{-# LANGUAGE
    ExistentialQuantification
  , UnicodeSyntax
  #-}
-- | WavPack metadata sub-blocks
module Codec.Audio.WavPack.Metadata
    ( Metadata(..)
    , SomeMetadata(..)
    )
    where
import Data.Binary
import Data.Binary.Put
import Data.Bits
import qualified Data.ByteString.Lazy as L
import Data.Typeable
import Prelude.Unicode

class (Binary α, Eq α, Show α, Typeable α) ⇒ Metadata α where
    metaID   ∷ α → Word8
    metaSize ∷ α → Word32

    metaSize = fromIntegral ∘ L.length ∘ runPut ∘ put

data SomeMetadata = ∀α. Metadata α ⇒ SomeMetadata α

instance Binary SomeMetadata where
    put (SomeMetadata a)
        = let size     = metaSize a
              oddBit   = if odd size   then 0x40 else 0
              largeBit = if size > 255 then 0x80 else 0
              idWord   = metaID a .|. oddBit .|. largeBit
          in
            do putWord8 idWord
               fail "FIXME"

    get = fail "FIXME"

instance Eq SomeMetadata where
    (SomeMetadata a) == (SomeMetadata b)
        = Just a ≡ cast b

instance Show SomeMetadata where
    show (SomeMetadata a)
        = show a