FIFO.hs

{-# LANGUAGE RecordWildCards #-}
module FRP.Rhine.ResamplingBuffer.FIFO where

-- base
import Prelude hiding (length)

-- containers
import Data.Sequence

-- rhine
import FRP.Rhine.ResamplingBuffer
import FRP.Rhine.ResamplingBuffer.Timeless

-- * FIFO (first-in-first-out) buffers

-- | An unbounded FIFO buffer.
--   If the buffer is empty, it will return 'Nothing'.
fifo :: Monad m => ResamplingBuffer m cl1 cl2 a (Maybe a)
fifo = timelessResamplingBuffer AsyncMealy {..} empty
  where
    amPut as a = return $ a <| as
    amGet as   = case viewr as of
      EmptyR   -> return (Nothing, empty)
      as' :> a -> return (Just a , as'  )


-- | An unbounded FIFO buffer that also returns its current size.
fifoWatch :: Monad m => ResamplingBuffer m cl1 cl2 a (Maybe a, Int)
fifoWatch = timelessResamplingBuffer AsyncMealy {..} empty
  where
    amPut as a = return $ a <| as
    amGet as   = case viewr as of
      EmptyR   -> return ((Nothing, 0         ), empty)
      as' :> a -> return ((Just a , length as'), as'  )