--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mod_minimix/README.markdown	Thu Mar 22 14:33:46 2018 +0100
@@ -0,0 +1,43 @@
+Account based MUC joining
+=========================
+
+Normally when joing a MUC groupchat, it is each individual client that
+joins. This means their presence in the group is tied to the session,
+which can be short-lived or unstable, especially in the case of mobile
+clients.
+
+This has a few problems. For one, for every message to the groupchat, a
+copy is sent to each joined client. This means that at the account
+level, each message would pass by once for each client that is joined,
+making it difficult to archive these messages in the users personal
+archive.
+
+A potentially better approach would be that the user account itself is
+the entity that joins the groupchat. Since the account is an entity that
+lives in the server itself, and the server tends to be online on a good
+connection most of the time, this may improve the experience and
+simplify some problems.
+
+This is one of the essential changes in the MIX architecture, which is
+being designed to replace MUC.
+
+`mod_minimix` is an experiment meant to determine if things can be
+improved without replacing the entire MUC standard. It works by
+pretending to each client that nothing is different and that they are
+joining MUCs directly, but behind the scenes, it arranges it such that
+only the account itself joins each groupchat. Which sessions have joined
+which groups are kept track of. Groupchat messages are then forked to
+those sessions, similar to how normal chat messages work.
+
+## Known issues
+
+-   You can never leave.
+-   You will never see anyone leave.
+
+## Unknown issues
+
+-   Probably many.
+
+# Compatibility
+
+Briefly tested with Prosody trunk (as of this writing).

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mod_minimix/mod_minimix.lua	Thu Mar 22 14:33:46 2018 +0100
@@ -0,0 +1,116 @@
+-- mod_minimix
+--
+-- Rewrite MUC stanzas suich that the account / bare JID joins rooms instead of clients / full JIDs
+--
+local jid_split, jid_join, jid_node, jid_bare = import("util.jid", "split", "join", "node", "bare");
+local st = require "util.stanza";
+
+local users = prosody.hosts[module.host].sessions;
+
+local joined_rooms = module:open_store("joined_rooms", "map"); -- TODO cache?
+local room_state = module:open_store("joined_rooms_state", "map");
+local all_room_state = module:open_store("joined_rooms_state");
+
+-- FIXME You can join but you can never leave.
+
+module:hook("pre-presence/full", function (event)
+	local origin, stanza = event.origin, event.stanza;
+
+	local room_node, room_host, nickname = jid_split(stanza.attr.to);
+	local room_jid = jid_join(room_node, room_host);
+	local username = origin.username;
+
+	if stanza.attr.type == nil and stanza:get_child("x", "http://jabber.org/protocol/muc") then
+		module:log("debug", "Joining %s as %s", room_jid, nickname);
+
+		-- TODO Should this be kept track of before the *initial* join has been confirmed or?
+		if origin.joined_rooms then
+			origin.joined_rooms[room_jid] = nickname;
+		else
+			origin.joined_rooms = { [room_jid] = nickname };
+		end
+
+		if joined_rooms:get(username, room_jid) then
+			module:log("debug", "Already joined to %s as %s", room_jid, nickname);
+			local state = assert(all_room_state:get(username));
+			for jid, stanza in pairs(state) do
+				if jid ~= room_jid and jid ~= stanza.attr.to then
+					origin.send(st.clone(st.deserialize(stanza)));
+				end
+			end
+			origin.send(st.deserialize(state[stanza.attr.to]));
+			origin.send(st.message({type="groupchat",to=origin.full_jid,from=room_jid}):tag("subject"):text(state[room_jid]));
+			-- Send on-join stanzas from local state, somehow
+			-- Maybe tell them their nickname was changed if it doesn't match the account one
+			return true;
+		end
+
+		joined_rooms:set(username, room_jid, nickname);
+
+		local account_join = st.clone(stanza);
+		account_join.attr.from = jid_join(origin.username, origin.host);
+		module:send(account_join);
+
+		return true;
+	elseif stanza.attr.type == "unavailable" and joined_rooms:get(username, room_jid) then
+		origin.send(st.reply(stanza));
+		return true;
+	end
+end);
+
+module:hook("pre-message/bare", function (event)
+	local origin, stanza = event.origin, event.stanza;
+	local username = origin.username;
+	local room_jid = jid_bare(stanza.attr.to);
+
+	module:log("info", "%s", stanza)
+	if joined_rooms:get(username, room_jid) then
+		local from_account = st.clone(stanza);
+		from_account.attr.from = jid_join(origin.username, origin.host);
+		module:log("debug", "Sending:\n%s\nInstead of:\n%s", from_account, stanza);
+		module:send(from_account, origin);
+		return true;
+	end
+end);
+
+local function handle_to_bare_jid(event)
+	local origin, stanza = event.origin, event.stanza;
+	local username = jid_node(stanza.attr.to);
+	local room_jid = jid_bare(stanza.attr.from);
+
+	if joined_rooms:get(username, room_jid) then
+		module:log("debug", "handle_to_bare_jid %q, %s", room_jid, stanza);
+		-- Broadcast to clients
+
+		if stanza.name == "message" and stanza.attr.type == "groupchat"
+			and not stanza:get_child("body") and stanza:get_child("subject") then
+			room_state:set(username, room_jid, stanza:get_child_text("subject"));
+		elseif stanza.name == "presence" then
+			if stanza.attr.type == nil then
+				room_state:set(username, stanza.attr.from, st.preserialize(stanza));
+			elseif stanza.attr.type == "unavailable" then
+				room_state:set(username, stanza.attr.from, nil);
+			end
+		end
+
+		if users[username] then
+			module:log("debug", "%s has sessions", username);
+			for _, session in pairs(users[username].sessions) do
+				module:log("debug", "Session: %s", jid_join(session.username, session.host, session.resource));
+				if session.joined_rooms and session.joined_rooms[room_jid] then
+					module:log("debug", "Is joined");
+					local s = st.clone(stanza);
+					s.attr.to = session.full_jid;
+					session.send(s);
+				else
+					module:log("debug", "session.joined_rooms = %s", session.joined_rooms);
+				end
+			end
+		end
+
+		return true;
+	end
+end
+
+module:hook("presence/bare", handle_to_bare_jid);
+module:hook("message/bare", handle_to_bare_jid);