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|
{-# LANGUAGE GeneralizedNewtypeDeriving, DeriveGeneric, FlexibleInstances, OverloadedStrings #-}
module Types where
import Data.ByteString
import GHC.Generics (Generic)
import Data.Aeson
import Data.Aeson.Types
import qualified Codec.Binary.Base64 as B64
import qualified Data.Text as T
import qualified Data.Text.Encoding as T
-- | Things that the developer sees.
data Seen = Seen
{ seenData :: Val
}
deriving (Show, Generic)
instance ToJSON Seen
instance FromJSON Seen
-- | Things that the developer enters.
data Entered = Entered
{ enteredData :: Val
, echoData :: Val
-- ^ Data that is expected to be Seen, but has not been received
-- at the time this was entered.
}
deriving (Show, Generic)
instance ToJSON Entered
instance FromJSON Entered
-- | An activity (either Entered or Seen) with a pointer
-- to the Activity before this one.
--
-- The Signature is over both the data in the activity, and its pointer.
data Activity a
= Activity a HashPointer Signature
| StartActivity a Signature
deriving (Show, Generic)
instance ToJSON (Activity Seen)
instance FromJSON (Activity Seen)
instance ToJSON (Activity Entered)
instance FromJSON (Activity Entered)
activityContent :: Activity a -> a
activityContent (Activity a _ _) = a
activityContent (StartActivity a _) = a
data Signature = Signature
{ signature :: Val
}
deriving (Show, Generic)
instance ToJSON Signature
instance FromJSON Signature
-- | A hash pointer to something that hashes to this value.
data HashPointer = HashPointer
{ hashMethod :: HashMethod
, hashValue :: Val
}
deriving (Show, Generic, Eq)
instance ToJSON HashPointer
instance FromJSON HashPointer
data HashMethod = SHA256
deriving (Show, Generic, Eq)
instance ToJSON HashMethod
instance FromJSON HashMethod
-- | Newtype of ByteString so we can have JSON instances without orphans.
newtype Val = Val { val :: ByteString }
deriving (Show, Generic, Eq, Monoid)
-- | JSON instances for Val, using base64 encoding.
instance ToJSON Val where
toJSON (Val b) = object [ "b" .= b64 b ]
instance FromJSON Val where
parseJSON (Object v) = Val <$> (unb64 =<< v .: "b")
parseJSON invalid = typeMismatch "ByteString" invalid
b64 :: ByteString -> T.Text
b64 = T.decodeUtf8 . B64.encode
unb64 :: Monad m => T.Text -> m ByteString
unb64 t = either
(\_ -> fail "bad base64 data")
return
( B64.decode $ T.encodeUtf8 t)
|
