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|
{-# LANGUAGE DeriveDataTypeable #-}
{-# LANGUAGE DeriveGeneric #-}
{-# LANGUAGE ExistentialQuantification #-}
{-# LANGUAGE FlexibleContexts #-}
{-# LANGUAGE GeneralizedNewtypeDeriving #-}
{-# LANGUAGE LambdaCase #-}
{-# LANGUAGE NamedFieldPuns #-}
{-# LANGUAGE NondecreasingIndentation #-}
module Announcer
( Announcer()
, AnnounceKey
, scheduleAbs
, scheduleToList
, packAnnounceKey
, unpackAnnounceKey
, forkAnnouncer
, stopAnnouncer
, cancel
, itemStatusNum
, runAction
, unschedule
, delayAction
, scheduleRel
-- lower level, Announcer.Tox needs these.
, scheduleImmediately
, ScheduledItem(ScheduledItem)
) where
import Data.Wrapper.PSQ as PSQ
import Control.Applicative
import Control.Concurrent.Lifted.Instrument
import Control.Concurrent.STM
import Control.Monad
import Data.ByteString (ByteString)
import qualified Data.ByteString.Char8 as Char8
import Data.Hashable
import Data.Time.Clock.POSIX
import qualified GHC.Generics as Generics
-- import Generic.Data.Internal.Meta as Lyxia
newtype AnnounceKey = AnnounceKey ByteString
deriving (Hashable,Ord,Eq)
instance Show AnnounceKey where
show (AnnounceKey bs) = "AnnounceKey " ++ show (Char8.unpack bs)
packAnnounceKey :: Announcer -> String -> AnnounceKey
packAnnounceKey _ = AnnounceKey . Char8.pack
unpackAnnounceKey :: Announcer -> AnnounceKey -> String
unpackAnnounceKey _ (AnnounceKey bs) = Char8.unpack bs
-- | Actions that can be scheduled to occur at some particular time in the
-- future. Since periodic event handlers are responsible for re-scheduling
-- themselves, they are typically bootstrapped using 'scheduleImmediately' with
-- 'NewAnnouncement' which triggers the ordinary recurring scheduling of
-- 'Announce'.
data ScheduledItem = ScheduledItem (Announcer -> AnnounceKey -> POSIXTime -> STM (IO ()))
-- Can't use Data because STM and IO. :(
-- deriving Data {- itemStatusNum sch = constrIndex $ toConstr sch -}
-- Using Generic works with Lyxia's generic-data package...
-- {- itemStatusNum sch = Lyxia.conIdToInt $ Lyxia.conId sch -}
-- For now, make sure to keep 'itemStatusNum' up to date with 'ScheduledItem'.
deriving Generics.Generic
itemStatusNum :: ScheduledItem -> Int
itemStatusNum = const 1
newtype Schedule = Schedule { unSchedule :: PSQ' AnnounceKey POSIXTime ScheduledItem }
emptySchedule :: Schedule
emptySchedule = Schedule PSQ.empty
type KPS = (AnnounceKey, POSIXTime, ScheduledItem)
scheduleToList :: Announcer -> STM [KPS]
scheduleToList announcer = PSQ.toList . unSchedule <$> readTVar (scheduled announcer)
data Announcer = Announcer
{ -- | The queue of scheduled events. The priority is the time at which an
-- event is supposed to occur. Do not write to this TVar ever.
scheduled :: TVar Schedule
-- | This TVar is False when the Announcer thread has finished.
, announcerActive :: TVar Bool
-- | This delay is used to wait until it's time to act on the earliest
-- scheduled item. It will be interrupted whenever a new item is
-- scheduled.
, commander :: TChan SchedulerCommand
}
scheduleImmediately :: Announcer -> AnnounceKey -> ScheduledItem -> STM ()
scheduleImmediately announcer k item =
writeTChan (commander announcer) $ RunActionSTM k item
scheduleAbs :: Announcer -> AnnounceKey -> ScheduledItem -> POSIXTime -> STM ()
scheduleAbs announcer k item absTime =
writeTChan (commander announcer) $ ScheduleAction (k, absTime, item)
scheduleRel, delayAction :: Announcer -> AnnounceKey -> ScheduledItem -> POSIXTime -> STM ()
scheduleRel announcer k item relTime =
writeTChan (commander announcer) $ DelayAction (k, relTime, item)
delayAction = scheduleRel
runAction :: Announcer -> IO () -> STM ()
runAction announcer = writeTChan (commander announcer) . RunAction
-- | Terminate the 'Announcer' thread. Don't use the Announcer after this.
stopAnnouncer :: Announcer -> IO ()
stopAnnouncer announcer = do
atomically $ writeTChan (commander announcer) ShutdownScheduler
atomically $ readTVar (announcerActive announcer) >>= check . not
unschedule :: Announcer -> AnnounceKey -> STM ()
unschedule announcer k = writeTChan (commander announcer) $ UnscheduleAction k
cancel :: Announcer -> AnnounceKey -> IO ()
cancel = ((.).(.)) atomically unschedule
-- | Construct an 'Announcer' object and fork a thread in which to perform the
-- Kademlia searches and announces.
forkAnnouncer :: IO Announcer
forkAnnouncer = do
announcer <- atomically $ Announcer <$> newTVar emptySchedule
<*> newTVar True
<*> newTChan
fork $ announceThread announcer
return announcer
readTChanTimeout :: TVar Bool -> TChan a -> STM (Maybe a)
readTChanTimeout delay pktChannel = do
Just <$> readTChan pktChannel <|> pure Nothing <* (readTVar >=> check) delay
data SchedulerCommand
= ShutdownScheduler
| ScheduleAction KPS -- run an action at an absolute time (todo: use UTCTime)
| DelayAction KPS -- run an action at a time relative to the present (todo: use NominalDiffTime)
| RunAction (IO ())
| RunActionSTM AnnounceKey ScheduledItem
| UnscheduleAction AnnounceKey
listener :: Announcer -> IO ()
listener announcer = relisten
-- This function assumes it is the only writer to the (scheduled announcer :: TVar Schedule).
-- If that TVar is written in another thread, the changes may be overwritten here.
where
chan = commander announcer
note :: String -> IO ()
note = if False then print else const (return ())
relisten = do
queue <- fmap unSchedule $ atomically $ readTVar $ scheduled announcer
case minView queue of
Nothing -> do
note "queue empty - listening indefinitely"
atomically (readTChan chan) >>= handleCommand
Just ((k, p, ScheduledItem f), queue') -> do
now <- getPOSIXTime
note $ "queue full - listening with timeout - " ++ show (p, now)
delay <- registerDelay (toMicroseconds (p - now))
join $ atomically $ do
readTChanTimeout delay chan >>= \case
Just cmd -> return $ handleCommand cmd
Nothing -> do
writeTVar (scheduled announcer) (Schedule queue')
(fmap (>> relisten) (fmap fork (f announcer k now)))
where
modifyScheduled f = modifyTVar (scheduled announcer) (Schedule . f . unSchedule)
declareInactive = writeTVar (announcerActive announcer) False
handleCommand ShutdownScheduler = atomically declareInactive
handleCommand cmd = (>> relisten) $
case cmd of
ScheduleAction (k, p, s) -> atomically $ modifyScheduled $ PSQ.insert' k s p
UnscheduleAction k -> atomically $ modifyScheduled $ PSQ.delete k
RunAction io -> void $ fork io
RunActionSTM k (ScheduledItem f) -> do
now <- getPOSIXTime
void . fork . join . atomically $ modifyScheduled (PSQ.delete k) >> f announcer k now
DelayAction (k, p, s) -> do
now <- getPOSIXTime
atomically $ modifyScheduled $ PSQ.insert' k s (now + p)
announceThread :: Announcer -> IO ()
announceThread announcer = do
myThreadId >>= flip labelThread "announcer"
listener announcer
|
