#!/usr/bin/lua

-- Created by jiaqiang.ye@lnxall.com
-- Check whether Network configuration has changed
-- If Network configuration has changed, restart network services
-- 2023/04/11

-- load external modules
local posix = require "posix"
local cjson = require "cjson"
local invoker = require "invoker"
local ubuslog = require "ubuslog"

-- global variables
local CFG_FILES = {} -- configuration files that should be checking
local CHECK_INFO = "/app/config/network_checksum.json"

CFG_FILES[#CFG_FILES + 0x1] = "/etc/config/dhcp"
CFG_FILES[#CFG_FILES + 0x1] = "/etc/config/network"
CFG_FILES[#CFG_FILES + 0x1] = "/etc/config/wireless"
CFG_FILES[#CFG_FILES + 0x1] = "/etc/config/firewall"
CFG_FILES[#CFG_FILES + 0x1] = "/etc/config/network"

local function load_checksum()
	local ch = io.open(CHECK_INFO, "rb")
	if not ch then return false end
	local chdat = ch:read("*a")
	ch:close(); ch = nil
	if type(chdat) ~= "string" or #chdat == 0 then return false end
	local okay, chsum = pcall(cjson.decode, chdat)
	if not okay or type(chsum) ~= "table" then return false end
	return chsum
end

local function get_md5sum(filp)
	local filst = posix.stat(filp)
	if not filst then return "" end
	local eval, output = invoker.invoke(invoker.OUTPUT + invoker.NOSTDIO, "md5sum", filp)
	if eval ~= 0 or type(output) ~= "string" or #output == 0 then
		return ""
	end
	local md5sum = string.match(output, "^(%x+)")
	if not md5sum then return "" end
	return md5sum
end

local function mainfunc()
	posix.chdir('/')
	invoker.setname('NETWORK_RESTART')
	local nowtim = invoker.uptime()

	-- fork child process before continuing
	-- local pid = posix.fork()
	-- if type(pid) == "number" and pid > 0 then os.exit(0) end
	local untim = nowtim + 60 -- delay 60 seconds
	nowtim = invoker.uptime()
	while nowtim < untim do
		invoker.waitsec(untim - nowtim)
		nowtim = invoker.uptime()
	end
	ubuslog.reinit("NETWORK_RESTART", 1);

	local oldchsum = load_checksum()
	if not oldchsum then oldchsum = {} end
	local newchsum, changed = {}, false
	for _, cfgfile in ipairs(CFG_FILES) do
		local md5 = get_md5sum(cfgfile)
		newchsum[cfgfile] = md5
		if md5 ~= oldchsum[cfgfile] then changed = true end
	end

	if changed then
		local filh = io.open(CHECK_INFO, "wb")
		if filh then
			filh:write(cjson.encode(newchsum))
			filh:close(); filh = nil; posix.sync()
		end
		ubuslog.log(ubuslog.LOG_ERR, "Warning, restarting network!")
		invoker.msleep(1000) -- delay one second
		invoker.invoke(invoker.NOSTDIO, "/etc/init.d/network",  "restart")
		invoker.invoke(invoker.NOSTDIO, "/etc/init.d/dnsmasq",  "restart")
		invoker.invoke(invoker.NOSTDIO, "/etc/init.d/firewall", "restart")
	else
		ubuslog.log(ubuslog.LOG_ERR, "Warning, no need to restart network!")
	end
	return true
end

mainfunc()
os.exit(0)