1 files changed, 35 insertions, 0 deletions
diff --git a/Types.hs b/Types.hs
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+module Types where
+
+import Data.ByteString
+import Crypto.Hash as H
+
+-- | Things that the developer sees.
+data Seen = Seen
+	{ seenData :: ByteString
+	}
+	deriving (Show)
+
+-- | Things that the developer enters.
+data Entered = Entered
+	{ enteredData :: ByteString
+	, echoData :: ByteString
+	-- ^ Data that is expected to be Seen, but has not been received
+	-- at the time this was entered.
+	}
+	deriving (Show)
+
+-- | 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)
+
+data Signature = Signature ByteString
+	deriving (Show)
+
+-- | A SHA2 hash pointer to something that hashes to this value.
+newtype HashPointer = HashPointer (H.Digest H.SHA256)
+	deriving (Show)