peertube-plugin-livechat/prosody-modules/mod_muc_moderation/mod_muc_moderation.lua

-- mod_muc_moderation
--
-- SPDX-FileCopyrightText: 2015-2021 Kim Alvefur
--
-- SPDX-License-Identifier: MIT
--
-- Implements: XEP-0425: Message Moderation
--
-- Imports
local dt = require "util.datetime";
local id = require "util.id";
local jid = require "util.jid";
local st = require "util.stanza";

-- Plugin dependencies
local mod_muc = module:depends "muc";

local muc_util = module:require "muc/util";
local valid_roles = muc_util.valid_roles;

local muc_log_archive = module:open_store("muc_log", "archive");

if not muc_log_archive.set then
	module:log("warn", "Selected archive storage module does not support message replacement, no tombstones will be saved");
end

-- Namespaces
local xmlns_fasten = "urn:xmpp:fasten:0";
local xmlns_moderate = "urn:xmpp:message-moderate:0";
local xmlns_occupant_id = "urn:xmpp:occupant-id:0";
local xmlns_retract = "urn:xmpp:message-retract:0";

-- Discovering support
module:hook("muc-disco#info", function (event)
	event.reply:tag("feature", { var = xmlns_moderate }):up();
end);

-- TODO error registry, requires Prosody 0.12+

-- moderate : function (string, string, string, boolean, string) : boolean, enum, enum, string
local function moderate(actor, room_jid, stanza_id, retract, reason)
	local room_node = jid.split(room_jid);
	local room = mod_muc.get_room_from_jid(room_jid);

	-- Permissions is based on role, which is a property of a current occupant,
	-- so check if the actor is an occupant, otherwise if they have a reserved
	-- nickname that can be used to retrieve the role.
	local actor_nick = room:get_occupant_jid(actor);
	if not actor_nick then
		local reserved_nickname = room:get_affiliation_data(jid.bare(actor), "reserved_nickname");
		if reserved_nickname then
			actor_nick = room.jid .. "/" .. reserved_nickname;
		end
	end

	-- Retrieve their current role, iff they are in the room, otherwise what they
	-- would have based on affiliation.
	local affiliation = room:get_affiliation(actor);
	local role = room:get_role(actor_nick) or room:get_default_role(affiliation);
	if valid_roles[role or "none"] < valid_roles.moderator then
		return false, "auth", "forbidden", "You need a role of at least 'moderator'";
	end

	-- Original stanza to base tombstone on
	local original, err;
	if muc_log_archive.get then
		original, err = muc_log_archive:get(room_node, stanza_id);
	else
		-- COMPAT missing :get API
		err = "item-not-found";
		for i, item in muc_log_archive:find(room_node, { key = stanza_id, limit = 1 }) do
			if i == stanza_id then
				original, err = item, nil;
			end
		end
	end

	if not original then
		if err == "item-not-found" then
			return false, "modify", "item-not-found";
		else
			return false, "wait", "internal-server-error";
		end
	end

	local actor_occupant = room:get_occupant_by_real_jid(actor) or room:new_occupant(jid.bare(actor), actor_nick);

	local announcement = st.message({ from = room_jid, type = "groupchat", id = id.medium(), })
		:tag("apply-to", { xmlns = xmlns_fasten, id = stanza_id })
			:tag("moderated", { xmlns = xmlns_moderate, by = actor_nick })

	if room.get_occupant_id then
		-- This isn't a regular broadcast message going through the events occupant_id.lib hooks so we do this here
		announcement:add_child(st.stanza("occupant-id", { xmlns = xmlns_occupant_id; id = room:get_occupant_id(actor_occupant) }));
	end

	if retract then
		announcement:tag("retract", { xmlns = xmlns_retract }):up();
	end

	if reason then
		announcement:text_tag("reason", reason);
	end

	local moderated_occupant_id = original:get_child("occupant-id", xmlns_occupant_id);
	if room.get_occupant_id and moderated_occupant_id then
		announcement:add_direct_child(moderated_occupant_id);
	end

	announcement:reset();

	local tombstone = nil;
	if muc_log_archive.set and retract then
		tombstone = st.message({ from = original.attr.from, type = "groupchat", id = original.attr.id })
			:tag("moderated", { xmlns = xmlns_moderate, by = actor_nick })
				:tag("retracted", { xmlns = xmlns_retract, stamp = dt.datetime() }):up();

		if reason then
			tombstone:text_tag("reason", reason);
		end

		if room.get_occupant_id then
			if actor_occupant then
				tombstone:add_child(st.stanza("occupant-id", { xmlns = xmlns_occupant_id; id = room:get_occupant_id(actor_occupant) }));
			end

			if moderated_occupant_id then
				-- Copy occupant id from moderated message
				tombstone:add_direct_child(moderated_occupant_id);
			end
		end
		tombstone:reset();
	end

	-- fire an event, that can be used to cancel the moderation, or modify stanzas.
	local event = {
		room = room;
		announcement = announcement;
		tombstone = tombstone;
		stanza_id = stanza_id;
		retract = retract;
		reason = reason;
		actor = actor;
		actor_nick = actor_nick;
	};
	if module:fire_event("muc-moderate-message", event) then
		-- TODO: allow to change the error message?
		return false, "wait", "internal-server-error";
	end

	if tombstone then
		local was_replaced = muc_log_archive:set(room_node, stanza_id, tombstone);
		if not was_replaced then
			return false, "wait", "internal-server-error";
		end
	end

	-- Done, tell people about it
	module:log("info", "Message with id '%s' in room %s moderated by %s, reason: %s", stanza_id, room_jid, actor, reason);
	room:broadcast_message(announcement);

	return true;
end

-- Main handling
module:hook("iq-set/bare/" .. xmlns_fasten .. ":apply-to", function (event)
	local stanza, origin = event.stanza, event.origin;

	local actor = stanza.attr.from;
	local room_jid = stanza.attr.to;

	-- Collect info we need
	local apply_to = stanza.tags[1];
	local moderate_tag = apply_to:get_child("moderate", xmlns_moderate);
	if not moderate_tag then return end -- some other kind of fastening?

	local reason = moderate_tag:get_child_text("reason");
	local retract = moderate_tag:get_child("retract", xmlns_retract);

	local stanza_id = apply_to.attr.id;

	local ok, error_type, error_condition, error_text = moderate(actor, room_jid, stanza_id, retract, reason);
	if not ok then
		origin.send(st.error_reply(stanza, error_type, error_condition, error_text));
		return true;
	end

	origin.send(st.reply(stanza));
	return true;
end);

module:hook("muc-message-is-historic", function (event)
	-- Ensure moderation messages are stored
	if event.stanza.attr.from == event.room.jid then
		return event.stanza:get_child("apply-to", xmlns_fasten);
	end
end, 1);