local unified_push_secret = assert(module:get_option_string("unified_push_secret"), "required option: unified_push_secret");

local push_registration_ttl = module:get_option_number("unified_push_registration_ttl", 86400);

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

local datetime = require "util.datetime";

local jwt_sign, jwt_verify = require "util.jwt".init("HS256", unified_push_secret);

local st = require "util.stanza";

local urlencode = require "util.http".urlencode;

local xmlns_up = "http://gultsch.de/xmpp/drafts/unified-push";

module:depends("http");

local function check_sha256(s)

	if not s then return nil, "no value provided"; end

	local d = base64.decode(s);

	if not d then return nil, "invalid base64"; end

	if #d ~= 32 then return nil, "incorrect decoded length, expected 32"; end

	return s;

end

-- Handle incoming registration from XMPP client

function handle_register(event)

	local origin, stanza = event.origin, event.stanza;

	local instance, instance_err = check_sha256(stanza.tags[1].attr.instance);

	if not instance then

		return st.error_reply(stanza, "modify", "bad-request", "instance: "..instance_err);

	end

	local application, application_err = check_sha256(stanza.tags[1].attr.application);

	if not application then

		return st.error_reply(stanza, "modify", "bad-request", "application: "..application_err);

	end

	local expiry = os.time() + push_registration_ttl;

	local url = module:http_url().."/"..urlencode(jwt_sign({

		instance = instance;

		application = application;

		sub = stanza.attr.from;

		exp = expiry;

	}));

	module:log("debug", "New push registration successful");

	return origin.send(st.reply(stanza):tag("registered", {

		expiration = datetime.datetime(expiry);

		endpoint = url;

		xmlns = xmlns_up;

	}));

end

module:hook("iq-set/host/"..xmlns_up..":register", handle_register);

-- Handle incoming POST

function handle_push(event, subpath)

	local data, err = jwt_verify(subpath);

	if not data then

		module:log("debug", "Received push to unacceptable token (%s)", err);

		return 404;

	end

	local payload = event.request.body;

	if not payload or payload == "" then

		return 400;

	elseif #payload > 4096 then

		return 413;

	end

	local push_iq = st.iq({ type = "set", to = data.sub, id = event.request.id })

		:text_tag("push", base64.encode(payload), { instance = data.instance, application = data.application, xmlns = xmlns_up });

	return module:send_iq(push_iq):next(function ()

		return 201;

	end, function (error_event)

		local e_type, e_cond, e_text = error_event.stanza:get_error();

		if e_cond == "item-not-found" or e_cond == "feature-not-implemented" then

			module:log("debug", "Push rejected");

			return 404;

		elseif e_cond == "service-unavailable" or e_cond == "recipient-unavailable" then

			return 503;

		end

		module:log("warn", "Unexpected push error response: %s/%s/%s", e_type, e_cond, e_text);

		return 500;

	end);

end

module:provides("http", {

	name = "push";

	route = {

		["GET /*"] = function (event)

			event.response.headers.content_type = "application/json";

			return [[{"unifiedpush":{"version":1}}]];

		end;

		["POST /*"] = handle_push;

	};

});