-- 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

	if room._data.occupant_ids == nil then

		room._data.occupant_ids = {};

	end

	if room._data.occupant_ids[bare] == nil then

		local unique_id = b64encode(hmac_sha256(bare, room._data.occupant_id_salt));

		room._data.occupant_ids[bare] = unique_id;

	end

	return room._data.occupant_ids[bare];

end

local function update_occupant(event)

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

	-- 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 })

		:text(unique_id)

		:up();

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-groupchat", update_occupant);