{-# LANGUAGE
    DoAndIfThenElse
  , FlexibleContexts
  , ScopedTypeVariables
  , UnicodeSyntax
  #-}
module Codec.Audio.WavPack.Unpack
    ( WavpackStream(..)
    , unpackSamples
    )
    where
import Codec.Audio.WavPack.Block
import Control.Monad.ST
import Data.Int
import Data.STRef
import qualified Data.Vector.Generic.Mutable as MV
import Data.Word
import Prelude.Unicode

-- | FIXME
data WavpackStream s
    = WavpackStream {
        wpsHeader      ∷ !BlockHeader
      , wpsMuteError   ∷ !(STRef s Bool)
      , wpsSampleIndex ∷ !(STRef s Word32)
      }

-- |This monster actually unpacks the WavPack bitstream(s) into the
-- specified buffer as 32-bit integers or floats (depending on orignal
-- data). Lossy samples will be clipped to their original limits
-- (i.e. 8-bit samples are clipped to -128/+127) but are still
-- returned in longs. It is up to the caller to potentially reformat
-- this for the final output including any multichannel distribution,
-- block alignment or endian compensation.
unpackSamples ∷ ∀v s. (MV.MVector v Int32)
              ⇒ WavpackStream s
              → Int    -- ^ Number of channels.
              → Int    -- ^ Reduced number of channels (1 or 2).
              → Word32 -- ^ Number of samples to get.
              → ST s (v s Int32)
{-# INLINEABLE unpackSamples #-}
unpackSamples wps numChannels reducedChannels nSamples0
    = do let hdr   = wpsHeader wps
             flags = bhFlags hdr
         nSamples ← do idx ← readSTRef (wpsSampleIndex wps)
                       if idx + nSamples0 > bhBlockIndex hdr + bhBlockSamples hdr then
                           return $ bhBlockIndex hdr + bhBlockSamples hdr - idx
                       else
                           return nSamples0

         muteError ← readSTRef (wpsMuteError wps)
         if muteError then
             do v ← if reducedChannels ≡ 1 ∨ numChannels ≡ 1 ∨ bfMono flags then
                        MV.replicate (fromIntegral nSamples) 0
                    else
                        MV.replicate (fromIntegral nSamples ⋅ 2) 0
                modifySTRef (wpsSampleIndex wps) (+ nSamples)
                return v
         else
             error "FIXME"