{-# LANGUAGE DeriveGeneric, FlexibleInstances #-}

{- | Main types for debug-me
 -
 - Note that changing types in ways that change the JSON serialization
 - changes debug-me's wire format.
 -}

module Types (
	module Types,
	Val(..)
) where

import Val

import GHC.Generics (Generic)
import Data.Aeson

-- | 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

-- | High level protocol.
data Proto a
	= Proto a
	-- ^ either Entered or Seen
	| Rejected (Activity Entered)
	-- ^ sent by user to indicate when an Entered value was rejected.
	deriving (Show, Generic)

instance ToJSON (Proto Seen)
instance FromJSON (Proto Seen)
instance ToJSON (Proto Entered)
instance FromJSON (Proto Entered)

-- | A Proto 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
	{ activity :: Proto a
	, prevActivity :: (Maybe Hash)
	, signature :: Signature
	}
	deriving (Show, Generic)

instance ToJSON (Activity Seen)
instance FromJSON (Activity Seen)
instance ToJSON (Activity Entered)
instance FromJSON (Activity Entered)

-- | A log of Activity both Entered and Seen, which can be recorded to
-- prove what happened in a debug-me session.
data ActivityLog
	= ActivitySeen
		{ activitySeen :: (Activity Seen, Hash)
		}
	| ActivityEntered
		{ activityEntered :: (Activity Entered, Hash)
		}
	deriving (Show, Generic)

instance ToJSON (ActivityLog)
instance FromJSON (ActivityLog)

newtype Signature = Signature Val
	deriving (Show, Generic)

instance ToJSON Signature
instance FromJSON Signature

data Hash = Hash
	{ hashMethod :: HashMethod
	, hashValue :: Val
	}
	deriving (Show, Generic, Eq)

instance ToJSON Hash
instance FromJSON Hash

-- | We use SHA256. (SHA3 is included to future proof, and because it
-- improves the generated JSON.)
data HashMethod = SHA256 | SHA3
	deriving (Show, Generic, Eq)

instance ToJSON HashMethod
instance FromJSON HashMethod