-- 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