Moderation delay WIP (#132):

* mod_muc_moderation_delay, first shot.

prosody-modules/mod_muc_moderation_delay/delay.lib.lua

@@ -0,0 +1,59 @@
+-- SPDX-FileCopyrightText: 2024 John Livingston <https://www.john-livingston.fr/>
+-- SPDX-License-Identifier: AGPL-3.0-only
+local async = require "util.async";
+local get_moderation_delay = module:require("config").get_moderation_delay;
+
+local muc_util = module:require "muc/util";
+local valid_roles = muc_util.valid_roles;
+
+local function handle_broadcast_message(event)
+  local room, stanza = event.room, event.stanza;
+  local delay = get_moderation_delay(room);
+  if delay == nil then
+    return;
+  end
+
+  -- only delay groupchat messages with body.
+  if stanza.attr.type ~= "groupchat" then
+    return;
+  end
+  if not stanza:get_child("body") then
+    return;
+  end
+
+  local id = stanza.attr.id;
+  if not id then
+    -- message should alway have an id, but just in case...
+    module:log("warn", "Message has no id, wont delay it.");
+    return;
+  end
+
+  -- TODO: detect message retractation, and stop broadcast for any waiting message.
+
+  -- Message must be delayed, except for:
+  -- * room moderators
+  -- * the user that sent the message (if they don't get the echo quickly, their clients could have weird behaviours)
+
+  module:log("debug", "Message must be delayed by %i seconds, sending first broadcast wave.", delay);
+  local moderator_role_value = valid_roles["moderator"];
+  local func = function (nick, occupant)
+    if valid_roles[occupant.role or "none"] >= moderator_role_value then
+      return true;
+    end
+    if nick == stanza.attr.from then
+      return true;
+    end
+    return false;
+  end;
+  room:broadcast(stanza, func);
+  async.sleep(delay);
+  module:log("debug", "Message has been delayed, sending to remaining participants.");
+  room:broadcast(stanza, function (nick, occupant)
+    return not func(nick, occupant);
+  end);
+  return true; -- stop the default process
+end
+
+return {
+  handle_broadcast_message = handle_broadcast_message;
+};