local config = require "core.configmanager";

local ssl = require"ssl";

local datetime_parse = require"util.datetime".parse;

local load_cert = ssl.loadcertificate;

local st = require"util.stanza"

-- These are in days.

local nag_time = module:get_option_number("checkcerts_notify", 7) * 86400;

if not load_cert then

	module:log("error", "This version of LuaSec (%s) does not support certificate checking", ssl._VERSION);

	return

end

local pat = "^([JFMAONSD][ceupao][glptbvyncr])  ?(%d%d?) (%d%d):(%d%d):(%d%d) (%d%d%d%d) GMT$";

local months = {Jan=1,Feb=2,Mar=3,Apr=4,May=5,Jun=6,Jul=7,Aug=8,Sep=9,Oct=10,Nov=11,Dec=12};

local function parse_x509_datetime(s)

	local month, day, hour, min, sec, year = s:match(pat); month = months[month];

	return datetime_parse(("%04d-%02d-%02dT%02d:%02d:%02dZ"):format(year, month, day, hour, min, sec));

end

local timeunits = {"minute",60,"hour",3600,"day",86400,"week",604800,"month",2629746,"year",31556952,};

local function humantime(timediff)

	local ret = {};

	for i=#timeunits,2,-2 do

		if timeunits[i] < timediff then

			local n = math.floor(timediff / timeunits[i]);

			if n > 0 and #ret < 2 then

				ret[#ret+1] = ("%d %s%s"):format(n, timeunits[i-1], n ~= 1 and "s" or "");

				timediff = timediff - n*timeunits[i];

			end

		end

	end

	return table.concat(ret, " and ")

end

local function check_certs_validity()

	local now = os.time();

	-- First, let's find out what certificate this host uses.

	local ssl_config = config.rawget(module.host, "ssl");

	if not ssl_config or not ssl_config.certificate then

		ssl_config = config.get(module.host:match("%.(.*)"), "ssl");

	end

	if not ssl_config or not ssl_config.certificate then

		ssl_config = config.get("*", "ssl");

	end

	if not ssl_config or not ssl_config.certificate then

		module:log("warn", "Could not find a certificate to check");

		return;

	end

	local certfile = ssl_config.certificate;

	local fh, ferr = io.open(certfile); -- Load the file.

	if not fh then

		module:log("warn", "Could not open certificate %s", ferr);

		return;

	end

	local cert, lerr = load_cert(fh:read("*a")); -- And parse

	fh:close();

	if not cert then

		module:log("warn", "Could not parse certificate %s: %s", certfile, lerr or "");

		return;

	end

	local expires_at = parse_x509_datetime(cert:notafter());

	local expires_in = os.difftime(expires_at, now);

	local fmt =  "Certificate %s expires in %s"

	local nag_admin = expires_in < nag_time;

	local log_warn = expires_in < nag_time * 2;

	local timediff = expires_in;

	if expires_in < 0 then

		fmt =  "Certificate %s expired %s ago";

		timediff = -timediff;

	end

	timediff = humantime(timediff);

	module:log(log_warn and "warn" or "info", fmt, certfile, timediff);

	if nag_admin then

		local body = fmt:format("for host ".. module.host, timediff);

		for admin in module:get_option_inherited_set("admins", {}) do

			module:send(st.message({ from = module.host, to = admin, type = "chat" }, body));

		end

	end

	return math.max(86400, expires_in / 3);

end

module:add_timer(1, check_certs_validity);