{-# OPTIONS_GHC -fno-warn-orphans #-}
{-# Language UndecidableInstances #-}
{-# Language AllowAmbiguousTypes #-}
{-# Language ImplicitParams #-}
{-# Language RecordWildCards #-}
module BlockDownloadNew where

import HBS2.Prelude.Plated
import HBS2.Clock
import HBS2.OrDie
import HBS2.Data.Detect
import HBS2.Hash
import HBS2.Merkle
import HBS2.Defaults
import HBS2.Events
import HBS2.Net.Proto.Service
import HBS2.Net.Proto.Sessions
import HBS2.Data.Bundle
import HBS2.Data.Types.SignedBox

import HBS2.Base58
import HBS2.Data.Types.Peer
import HBS2.Data.Types.Refs
import HBS2.Actors.Peer
import HBS2.Peer.Proto.Peer
import HBS2.Peer.Proto.BlockInfo
import HBS2.Peer.Proto.BlockChunks
import HBS2.Peer.Brains
import HBS2.Storage
import HBS2.Storage.Operations.Missed
import HBS2.Misc.PrettyStuff
import HBS2.Clock
import HBS2.Net.Auth.Schema

import HBS2.Peer.RPC.Internal.Types
import HBS2.Peer.RPC.API.Peer

import HBS2.Net.Messaging.TCP

import PeerTypes
import PeerInfo

import Control.Monad.Trans.Maybe
import Control.Monad.Trans.Cont
import Control.Concurrent.STM (flushTQueue,retry)
import Data.Map qualified as Map
import Data.Map (Map)
import Data.HashPSQ qualified as HPSQ
import Data.HashPSQ ( HashPSQ(..) )
import Data.HashMap.Strict (HashMap)
import Data.HashMap.Strict qualified as HM
import Data.HashSet (HashSet)
import Data.HashSet qualified as HS
import Data.IntMap qualified as IntMap
import Data.IntMap (IntMap)
import Data.List.Split qualified as Split
import Data.Text qualified as Text
import Data.Either
import Data.Maybe
import Data.ByteString.Lazy qualified as LBS
import Data.ByteString.Lazy (ByteString)
import Data.Vector qualified as V
import Data.Vector ((!?))
import Data.ByteString qualified as BS
import Data.List qualified as L
import Data.Coerce
import Numeric
import UnliftIO
import Control.Concurrent.STM qualified as STM
import UnliftIO.Concurrent
import System.Random
import Lens.Micro.Platform

import System.Random qualified as R
import System.Random.Shuffle qualified as Shuffle

import Streaming.Prelude qualified as S


data DownloadError e =
   DownloadStuckError HashRef (Peer e)
 | StorageError
 | UnknownPeerError   (Peer e)
 | InternalError Int
 | PeerMissBlockError HashRef (Peer e)
 | PeerBlockHashMismatch (Peer e)
 | PeerRequestTimeout (Peer e)
 | Incomplete HashRef
  deriving stock (Generic,Typeable)

instance Pretty (Peer e) => Show (DownloadError e) where
  show (DownloadStuckError h p)  = show $ parens $ "DownloadStuck" <+> pretty h <+> pretty p
  show (UnknownPeerError p)  = show $ parens $ "UnknownPeerError" <+> pretty p
  show (PeerMissBlockError h p)  = show $ parens $ "PeerMissBlockError" <+> pretty h <+> pretty p
  show (PeerRequestTimeout p)  = show $ parens $ "PeerRequestTimeout" <+> pretty p
  show (PeerBlockHashMismatch p)  = show $ parens $ "PeerBlockHashMismatch" <+> pretty p
  show StorageError  = show "StorageError"
  show (InternalError n) = show $ parens "InternalError" <+> pretty n
  show (Incomplete h) = show $ parens "Incomplete" <+> pretty h

instance (Typeable e, Pretty (Peer e)) => Exception (DownloadError e)


class BlockSizeCache e cache where

  cacheBlockSize :: forall m . MonadUnliftIO m
                 => cache
                 -> PubKey 'Sign (Encryption e)
                 -> Hash HbSync
                 -> Integer
                 -> m ()

  findBlockSize :: forall m . MonadUnliftIO m
                => cache
                -> PubKey 'Sign (Encryption e)
                -> Hash HbSync
                -> m (Maybe Integer)

instance BlockSizeCache e () where
  cacheBlockSize _ _ _ _ = pure ()
  findBlockSize _ _ _ = pure Nothing

instance BlockSizeCache e (SomeBrains e) where
  cacheBlockSize = brainsCacheBlockSize @e
  findBlockSize = brainsFindBlockSize @e

queryBlockSizeFromPeer :: forall e cache m . ( e ~ L4Proto
                                             , MonadUnliftIO m
                                             , BlockSizeCache e cache
                                             )
                 => cache
                 -> PeerEnv e
                 -> Hash HbSync
                 -> Peer e
                 -> m (Either (DownloadError e) (Maybe Integer))

queryBlockSizeFromPeer cache e h peer = do

  what <- try @_ @(DownloadError e) $ liftIO $ withPeerM e do

    flip runContT pure $ callCC \exit -> do

      PeerData{..} <- lift $ find (KnownPeerKey peer) id
                       >>= orThrow (UnknownPeerError peer)

      s <- lift $ findBlockSize @e cache _peerSignKey h

      -- debug $ "FOUND CACHED VALUE" <+> pretty h <+> pretty s

      maybe none (exit . Just) s

      lift do

        sizeQ <- newTQueueIO

        subscribe @e (BlockSizeEventKey peer) $ \case
          BlockSizeEvent (that, hx, sz) | hx == h -> do
            atomically $ writeTQueue sizeQ (Just sz)
            cacheBlockSize @e cache _peerSignKey h sz

          _ -> do
            atomically $ writeTQueue sizeQ Nothing

        request peer (GetBlockSize @e h)

        race ( pause defBlockInfoTimeout ) (atomically $ readTQueue sizeQ )
           >>= orThrow (PeerRequestTimeout peer)

  case what of
    Left{}  -> pure $ Left (PeerRequestTimeout peer)
    Right x -> pure (Right x)


data BurstMachine =
  BurstMachine
  { _buTimeout  :: Double
  , _buBurstMax :: Int
  , _buStepUp   :: Double
  , _buStepDown :: Double
  , _buCurrent  :: TVar Double
  , _buErrors   :: TVar Int
  }

burstMachineAddErrors :: MonadUnliftIO m => BurstMachine -> Int -> m ()
burstMachineAddErrors BurstMachine{..} n =
  atomically $ modifyTVar _buErrors (+n)

newBurstMachine :: MonadUnliftIO m
                => Double      -- ^ timeout
                -> Int         -- ^ max burst
                -> Maybe Int   -- ^ start burst
                -> Double      -- ^ step up
                -> Double      -- ^ step down
                -> m BurstMachine

newBurstMachine t0 buMax buStart up' down' = do
  BurstMachine t0 buMax up down
    <$> newTVarIO bu0
    <*> newTVarIO 0

  where
    bu0 = realToFrac $ fromMaybe (max 2 (buMax `div` 2)) buStart
    down = min 0.85 down'
    up   = min 0.5 up'

getCurrentBurst :: MonadUnliftIO m => BurstMachine -> m Int
getCurrentBurst BurstMachine{..} = readTVarIO _buCurrent <&> round

runBurstMachine :: MonadUnliftIO m
                => BurstMachine
                -> m ()

runBurstMachine BurstMachine{..} = do


  bu0  <- readTVarIO _buCurrent <&> realToFrac
  let buMax = realToFrac _buBurstMax
  let down  = _buStepDown
  let up    = _buStepUp

  _dEdT <- newTVarIO 0.00

  _rates <- newTVarIO (mempty :: Map Double Double)

  _buMaxReal <- newTVarIO buMax

  pause @'Seconds (realToFrac _buTimeout)

  flip runContT pure do

    void $ ContT $ withAsync do
      forever do
        pause @'Seconds (realToFrac _buTimeout * 10)

        atomically do
          e <- headDef bu0 . Map.elems <$> readTVar _rates
          nrates <- readTVar _rates <&> take 100 . Map.toList
          writeTVar _rates (Map.fromList nrates)
          modifyTVar _buMaxReal (max e)

    void $ ContT $ withAsync do
      forever do
        pause @'Seconds 600
        atomically $ writeTVar _buMaxReal buMax


    void $ ContT $ withAsync do
      forever do
        pause @'Seconds (realToFrac _buTimeout * 2.0)
        ddt <- readTVarIO _dEdT

        when (ddt <= 0) do
          atomically do
            buMaxReal <- readTVar _buMaxReal
            current <- readTVar _buCurrent
            let new =  min buMaxReal (current * (1.0 + up))
            writeTVar _buCurrent new

    flip fix 0 $ \next e1 -> do

      let dt = realToFrac _buTimeout

      eNew <- atomically do

        e2      <- readTVar _buErrors
        current <- readTVar _buCurrent

        new <- if e2 > e1 then do
                    let d = max 2.0 (current * (1.0 - down))
                    nrates <- readTVar _rates <&> drop 3 . Map.toList
                    let newFucked = maybe d snd (headMay nrates)
                    writeTVar _rates (Map.fromList nrates)
                    pure newFucked

                  else
                    pure current -- $ min buMaxReal (current * (1.0 + up))

        writeTVar _buErrors 0
        writeTVar _buCurrent new

        let dedt = realToFrac (e2 - e1) / realToFrac dt

        writeTVar _dEdT (realToFrac dedt)

        modifyTVar _rates ( Map.insertWith max dedt current )

        pure e2

      pause @'Seconds dt
      next eNew

data S =
    SInit
  | SFetchQ
  | SFetchPost (Hash HbSync) ByteString
  | SCheckBefore
  | SCheckAfter

-- | downloads block with dependencies recursively
downloadFromPeerRec :: forall e t cache m . ( e ~ L4Proto
                                            , MonadUnliftIO m
                                            , IsTimeout t
                                            , BlockSizeCache e cache
                                            )
                 => Timeout t
                 -> Int
                 -> cache
                 -> PeerEnv e
                 -> Hash HbSync
                 -> Peer e
                 -> m (Either (DownloadError e) ())

downloadFromPeerRec t bu0 cache env h0 peer = do

  sto <- withPeerM env getStorage

  p <- newTQueueIO
  q <- newTQueueIO
  qq <- newTQueueIO
  toq <- newTVarIO ( mempty :: [Int] )

  bm <- newBurstMachine 10 256 (Just bu0) 0.10 0.35

  flip runContT pure do

    ContT $ withAsync $ forever do
      join $ atomically (readTQueue p)

    ContT $ withAsync $ forever do
      h <- atomically (readTQueue qq)
      void $ queryBlockSizeFromPeer cache env h peer
      pause @'Seconds 1.5

    ContT $ withAsync $ flip fix 10000000 $ \next m0 -> do
      txs <- readTVarIO toq <&> L.take 1000
      let m1 = fromMaybe m0 $ median txs
      when ( m1 > m0 ) $ burstMachineAddErrors bm 1
      pause @'Seconds 3
      next m1

    ContT $ withAsync $ runBurstMachine bm

    flip fix SInit $ \next -> \case

      SInit -> do
        debug "SInit"
        atomically $ writeTQueue q h0
        next SCheckBefore

      SCheckBefore -> do
        here <- hasBlock sto h0 <&> isJust
        if here then next SCheckAfter else next SFetchQ

      SFetchQ -> do
        debug "SFetchQ"

        done <- atomically do
          pe <- isEmptyTQueue p
          qe <- isEmptyTQueue q
          when (qe && not pe) retry
          -- when (not pe) retry
          pure qe

        if done then
          next SCheckAfter
        else do

          h <- atomically $ readTQueue q
          mbs <- getBlock sto h

          case mbs of
            Just bs -> next (SFetchPost h bs)
            Nothing -> none

          bu <- lift $ getCurrentBurst bm

          t0 <- getTimeCoarse
          w  <- lift $ downloadFromPeer t bu cache env (coerce h) peer
          t1 <- getTimeCoarse
          let dt = toMicroSeconds $ TimeoutTS (t1 - t0)
          atomically $ modifyTVar toq ( dt : )

          case w of
            Right bs -> do
              next (SFetchPost h bs)

            Left e -> do
             lift $ burstMachineAddErrors bm 1
             err $ "DOWNLOAD ERROR" <+> viaShow e
             next SFetchQ

      SFetchPost h bs -> do
        debug $ "SFetchPost" <+> pretty h

        let parse = do
             let refs = extractBlockRefs h bs
             atomically $ mapM_ (writeTQueue q . coerce) refs
             mapM_ (atomically . writeTQueue qq . coerce) refs

        atomically $ writeTQueue p parse

        next SFetchQ

      SCheckAfter -> do
        debug "SCheckAfter"
        missed <- findMissedBlocks sto (HashRef h0)
        mapM_ (atomically . writeTQueue q . coerce) missed
        mapM_ (atomically . writeTQueue qq . coerce) missed
        unless (L.null missed) $ next SFetchQ

    pure $ Right ()


downloadFromPeer :: forall e t cache m . ( e ~ L4Proto
                                         , MonadUnliftIO m
                                         , IsTimeout t
                                         , BlockSizeCache e cache
                                         )
                 => Timeout t
                 -> Int
                 -> cache
                 -> PeerEnv e
                 -> Hash HbSync
                 -> Peer e
                 -> m (Either (DownloadError e) ByteString)

downloadFromPeer t bu cache env h peer = liftIO $ withPeerM env do

  pd@PeerData{..} <- find (KnownPeerKey peer) id
                   >>= orThrow (UnknownPeerError peer)

  pinfo <- find (PeerInfoKey peer) id
             >>= orThrow (UnknownPeerError peer)

  rtt <- liftIO $ medianPeerRTT pinfo
             <&> fmap ((*1) . realToFrac)
             <&> fromMaybe 1000
             <&> (/1e6)

  let waity = 20 * rtt

  sto <- getStorage

  let chunkSize = defChunkSize

  flip runContT pure $ callCC \exit -> do

    size <- lift (findBlockSize @e cache _peerSignKey h)
             >>= maybe (queryBlockSize exit) pure

    coo <- genCookie (peer,h)
    let key = DownloadSessionKey (peer, coo)
    down@BlockDownload{..} <- newBlockDownload h
    let chuQ = _sBlockChunks
    let new =   set sBlockChunkSize chunkSize
              . set sBlockSize (fromIntegral size)
                $ down

    lift $ update @e new key id

    let offsets = calcChunks size (fromIntegral chunkSize)  :: [(Offset, Size)]

    let chunkNums = [ 0 .. pred (length offsets) ]

    let bursts = calcBursts bu chunkNums

    callCC $ \exit2 -> do

      _wx <- newTVarIO waity

      for_ bursts $ \(i,chunkN) -> do

        -- atomically $ flushTQueue chuQ

        let req = BlockChunks @e coo (BlockGetChunks h chunkSize (fromIntegral i) (fromIntegral chunkN))

        lift $ request peer req

        -- pause @'MilliSeconds ( rtt * 0.01 )

        t0 <- getTimeCoarse

        let watchdog = fix \next -> do
             wx <- readTVarIO _wx <&> realToFrac
             -- debug $ "WATCHDOG" <+> pretty wx <+> pretty waity
             r <- race (pause @'MilliSeconds (min wx waity)) do
                    void $ atomically $ readTQueue chuQ
             either (const none) (const next) r

        r <- liftIO $ race watchdog do
            atomically do
              pieces <- readTVar _sBlockChunks2
              let done =  and [ IntMap.member j pieces | j <- [i .. i + chunkN-1] ]
              unless done retry -- $ pause @'MilliSeconds ( 0.25 * rtt ) >> next

        atomically $ flushTQueue chuQ

        t1 <- getTimeCoarse

        atomically do
          -- wx0 <- readTVar _wx
          let wx1 = 1.50 * realToFrac (t1 - t0) * 100 / 1e6 -- millis
          writeTVar _wx wx1

        case r of
          Left{} -> exit2 (Left $ DownloadStuckError (HashRef h) peer)
          _ -> pure ()


      blk <- readTVarIO _sBlockChunks2
      let rs = LBS.concat $ IntMap.elems blk

      ha <- putBlock sto rs

      -- let ha = Just $ hashObject @HbSync rs

      lift $ expire @e key

      case ha of
        Nothing -> pure $ Left StorageError

        Just h1 | h1 == h -> do
          pure $ Right rs

        Just h1 -> do
          delBlock sto h1
          pure $ Left (PeerBlockHashMismatch peer)

  where

    queryBlockSize exit = do
      what <- lift $ queryBlockSizeFromPeer cache env h peer
      case what of
        Left{}  -> exit (Left (PeerRequestTimeout peer))
        Right Nothing -> exit (Left (PeerMissBlockError (HashRef h) peer))
        Right (Just s) -> pure s



data S1 =
    S1Init
  | S1QuerySize (Hash HbSync)
  | S1CheckMissed (Hash HbSync)


data S2 =
    S2Init (Hash HbSync)
  | S2CheckBlock1 (Hash HbSync) ByteString
  | S2CheckBlock2 (Hash HbSync)
  | S2FetchBlock (Hash HbSync)
  | S2Exit

newtype KnownSize = KnownSize Integer

instance BlockSizeCache  e KnownSize where
  cacheBlockSize _ y_ _ _ = pure ()
  findBlockSize (KnownSize s) _ _ = pure (Just s)

data BlockFetchResult =
        BlockFetchError
      | BlockFetched ByteString
      | BlockAlreadyHere

data Work =
    RequestSize HashRef (Maybe Integer -> IO ())
  | FetchBlock  HashRef Integer (BlockFetchResult -> IO ())


-- | Download control block
data DCB =
  DCB
  { dcbStart      :: TimeSpec
  , dcbBusy       :: TVar Int
  , dcbDownloaded :: TVar Bool
  }

newDcbSTM :: TimeSpec -> STM DCB
newDcbSTM ts = DCB ts <$> newTVar 0 <*> newTVar False

data PSt =
    PChoose
  | PInit         HashRef DCB
  | PQuerySize    HashRef DCB
  | PFetchBlock   HashRef DCB Integer
  | PReleaseBlock HashRef DCB Bool

downloadDispatcher :: forall e m . ( e ~ L4Proto
                                   , MonadUnliftIO m
                                   )
                 => SomeBrains e
                 -> PeerEnv e
                 -> m ()
downloadDispatcher brains env = flip runContT pure do

  pts   <- newTVarIO ( mempty :: HashMap (Peer e) (Async ()) )
  -- tasks <- newTVarIO ( HPSQ.empty :: HashPSQ (Work e) Double (TVar Int) )

  _blkNum   <- newTVarIO 0
  wip       <- newTVarIO ( HPSQ.empty @HashRef @Double @DCB )
  parseQ    <- newTQueueIO


  let
    onBlockSTM :: HashRef -> STM ()
    onBlockSTM = writeTQueue parseQ

  void $ ContT $ withAsync $ manageThreads onBlockSTM wip pts

  sto <- withPeerM env getStorage

  liftIO $ withPeerM env do
    subscribe @e DownloadReqKey $ \(DownloadReqData h) -> do
      here <- hasBlock sto h <&> isJust
      unless here do
        now <- getTimeCoarse
        debug $ green "New download request" <+> pretty h
        atomically do
          already <- readTVar wip <&> HPSQ.member (HashRef h)
          dcb <- newDcbSTM now
          let w = 1.0 -- realToFrac now
          unless already do
            modifyTVar wip  (HPSQ.insert (HashRef h) w dcb)

  ContT $ withAsync $ forever $ (>> pause @'Seconds 5) do
    debug "Sweep blocks"
    atomically do
      total <- readTVar wip <&> HPSQ.toList

      alive <- for total $ \e@(h,_,DCB{..}) -> do
        down <- readTVar dcbDownloaded
        if down then
          pure Nothing
        else
          pure (Just e)

      writeTVar wip (HPSQ.fromList (catMaybes alive))


  ContT $ withAsync $ replicateM_ 4 $ forever do
    what <- atomically $ readTQueue parseQ
    missed <- findMissedBlocks sto what
    now <- getTimeCoarse
    for_ missed $ \hi -> do
      atomically do
        dcb <- newDcbSTM now
        let w = realToFrac now
        modifyTVar wip (HPSQ.insert hi 1.0 dcb)

  forever $ (>> pause @'Seconds 10) do
    sw0  <- readTVarIO wip <&> HPSQ.size
    debug $ yellow $ "wip0"   <+> pretty sw0

  where

    manageThreads onBlock wip pts = forever $ (>> pause @'Seconds 10) $ withPeerM env do
      debug "MANAGE THREADS"

      peers <- getKnownPeers @e <&> HS.fromList

      for_ peers $ \p -> do
        here <- readTVarIO pts <&> HM.member p
        unless here do
          a <- async (peerThread onBlock p wip)
          atomically $ modifyTVar pts (HM.insert p a)

      loosers <- atomically do
        xs <- readTVar pts <&> HM.toList
        -- FIXME: filter-stopped-tasks
        let (alive,dead) = L.partition ( \(x,_) -> HS.member x peers ) xs
        writeTVar pts (HM.fromList alive)
        pure dead

      mapM_ cancel (fmap snd loosers)

    peerThread onBlock p wip = flip runContT pure do

      btimes <- newTVarIO ( mempty :: [Double] )

      _errors <- newTVarIO 0
      _avg <- newTVarIO 600

      sto <- withPeerM env getStorage

      _sizeCache <- newTVarIO ( mempty :: HashMap HashRef (Maybe Integer) )

      bm <- liftIO $ newBurstMachine 10 256 (Just 50) 0.10 0.25

      void $ ContT $ bracket none $ const do
        debug $ "Cancelling thread for" <+> pretty p

      debug $ yellow "Started thread for" <+> pretty p

      -- TODO: sweep size cache!

      ContT $ withAsync $ forever $ (>> pause @'Seconds 60) do
        atomically $ writeTVar _errors 0

      tsweep <- ContT $ withAsync do
        let hashes = readTVarIO _sizeCache <&> fmap (,60) . HM.keys
        polling (Polling 1 10) hashes $ \h -> do
          atomically do
            here <- readTVar wip <&> HPSQ.member h
            unless here do
              modifyTVar _sizeCache (HM.delete h)

      parseQ <- newTQueueIO

      bmt <- ContT $ withAsync $ runBurstMachine bm

      tstat <- ContT $ withAsync $ forever $ (>> pause @'Seconds 5) do
                 tss <- readTVarIO btimes
                 unless (L.null tss) do
                  let avg = sum tss / realToFrac (L.length tss)
                  atomically do
                    writeTVar _avg avg

      twork <- ContT $ withAsync $ forever do

        flip fix PChoose $ \go -> \case

          PChoose -> do

            what <- atomically do
                     blocks <- readTVar wip <&> HPSQ.toList
                     let todo = blocks
                     flip fix todo $ \loop w -> do
                       erno <- readTVar _errors
                       if erno > 10 then
                         pure Nothing
                       else do
                         case w of
                           []  -> retry
                           (h,_,dcb):xs -> do
                            wpsize <- readTVar wip <&> HPSQ.size
                            let trsh = if wpsize < 10 then 3 else 0
                            busy   <- readTVar (dcbBusy dcb)
                            down   <- readTVar (dcbDownloaded dcb)
                            absent <- readTVar _sizeCache <&> (== Just Nothing) . HM.lookup h
                            if busy > trsh || down || absent then
                              loop xs
                            else do
                              modifyTVar (dcbBusy dcb) succ
                              pure $ Just (h,dcb)

            case what of
              Just (hx, dcb) -> go (PInit hx dcb)
              Nothing -> do
                erno <- readTVarIO _errors
                if erno > 50 then do
                  pause @'Seconds 60
                else do
                  pause @'Seconds 1
                go PChoose

          PInit hx dcb -> do

            debug $ yellow "Block choosen" <+> pretty p <+> pretty hx

            hereSize <- readTVarIO _sizeCache <&> HM.lookup hx

            case hereSize of
              Just (Just size) -> do
                go (PFetchBlock hx dcb size)

              Just Nothing -> do
                debug $ blue "Release block" <+> pretty p <+> pretty hx
                go (PReleaseBlock hx dcb False)

              Nothing -> do
                debug $ blue "Query size" <+> pretty p <+> pretty hx
                go (PQuerySize hx dcb)

          PQuerySize hx dcb -> do
            s <- queryBlockSizeFromPeer brains env (coerce hx) p
            case s of
              Right (Just size) -> do
                debug $ green "HAS BLOCK" <+> pretty p <+> pretty hx <+> pretty size
                atomically $ modifyTVar _sizeCache (HM.insert hx (Just size))
                go (PFetchBlock hx dcb size)

              Right Nothing -> do
                debug $ red "HAS NO BLOCK" <+> pretty p <+> pretty hx
                atomically $ modifyTVar _sizeCache (HM.insert hx Nothing)
                go (PReleaseBlock hx dcb False)

              Left{} -> do
                atomically $ modifyTVar _errors succ
                go (PReleaseBlock hx dcb False)

          PFetchBlock hx dcb size -> do

            bu <- lift $ getCurrentBurst bm

            t0 <- getTimeCoarse
            r <- lift $ downloadFromPeer (TimeoutSec 10) bu (KnownSize size) env (coerce hx) p
            t1 <- getTimeCoarse

            case r of
              Right bs -> do
                let dtsec = realToFrac (toNanoSeconds (TimeoutTS (t1 - t0))) / 1e9

                avg <- readTVarIO _avg

                when (dtsec > avg * 1.10) do
                  burstMachineAddErrors bm 1

                atomically $ modifyTVar  btimes ( take 100 . (dtsec :) )
                atomically $ writeTVar (dcbDownloaded dcb) True

                go (PReleaseBlock hx dcb True)

              Left e -> do
                burstMachineAddErrors bm 1
                atomically $ modifyTVar _errors succ
                debug $ red "BLOCK DOWNLOAD FUCKED" <+> pretty p <+> pretty hx <+> viaShow e

                go (PReleaseBlock hx dcb False)

          PReleaseBlock hx dcb done -> do
            atomically do
              if not done  then do
                modifyTVar (dcbBusy dcb) pred
              else do
                -- modifyTVar (dcbBusy dcb) pred
                modifyTVar wip (HPSQ.delete hx)
                onBlock hx

      bs <- ContT $ withAsync $ forever do
        pause @'Seconds 10
        debug $ yellow "I'm thread" <+> pretty p

      void $ waitAnyCatchCancel [bmt,bs,twork,tstat,tsweep]