#!/usr/bin/lua

--! LibreMesh
--! Copyright (C) 2019  Gioacchino Mazzurco <gio@altermundi.net>
--! Copyright (C) 2019  Nicolas Echaniz <nicoechaniz@altermundi.net>
--!
--! This program is free software: you can redistribute it and/or modify
--! it under the terms of the GNU Affero General Public License version 3
--! published by the Free Software Foundation.
--!
--! This program is distributed in the hope that it will be useful,
--! but WITHOUT ANY WARRANTY; without even the implied warranty of
--! MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
--! GNU Affero General Public License for more details.
--!
--! You should have received a copy of the GNU Affero General Public License
--! along with this program.  If not, see <http://www.gnu.org/licenses/>.

local http = require("luci.httpclient")
local libuci = require("uci")


local config = libuci:cursor()
local url = config:get("check-date", "http", "server")
url = url or { "http://openwrt.org" }
math.randomseed(os.time())
url = url[math.random(#url)]
local resetDate = config:get("check-date", "system", "reset_date") or false
local restartSysntpd = config:get("check-date", "system", "restart_sysntpd")
restartSysntpd = (restartSysntpd == nil) or restartSysntpd
config = nil

local localCurrDate = assert(io.popen("date --utc -Iminutes", 'r'):read())
local lFormat="(%d+)-(%d+)-(%d+)T(%d+):(%d+)UTC"
local lYear, lMonth, lDay, lHour, lMin = localCurrDate:match(lFormat)

local httpOptions = {}
httpOptions.rcvtimeo = 5
httpOptions.sndtimeo = 5
httpOptions.depth = 0 -- Avoid annoying redirects
httpOptions.method = 'HEAD'
local success, response, algo = pcall(http.request_raw, url, httpOptions)

if(not success) then
	print(arg[0], "HTTP request failed", url, success, response, algo)
	os.exit(42)
elseif response == nil then
	print(arg[0], "The server cannot be reached", url)
	os.exit(43)
end

local s = algo['headers']['Date']
local p="%a+, (%d+) (%a+) (%d+) (%d+):(%d+):(%d+) GMT"
local day, month, year, hour, min, sec = s:match(p)
local MON = { Jan="01", Feb="02", Mar="03", Apr="04", May="05", Jun="06", Jul="07", Aug="08", Sep="09", Oct="10", Nov="11", Dec="12"}
month = MON[month]

local skewDetected = false

local lTdate = { lYear, lMonth, lDay, lHour }
local rTdate = { year,  month,  day,  hour }

for i=1,#lTdate do
	if(lTdate[i] ~= rTdate[i]) then
		skewDetected = true
		break
	end
end

skewDetected = skewDetected or (math.abs(lMin - min) > 13)

if(skewDetected) then
	local currDate = string.format(
		"%s.%s.%s-%s:%s:%s", lYear, lMonth, lDay, lHour, lMin, "XX" )
	local newDate = string.format(
		"%s.%s.%s-%s:%s:%s", year, month, day, hour, min, sec )

	print( arg[0].." Too far away clock skew detected "..
	       " local "..currDate.." "..url.." "..newDate )

	if resetDate then
		local newDate = string.format(
			"%s.%s.%s-%s:%s:%s", year, month, day, hour, min, sec )
		os.execute("date --utc --set "..newDate)
	end
	if restartSysntpd then os.execute("/etc/init.d/sysntpd restart") end
end