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33 lines
705 B
Haskell
33 lines
705 B
Haskell
module Urbit.Vere.Ames.LaneCache (cache) where
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import Urbit.Prelude
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import Urbit.Noun.Time
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expiry :: Gap
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expiry = (2 * 60) ^. from secs
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cache :: forall a b m n
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. (Ord a, MonadIO m, MonadIO n)
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=> (a -> m b)
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-> n (a -> m b)
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cache act = do
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cas <- newTVarIO (mempty :: Map a (Wen, b))
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let fun x = lookup x <$> readTVarIO cas >>= \case
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Nothing -> thru
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Just (t, v) -> do
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t' <- io now
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if gap t' t > expiry
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then thru
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else pure v
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where
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thru :: m b
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thru = do
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t <- io now
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v <- act x
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atomically $ modifyTVar' cas (insertMap x (t, v))
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pure v
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pure fun
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