--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mod_muc_slow_mode/mod_muc_slow_mode.lua	Fri Jul 26 15:47:18 2024 +0200
@@ -0,0 +1,163 @@
+-- mod_muc_slow_mode
+--
+-- SPDX-FileCopyrightText: 2024 John Livingston <https://www.john-livingston.fr/>
+-- SPDX-License-Identifier: AGPL-3.0-only
+--
+-- Implements: XEP-????: MUC Slow Mode (XEP to come).
+--
+-- Imports
+local st = require "util.stanza";
+local jid_bare = require "util.jid".bare;
+local gettime = require 'socket'.gettime;
+
+-- Plugin dependencies
+local mod_muc = module:depends "muc";
+
+local muc_util = module:require "muc/util";
+local valid_roles = muc_util.valid_roles;
+
+-- Namespaces
+local xmlns_muc = "http://jabber.org/protocol/muc";
+
+-- Options
+
+-- form_position: the position in the room config form (this value will be passed as priority for the "muc-config-form" hook).
+-- Depending on your application, it is possible that the slow mode is more important than other fields (for example for a video streaming service).
+-- So there is an option to change this.
+-- By default, field will be between muc#roomconfig_changesubject and muc#roomconfig_moderatedroom
+local form_position = module:get_option_number("slow_mode_duration_form_position") or 80-2;
+
+-- Getter/Setter
+local function get_slow_mode_duration(room)
+  return room._data.slow_mode_duration or 0;
+end
+
+local function set_slow_mode_duration(room, duration)
+  if duration then
+    duration = assert(tonumber(duration), "Slow mode duration is not a valid number");
+  end
+  if duration and duration < 0 then
+    duration = 0;
+  end
+
+  if get_slow_mode_duration(room) == duration then return false; end
+
+  room._data.slow_mode_duration = duration;
+  return true;
+end
+
+-- Discovering support
+local function add_disco_form(event)
+  table.insert(event.form, {
+    name = "muc#roominfo_slow_mode_duration";
+    value = "";
+  });
+  event.formdata["muc#roominfo_slow_mode_duration"] = get_slow_mode_duration(event.room);
+end
+
+module:hook("muc-disco#info", add_disco_form);
+
+-- Config form declaration
+local function add_form_option(event)
+  table.insert(event.form, {
+    name = "muc#roomconfig_slow_mode_duration";
+    type = "text-single";
+    datatype = "xs:integer";
+    range_min = 0;
+    label = "Slow Mode (0=disabled, any positive integer= users can send a message every X seconds.)";
+    -- desc = "";
+    value = get_slow_mode_duration(event.room);
+  });
+end
+
+module:hook("muc-config-submitted/muc#roomconfig_slow_mode_duration", function(event)
+  if set_slow_mode_duration(event.room, event.value) then
+    -- status 104 = configuration change: Inform occupants that a non-privacy-related room configuration change has occurred
+    event.status_codes["104"] = true;
+  end
+end);
+
+module:hook("muc-config-form", add_form_option, form_position);
+
+-- handling groupchat messages
+function handle_groupchat(event)
+  local origin, stanza = event.origin, event.stanza;
+  local room = event.room;
+
+  -- only consider messages with body (ie: ignore chatstate and other non-text xmpp messages)
+  local body = stanza:get_child_text("body")
+  if not body or #body < 1 then
+    -- module:log("debug", "No body, message accepted");
+    return;
+  end
+
+  local duration = get_slow_mode_duration(room) or 0;
+  if duration <= 0 then
+    -- no slow mode for this room
+    -- module:log("debug", "No slow mode for this room");
+    return;
+  end
+
+  -- Checking user's permissions (moderators are not subject to slow mode)
+  local actor = stanza.attr.from;
+  local actor_nick = room:get_occupant_jid(actor);
+  local actor_jid = jid_bare(actor);
+  -- Only checking role, not affiliation (slow mode only applies on users currently connected to the room)
+  local role = room:get_role(actor_nick);
+  if valid_roles[role or "none"] >= valid_roles.moderator then
+    -- user bypasses the slow mode.
+    -- module:log("debug", "User is moderator, bypassing slow mode");
+    return;
+  end
+
+  if not room.slow_mode_last_messages then
+    -- We store last message time for each users in room.slow_mode_last_messages:
+    -- * key: bare jid (without the nickname)
+    -- * value: last message timestamp
+    -- If room is cleared from memory, these data are lost. But should not be an issue.
+    -- For now, i don't clean slow_mode_last_messages, it should not use too much memory.
+    -- module:log("debug", "Initializing slow_mode_last_messages for the room.");
+    room.slow_mode_last_messages = {};
+  end
+
+  local now = gettime();
+  local previous = room.slow_mode_last_messages[actor_jid];
+  -- module:log(
+  --   "debug",
+  --   "Last message for user %s was at %s, now is %s, duration is %s, now - previous is %s",
+  --   actor_jid,
+  --   previous or 0,
+  --   now,
+  --   duration,
+  --   (now - (previous or 0))
+  -- );
+  if ((not previous) or (now - previous > duration)) then
+    -- module:log("debug", "Message accepted");
+    room.slow_mode_last_messages[actor_jid] = now;
+    return;
+  end
+
+  module:log("debug", "Bouncing message for user %s", actor_nick);
+  local reply = st.error_reply(
+    stanza,
+    -- error_type = 'wait' (see descriptions in RFC 6120 https://xmpp.org/rfcs/rfc6120.html#stanzas-error-syntax)
+    "wait",
+    -- error_condition = 'policy-violation' (see RFC 6120 Defined Error Conditions https://xmpp.org/rfcs/rfc6120.html#stanzas-error-conditions)
+    "policy-violation",
+    "You have exceeded the limit imposed by the slow mode in this room. You have to wait " .. duration .. " seconds between messages. Please try again later"
+  );
+
+  -- Note: following commented lines were inspired by mod_muc_limits, but it seems it is not required.
+  -- if body then
+  --   reply:up():tag("body"):text(body):up();
+  -- end
+  -- local x = stanza:get_child("x", xmlns_muc);
+  -- if x then
+  --   reply:add_child(st.clone(x));
+  -- end
+
+  origin.send(reply);
+  return true; -- stoping propagation
+end
+
+module:hook("muc-occupant-groupchat", handle_groupchat);