local it = require "util.iterators";

local new_id = require "util.id".medium;

local max_user_devices = module:get_option_number("max_user_devices", 5);

local device_store = module:open_store("devices");

local device_map_store = module:open_store("devices", "map");

--- Helper functions

local function _compare_device_timestamps(a, b)

	return (a.last_activity_at or 0) < (b.last_activity_at or 0);

end

local function sorted_devices(devices)

	return it.sorted_pairs(devices, _compare_device_timestamps);

end

local function new_device(username, alt_ids)

	local current_time = os.time();

	local device = {

		id = "dv-"..new_id();

		created_at = current_time;

		last_activity = "created";

		last_activity_at = current_time;

		alt_ids = alt_ids or {};

	};

	local devices = device_store:get(username);

	if not devices then

		devices = {};

	end

	devices[device.id] = device;

	local devices_ordered = {};

	for id in sorted_devices(devices) do

		table.insert(devices_ordered, id);

	end

	if #devices_ordered > max_user_devices then

		-- Iterate through oldest devices that are above limit, backwards

		for i = #devices_ordered, max_user_devices+1, -1 do

			local id = table.remove(devices_ordered, i);

			devices[id] = nil;

			module:log("debug", "Removing old device for %s: %s", username, id);

		end

	end

	device_store:set(username, devices);

	return device;

end

local function get_device_with_alt_id(username, alt_id_type, alt_id)

	local devices = device_store:get(username);

	if not devices then

		return nil;

	end

	for _, device in pairs(devices) do

		if device.alt_ids[alt_id_type] == alt_id then

			return device;

		end

	end

end

local function set_device_alt_id(username, device_id, alt_id_type, alt_id)

	local devices = device_store:get(username);

	if not devices or not devices[device_id] then

		return nil, "no such device";

	end

	devices[device_id].alt_ids[alt_id_type] = alt_id;

end

local function record_device_state(username, device_id, activity, time)

	local device = device_map_store:get(username, device_id);

	device.last_activity = activity;

	device.last_activity_at = time or os.time();

	device_map_store:set(username, device_id, device);

end

local function find_device(username, info)

	for _, alt_id_type in ipairs({ "resumption_token", "resource" }) do

		local alt_id = info[alt_id_type];

		if alt_id then

			local device = get_device_with_alt_id(username, alt_id_type, alt_id);

			if device then

				return device, alt_id_type;

			end

		end

	end

end

--- Information gathering

module:hook("pre-resource-bind", function (event)

	event.session.device_requested_resource = event.resource;

end, 1000);

local function store_resumption_token(session, stanza)

	session.device_requested_resume = stanza.attr.previd;

end

module:hook_stanza("urn:xmpp:sm:2", "resume", store_resumption_token, 5);

module:hook_stanza("urn:xmpp:sm:3", "resume", store_resumption_token, 5);

--- Identify device after resource bind

module:hook("resource-bind", function (event)

	local info = {

		resource = event.session.device_requested_resource;

		resumption_token = event.session.device_requested_resume;

	};

	local device, source = find_device(event.session.username, info);

	if device then

		event.session.log("debug", "Associated with device %s (from %s)", device.id, source);

		event.session.device_id = device.id;

	else

		device = new_device(event.session.username, info);

		event.session.log("debug", "Creating new device %s for session", device.id);

		event.session.device_id = device.id;

	end

	record_device_state(event.session.username, device.id, "login");

end, 1000);

module:hook("resource-unbind", function (event)

	if event.session.device_id then

		record_device_state(event.session.username, event.session.device_id, "logout");

	end

end);