schedule (empty) → 0.1.0.0

raw patch · 18 files changed

+2109/−0 lines, 18 filesdep +asyncdep +basedep +checkerssetup-changed

Dependencies added: async, base, checkers, containers, doctest, extra, lens, primitive, safe, schedule, stm, system-time-monotonic, tasty, tasty-hunit, tasty-quickcheck, text, time, transformers

Files

• CHANGELOG.md +5/−0
• LICENSE.GPL-3 +674/−0
• Setup.hs +2/−0
• schedule.cabal +154/−0
• src/Control/Arrow/Schedule.hs +102/−0
• src/Control/Clock.hs +96/−0
• src/Control/Clock/IO.hs +146/−0
• src/Control/Monad/Primitive/Extra.hs +43/−0
• src/Control/Monad/Schedule.hs +100/−0
• src/Control/Schedule/Future.hs +198/−0
• src/Data/Rsv/Common.hs +72/−0
• src/Data/Rsv/RMMap.hs +135/−0
• src/Data/Schedule.hs +72/−0
• src/Data/Schedule/Internal.hs +195/−0
• test/Control/Monad/ScheduleTest.hs +80/−0
• test/Data/Rsv/Example.hs +24/−0
• test/DocTests.hs +4/−0
• test/UnitTests.hs +7/−0

@@ -0,0 +1,5 @@+# Revision history for schedule++## 0.1.0.0 -- 2019-12-20++* Initial release.

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Of course, your program's commands+might be different; for a GUI interface, you would use an "about box".++  You should also get your employer (if you work as a programmer) or school,+if any, to sign a "copyright disclaimer" for the program, if necessary.+For more information on this, and how to apply and follow the GNU GPL, see+<http://www.gnu.org/licenses/>.++  The GNU General Public License does not permit incorporating your program+into proprietary programs.  If your program is a subroutine library, you+may consider it more useful to permit linking proprietary applications with+the library.  If this is what you want to do, use the GNU Lesser General+Public License instead of this License.  But first, please read+<http://www.gnu.org/philosophy/why-not-lgpl.html>.

@@ -0,0 +1,2 @@+import Distribution.Simple+main = defaultMain

@@ -0,0 +1,154 @@+Cabal-Version:       2.4+Name:                schedule+Version:             0.1.0.0+Synopsis:            Pure deterministic scheduled computations+Description:+  Schedule computations to run later, in a pure and deterministic way.+  .+  This library is a pure alternative to "System.Timeout" suitable for IO-bound+  non-blocking computations. "System.Timeout" has a few issues that are at-odds+  with a Haskell or purely functional paradigm: (1) it is not deterministic,+  (2) the timeout state is not serialisable, and (3) the timeout functionality+  must be shared between unrelated components, making it harder to design+  components that are easily decomposable and reusable.+  .+  This library solves these issues by implementing all schedule and timeout+  logic as a pure deterministic computation, with callbacks represented in+  defunctionalised serialisable form. The interface with the runtime execution+  environment is minimal: a simple source of clock inputs similar to other+  inputs such as network traffic or user commands, which can either be an+  IO-based impure "real" runtime, or a pure "mock" one e.g. that replays+  previous inputs to reproduce previous outputs.+  .+  This library does /no pre-emption/ e.g. by sending interrupts or asynchronous+  exceptions, so it is probably /not suitable/ for blocking computations. To be+  clear, things will /work/, but clock inputs will be delivered only after the+  blocking is over. A workaround is to separate the blocking computations from+  your main computation, arrange to have these run externally (e.g. in worker+  threads) with the results being sent back to your main computation via some+  pure abstract input interface, similar to how we deliver clock inputs.+  .+  If this is not suitable and you absolutely need pre-emption, then you'll need+  a richer runtime interface than the one expected by this library; luckily the+  Haskell runtime itself is such an example. In other words, simply use other+  existing IO-based utilities for setting timeouts, that typically rely on+  concurrency or asynchronous exceptions. But then, you'll have to figure out+  your own way of overcoming the issues mentioned in the first paragraph.+  .+  The original motivation for this library comes from implementing secure+  communications protocols and decentralised distributed systems. In these+  contexts one must often set local timeouts for remote events that may or may+  not happen in the future, or periodically synchronise local views of shared+  data with remote peers. Most operations are IO-bound and can be written to be+  non-blocking; the main exception is heavy cryptography which can be delegated+  to worker threads as described above. Of course, this library is not tied to+  these use-cases and is a general replacement for "System.Timeout".+  .+  See "Control.Monad.Schedule" for the main monad-based API of this library.+  .+  See "Control.Arrow.Schedule" for the main arrow-based API of this library.+  .+  See "Control.Clock.IO" for various ways of combining clock inputs with other+  inputs and injecting them into your pure computations.+  .+  See @Control.Schedule.*@ for higher-level utilities that one often wants to+  use on top of a timeout primitive, such as futures and monitors.+  .+  See unit tests for example usage.+Homepage:            https://github.com/infinity0/hs-schedule+Bug-Reports:         https://github.com/infinity0/hs-schedule/issues+License:             GPL-3.0-or-later+License-File:        LICENSE.GPL-3+Author:              Ximin Luo+Maintainer:          infinity0@pwned.gg+Copyright:           2016-2019 Ximin Luo+Category:            Control, Schedule, Delay, Time, Timeout+Tested-With:         GHC >= 8.6+Extra-Source-Files:  CHANGELOG.md++Source-Repository head+  Type: git+  Location: https://github.com/infinity0/hs-schedule++Flag dev+  Description: Set compile flags for development+  Default:     False+  Manual:      True++Common generic+  Default-Language: Haskell2010+  Build-Depends: base >= 4 && < 5,+  GHC-Options:+    -Wall+    -Wno-unused-matches+    -Wredundant-constraints+    -Wincomplete-record-updates+    -Wincomplete-uni-patterns+  if flag(dev)+    GHC-Options:+      -Werror+      -O2+    -- some optimisations cause memory leaks; switch on -O2 and profiling so we+    -- can detect this during development so it doesn't cause surprises later+    GHC-Prof-Options:+      -fprof-auto++Library+  Import: generic+  Build-Depends:+      extra+    -- for Data.Rsv.*+    , containers+    , lens+    , text+    -- for Control.Clock.System+    , async+    , safe+    , stm+    , time                    >= 1.5+    , system-time-monotonic   >= 0.2+    -- for Control.Monad.Primitive.*+    , primitive+    -- for Data.Schedule.Applied+    , transformers+  HS-Source-Dirs: src+  Exposed-Modules:+      Control.Clock+    , Control.Clock.IO+    , Control.Arrow.Schedule+    , Control.Monad.Schedule+    , Control.Monad.Primitive.Extra+    , Control.Schedule.Future+    , Data.Schedule+    , Data.Schedule.Internal+    -- the below modules are exposed for testing only+    , Data.Rsv.Common+    , Data.Rsv.RMMap++Test-Suite doctests+  Import: generic+  GHC-Options: -threaded+  Build-Depends:+      doctest+    , schedule+  HS-Source-Dirs: test+  Type: exitcode-stdio-1.0+  Main-Is: DocTests.hs++Test-Suite unit+  Import: generic+  GHC-Options: -threaded+  Build-Depends:+      tasty+    , tasty-quickcheck+    , tasty-hunit+    , checkers+    , primitive+    , transformers+    , schedule+  HS-Source-Dirs: test+  Type: exitcode-stdio-1.0+  Main-Is: UnitTests.hs+  Other-Modules:+      Control.Monad.ScheduleTest+    , Data.Rsv.Example

@@ -0,0 +1,102 @@+{-# LANGUAGE Arrows        #-}+{-# LANGUAGE RankNTypes    #-}+{-# LANGUAGE TupleSections #-}++{-| Run scheduled computations in any (stateful) arrow, using an adapter.++This module mostly contains utilities for dealing with clock inputs. To get or+set the existing timeouts, use your 'RunSchedA' adapter on one of the functions+from "Data.Schedule", which this module also re-exports.+-}+module Control.Arrow.Schedule+  ( RunSchedA+  , runTick+  , runTicksTo+  , getInput+  , mkOutput+  , tickTask+  , module Data.Schedule+  )+where++-- external+import           Control.Arrow+import           Data.Functor.Identity  (Identity (..))+import           Data.Maybe             (fromMaybe)++-- internal+import           Data.Schedule+import           Data.Schedule.Internal+++-- TODO: export to upstream arrows or extra+whileJustA :: (ArrowChoice a, Monoid o) => a i (Maybe o) -> a i o+whileJustA act = (, mempty) ^>> go+ where+  go = proc (i, rr) -> do+    r' <- act -< i+    case r' of+      Nothing -> returnA -< rr+      Just r  -> go -< (i, rr <> r)+++-- | Something that can run 'Schedule' state transition arrows.+--+-- This could be pure (e.g. 'Control.Arrow.Transformer.State.StateArrow') or+-- impure (e.g. reference to a 'Control.Monad.Primitive.Extra.PrimST').+type RunSchedA t a = forall i o . ((i, Schedule t) -> (o, Schedule t)) -> a i o++runTick+  :: (ArrowChoice a, Monoid o) => RunSchedA t a -> a (Tick, t) o -> a Tick o+runTick runS runTickTask = whileJustA $ proc tick -> do+  r' <- runS (stA popOrTick) -< ()+  case r' of+    Nothing     -> returnA -< Nothing+    Just (t, p) -> do+      () <- runS (imodA acquireTask) -< (t, p)+      r  <- runTickTask -< (tick, p) -- TODO: catch Haskell exceptions here+      () <- runS (imodA releaseTask) -< t+      returnA -< Just r++runTicksTo+  :: (ArrowChoice a, Monoid o) => RunSchedA t a -> a (Tick, t) o -> a Tick o+runTicksTo runS runTask = whileJustA $ proc tick -> do+  tick' <- runS (getA tickNow) -< ()+  if tick' >= tick+    then returnA -< Nothing+    else Just ^<< runTick runS runTask -< tick++getInput+  :: (Arrow a)+  => RunSchedA t a+  -> a TickDelta (Either Tick i)+  -> a i' (Either Tick i)+getInput runS getTimedInput =+  runS (getA ticksToIdle) >>> fromMaybe maxBound ^>> getTimedInput++mkOutput+  :: (ArrowChoice a, Monoid o)+  => RunSchedA t a+  -> a (Tick, t) o+  -> a i o+  -> a (Either Tick i) o+mkOutput runS runTask runInput = runTicksTo runS runTask ||| runInput++-- | A more general version of 'mkOutput' that uses a prism-like optic.+--+-- Given an inner computation @a it o@ where one branch of the @it@ type has+-- a @(Tick, t)@ tuple that represents individual input tasks, return an outer+-- computation of type @a i o@ where the @i@ type only has a @Tick@. When the+-- outer computation receives these @Tick@ inputs, it automatically resolves+-- the relevant tasks of type @t@ that are active for that @Tick@, and passes+-- each tuple in sequence to the wrapped inner computation.+tickTask+  :: (ArrowChoice a, ArrowApply a, Monoid o)+  => RunSchedA t a+  -> (forall f . Applicative f => (Tick -> f (Tick, t)) -> i -> f it)+  -> a it o+  -> a i o+tickTask runS prism runTaskOr = proc input -> case prism Left input of+  Right it   -> runTaskOr -< it+  Left  tick -> runTicksTo runS (runTaskOr <<^ inputWithTask) -<< tick+    where inputWithTask tk = runIdentity (prism (const (pure tk)) input)

@@ -0,0 +1,96 @@+{-# LANGUAGE RankNTypes #-}++{-| Pure abstractions for time and clocks. -}++module Control.Clock+  ( Clock(..)+  , clockTick+  , Clocked(..)+  , module Data.Schedule+  )+where++-- internal+import           Data.Schedule (Tick, TickDelta)++{-| A maybe-impure supplier of time, to a pure scheduled computation.++    The type @c@ is the computational context where clock operations occur,+    e.g. a 'Monad' such as 'IO'.++    Clock implementations /must/ be monotonic. See "System.Time.Monotonic" for+    an example on how to wrap non-monotonic clocks to be monotonic.+-}+data Clock c = Clock {+    -- | Get the current time.+    clockNow   :: !(c Tick)+    {-| Suspend the current computation for a given number of ticks.++        Nothing else in the computation runs until the suspension is over.+        Afterwards, 'clockNow' will give the expected value, i.e. for all @n@:++        > do+        >     old <- clockNow+        >     clockDelay n+        >     new <- clockNow+        >     let new' = assert (old + n <= new) new++        The relation is '<=' not '==', because the computer might have slept+        during the mean time or something. On the other hand, if the underlying+        physical clock might delay for a shorter period than requested, then+        implementations of this function /must/ loop-delay until the '<='+        condition is satisfied.++        The above is the only condition that scheduled computations should rely+        on, and any actual physical real delay is up to the implementation.+     -}+  , clockDelay :: !(TickDelta -> c ())+    {-| Interleave actions with ticks.++        This is typically recommended for the use-case where your action+        represents a stream of inputs, e.g. from the network or the user. It+        is meant to satisfy the same functionality as the @select@ system call+        found in common operating systems, used with a timeout parameter.++        If @action@ when executed repeatedly gives a sequence of results, then+        in the expression @clkAct <- clock `clockWith` action@, @runClocked+        clkAct@ when executed repeatedly gives the same sequence of results but+        with ticks interleaved in between them. Executing @finClocked clkAct@+        closes any resources and invalidates any future calls to @clkAct@.++        It is not necessary to call @finClocked@ if any part of @runClocked@+        (e.g. child threads) throws an exception - implementations should+        detect these situations and clean these up automatically. This frees+        the user of this function from requiring extra constraints which would+        be necessary if it's necessary to run @`finally` finClocked clkAct@ as+        cleanup.+    -}+  , clockWith  :: !(forall a. c a -> c (Clocked c a))+    {-| Given an action, run it with a timeout.++        This is typically recommended for the use-case where your action+        represents the response to a single previously-sent request.++        The action may complete despite the timeout firing, in which case its+        result will be lost. This is in general unavoidable and is a common+        property that one simply has to live with in distributed systems. If+        you run the input action repeatedly, then this property applies *for+        every execution*, i.e. it is possible that you get 10 timeouts even+        though the action succeeded 10 times, and you'll lose 10 results.++        If you want all results of all actions, use @clockWith@ instead. The+        downside with that, is that it's slightly less efficient than this, as+        it will interleave every single 'Tick' event and it is up to you to+        deal with skipping/ignoring any of them.+    -}+  , clockTimer :: !(forall a. TickDelta -> c a -> c (Either Tick a))+}++clockTick :: Monad c => Clock c -> TickDelta -> c Tick+clockTick clock d = clockDelay clock d >> clockNow clock++-- | See 'clockWith' for details on what this is for.+data Clocked c a = Clocked {+    runClocked :: !(c (Either Tick a))+  , finClocked :: !(c ())+  }

@@ -0,0 +1,146 @@+{-# LANGUAGE LambdaCase #-}+{-# LANGUAGE RankNTypes #-}++{-| Implementations of 'Clock' in the 'IO' monad. -}+module Control.Clock.IO+  ( newClock+  , newClockPico+  , newClockMilli+  , newClock1ms+  , newClock1s+  , convClock+  , clockWithIO+  , clockTimerIO+  , voidInput+  , module Control.Clock+  )+where++-- external+import qualified System.Time.Monotonic          as T++import           Control.Concurrent             (threadDelay)+import           Control.Concurrent.Async       (async, cancel, link, link2,+                                                 race)+import           Control.Concurrent.STM         (STM, atomically, orElse)+import           Control.Concurrent.STM.TBQueue (TBQueue, isEmptyTBQueue,+                                                 newTBQueueIO, readTBQueue,+                                                 tryPeekTBQueue, tryReadTBQueue,+                                                 writeTBQueue)+import           Control.Monad                  (forever, unless, when)+import           Data.Time.Clock                (DiffTime,+                                                 diffTimeToPicoseconds,+                                                 picosecondsToDiffTime)+import           Data.Void                      (Void)+import           GHC.Stack                      (HasCallStack)++-- internal+import           Control.Clock+++-- | Create a new clock ticking at a given interval.+newClock :: DiffTime -> IO (Clock IO)+newClock intv = convClock intv <$> T.newClock++-- | Create a new clock ticking at a given interval in picoseconds.+newClockPico :: Integer -> IO (Clock IO)+newClockPico = newClock . picosecondsToDiffTime++-- | Create a new clock ticking at a given interval in milliseconds.+newClockMilli :: Integer -> IO (Clock IO)+newClockMilli ms = newClockPico (1000000000 * ms)++-- | Create a new clock ticking at 1 millisecond.+newClock1ms :: IO (Clock IO)+newClock1ms = newClockMilli 1++-- | Create a new clock ticking at 1 second.+newClock1s :: IO (Clock IO)+newClock1s = newClockMilli 1000++-- | Check for a non-negative number.+checkNonNeg :: (HasCallStack, Num a, Ord a, Show a) => a -> a+checkNonNeg n =+  if n >= 0 then n else error $ "must be non-negative: " ++ show n++-- | Check for a positive number.+checkPos :: (HasCallStack, Num a, Ord a, Show a) => a -> a+checkPos n = if n > 0 then n else error $ "must be positive: " ++ show n++{-| Convert a "System.Time.Monotonic.Clock" into an abstract 'Clock' for+    scheduled computations, ticking at the given interval.+-}+convClock :: DiffTime -> T.Clock -> Clock IO+convClock intv c =+  let r  = diffTimeToPicoseconds $ checkPos intv+      c' = Clock+        { clockNow   = (`div` r) <$> clockNowPico c+        , clockDelay = \d -> when (d > 0) $ do+                         remain <- (`rem` r) <$> clockNowPico c+                         -- wait a bit past the tick, make sure we've gone over+                         let t = r * fromIntegral d * 16 `div` 15 - remain+                         clockDelayPico t+        , clockWith  = clockWithIO c'+        , clockTimer = clockTimerIO c'+        }+  in  c'++clockNowPico :: T.Clock -> IO Integer+clockNowPico c = diffTimeToPicoseconds <$> T.clockGetTime c++clockDelayPico :: Integer -> IO ()+clockDelayPico d = T.delay $ picosecondsToDiffTime $ checkNonNeg d++-- assert that a writeTBQueue is non-blocking+writeTBQueue' :: HasCallStack => TBQueue a -> a -> STM ()+writeTBQueue' q r = do+  e <- isEmptyTBQueue q+  unless e $ error "failed to assert non-blocking write on TBQueue"+  writeTBQueue q r++clockWithIO :: Clock IO -> IO a -> IO (Clocked IO a)+clockWithIO clock action = do+  qi           <- newTBQueueIO 1+  qo           <- newTBQueueIO 1+  qt           <- newTBQueueIO 1++  -- keep running action+  actionThread <- async $ forever $ do+    -- block until we get a request to run action, but don't pop the queue+    atomically $ do+      readTBQueue qi+      writeTBQueue' qi ()+    r <- action+    -- pop the queue after we write the result of action+    atomically $ do+      writeTBQueue' qo r+      readTBQueue qi+  link actionThread++  -- keep producing ticks+  tickThread <- async $ forever $ do+    t <- clockTick clock 1+    atomically $ do+      _ <- tryReadTBQueue qt -- empty the queue before we write a tick+      writeTBQueue' qt t+  link tickThread++  -- Kill both threads if any one of them dies. This ensures that the user+  -- doesn't need to call fin themselves if anything throws an exception.+  link2 actionThread tickThread++  let fin     = cancel actionThread >> cancel tickThread+      action' = do+        atomically $ tryPeekTBQueue qi >>= \case+          Nothing -> writeTBQueue qi ()+          Just () -> pure ()+        atomically $ do+          (Right <$> readTBQueue qo) `orElse` (Left <$> readTBQueue qt)++  pure (Clocked action' fin)++clockTimerIO :: Clock IO -> TickDelta -> IO a -> IO (Either Tick a)+clockTimerIO c d = race (clockTick c d)++voidInput :: IO Void+voidInput = forever $ threadDelay maxBound

@@ -0,0 +1,43 @@+-- TODO: export to upstream primitive++{-# LANGUAGE RankNTypes    #-}+{-# LANGUAGE TupleSections #-}++{-| Extra utilities and abstractions for "Control.Monad.Primitive".++The API structure is stable, but the naming is not very good and may change.+Ideally we would push this upstream into "Control.Monad.Primitive" itself.+-}+module Control.Monad.Primitive.Extra+  ( PrimST(..)+  , readPrimST+  , writePrimST+  , modifyPrimST+  , stMutVar+  , module Control.Monad.Primitive+  )+where++import           Control.Monad.Primitive (PrimMonad, PrimState)+import           Data.Primitive.MutVar+import           Data.Tuple              (swap)+import           Data.Tuple.Extra        (dupe)+++-- | Type abstracting a mutable reference.+--+-- This can be thought of as a mutable version of a @Lens' (PrimState m) s@+-- with the lens functor specialised to @(,) a@ for each @a@.+newtype PrimST m s = PrimST { statePrimST :: forall a. (s -> (a, s)) -> m a }++readPrimST :: PrimST m s -> m s+readPrimST st = statePrimST st dupe++writePrimST :: PrimST m s -> s -> m ()+writePrimST st s1 = statePrimST st (const ((), s1))++modifyPrimST :: PrimST m s -> (s -> s) -> m ()+modifyPrimST st f = statePrimST st (((), ) . f)++stMutVar :: PrimMonad m => MutVar (PrimState m) s -> PrimST m s+stMutVar mv = PrimST (atomicModifyMutVar' mv . (swap .))

@@ -0,0 +1,100 @@+{-# LANGUAGE LambdaCase #-}+{-# LANGUAGE RankNTypes #-}++{-| Run scheduled computations in any (stateful) monad, using an adapter.++This module mostly contains utilities for dealing with clock inputs. To get or+set the existing timeouts, use your 'RunSched' adapter on one of the functions+from "Data.Schedule", which this module also re-exports.+-}+module Control.Monad.Schedule+  ( RunSched+  , runTick+  , runTicksTo+  , getInput+  , mkOutput+  , tickTask+  , module Data.Schedule+  )+where++-- external+import           Control.Monad.Extra    (whenMaybe)+import           Data.Either            (either)+import           Data.Functor.Identity  (Identity (..))+import           Data.Maybe             (fromMaybe)++-- internal+import           Data.Schedule+import           Data.Schedule.Internal+++-- | Something that can run 'Schedule' state transition functions.+--+-- This could be pure (e.g. 'Control.Monad.Trans.State.Strict.StateT') or+-- impure (e.g. reference to a 'Control.Monad.Primitive.Extra.PrimST').+--+-- Examples:+--+-- @+--    primState :: PrimMonad m => RunSched t (ReaderT (PrimST m (Schedule t)) m)+--    primState sched = asks statePrimST >>= \run -> lift (run sched)+--+--    state :: Monad m => RunSched t (StateT (Schedule t) m)+--    zoom _lens . state :: Monad m => RunSched t (StateT s m)+-- @+--+-- See the unit tests for more examples.+type RunSched t m = forall a . (Schedule t -> (a, Schedule t)) -> m a++runTick :: (Monad m, Monoid a) => RunSched t m -> (t -> m a) -> m a+runTick runS runTickTask = whileJustM $ do+  runS popOrTick >>= \case+    Nothing     -> pure Nothing+    Just (t, p) -> do+      runS $ modST $ acquireTask (t, p)+      r <- runTickTask p -- TODO: catch Haskell exceptions here+      runS $ modST $ releaseTask t+      pure (Just r)++runTicksTo+  :: (Monad m, Monoid a) => RunSched t m -> (Tick -> t -> m a) -> Tick -> m a+runTicksTo runS runTask tick = whileJustM $ do+  tick' <- runS $ getST tickNow+  whenMaybe (tick' < tick) $ runTick runS $ runTask tick++getInput+  :: (Monad m)+  => RunSched t m+  -> (TickDelta -> m (Either Tick i))+  -> m (Either Tick i)+getInput runS getTimedInput = do+  d <- runS $ getST ticksToIdle+  getTimedInput (fromMaybe maxBound d)++mkOutput+  :: (Monad m, Monoid a)+  => RunSched t m+  -> (Tick -> t -> m a)+  -> (i -> m a)+  -> (Either Tick i -> m a)+mkOutput runS runTask runInput = runTicksTo runS runTask `either` runInput++-- | A more general version of 'mkOutput' that uses a prism-like optic.+--+-- Given an inner computation @it -> m a@ where one branch of the @it@ type has+-- a @(Tick, t)@ tuple that represents individual input tasks, return an outer+-- computation of type @i -> m a@ where the @i@ type only has a @Tick@. When+-- the outer computation receives these @Tick@ inputs, it automatically+-- resolves the relevant tasks of type @t@ that are active for that @Tick@, and+-- passes each tuple in sequence to the wrapped inner computation.+tickTask+  :: (Monad m, Monoid a)+  => RunSched t m+  -> (forall f . Applicative f => (Tick -> f (Tick, t)) -> i -> f it)+  -> (it -> m a)+  -> (i -> m a)+tickTask runS prism runTaskOr input = case prism Left input of+  Right it   -> runTaskOr it+  Left  tick -> runTicksTo runS (fmap runTaskOr . inputWithTask) tick+  where inputWithTask t k = runIdentity (prism (const (pure (t, k))) input)

@@ -0,0 +1,198 @@+{-# LANGUAGE DeriveGeneric   #-}+{-# LANGUAGE LambdaCase      #-}+{-# LANGUAGE RankNTypes      #-}+{-# LANGUAGE RecordWildCards #-}+{-# LANGUAGE TemplateHaskell #-}+{-# LANGUAGE TupleSections   #-}++{-| Pure serialisable futures.++This API is experimental at the moment, and parts of it may change.+-}+module Control.Schedule.Future where++import qualified Data.Map.Strict                  as M+import qualified Data.Set                         as S++-- external+import           Control.Lens                     (IndexedTraversal', Lens', at,+                                                   contains, indices, (%%~),+                                                   (%~), (.~), (?~), (^.))+import           Control.Lens.TH                  (makeLensesFor, makePrisms)+import           Control.Monad.Trans.State.Strict (runState, state)+import           Data.Function                    ((&))+import           Data.Functor.Compose             (Compose (..))+import           Data.Schedule                    (Schedule, Task, TickDelta,+                                                   after, cancel_)+import           GHC.Generics                     (Generic)+import           GHC.Stack                        (HasCallStack)+import           Safe                             (fromJustNote)+++type OSet a = S.Set a -- TODO: ideally should be set ordered by insertion time+type OMap k v = M.Map k v -- TODO: ideally should be map ordered by insertion time++data TimedResult tk r =+    TimedOut !tk+  | GotResult !r+   deriving (Show, Read, Generic, Eq, Ord)++data SFuture wo ro =+    SFWaiting !(OSet wo)+    -- ^ SExpects waiting on us+  | SFResult !ro+    -- ^ Result of the Future+  deriving (Show, Read, Generic, Eq, Ord)+makePrisms ''SFuture++data SExpect wi ri tk = SExpect {+    seExpects :: !(OMap wi (Task tk))+    -- ^ SFutures we're waiting for, with our own timeout.+    --+    -- Note that the SFuture might have its own separate timeout which is+    -- different; this @t@ timeout is when *we* stop waiting on it.+    --+    -- For example if @(i ~ TimedResult a)@ and our timeout is longer than+    -- their timeout then 'seResults' will get a @GotResult (TimedOut t)@.+  , seResults :: !(OMap wi (TimedResult tk ri))+    -- ^ SFutures that have completed, with the result. This is meant to be a+    -- holding place and the caller of this should move items from here into+    -- some other place to indicate that the results have been processed, so+    -- that if it is called twice it does not process these results twice.+  } deriving (Show, Read, Generic, Eq, Ord)+makeLensesFor ((\x -> (x, "_" <> x)) <$> ["seExpects", "seResults"]) ''SExpect++instance Ord wi => Semigroup (SExpect wi ri tk) where+  s1 <> s2 =+    SExpect (seExpects s1 <> seExpects s2) (seResults s1 <> seResults s2)++instance Ord wi => Monoid (SExpect wi ri tk) where+  mempty = SExpect mempty mempty++data SFStatus e = Expecting e | NotExpecting deriving (Show, Read, Generic, Eq, Ord)+type SFStatusFull wo tk = SFStatus (OSet wo, Task tk)++data SFError =+    SFEAlreadyFinished+  | SFEInvalidPrecondition {+        sfePreExpect :: !(SFStatus ())+      , sfePreActual :: !(SFStatus ())+    }+  deriving (Show, Read, Generic, Eq, Ord)++sCheckStatus+  :: (HasCallStack, Ord wi, Ord wo)+  => wi+  -> wo+  -> Lens' s (SFuture wo r)+  -> Lens' s (SExpect wi r tk)+  -> s+  -> SFStatusFull wo tk+sCheckStatus sfi sei lsf lse s =+  case (s ^. lsf, s ^. lse . _seExpects . at sfi) of+    (SFResult  _      , Just _ ) -> error "SFuture result but SExpect expects"+    (SFWaiting waiting, Just lt) -> if waiting ^. contains sei+      then Expecting (waiting, lt)+      else error "SFuture not waiting but SExpect expects"+    (SFResult  _      , Nothing) -> NotExpecting+    (SFWaiting waiting, Nothing) -> if waiting ^. contains sei+      then error "SFuture waiting but SExpect not expects"+      else NotExpecting++sExpectFuture+  :: (Ord wi, Ord wo)+  => TickDelta+  -> tk+  -> wi+  -> wo+  -> Lens' s (SFuture wo r)+  -> Lens' s (SExpect wi r tk)+  -> Lens' s (Schedule tk)+  -> s+  -> Either SFError s+sExpectFuture d t sfi sei lsf lse lsch s0 = case status of+  Expecting _  -> Left $ SFEInvalidPrecondition NotExpecting (Expecting ())+  NotExpecting -> case s0 ^. lsf of+    SFWaiting sfWaiting -> do+      let (lt, s1) = s0 & lsch %%~ after d t+      Right+        $ s1+        -- SExpect add expecting, set timeout+        & (lse . _seExpects . at sfi ?~ lt)+        -- SFuture add sfWaiting+        & (lsf .~ SFWaiting (sfWaiting & contains sei .~ True))+    SFResult r -> do+      -- SExpect add result to seResults+      Right $ s0 & lse . _seResults . at sfi ?~ GotResult r+  where status = sCheckStatus sfi sei lsf lse s0++sExpectCancel+  :: (Ord wi, Ord wo)+  => wi+  -> wo+  -> Lens' s (SFuture wo r)+  -> Lens' s (SExpect wi r tk)+  -> Lens' s (Schedule tk)+  -> s+  -> Either SFError s+sExpectCancel sfi sei lsf lse lsch s0 = case status of+  NotExpecting -> Left $ SFEInvalidPrecondition (Expecting ()) NotExpecting+  Expecting (sfWaiting, lt) -> do+    Right+      $ s0+      -- SExpect drop expects, clear timeout+      & (lsch %~ (snd . cancel_ lt))+      & (lse . _seExpects . at sfi .~ Nothing)+      -- SFuture drop sfWaiting+      & (lsf .~ SFWaiting (sfWaiting & contains sei .~ False))+  where status = sCheckStatus sfi sei lsf lse s0++sExpectTimeout+  :: (HasCallStack, Ord wi, Ord wo)+  => tk+  -> wi+  -> wo+  -> Lens' s (SFuture wo r)+  -> Lens' s (SExpect wi r tk)+  -> Lens' s (Schedule tk)+  -> s+  -> Either SFError s+sExpectTimeout tk sfi sei lsf lse lsch s0 = case status of+  NotExpecting      -> Left $ SFEInvalidPrecondition (Expecting ()) NotExpecting+  Expecting (_, lt) -> do+    -- SExcept add (TimedOut tick) result+    let s1 = s0 & lse . _seResults . at sfi %~ \case+          Just _  -> error "SExpect expects but also results"+          Nothing -> Just (TimedOut tk)+    sExpectCancel sfi sei lsf lse lsch s1+  where status = sCheckStatus sfi sei lsf lse s0++sFutureResult+  :: (Ord wi, Ord wo)+  => r+  -> wi+  -> Lens' s (SFuture wo r)+  -> IndexedTraversal' wo s (SExpect wi r tk)+  -> Lens' s (Schedule tk)+  -> s+  -> Either SFError s+sFutureResult r sfi lsf lsse lsch s0 = do+  (waiting, s1) <- getCompose $ s0 & lsf %%~ \case+    SFResult  _ -> Compose (Left SFEAlreadyFinished)+    SFWaiting w -> Compose (Right (w, SFResult r))+  let sch0       = s1 ^. lsch+  let (s2, sch1) = f waiting s1 sch0+  let s3         = s2 & lsch .~ sch1+  Right s3+ where+  -- TODO: iterate in order of w, not the traversal+  f w s = runState $ s & lsse . indices (`S.member` w) %%~ g+  g se = do+    let SExpect {..} = se+    -- SExpect drop expects, clear timeout+    let (lt', seExpects') = seExpects & at sfi %%~ (, Nothing)+        lt = fromJustNote "SFuture idx not found in SExpect expects" lt'+    state $ cancel_ lt+    let seResults' = seResults & at sfi ?~ GotResult r+    -- SExpect add result to seResults+    pure $ se { seExpects = seExpects', seResults = seResults' }

@@ -0,0 +1,72 @@+{-# LANGUAGE DeriveGeneric              #-}+{-# LANGUAGE GeneralizedNewtypeDeriving #-}++module Data.Rsv.Common+  ( RHandles(..)+  , RHandle+  , newHandles+  , nextHandle+  , checkHandle+  , withHandle+  , sEnqueue+  , sUnqueue+  , sDequeue+  )+where++-- external+import qualified Data.Sequence.Internal as Seq++import           Data.Sequence          (Seq (..), (|>))+import           Data.Word              (Word64)+import           GHC.Generics           (Generic)+import           GHC.Stack              (HasCallStack)+++-- Handle generator. Runtime invariants:+--+-- 1. A handle from one generator is not used in a context that expects a+-- handle from a different generator. TODO: use a string or other data to+-- distinguish the contexts.+--+-- 2. Newly generated handles are distinguishable from previously-generated+-- ones. 'checkHandle' is used to check this.+newtype RHandles = RHandles { getNextHandle :: RHandle }+  deriving (Show, Read, Generic, Eq)+newtype RHandle = RHandle { getHandle :: Word64 }+  deriving (Show, Read, Generic, Eq, Ord, Enum, Bounded)++newHandles :: RHandles+newHandles = RHandles (RHandle 0)++nextHandle :: RHandles -> (RHandle, RHandles)+nextHandle (RHandles h) = (h, RHandles (succ h))++-- | Check that an existing handle is consistent with the current state of a+-- handle generator, i.e. it must not be part of the generator's future.+checkHandle :: RHandles -> RHandle -> Bool+checkHandle (RHandles hh) h = hh > h++withHandle+  :: ((RHandle, i) -> c -> c) -> i -> (RHandles, c) -> (RHandle, (RHandles, c))+withHandle doWith item (handles0, container0) =+  let (handle, handles1) = nextHandle handles0+      container1         = doWith (handle, item) container0+  in  (handle, (handles1, container1))++sEnqueue :: a -> Seq a -> Seq a+sEnqueue x slm = slm |> x++sUnqueue :: (HasCallStack, Eq k) => k -> Seq (k, a) -> (Maybe a, Seq (k, a))+sUnqueue idx' slm = (snd <$> found', others)+ where+  -- TODO: this is O(n); maybe it should be more efficient...+  (Seq.Seq found, others) = Seq.partition ((== idx') . fst) $ slm+  found'                  = case found of+    Seq.EmptyT              -> Nothing+    Seq.Single (Seq.Elem x) -> Just x+    _                       -> error "sUnqueue found more than one key"++sDequeue :: Seq a -> (Maybe a, Seq a)+sDequeue (h :<| t) = (Just h, t)+sDequeue Seq.Empty = (Nothing, Seq.Empty)

@@ -0,0 +1,135 @@+{-# LANGUAGE DeriveGeneric   #-}+{-# LANGUAGE TemplateHaskell #-}+{-# LANGUAGE TupleSections   #-}++{-| This module implements a /reservation/ multi-map.++Each insert is indexed by a key; many inserts (of the same or different items)+may be performed on the same key.++A /reservation/ data structure is one that allows multiple inserts of the same+item, by returning a unique handle for each insert operation that must be given+to the deletion operation. If you need to store the handle together with the+item, e.g. so that the item knows how to delete itself, you can achieve this by+the standard Haskell "tying the knot" technique.+-}+module Data.Rsv.RMMap+  ( RMMap(..)+  , _handles+  , _content+  , Delete+  , checkValidity+  , checkHandle+  , empty+  -- * Read operations+  , isEmpty+  , (!)+  , toList+  -- * Write operations+  , enqueue+  , unqueue+  , dequeue+  )+where++-- external+import           Control.Lens    (Iso, anon, at, iso, makeLensesFor, (%%~),+                                  (%~), (&))+import           Data.Bifunctor  (first)+import qualified Data.Foldable   as F (toList)+import           Data.Maybe      (mapMaybe)+import           Data.Text       (Text, pack)+import           GHC.Generics    (Generic)++import qualified Data.Map.Strict as M+import           Data.Sequence   (Seq (..))++-- internal+import           Data.Rsv.Common hiding (checkHandle)+import qualified Data.Rsv.Common as R (checkHandle)+++type Entries a = Seq (RHandle, a)++data RMMap k a = RMMap {+  handles :: !RHandles,+  content :: !(M.Map k (Entries a))+} deriving (Show, Read, Generic, Eq)+makeLensesFor ((\x -> (x, "_" <> x)) <$> ["handles", "content"]) ''RMMap++data Delete k a = Delete !k !RHandle+  deriving (Show, Read, Generic, Eq, Ord)++toPair+  :: Iso+       (RMMap k0 a0)+       (RMMap k1 a1)+       (RHandles, M.Map k0 (Entries a0))+       (RHandles, M.Map k1 (Entries a1))+toPair = iso (\(RMMap x y) -> (x, y)) (uncurry RMMap)++-- | Check the map that its internal invariants all hold.+--+-- You must run this on every instance obtained not via the API functions here.+-- For example, you must run this on instances obtained via deserialisation,+-- which in general cannot check the complex invariants maintained by the API+-- functions. Also, for all handles you obtain via a similarly non-standard+-- method, including by deserialisation of a parent data structure, you must+-- run @checkHandle map handle@.+--+-- @Nothing@ means the check passed, else @Just errmsg@ gives a failure reason.+--+-- Note: this does not guard against all malicious behaviour, but it does guard+-- against violation (either malicious or accidental) of the runtime invariants+-- assumed by this data structure.+checkValidity :: RMMap k a -> Maybe Text+checkValidity (RMMap handles' content') =+  let res = flip mapMaybe (M.toList content') $ \(k, hh) -> do+        if any (not . R.checkHandle handles' . fst) hh then Just k else Nothing+  in  case res of+        [] -> Nothing+        e  -> Just $ pack "some handles were reused in the input"++-- | Check that an existing handle is consistent with the current state of the+-- structure, i.e. it is not a handle that could be generated in the future.+checkHandle :: RMMap k a -> Delete k a -> Bool+checkHandle (RMMap handles' _) (Delete _ h) = R.checkHandle handles' h++empty :: RMMap k a+empty = RMMap { handles = newHandles, content = M.empty }++isEmpty :: RMMap k a -> Bool+isEmpty sm = M.null m || all null m where m = content sm++(!) :: Ord k => RMMap k a -> k -> Seq a+m ! k = case M.lookup k $ content m of+  Just l  -> snd <$> l+  Nothing -> mempty++toList :: RMMap k a -> [Delete k a]+toList (RMMap _ content') =+  M.toList content' >>= \(k, hh) -> F.toList hh & fmap (Delete k . fst)++-- | Append an item on a key, returning a handle to remove it with.+-- The same item may be added twice, in which case it will occupy multiple+-- positions in the map, and the handles distinguish these occurences.+enqueue :: Ord k => (k, a) -> RMMap k a -> (Delete k a, RMMap k a)+enqueue i@(k, _) m = m & toPair %%~ withHandle enq i & first (Delete k)+ where+  enq+    :: Ord k => (RHandle, (k, a)) -> M.Map k (Entries a) -> M.Map k (Entries a)+  enq (h', (k', v')) m' = m' & at k' . anon mempty null %~ sEnqueue (h', v')++req :: (a -> b) -> (Maybe a, c) -> (Maybe b, c)+req = first . fmap++-- | Delete an item corresponding to a given handle.+-- If the item was already removed, 'Nothing' is returned instead.+unqueue :: Ord k => Delete k a -> RMMap k a -> (Maybe (k, a), RMMap k a)+unqueue (Delete k idx) m =+  m & _content . at k . anon mempty null %%~ sUnqueue idx & req (k, )++-- | Remove an item from a key, from the front. Return Nothing if key is empty.+dequeue :: Ord k => k -> RMMap k a -> (Maybe (Delete k a, a), RMMap k a)+dequeue k m =+  m & _content . at k . anon mempty null %%~ sDequeue & req (first (Delete k))

@@ -0,0 +1,72 @@+{-# LANGUAGE LambdaCase    #-}+{-# LANGUAGE TupleSections #-}++{-| Data structure representing scheduled tasks.++Most of the time you will want the more fully-featured "Control.Monad.Schedule"+or "Control.Arrow.Schedule" modules instead, which re-export this module.+-}+module Data.Schedule+  ( Tick+  , TickDelta+  , Task+  , TaskStatus(..)+  , Schedule+  , newSchedule+  , checkValidity+  , tickNow+  , tickPrev+  , ticksToIdle+  , taskStatus+  , after+  , cancel+  , cancel_+  , renew+  -- | = Other general utilities+  -- General monad / state-transition utils to be exported to another library+  , whileJustM+  , modST+  , getST+  , stA+  , imodA+  , getA+  )+where++import           Data.Schedule.Internal+++-- | Run an action, accumulating its monoid result until it returns @Nothing@.+--+-- TODO: export to upstream extra+whileJustM :: (Monad m, Monoid a) => m (Maybe a) -> m a+whileJustM act = go mempty+ where+  go accum = act >>= \case+    Just r  -> go (accum <> r)+    Nothing -> pure accum++-- | Convert a modification function into a state transition function.+modST :: (s -> s) -> (s -> ((), s))+modST f s = ((), f s)+{-# INLINE modST #-}++-- | Convert a getter function into a state transition function.+getST :: (s -> o) -> (s -> (o, s))+getST f s = (f s, s)+{-# INLINE getST #-}++-- | Convert a state transition function into a state transition arrow.+stA :: (s -> os) -> ((i, s) -> os)+stA f = f . snd+{-# INLINE stA #-}++-- | Convert a modification arrow into a state transition arrow.+imodA :: (i -> s -> s) -> ((i, s) -> ((), s))+imodA f = ((), ) . uncurry f+{-# INLINE imodA #-}++-- | Convert a getter function into a state transition arrow.+getA :: (s -> a) -> ((i, s) -> (a, s))+getA f = getST f . snd+{-# INLINE getA #-}

@@ -0,0 +1,195 @@+{-# LANGUAGE DeriveGeneric   #-}+{-# LANGUAGE RecordWildCards #-}++module Data.Schedule.Internal where++-- external+import           Data.Bifunctor  (first)+import           Data.Text       (Text, pack)+import           Data.Word       (Word64)+import           GHC.Generics    (Generic)+import           GHC.Stack       (HasCallStack)++-- internal+import qualified Data.Map.Strict as M+import qualified Data.Rsv.RMMap  as RM+import qualified Data.Set        as S++import           Data.Rsv.RMMap  (RMMap)+++type Tick = Integer+type TickDelta = Word64++-- | A task that is currently or was part of a schedule.+--+-- @t@ is the type of input parameter for each task, i.e. the task contents.+newtype Task t = Task (RM.Delete Tick t)+  deriving (Show, Read, Generic, Eq, Ord)++-- | The current status of a task as returned by 'taskStatus'.+data TaskStatus t =+    TaskNotPending+  -- ^ The task is not pending - either it was already run, or cancelled.+  | TaskPending !Tick !t+  -- ^ The task is due to run at some future tick.+  | TaskRunning !t+  -- ^ The task is running right now.+  deriving (Show, Read, Generic, Eq, Ord)++-- | The state of all scheduled pending tasks.+--+-- @t@ is the type of task-params.+data Schedule t = Schedule {+    now     :: !Tick+  , tasks   :: !(RMMap Tick t)+  , pending :: !(S.Set (Task t))+  , running :: !(Maybe (Task t, t))+} deriving (Show, Read, Generic, Eq)++newSchedule :: Schedule t+newSchedule =+  Schedule { now = 0, tasks = RM.empty, pending = mempty, running = Nothing }++-- | Check the schedule that its internal invariants all hold.+--+-- You must run this on every instance obtained not via the API functions here.+-- For example, you must run this on instances obtained via deserialisation,+-- which in general cannot check the complex invariants maintained by the API+-- functions. Also, for all 'Task's you obtain via a similarly non-standard+-- method, including by deserialisation of a parent data structure, you must+-- run @checkHandle schedule task@.+--+-- @Nothing@ means the check passed, else @Just errmsg@ gives a failure reason.+--+-- Note: this does not guard against all malicious behaviour, but it does guard+-- against violation (either malicious or accidental) of the runtime invariants+-- assumed by this data structure.+checkValidity :: Schedule t -> Maybe Text+checkValidity Schedule {..} =+  let tasksValid = RM.checkValidity tasks+      tasks'     = RM.content tasks+      nowMatch   = case M.lookupMin tasks' of+        Nothing                -> True+        Just (nextTaskTick, _) -> now <= nextTaskTick+      pending' = S.fromList $ Task <$> RM.toList tasks+  in  case tasksValid of+        Just e -> Just e+        Nothing+          | not nowMatch        -> Just $ pack "has tasks for before now"+          | pending /= pending' -> Just $ pack "inconsistent pending tasks"+          | otherwise           -> Nothing++-- | Check that an existing task is consistent with the current state of the+-- structure, i.e. it is not a task that could be generated in the future.+checkTask :: Schedule t -> Task t -> Bool+checkTask sch (Task d) = RM.checkHandle (tasks sch) d++-- | Get the current tick, whose tasks have not all run yet.+--+-- From the perspective of the pure computation that is running this schedule,+-- you should treat this as the current "logical time", even if an impure clock+-- is telling you that the "environment time" is in the future.+tickNow :: Schedule t -> Tick+tickNow = now++-- | Get the previous tick, whose tasks have all already run.+tickPrev :: Schedule t -> Tick+tickPrev = pred . now++-- | Get the number of ticks until the next scheduled task.+--+-- This may be used by an impure runtime environment to set an actual timeout;+-- see "Control.Clock" for a starting point.+ticksToIdle :: Schedule t -> Maybe TickDelta+ticksToIdle Schedule {..} = do+  (m, _) <- M.lookupMin (RM.content tasks)+  pure (fromIntegral (m - now))++taskStatus :: HasCallStack => Task t -> Schedule t -> TaskStatus t+taskStatus t@(Task d) Schedule {..} = if S.member t pending+  then case RM.unqueue d tasks of -- ofc this doesn't actually unqueue+    (Nothing             , _) -> error "inconsistent pending tasks"+    (Just (tick, tParams), _) -> TaskPending tick tParams+  else case running of+    Just (t', tParams) | t == t' -> TaskRunning tParams+    _                            -> TaskNotPending++-- | Schedule a task to run after a given number of ticks.+--+-- This is relative to 'tickNow'; a @0@ delta schedules the task to be run at+-- the end of the current tick, i.e. as soon as possible but not immediately.+--+-- If your task params needs to refer to the task itself, you may achieve this+-- by using the standard Haskell "tying the knot" technique, e.g.:+--+-- >>> data TPar = TPar !(Task TPar) deriving (Show, Eq)+-- >>> s = newSchedule+-- >>> let (t, s') = after 1 (TPar t) s -- @t@ on LHS & RHS, tying the knot+-- >>> t+-- Task (Delete 1 (RHandle {getHandle = 0}))+-- >>> taskStatus t s+-- TaskNotPending+-- >>> taskStatus t s'+-- TaskPending 1 (TPar (Task (Delete 1 (RHandle {getHandle = 0}))))+-- >>> taskStatus t s' == TaskPending 1 (TPar t)+-- True+--+after :: TickDelta -> t -> Schedule t -> (Task t, Schedule t)+after tDelta tParams s0@(Schedule now tasks0 pending0 _) =+  let tick        = now + toInteger tDelta+      (d, tasks1) = RM.enqueue (tick, tParams) tasks0+      pending1    = S.insert (Task d) pending0+  in  (Task d, s0 { tasks = tasks1, pending = pending1 })++-- | Cancel a task. Result is Nothing if task was not already pending.+cancel :: Task t -> Schedule t -> (Maybe t, Schedule t)+cancel (Task d) s0@(Schedule _ tasks0 pending0 _) = case RM.unqueue d tasks0 of+  (Nothing, _) -> (Nothing, s0)+  (Just (_, tParams), tasks1) ->+    let pending1 = S.delete (Task d) pending0+    in  (Just tParams, s0 { tasks = tasks1, pending = pending1 })++-- | Cancel a task, discarding the result.+cancel_ :: Task t -> Schedule t -> ((), Schedule t)+cancel_ t s = ((), snd $ cancel t s)++-- | Reschedule a pending task to instead run after a given number of ticks.+--+-- If the task was not already pending, do nothing. If you need to reschedule+-- a task unconditionally even if it was already cancelled or run, use both+-- 'cancel_' and 'after' in combination.+renew :: TickDelta -> Task t -> Schedule t -> (Maybe (Task t), Schedule t)+renew tDelta (Task d) s0 = case RM.unqueue d (tasks s0) of+  (Nothing, _) -> (Nothing, s0)+  (Just (_, tParams), tasks1) ->+    first Just $ after tDelta tParams (s0 { tasks = tasks1 })++-- | Pop the next task to be run in this tick.+-- If there are no more tasks remaining, then advance to the next tick.+popOrTick :: HasCallStack => Schedule t -> (Maybe (Task t, t), Schedule t)+popOrTick s0@(Schedule now0 tasks0 pending0 running) = case running of+  Just _  -> error "tried to pop tick while task was running"+  Nothing -> case RM.dequeue now0 tasks0 of+    (Nothing, _) -> (Nothing, s0 { now = succ now0 })+    (Just (d, tParams), tasks1) ->+      let pending1 = S.delete (Task d) pending0+      in  (Just (Task d, tParams), s0 { tasks = tasks1, pending = pending1 })++-- | Lock the schedule before running a particular task.+--+-- This prevents popOrTick from being called, or other tasks from running.+-- It is not re-entrant; only one task is supposed to run at once.+acquireTask :: HasCallStack => (Task t, t) -> Schedule t -> Schedule t+acquireTask k s = case running s of+  Just _ -> error "tried to acquire on unreleased task"+  _      -> s { running = Just k }++-- | Unlock the schedule after running a particular task.+--+-- This allows popOrTick to be called again and other tasks to run.+-- It is not re-entrant; only one task is supposed to run at once.+releaseTask :: HasCallStack => Task t -> Schedule t -> Schedule t+releaseTask t s = case running s of+  Just (t', _) | t' == t -> s { running = Nothing }+  _                      -> error "tried to release on unacquired task"

@@ -0,0 +1,80 @@+{-# LANGUAGE RankNTypes #-}++module Control.Monad.ScheduleTest where++-- external+import           Test.Tasty                       hiding (after)+import           Test.Tasty.HUnit++import           Control.Monad                    (when)+import           Control.Monad.Trans.Class        (MonadTrans (lift))+import           Control.Monad.Trans.Maybe        (MaybeT (MaybeT, runMaybeT))+import           Control.Monad.Trans.Reader       (ReaderT (..), asks)+import           Control.Monad.Trans.State.Strict (StateT (..), state)+import           Data.Primitive.MutVar            (newMutVar, readMutVar)++-- internal+import           Control.Clock.IO+import           Control.Monad.Primitive.Extra+import           Control.Monad.Schedule+import           Data.Rsv.RMMap                   (RMMap (..), empty)+import           Data.Schedule.Internal+++runSchedMV :: PrimMonad m => RunSched t (ReaderT (PrimST m (Schedule t)) m)+runSchedMV sched = asks statePrimST >>= \run -> lift (run sched)++runSchedST :: Monad m => RunSched t (StateT (Schedule t) m)+runSchedST = state+++tests :: TestTree+tests = testGroup+  "Control.Monad.Trans.ScheduleTest"+  [ testCase "smoke clockTimer" $ do+    smoke (\clock -> pure (flip (clockTimer clock) voidInput))+          (flip runStateT)+          runSchedST+  , testCase "smoke clockWith" $ do+    -- TODO: we should call 'fin' (see clockWith) after the test but meh+    smoke+      (\clock -> const . runClocked <$> clockWith clock voidInput)+      (\s0 act -> do+        mv <- newMutVar s0+        r  <- runReaderT act (stMutVar mv)+        s1 <- readMutVar mv+        pure (r, s1)+      )+      runSchedMV+  ]++smoke+  :: (MonadTrans tm, Monad (tm IO))+  => (Clock IO -> IO (TickDelta -> IO (Either Tick i)))+  -> (Schedule t -> tm IO [Tick] -> IO ([Tick], Schedule Tick))+  -> RunSched Tick (tm IO)+  -> IO ()+smoke mkRecv runWithNew runSched = do+  clock <- newClock1ms+  recv  <- mkRecv clock+  let top = 17+  (r, s) <- runWithNew newSchedule $ do+    _ <- runSched $ after 1 top+    whileJustM $ runMaybeT $ do+      MaybeT (runSched $ getST $ ticksToIdle) >>= \d -> lift $ do+        lift (recv d) >>= mkOutput runSched countdown undefined+  assertEqual "results" [top, top - 1 .. 0] r+  assertBool "schedule.now" $ now s > top+  assertEqual "schedule.tasks" (empty { handles = handles (tasks s) }) (tasks s)+  assertEqual "schedule.*" (newSchedule { now = now s, tasks = tasks s }) s+  assertEqual "schedule valid" (checkValidity s) Nothing+ where+  countdown _ x = do+    when (x > 0) $ do+      n <- runSched $ getST $ tickNow+      t <- runSched $ after 1 $ pred x+      s <- runSched $ getST $ taskStatus t+      lift $ assertEqual "task status is pending after 'after'"+                         s+                         (TaskPending (n + 1) (pred x))+    pure [x]

@@ -0,0 +1,24 @@+{-# OPTIONS_GHC -fno-warn-type-defaults #-}++{-| Examples for various "Data.Rsv" structures. -}++module Data.Rsv.Example where++-- external+import           Control.Monad.Trans.State.Strict (evalStateT, state)+import           Data.Functor.Identity            (runIdentity)+import           Data.Maybe                       (isJust)++-- internal+import qualified Data.Rsv.RMMap                   as RM+++-- | Basic usage example for 'RMMap'+--+-- >>> rMMapExample0+-- True+rMMapExample0 :: Bool+rMMapExample0 = runIdentity $ (`evalStateT` RM.empty) $ do+  sDelete           <- state $ RM.enqueue (1000, const "my callback")+  notAlreadyRemoved <- state $ RM.unqueue sDelete+  return $ isJust notAlreadyRemoved

@@ -0,0 +1,4 @@+import           Test.DocTest++main :: IO ()+main = doctest ["-i", "src"]

@@ -0,0 +1,7 @@+import           Test.Tasty++import           Control.Monad.ScheduleTest (tests)++main :: IO ()+main = do+  defaultMain $ testGroup "Schedule *" [Control.Monad.ScheduleTest.tests]