    -- CryptoCipherTypes.hs: shim for crypto-cipher-types stuff (current nettle)
    -- Copyright © 2016  Clint Adams
    -- This software is released under the terms of the Expat license.
    -- (See the LICENSE file).

    {-# LANGUAGE FlexibleInstances #-}
    {-# LANGUAGE PackageImports #-}
    {-# LANGUAGE UndecidableInstances #-}

    module Codec.Encryption.OpenPGP.Internal.CryptoCipherTypes (
        HOWrappedOldCCT(..)
    ) where

    import Control.Error.Util (note)
    import qualified "crypto-cipher-types" Crypto.Cipher.Types as OldCCT
    import qualified "cryptonite" Crypto.Cipher.Types as CCT
    import qualified Data.ByteString as B

    import Codec.Encryption.OpenPGP.Internal.HOBlockCipher

    newtype HOWrappedOldCCT a = HWOCCT a

    instance OldCCT.BlockCipher cipher => HOBlockCipher (HOWrappedOldCCT cipher) where
        cipherInit = fmap HWOCCT . either (const (Left "nettle invalid key"))
                            (Right . OldCCT.cipherInit) . OldCCT.makeKey
        cipherName (HWOCCT c) = OldCCT.cipherName c
        cipherKeySize (HWOCCT c) = convertKSS . OldCCT.cipherKeySize $ c
        blockSize (HWOCCT c) = OldCCT.blockSize c
        cfbEncrypt (HWOCCT c) iv bs = hammerIV iv >>= \i -> return (OldCCT.cfbEncrypt c i bs)
        cfbDecrypt (HWOCCT c) iv bs = hammerIV iv >>= \i -> return (OldCCT.cfbDecrypt c i bs)
        paddedCfbEncrypt _ _ _ = Left "padding for nettle-encryption not implemented yet"
        paddedCfbDecrypt (HWOCCT cipher) iv ciphertext = hammerIV iv >>= \i -> return (B.take (B.length ciphertext) (OldCCT.cfbDecrypt cipher i padded))
            where
                padded = ciphertext `B.append`
                                 B.pack (replicate (OldCCT.blockSize cipher - (B.length ciphertext `mod` OldCCT.blockSize cipher)) 0)

    convertKSS :: OldCCT.KeySizeSpecifier -> CCT.KeySizeSpecifier
    convertKSS (OldCCT.KeySizeRange a b) = CCT.KeySizeRange a b
    convertKSS (OldCCT.KeySizeEnum as) = CCT.KeySizeEnum as
    convertKSS (OldCCT.KeySizeFixed a) = CCT.KeySizeFixed a

    hammerIV :: OldCCT.BlockCipher cipher => B.ByteString -> Either String (OldCCT.IV cipher)
    hammerIV = note "nettle bad IV" . OldCCT.makeIV