-- Implementation of https://xmpp.org/extensions/inbox/occupant-id.html

-- XEP-0421: Anonymous unique occupant identifiers for MUCs

module:depends("muc");

local uuid = require "util.uuid";

local hmac_sha256 = require "util.hashes".hmac_sha256;

local b64encode = require "util.encodings".base64.encode;

local xmlns_occupant_id = "urn:xmpp:occupant-id:0";

local function generate_id(occupant, room)

	local bare = occupant.bare_jid;

	if room._data.occupant_id_salt == nil then

		room._data.occupant_id_salt = uuid.generate();

	end

	-- XXX: Temporary not-so-important migration measure. Remove this next time

	-- somebody looks at it. This module used to store every participant's

	-- occupant-id all the time forever.

	room._data.occupant_ids = nil;

	return b64encode(hmac_sha256(bare, room._data.occupant_id_salt));

end

local function update_occupant(event)

	local stanza, room, occupant, dest_occupant = event.stanza, event.room, event.occupant, event.dest_occupant;

	-- "muc-occupant-pre-change" provides "dest_occupant" but not "occupant".

	if dest_occupant ~= nil then

		occupant = dest_occupant;

	end

	-- strip any existing <occupant-id/> tags to avoid forgery

	stanza:remove_children("occupant-id", xmlns_occupant_id);

	local unique_id = generate_id(occupant, room);

	stanza:tag("occupant-id", { xmlns = xmlns_occupant_id, id = unique_id }):up();

end

local function muc_private(event)

	local stanza, room = event.stanza, event.room;

	local occupant = room._occupants[stanza.attr.from];

	update_occupant({

		stanza = stanza,

		room = room,

		occupant = occupant,

	});

end

module:add_feature(xmlns_occupant_id);

module:hook("muc-disco#info", function (event)

	event.reply:tag("feature", { var = xmlns_occupant_id }):up();

end);

module:hook("muc-broadcast-presence", update_occupant);

module:hook("muc-occupant-pre-join", update_occupant);

module:hook("muc-occupant-pre-change", update_occupant);

module:hook("muc-occupant-groupchat", update_occupant);

module:hook("muc-private-message", muc_private);