local adns = require "net.adns";

local async = require "util.async";

local inet_pton = require "util.net".pton;

local to_hex = require "util.hex".to;

local rbl = module:get_option_string("registration_rbl");

local function reverse(ip, suffix)

	local n, err = inet_pton(ip);

	if not n then return n, err end

	if #n == 4 then

		local a,b,c,d = n:byte(1,4);

		return ("%d.%d.%d.%d.%s"):format(d,c,b,a, suffix);

	elseif #n == 16 then

		return to_hex(n):reverse():gsub("%x", "%1.") .. suffix;

	end

end

module:hook("user-registering", function (event)

	local session, ip = event.session, event.ip;

	local log = (session and session.log) or module._log;

	if not ip then

		log("debug", "Unable to check DNSBL when IP is unknown");

		return;

	end

	local rbl_ip, err = reverse(ip, rbl);

	if not rbl_ip then

		log("debug", "Unable to check DNSBL for ip %s: %s", ip, err);

		return;

	end

	local wait, done = async.waiter();

	adns.lookup(function (reply)

		if reply and reply[1] and reply[1].a then

			log("debug", "DNSBL response: %s IN A %s", rbl_ip, reply[1].a);

			log("info", "Blocking %s from registering %s (dnsbl hit)", ip, event.username);

			event.allowed = false;

			event.reason = "Blocked by DNSBL";

		end

		done();

	end, rbl_ip);

	wait();

end);