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50 lines
1.2 KiB
Haskell
50 lines
1.2 KiB
Haskell
{-
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# Behn
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This provides a timer. To use this,
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- Create a new timer with `init`.
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- Use `doze` to start the timer.
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- Call `wait` to wait until the timer fires.
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Then, `wait` will return when the specified time has come.
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- If the specified time was in the past, `wait` will return immediately.
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- If a timer is set again, the old timer will not fire. The new time
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replaces the old one.
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- If a timer is unset (with `doze _ Nothing`), the timer will not fire
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until a new time has been set.
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-}
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module Urbit.Behn (Behn(..), init, wait, doze) where
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import Control.Lens
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import Prelude hiding (init)
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import Control.Concurrent.MVar (MVar, newEmptyMVar, putMVar, takeMVar)
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import qualified Urbit.Time as Time
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import qualified Urbit.Timer as Timer
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-- Behn Stuff ------------------------------------------------------------------
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data Behn = Behn
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{ bTimer :: Timer.Timer
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, bSignal :: MVar ()
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}
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init :: IO Behn
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init = do
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tim <- Timer.init
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sig <- newEmptyMVar
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pure (Behn tim sig)
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wait :: Behn -> IO ()
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wait (Behn _ sig) = takeMVar sig
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doze :: Behn -> Maybe Time.Wen -> IO ()
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doze behn Nothing = Timer.stop (bTimer behn)
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doze (Behn tim sig) (Just t) =
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Timer.start tim (t ^. Time.systemTime) (putMVar sig ())
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