1 files changed, 37 insertions, 0 deletions
diff --git a/src/Erebos/Conversation/Class.hs b/src/Erebos/Conversation/Class.hs
new file mode 100644
index 0000000..7c3652d
--- /dev/null
+++ b/src/Erebos/Conversation/Class.hs
@@ -0,0 +1,37 @@
+module Erebos.Conversation.Class (
+    ConversationType(..),
+    MessageExtra(..),
+    RefDigest,
+) where
+
+import Control.Monad.Except
+
+import Data.Text (Text)
+import Data.Time.LocalTime
+import Data.Typeable
+
+import Erebos.Error
+import Erebos.Identity
+import Erebos.Object
+import Erebos.State
+
+
+data MessageExtra
+    = UserJoined
+    | UserLeft
+
+
+class (Typeable conv, Typeable msg) => ConversationType conv msg | conv -> msg, msg -> conv where
+    convMessageFrom :: msg -> ComposedIdentity
+    convMessageTime :: msg -> ZonedTime
+    convMessageText :: msg -> Maybe Text
+    convMessageExtra :: msg -> [ MessageExtra ]
+    convMessageExtra _ = []
+
+    convReference :: conv -> RefDigest
+    convMessageListSince
+        :: Maybe conv -- ^ Original state to diff from
+        -> conv       -- ^ Current state
+        -> ( Int, [ ( msg, Bool ) ] ) -- ^ Number of removed, list of added messages
+
+    convMarkAllSeen :: (MonadHead LocalState m, MonadError e m, FromErebosError e) => conv -> m ()