchResult sch@SearchState{..} (ni :-> d) = do
    myThreadId >>= flip labelThread ("searchQuery." ++ show searchTarget)
    reply <- searchQuery searchTarget ni `catchIOError` const (return Nothing)
    -- (ns,rs)
    let tok = error "TODO: token"
    atomically $ do
        modifyTVar searchPendingCount pred
        maybe (return ()) go reply
 where
    go (ns,rs,tok) = do
        vs <- readTVar searchVisited
        -- We only queue a node if it is not yet visited
        let insertFoundNode :: ni
                           -> MinMaxPSQ ni nid
                           -> MinMaxPSQ ni nid
            insertFoundNode n q
             | searchNodeAddress n `Set.member` vs
                         = q
             | otherwise = MM.insertTake searchK n ( kademliaXor searchSpace searchTarget
                                                     $ kademliaLocation searchSpace n )
                                                   q
        modifyTVar searchQueued    $ \q -> foldr insertFoundNode q ns
        modifyTVar searchInformant $ MM.insertTake' searchK ni tok d
        flip fix rs $ \loop -> \case
            r:rs' -> do
                wanting <- searchResult r
                if wanting then loop rs'
                           else searchCancel sch
            [] -> return ()


searchIsFinished :: ( PSQKey nid
                    , PSQKey ni
                    ) => SearchState nid addr tok ni r -> STM Bool
searchIsFinished SearchState{ ..} = do
    q <- readTVar searchQueued
    cnt <- readTVar searchPendingCount
    informants <- readTVar searchInformant
    return $ cnt == 0
             && ( MM.null q
                  || ( MM.size informants >= searchK
                       && ( PSQ.prio (fromJust $ MM.findMax informants)
                            <= PSQ.prio (fromJust $ MM.findMin q))))

searchCancel :: SearchState nid addr tok ni r -> STM ()
searchCancel SearchState{..} = do
    writeTVar searchPendingCount 0
    writeTVar searchQueued MM.empty

search ::
    ( Ord r
    , Ord addr
    , PSQKey nid
    , PSQKey ni
    , Show nid
    ) => Search nid addr tok ni r -> R.BucketList ni -> nid -> (r -> STM Bool) -> IO (SearchState nid addr tok ni r)
search sch buckets target result = do
    let ns = R.kclosest (searchSpace sch) searchK target buckets
    st <- atomically $ newSearch sch target ns
    fork $ searchLoop sch target result st
    return st

searchLoop sch@Search{..} target result s@SearchState{..} = do
    myThreadId >>= flip labelThread ("search."++show target)
    withTaskGroup ("search.g."++show target) searchAlpha $ \g -> fix $ \again -> do
        join $ atomically $ do
            cnt <- readTVar $ searchPendingCount
            informants <- readTVar searchInformant
            found <- MM.minView <$> readTVar searchQueued
            case found of
                Just (ni :-> d, q)
                  | -- If there's fewer than /k/ informants and there's any
                    -- node we haven't yet got a response from.
                    (MM.size informants < searchK) && (cnt > 0 || not (MM.null q))
                    -- Or there's no informants yet at all.
                    || MM.null informants
                    -- Or if the closest scheduled node is nearer than the
                    -- nearest /k/ informants.
                    || (d < PSQ.prio (fromJust $ MM.findMax informants))
                  -> -- Then the search continues, send a query.
                     do writeTVar searchQueued q
                        modifyTVar searchVisited $ Set.insert (searchNodeAddress ni)
                        modifyTVar searchPendingCount succ
                        return $ do
                            forkTask g
                                     "searchQuery"
                                     $ sendQuery sch target result s (ni :-> d)
                            again
                _ -> -- Otherwise, we are finished.
                     do check (cnt == 0)
                        return $ return ()