diff --git a/CHANGELOG.md b/CHANGELOG.md
new file mode 100644
--- /dev/null
+++ b/CHANGELOG.md
@@ -0,0 +1,5 @@
+# Revision history for schedule
+
+## 0.1.0.0 -- 2019-12-20
+
+* Initial release.
diff --git a/LICENSE.GPL-3 b/LICENSE.GPL-3
new file mode 100644
--- /dev/null
+++ b/LICENSE.GPL-3
@@ -0,0 +1,674 @@
+ GNU GENERAL PUBLIC LICENSE
+ Version 3, 29 June 2007
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+EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF
+SUCH DAMAGES.
+
+ 17. Interpretation of Sections 15 and 16.
+
+ If the disclaimer of warranty and limitation of liability provided
+above cannot be given local legal effect according to their terms,
+reviewing courts shall apply local law that most closely approximates
+an absolute waiver of all civil liability in connection with the
+Program, unless a warranty or assumption of liability accompanies a
+copy of the Program in return for a fee.
+
+ END OF TERMS AND CONDITIONS
+
+ How to Apply These Terms to Your New Programs
+
+ If you develop a new program, and you want it to be of the greatest
+possible use to the public, the best way to achieve this is to make it
+free software which everyone can redistribute and change under these terms.
+
+ To do so, attach the following notices to the program. It is safest
+to attach them to the start of each source file to most effectively
+state the exclusion of warranty; and each file should have at least
+the "copyright" line and a pointer to where the full notice is found.
+
+
+ Copyright (C)
+
+ This program is free software: you can redistribute it and/or modify
+ it under the terms of the GNU General Public License as published by
+ the Free Software Foundation, either version 3 of the License, or
+ (at your option) any later version.
+
+ This program is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with this program. If not, see .
+
+Also add information on how to contact you by electronic and paper mail.
+
+ If the program does terminal interaction, make it output a short
+notice like this when it starts in an interactive mode:
+
+ Copyright (C)
+ This program comes with ABSOLUTELY NO WARRANTY; for details type `show w'.
+ This is free software, and you are welcome to redistribute it
+ under certain conditions; type `show c' for details.
+
+The hypothetical commands `show w' and `show c' should show the appropriate
+parts of the General Public License. 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
+.
+
+ 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
+.
diff --git a/Setup.hs b/Setup.hs
new file mode 100644
--- /dev/null
+++ b/Setup.hs
@@ -0,0 +1,2 @@
+import Distribution.Simple
+main = defaultMain
diff --git a/schedule.cabal b/schedule.cabal
new file mode 100644
--- /dev/null
+++ b/schedule.cabal
@@ -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
diff --git a/src/Control/Arrow/Schedule.hs b/src/Control/Arrow/Schedule.hs
new file mode 100644
--- /dev/null
+++ b/src/Control/Arrow/Schedule.hs
@@ -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)
diff --git a/src/Control/Clock.hs b/src/Control/Clock.hs
new file mode 100644
--- /dev/null
+++ b/src/Control/Clock.hs
@@ -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 ())
+ }
diff --git a/src/Control/Clock/IO.hs b/src/Control/Clock/IO.hs
new file mode 100644
--- /dev/null
+++ b/src/Control/Clock/IO.hs
@@ -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
diff --git a/src/Control/Monad/Primitive/Extra.hs b/src/Control/Monad/Primitive/Extra.hs
new file mode 100644
--- /dev/null
+++ b/src/Control/Monad/Primitive/Extra.hs
@@ -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 .))
diff --git a/src/Control/Monad/Schedule.hs b/src/Control/Monad/Schedule.hs
new file mode 100644
--- /dev/null
+++ b/src/Control/Monad/Schedule.hs
@@ -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)
diff --git a/src/Control/Schedule/Future.hs b/src/Control/Schedule/Future.hs
new file mode 100644
--- /dev/null
+++ b/src/Control/Schedule/Future.hs
@@ -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' }
diff --git a/src/Data/Rsv/Common.hs b/src/Data/Rsv/Common.hs
new file mode 100644
--- /dev/null
+++ b/src/Data/Rsv/Common.hs
@@ -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)
diff --git a/src/Data/Rsv/RMMap.hs b/src/Data/Rsv/RMMap.hs
new file mode 100644
--- /dev/null
+++ b/src/Data/Rsv/RMMap.hs
@@ -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))
diff --git a/src/Data/Schedule.hs b/src/Data/Schedule.hs
new file mode 100644
--- /dev/null
+++ b/src/Data/Schedule.hs
@@ -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 #-}
diff --git a/src/Data/Schedule/Internal.hs b/src/Data/Schedule/Internal.hs
new file mode 100644
--- /dev/null
+++ b/src/Data/Schedule/Internal.hs
@@ -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"
diff --git a/test/Control/Monad/ScheduleTest.hs b/test/Control/Monad/ScheduleTest.hs
new file mode 100644
--- /dev/null
+++ b/test/Control/Monad/ScheduleTest.hs
@@ -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]
diff --git a/test/Data/Rsv/Example.hs b/test/Data/Rsv/Example.hs
new file mode 100644
--- /dev/null
+++ b/test/Data/Rsv/Example.hs
@@ -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
diff --git a/test/DocTests.hs b/test/DocTests.hs
new file mode 100644
--- /dev/null
+++ b/test/DocTests.hs
@@ -0,0 +1,4 @@
+import Test.DocTest
+
+main :: IO ()
+main = doctest ["-i", "src"]
diff --git a/test/UnitTests.hs b/test/UnitTests.hs
new file mode 100644
--- /dev/null
+++ b/test/UnitTests.hs
@@ -0,0 +1,7 @@
+import Test.Tasty
+
+import Control.Monad.ScheduleTest (tests)
+
+main :: IO ()
+main = do
+ defaultMain $ testGroup "Schedule *" [Control.Monad.ScheduleTest.tests]