ChanScript.hs

{-# LANGUAGE DeriveGeneric #-}
module PaymentChannel.Internal.ChanScript
(
  module PaymentChannel.Internal.ChanScript
, module Network.Haskoin.Script
)
where


import PaymentChannel.Internal.Crypto.PubKey
import Bitcoin.LockTime.Util
import Bitcoin.Util
import Network.Haskoin.Script

import qualified Network.Haskoin.Internals as HI
import qualified Network.Haskoin.Crypto as HC
import qualified Data.ByteString as B


-- |Defines channel: sender, receiver, and expiration date
data ChanParams = MkChanParams {
    cpSenderPubKey      ::  SendPubKey,
    cpReceiverPubKey    ::  RecvPubKey,
    -- |Channel expiration date/time
    cpLockTime          ::  LockTimeDate
} deriving (Eq, Show, Typeable, Generic)

instance HasSendPubKey ChanParams where
    getSendPubKey = cpSenderPubKey

instance HasRecvPubKey ChanParams where
    getRecvPubKey = cpReceiverPubKey

instance ToJSON ChanParams where
    toJSON = String . serHex . getRedeemScript

instance FromJSON ChanParams where
    parseJSON = withText "RedeemScriptHex" $
        deserHex >=> either fail return . fromRedeemScript

instance Serialize ChanParams where
    put (MkChanParams pks pkr lt) =
        put pks >> put pkr >> put lt
    get = MkChanParams <$> get <*> get <*> get

instance HasLockTimeDate ChanParams where
    getLockTimeDate MkChanParams{..} = cpLockTime

-- |Generate OP_CHECKLOCKTIMEVERIFY redeemScript, which can be redeemed in two ways:
--  1) by providing a signature from both server and client
--  2) after the date specified by lockTime: by providing only a client signature
getRedeemScript :: ChanParams -> Script
getRedeemScript MkChanParams{..} =
    let
        serverPubKey    = getPubKey cpReceiverPubKey
        clientPubKey    = getPubKey cpSenderPubKey
    in Script
             [OP_IF,
                 opPushData $ serialize serverPubKey, OP_CHECKSIGVERIFY,
             OP_ELSE,
                  encodeScriptLocktime cpLockTime, op_CHECKLOCKTIMEVERIFY, OP_DROP,
             OP_ENDIF,
             opPushData $ serialize clientPubKey, OP_CHECKSIG]

-- |Parse a redeemScript generated by 'mkChannelRedeemScript'
fromRedeemScript :: Script -> Either String ChanParams
fromRedeemScript (Script
            [OP_IF,
                OP_PUSHDATA serverPubKeyData OPCODE, OP_CHECKSIGVERIFY,
            OP_ELSE,
                lockTimeData, OP_NOP2, OP_DROP,    -- OP_NOP2 is OP_CHECKLOCKTIMEVERIFY
            OP_ENDIF,
            OP_PUSHDATA clientPubKeyData OPCODE, OP_CHECKSIG])
    = MkChanParams
        <$> deserEither clientPubKeyData
        <*> deserEither serverPubKeyData
        <*> decodeScriptLocktime lockTimeData
fromRedeemScript _ = Left "Unrecognized redeemScript format"


-----Util-----

op_CHECKLOCKTIMEVERIFY = OP_NOP2

scriptToP2SHAddress :: Script -> HC.Address
scriptToP2SHAddress = HC.ScriptAddress . hash160

getP2SHFundingAddress :: ChanParams -> HC.Address
getP2SHFundingAddress = scriptToP2SHAddress . getRedeemScript

getRedeemScriptBS :: ChanParams -> B.ByteString
getRedeemScriptBS = serialize . getRedeemScript

-- Note: HI.encodeInt encodes values up to and including
-- 2^31-1 (maxBound :: Int32) as 4 bytes
-- and values 2^31 to 2^32-1 (maxBound :: Word32) as 5 bytes.
encodeScriptLocktime :: BtcLockTime lt => lt -> ScriptOp
encodeScriptLocktime =
    opPushData . B.pack . HI.cltvEncodeInt . toWord32

decodeScriptLocktime :: forall lt. BtcLockTime lt => ScriptOp -> Either String lt
decodeScriptLocktime op =
    maybe (Left "LockTime: Failed to decode script integer")
        (maybe (Left "LockTIme: Failed to parse lockTime") Right . parseLockTime . fromIntegral)
        . HI.cltvDecodeInt . B.unpack
        =<< getPushBS op
  where
    -- TODO: Temporary. See https://github.com/haskoin/haskoin/issues/287
    getPushBS (OP_PUSHDATA pushBS OPCODE) = Right pushBS
    getPushBS OP_0 = Right ""
    getPushBS op = Left $ "LockTime: Expected data push, found: " ++ show op