#!/opt/lnxall_app/bin/lua

-- Created by jiaqiang.ye@lnxall.com
-- Simple System Monitor for Non-openwrt system
-- 2023/07/13

local bit = require 'bit'
local uci = require 'uci'
local cjson = require "cjson"
local posix = require "posix"
local invoker = require "invoker"
local tasklua = require "tasklua"

-- global variables
local CHECK_INTERVAL = 120 -- 120 seconds
local gfmt = string.format
local board_name = 'unknown' -- name of board, RK3568/EM1000
local g_iccid = "/tmp/simcard_iccid"

local function network_enabled(which)
	local netw = uci.cursor('/etc/config')
	local netcfg = netw:get('network', which)
	if netcfg ~= "interface" then
		netw:close(); netw = nil
		return false
	end

	local dis = netw:get('network', which, 'disabled')
	netw:close(); netw = nil
	if dis == nil then return true end
	if dis == "0" then return true end
	return false
end

local function lan_ports_contain(netdev)
	local netw = uci.cursor('/etc/config')
	local ports = netw:get('network', '@device[0]', 'ports')
	netw:close(); netw = nil
	if type(ports) ~= "table" then return false end
	ports = table.concat(ports, " ")
	if type(ports) == "string" then return string.find(ports, netdev, 1, true) end
	return false
end

local function is_rk3568()
	local output = invoker.readfile("/proc/device-tree/model")
	if not output or not string.find(output, "RK3568", 1, true) then
		return false
	end
	output = invoker.readfile("/tmp/sysinfo/board_name", invoker.TRIMEND)
	return output == 'WLOSANY_RK3568'
end

local function is_imx6ul()
	local output = invoker.readfile("/proc/cpuinfo")
	if not output then return false end
	if not string.find(output, "Freescale i.MX6", 1, true) then return false end
	return true
end

local function check_filesize(fpath, maxsize, action)
	local fst = posix.stat(fpath)
	if type(fst) ~= "table" then return false end
	if fst['size'] < 0 or fst['size'] >= maxsize then
		if type(action) == "table" then
			io.stdout:write(gfmt("Warning, taking action for '%s'...\n", fpath))
			io.stdout:flush()
			invoker.invoke(0, action)
			return true
		end
		io.stdout:write(gfmt("Warning: removing file %s...\n", fpath))
		io.stdout:flush()
		posix.unlink(fpath) -- just remove the file
		posix.sync()
		return true
	end
	return false
end

local function ping_host(ipaddr, netdev)
	local cmds = { "ping", "-c3", "-w12" }
	if type(netdev) == "string" then
		cmds[#cmds + 1] = string.format("-I%s", netdev)
	end
	cmds[#cmds + 1] = ipaddr
	local eval, output = invoker.invoke(invoker.OUTPUT + invoker.NOSTDIO, cmds)
	if type(output) == "string" and string.find(output, 'packet loss', 1, true) then
		if string.find(output, '100% packet loss', 1, true) then return false end
		-- io.stdout:write(string.format("[%s] Ping %s OK.\n", os.date(), ipaddr))
		-- io.stdout:flush()
		return true
	end
	if eval == 0 then return true end
	return false
end

local function get_pinghost(cfgfile)
	local dhost, dport = "mqtt.lnxall.com", 3883
	local filp = io.open(cfgfile, "rb")
	if not filp then return dhost, dport end

	local fild = filp:read("*a")
	filp:close(); filp = nil
	if not fild or #fild == 0 then return dhost, dport end

	local okay, jdat = pcall(cjson.decode, fild)
	if not okay or type(jdat) ~= "table" then return dhost, dport end

	local host = jdat["host"]
	local port = jdat["port"]
	if type(host) == "string" and type(port) == "number" then
		return host, port
	else
		return dhost or dport
	end
end

local function isat_time(when)
	local nowt = os.date("*t")
	return nowt["hour"] == when
end

local function nslookup(hostn)
	local pid, outfd = invoker.invoke(invoker.NOWAIT + invoker.OUTPUT, "nslookup", hostn)
	if type(pid) ~= "number" then return nil end
	while true do
		if invoker.waitpid(pid, true) then break end
		tasklua.delay(3000)
	end

	local output = invoker.readfd(outfd, 4096)
	if type(outfd) == "number" and outfd >= 0 then
		posix.close(outfd); outfd = -1
	end
	if type(output) ~= "string" then return nil end

	local iptab, ipn, ans = {}, 0, false
	for line in string.gmatch(output, "[^\r\n]+") do
		if not ans then
			if string.find(line, "answer:", 1, true) then ans = true end
		else
			local ipv4 = string.match(line, "Address:%s+([%d%.]+)")
			if ipv4 and invoker.isipv4(ipv4) then
				ipn = ipn + 1
				iptab[ipn] = ipv4
			end
		end
	end

	if ipn == 0 then return nil end
	return iptab
end

local function entry_netping()
	local disc = nil
	-- try to read ICCID before ping
	while disc == nil do
		disc = invoker.readfile(g_iccid, invoker.TRIMEND)
		if disc and #disc >= 0x8 then break end
		disc = nil; tasklua.delay(15000)
	end

	disc = 0
	local phost, pport = get_pinghost('/app/config/mqtt_server.json')
	if not invoker.isipv4(phost) then
		-- resolve address as IPv4 address
		while true do
			local ips = nslookup(phost)
			if ips then
				io.stdout:write(gfmt("hostname resolved: %s => %s\n", phost, ips[1]))
				io.stdout:flush()
				phost = ips[1]
				break
			end
			tasklua.delay(15000)
		end
	end

	local nowt = invoker.uptime()
	local thet = nowt + CHECK_INTERVAL
	while true do
		if ping_host(phost) or invoker.tcpcheck(phost, pport, 2000) then
			if disc > 0 then disc = 0 end
		else
			disc = disc + 1
			io.stdout:write(string.format("Network is down, cannot ping %s: %d\n", phost, disc))
			io.stdout:flush()
			if disc > 10 then disc = 0 end
		end

		nowt = invoker.uptime()
		while nowt < thet do
			tasklua.delay((thet - nowt) * 1000)
			nowt = invoker.uptime()
		end
		thet = thet + CHECK_INTERVAL
		if thet <= nowt then thet = nowt end
	end
end

local function entry_meminfo()
	local lowcount = 0
	while true do
		local memi = invoker.readfile("/proc/meminfo")
		if type(memi) ~= "string" or string.len(memi) == 0 then
			io.stderr:write("Error, failed to read meminfo\n")
			io.stderr:flush()
			tasklua.delay(10000)
			break
		end

		-- get available memory size, in KBytes
		local avail = string.match(memi, "MemAvailable:%s+(%d+)%s+kB")
		if type(avail) ~= "string" then
			avail = -1
			io.stderr:write("Error, failed to get MemAvailable!\n")
			io.stderr:flush()
		else
			avail = tonumber(avail) -- convert to number
			if not avail then
				avail = -1
				io.stderr:write("Error, invalid MemAvailable found.\n")
				io.stderr:flush()
			end
		end

		io.stdout:write(string.format("[%s] Memory available: %d kB\n", os.date(), avail))
		io.stdout:flush()
		-- minimum memory: 4MB
		if avail >= 0 then
			if avail < 4096 then
				-- flush memory cache
				local drop = io.open("/proc/sys/vm/drop_caches", "wb")
				if drop then
					drop:write("3\n")
					drop:close(); drop = nil
				end

				-- increment low-memory-counter
				lowcount = lowcount + 0x1
				if lowcount > 5 then lowcount = 0 end
			elseif lowcount > 0 then
				lowcount = 0 -- reset low-memory-counter
			end
		end
		tasklua.delay(120000)
	end
	return true
end

local function remove_logs(pattern, howold)
	local logs = posix.glob(pattern)
	if type(logs) ~= "table" or #logs == 0 then
		-- io.stdout:write(gfmt("Warning, no files found for pattern: %s\n", pattern))
		-- io.stdout:flush()
		return false
	end

	local lfiles = {}
	for _, file in ipairs(logs) do
		local fst = posix.stat(file)
		if type(fst) ~= "table" then
			posix.unlink(file)
			io.stderr:write(gfmt("Error, failed to stat: %s\n", file))
			io.stderr:flush()
		elseif fst['type'] == 'regular' and type(fst['mtime']) == "number" then
			lfiles[file] = fst['mtime']
		end
	end

	local nowtim = os.time()
	howold = howold * 86400 -- translate days into seconds
	for filog, mtime in pairs(lfiles) do
		if nowtim > mtime and (nowtim - mtime) >= howold then
			posix.unlink(filog)
			io.stdout:write(gfmt("Remove too old log file: %s\n", filog))
			io.stdout:flush()
		end
	end
	posix.sync()
	return true
end

local function entry_logremove()
	local LR_INTERVAL = 600 --
	local n0, ntim = invoker.uptime(), 0
	local n1 = n0 + LR_INTERVAL
	io.stdout:write("Log remove task up and running...\n")
	io.stdout:flush()

	local gztab = { 'dmesg.*.gz', 'syslog.*.gz', 'mail.*.gz', 'daemon.*.gz',
		'kern.*.gz', 'auth.*.gz', 'user.*.gz', 'lpr.*.gz', 'cron.*.gz',
		'debug.*.gz', 'messages.*.gz' }

	local chktab = { 'syslog', 'mail.info', 'mail.warn', 'mail.err', 'mail.log',
		'daemon.log', 'kern.log', 'auth.log', 'user.log', 'lpr.log', 'cron.log',
		'debug', 'messages' }

	local daily = invoker.uptime()
	while true do
		for _, glop in ipairs(gztab) do
			remove_logs(gfmt('/var/log/%s', glop), 7)
		end

		local dorot = false
		for _, logf in ipairs(chktab) do
			if check_filesize(gfmt('/var/log/%s', logf), 268435456,
					{ "/bin/sh", "-c", "chmod 644 /etc/logrotate.d/*" }) then
				dorot = true
				break
			end
		end

		n0 = invoker.uptime()
		if dorot and (ntim == 0 or (n0 - ntim) >= 5400) then
			ntim, daily = n0, n0
			invoker.invoke(0, "logrotate", "-f", "/etc/logrotate.conf")
			invoker.invoke(0, "logrotate", "-f", "/etc/logrotate.d/rsyslog")
			n0 = invoker.uptime()
		elseif (n0 - daily) >= 86400 then -- for `daily log-rotate
			ntim, daily = n0, n0
			invoker.invoke(0, "logrotate", "-f", "/etc/logrotate.conf")
			invoker.invoke(0, "logrotate", "-f", "/etc/logrotate.d/rsyslog")
			n0 = invoker.uptime()
		end
		while n1 > n0 do
			tasklua.delay((n1 - n0) * 1000)
			n0 = invoker.uptime()
		end
		n1 = n1 + LR_INTERVAL
	end
end

local function sort_by_mtime(f0, f1)
	if type(f0) ~= "string" then return false end
	if type(f1) ~= "string" then return false end
	local st0 = posix.stat(f0)
	local st1 = posix.stat(f1)
	if type(st0) ~= "table" then return false end
	if type(st1) ~= "table" then return false end

	st0, st1 = st0['mtime'], st1['mtime']
	if type(st0) ~= "number" then st0 = 0 end
	if type(st1) ~= "number" then st1 = 0 end
	return st0 > st1
end

local function entry_coredump()
	local chkival = 180 * 1000 -- Every 3 minutes
	local sysup = invoker.uptime()
	posix.unlink('/core') -- remove existing coredump if any
	if sysup < 180 then
		-- for system fresh boot, delay 3 minutes
		tasklua.delay((180 - sysup) * 1000)
	end

	while true do
		local cores = posix.glob('/var/crash/coredumps/*.core')
		if type(cores) == "table" then
			local numc, numd = #cores, 2
			if numc > 1 then table.sort(cores, sort_by_mtime) end
			while true do
				numd = numd + 1
				local core = cores[numd]
				if type(core) ~= "string" then break end
				io.stdout:write(gfmt("Deleting core file: %s\n", core))
				io.stdout:flush()
				posix.unlink(core)
			end
			if numc > 5 then posix.sync() end
		end
		tasklua.delay(chkival)
	end
end

-- task disabled:
local function entry_space_check()
	local rootp = { ["EM1000"] = "/dev/mmcblk0p3", ["RK3568"] = "/dev/root",
		["RK3568_XDDL"] = "/dev/root", ["LC100"] = "/dev/root" }
	rootp = rootp[board_name]
	if not rootp then
		io.stdout:write(gfmt("Error, cannot find root partion for %s\n", board_name))
		io.stdout:flush()
		while true do tasklua.delay(900 * 1000) end
	end

	if invoker.uptime() < 180 then
		tasklua.delay(120000)
	end

	while true do
		local percent = 0
		local okay, output = invoker.invoke(invoker.OUTPUT, "df")
		if okay == 0 and type(output) == "string" then
			for line in string.gmatch(output, "[^\r\n]+") do
				if string.find(line, rootp, 1, true) then
					local free = string.match(line, "(%d+)%%")
					if free then free = tonumber(free) end
					if not free then
						io.stderr:write("Disk free percentage not found.\n")
						io.stderr:flush()
					else
						percent = free
					end
					break
				end
			end
		end

		if percent >= 95 then
			local rmlist = {}
			local chkfiles, restart = {}, false
			io.stdout:write(gfmt("Warning, disk storage memory low: %d%%\n", percent))
			io.stdout:flush()

			chkfiles[#chkfiles + 1] = "/var/log/auth.log"
			chkfiles[#chkfiles + 1] = "/var/log/daemon.log"
			chkfiles[#chkfiles + 1] = "/var/log/debug"
			chkfiles[#chkfiles + 1] = "/var/log/messages"
			chkfiles[#chkfiles + 1] = "/var/log/user.log"
			chkfiles[#chkfiles + 1] = "/var/log/syslog"
			for _, cf in ipairs(chkfiles) do
				if check_filesize(cf, 268435456, { "rm", "-rf", cf }) then
					restart = true
					rmlist[#rmlist + 1] = cf
				end
				local idx = 0
				while idx <= 5 do
					local fpath = gfmt("%s.%d", cf, idx)
					if check_filesize(fpath, 268435456, { "rm", "-rf", fpath }) then
						restart = true
						rmlist[#rmlist + 1] = fpath
					end
					idx = idx + 1
				end
			end

			if restart then
				invoker.invoke(invoker.NOSTDIO, "systemctl", "stop", "rsyslog")
				invoker.invoke(invoker.NOSTDIO, "systemctl", "stop", "syslog.socket")
				tasklua.delay(3000); posix.sync() -- delay 3 seconds
				local dflog = "/etc/free-space-remove.log"
				check_filesize(dflog, 256 * 1024, { "rm", "-rf", dflog })
				local filp = io.open(dflog, "ab")
				if filp then
					filp:write(gfmt("%s: Removing log files...\n", os.date()))
					filp:write(table.concat(rmlist, "\n"))
					filp:write("\n=========================================\n")
					filp:close()
				end
				invoker.invoke(invoker.NOSTDIO, "systemctl", "restart", "rsyslog")
				invoker.invoke(invoker.NOSTDIO, "systemctl", "restart", "syslog.socket")
			end
		end
		tasklua.delay(600000) -- delay 600 seconds
	end
end

local function check_board_name()
	local output = invoker.readfile("/proc/device-tree/model")
	if type(output) ~= "string" then
		io.stderr:write("Error, cannot read device model for board_name!\n")
		io.stderr:flush()
		return false
	end

	if string.find(output, "AM654", 1, true) then
		board_name = "EM1000"
		return true
	end

	if string.find(output, "RK3568", 1, true) then
		board_name = "RK3568"
		return true
	end

	if string.find(output, "XDDL3568", 1, true) then
		board_name = "RK3568_XDDL"
		return true
	end

	output = invoker.readfile("/proc/cpuinfo")
	if type(output) ~= "string" then output = "" end
	if string.find(output, "i.MX6 Ultralite", 1, true) then
		board_name = "LC100"
		return true
	end

	io.stderr:write(gfmt("Error, invalid device model: %s\n", output))
	io.stderr:flush()
	return false
end

local function count_true(ctab, maxn)
	local rval = 0
	for idx = 1, maxn do
		if ctab[idx] then rval = rval + 1 end
	end
	return rval
end

-- RK3568, W5500 work as br-lan
local function entry_brlan_reset()
	local tim0 = invoker.uptime()
	if tim0 < 50 then tasklua.delay((50 - tim0) * 1000) end
	local okfile, delay_sec = "/tmp/br-lan-ping.ok", 40
	if posix.access(okfile) == 0 then delay_sec = 320 end

	local lanen = network_enabled('lan') and lan_ports_contain('eth2')
	while not lanen do
		-- io.stdout:write("Warning, LAN disabled!!!\n")
		-- io.stdout:flush()
		tasklua.delay(60000)
		lanen = network_enabled('lan') and lan_ports_contain('eth2')
	end

	tim0 = invoker.uptime()
	local itercnt, reset_cnt = 0, 0
	local okcnt = { [1] = true, [2] = true, [3] = true, [4] = true }
	while lanen do
		local arplist, anyok = invoker.readfile("/proc/net/arp"), false
		if type(arplist) ~= "string" then
			io.stderr:write("Error, failed to read ARP file\n")
			io.stderr:flush()
		else
			local iplist = {}
			for line in string.gmatch(arplist, "[^\r\n]+") do
				if string.find(line, "br-lan", 1, true) then
					local ip = string.match(line, "^([%d%.]+)")
					if ip then iplist[#iplist + 1] = ip end
				end
			end

			for _, ip in pairs(iplist) do
				local okay, out = invoker.invoke(invoker.OUTPUT, "ping", "-A", "-c8", "-w4", "-Ibr-lan", ip)
				if okay == 0 and type(out) == "string" and string.find(out, "packet loss", 1, true) then
					if string.find(out, "%s0%% packet loss") then
						anyok = true
						break
					end
				end
			end
		end
		okcnt[1], okcnt[2], okcnt[3], okcnt[4] = okcnt[2], okcnt[3], okcnt[4], anyok

		itercnt = itercnt + 1
		anyok = count_true(okcnt, 0x4)
		if anyok >= 3 and itercnt >= 4 then
			check_filesize(okfile, 524288)
			local fp = io.open(okfile, "ab")
			if fp then
				fp:write(gfmt("%s Ping okay on br-lan: %d, okcnt: %d\n", os.date(), reset_cnt, anyok))
				fp:close(); fp = nil
			end
			delay_sec = 320 -- break
		end
		if anyok == 0 then
			reset_cnt = reset_cnt + 1
			-- lock file to avoid confliction, refer to script: /opt/lnxall_app/bin/netuci:
			local lockfd = invoker.waitlock('/tmp/.netuci-lock')
			invoker.invoke(invoker.NOSTDIO, "ip", "link", "set", "dev", "eth2", "up")
			invoker.invoke(0, "/bin/bash", "-c", "echo -e -n '\\x00\\x00\\x55\\x00\\x00\\x00\\x55\\x00' | ethtool -E eth2 magic 0x0 offset 0x0 length 0x8")
			invoker.invoke(invoker.NOSTDIO, "ip", "link", "set", "dev", "eth2", "down")
			invoker.invoke(invoker.NOSTDIO, "nmcli", "con", "del", "lan")
			invoker.invoke(invoker.NOSTDIO, "nmcli", "con", "del", "lxbr_eth2")
			invoker.invoke(invoker.NOSTDIO, "nmcli", "con", "del", "lxbr_wlan0")

			tasklua.delay(3000)
			-- important: do not forget release netuci file lock:
			if type(lockfd) == "number" then
				invoker.closefd(lockfd)
				posix.close(lockfd) -- do it again, problem?
			end
			if (reset_cnt % 10) == 0 then
				invoker.invoke(invoker.NOSTDIO, "systemctl", "restart", "NetworkManager")
				tasklua.delay(3000)
			end

			local pid = invoker.invoke(invoker.NOWAIT + invoker.NOSTDIO, "netuci")
			while pid do
				tasklua.delay(1000)
				local term = invoker.waitpid(pid, true)
				if term == nil or term then pid = nil end
			end
			itercnt = 0 -- reset iteration count as zero
			for idx = 1, 4 do okcnt[idx] = true end
		end

		local tim1 = invoker.uptime()
		if tim1 >= 4000 and delay_sec < 120 then delay_sec = 120 end
		tim0 = tim0 + delay_sec
		while tim1 < tim0 do
			tasklua.delay((tim0 - tim1) * 1000)
			tim1 = invoker.uptime()
		end
		lanen = network_enabled('lan') and lan_ports_contain('eth2')
	end
	return false
end

local function check_ttyACM(sysp, slink)
	local gltp = posix.glob(sysp)
	if not gltp or type(gltp[1]) ~= "string" then
		io.stderr:write(gfmt("Error, failed to check %s\n", sysp))
		io.stderr:flush()
		return false
	end

	local tdev = string.match(gltp[1], "/([^/]+)$")
	if not tdev then return false end

	tdev = "/dev/" .. tdev
	if posix.access(tdev) ~= 0 then
		io.stderr:write(gfmt("Error, device not found: %s\n", tdev))
		io.stderr:flush()
		return false
	end
	local rdev = invoker.readlink(slink)
	if rdev ~= tdev then
		posix.unlink(slink)
		if invoker.invoke(0, "ln", "-sv", tdev, slink) == 0 then
			return true
		end
		io.stderr:write(gfmt("Error, failed to symlink %s => %s\n", tdev, slink))
		io.stderr:flush()
		return false
	end
	return true
end

local function entry_check_electron()
	local now = invoker.uptime()
	if now < 60 then tasklua.delay((60 - now) * 1000) end

	local chkcnt, errcnt = 0, 0
	now = invoker.uptime()
	while true do
		if not invoker.tcpcheck("127.0.0.1", 80, 1500) then
			errcnt = errcnt + 1
		elseif errcnt > 0 then
			errcnt = 0
		end

		chkcnt = chkcnt + 1
		if (chkcnt % 2) == 0 and errcnt >= 2 then
			local logfile = "/app/electron_restart.log"
			check_filesize(logfile, 0x200000)
			local logh = io.open(logfile, "ab")
			if logh then
				logh:write(gfmt("%s: restarting lightdm due to 127.0.0.1:80 unavailable.\n", os.date()))
				logh:close(); logh = nil
			end
			invoker.invoke(invoker.NOSTDIO, "systemctl", "restart", "lightdm")
		end

		now = now + 30
		local tim = invoker.uptime()
		while tim < now do
			tasklua.delay((now - tim) * 1000)
			tim = invoker.uptime()
		end
	end
	return true
end

local function entry_check_ch344()
	local errlist, chknum = {}, 0

	while true do
		local found = false
		local _, output = invoker.invoke(invoker.OUTPUT, "/bin/sh", "-c", "dmesg | grep -E -e 'usb usb1-port1: disabled by hub.+re-enabling'")
		if type(output) ~= "string" then output = "" end

		for line in string.gmatch(output, "[^\r\n]+") do
			if not errlist[line] then
				found = true
				errlist[line] = true
			end
		end

		chknum = chknum + 1
		if found then
			io.stdout:write("Warning, found new CH344 USB reconnect, restarting...\n")
			io.stdout:flush()
		end
		if found or bit.band(chknum, 0xF) == 0 then
			local symlinks = { "/dev/ttylnx3", "/dev/ttylnx1", "/dev/ttylnx2" }
			local redo, fmtstr = false, "/sys/devices/platform/fd800000.usb/usb1/1-1/1-1:1.%d/tty/*"
			for idx = 0, 2 do
				local sp = gfmt(fmtstr, idx * 2)
				if not check_ttyACM(sp, symlinks[idx + 1]) then
					redo = true
					break
				end
			end
			if redo then
				-- reconnect CH344 USB-TO-SERIAL CONVERTER
				invoker.invoke(invoker.NOSTDIO, "usbreset", "1a86:55d5")
				tasklua.delay(1500)
				for idx = 0, 2 do
					local sp = gfmt(fmtstr, idx * 2)
					check_ttyACM(sp, symlinks[idx + 1])
				end
			end
		end

		tasklua.delay(5000)
	end
end

local function entry_imx6ul_ch344()
	local uptim = invoker.uptime()
	if uptim < 120 then tasklua.delay((120 - uptim) * 1000) end

	-- /dev/ttylnx1 -> /dev/ttyACM1
	-- /dev/ttylnx2 -> /dev/ttyACM2
	-- /dev/ttylnx3 -> /dev/ttyACM0
	-- /dev/ttylnx4 -> /dev/ttyACM3

	local symlinks = { "/dev/ttylnx3", "/dev/ttylnx1", "/dev/ttylnx2", "/dev/ttylnx4" }
	local fmtstr = "/sys/devices/platform/soc/2100000.aips-bus/2184200.usb/ci_hdrc.1/usb1/1-1/1-1.1/1-1.1:1.%d/tty/ttyACM*"
	local una = posix.uname()
	if type(una) == "string" and string.find(una, "5.4.70", 1, true) then
		fmtstr = "/sys/devices/soc0/soc/2100000.aips-bus/2184200.usb/ci_hdrc.1/usb2/2-1/2-1.1/2-1.1:1.%d/tty/ttyACM*"
	end
	while true do
		for idx = 0, 3 do
			local sp = gfmt(fmtstr, idx * 2)
			if not check_ttyACM(sp, symlinks[idx + 1]) then
				io.stderr:write(gfmt("Error, failed to check symlink for '%s'\n", symlinks[idx + 1]))
				io.stderr:flush()
			end
		end
		tasklua.delay(60000)
	end
end

local function load_can_bitrate(pcfg, candev)
	if not candev then return nil end
	local chdl = io.open(pcfg, "rb")
	if not chdl then return nil end
	local dcfg = chdl:read("*a")
	chdl:close(); chdl = nil
	local okay, jcfg = pcall(cjson.decode, dcfg)
	if not okay then
		io.stderr:write(gfmt("Error, failed to decode as json: %s\n", pcfg))
		io.stderr:flush()
		return nil
	end

	local empty = {}
	local json = jcfg["dev_cfg"]
	if type(json) ~= "table" then json = empty end

	json = json["can"]
	if type(json) ~= "table" then json = empty end

	json = json["attr"]
	if type(json) ~= "table" then json = empty end

	local i = 0
	while true do
		i = i + 1
		local cancfg = json[i]
		if type(cancfg) ~= "table" then break end
		if cancfg["name"] == candev then
			local bitr = cancfg["baud"]
			if type(bitr) ~= "number" then return nil end
			return bitr
		end
	end
	return nil
end

-- refer to `check_can function from `/lib/dyiot/bin/supervisor.sh
-- is this really necessary?
local function taskentry_candev()
	local devs = invoker.uptime()
	if devs < 120 then tasklua.delay((120 - devs) * 1000) end
	devs = posix.glob('/sys/class/net/can*')
	if not devs then
		devs = {}
		io.stderr:write("Error, no can device found!\n")
		io.stderr:flush()
	end
	local errcnt = {}
	local cfgmap = { ["can0"] = "CAN1", ["can1"] = "CAN2" }
	local iflags, canbit = invoker.CLOSEFD + invoker.NOSTDIO, 500000
	while true do
		tasklua.delay(8000)
		for _, cdev in ipairs(devs) do
			local stat = invoker.readfile(cdev .. '/operstate', invoker.TRIMEND)
			if stat == 'down' then
				local candev, ecnt = string.match(cdev, "/([^/]+)$"), 0
				if candev then
					ecnt = errcnt[candev] or 0
					ecnt = ecnt + 1
					errcnt[candev] = ecnt
				end
				if ecnt >= 3 then
					io.stdout:write("try to bring up " .. candev .. "...\n")
					io.stdout:flush()
					invoker.invoke(iflags, 'ifconfig', candev, 'down')
					tasklua.delay(1000)
					local bitrate = load_can_bitrate('/app/config/port_config.json', cfgmap[candev])
					if not bitrate then bitrate = canbit else canbit = bitrate end
					if invoker.invoke(iflags, "ip", "link", "set", "dev", candev,
						"type", "can", "bitrate", tostring(bitrate), "triple-sampling", "on") ~= 0 then
						invoker.invoke(iflags, "ip", "link", "set", "dev", candev,
							"type", "can", "bitrate", tostring(bitrate))
					end
					errcnt[candev] = nil
					invoker.invoke(iflags, 'ifconfig', candev, 'up')
				end
			end
		end
	end
	return true
end

-- check whether we should start task `entry_brlan_reset
local function check_w5500_yt6801()
	if invoker.readfile("/sys/bus/pci/devices/0000:01:00.0/vendor", invoker.TRIMEND) == "0x1f0a" then
		-- device has YT6801 PCIe network card support
		return false
	end

	local ofnode = invoker.readlink("/sys/bus/spi/devices/spi3.0/of_node")
	if not ofnode or not string.find(ofnode, "eth_w550") then
		-- No W5500 driver found
		return false
	end

	tasklua.taskadd(entry_brlan_reset, true)
	return true
end

local function fix_debian_ntp()
	local wrap = "/usr/lib/ntp/ntp-systemd-wrapper"
	if posix.access(wrap) ~= 0 then return false end
	local cont = invoker.readfile(wrap)
	if type(cont) ~= "string" or #cont == 0 then return false end

	local exel = "exec $DAEMON -p $PIDFILE $NTPD_OPTS"
	if not string.find(cont, exel, 1, true) then return false end
	local exef = exel .. " -I lo -L"
	if string.find(cont, exef, 1, true) then return false end

	invoker.invoke(0, "sed", "-e", gfmt("s#%s.+$#%s#g", exel, exef), "-i", wrap)
	io.stdout:write("Warning, NTP-server wrapper modified.\n")
	io.stdout:flush()
	invoker.invoke(invoker.NOSTDIO, "systemctl", "restart", "ntp")
	return true
end

local function disable_busyboxntp()
	local pinfo = invoker.readfile("/proc/cpuinfo")
	if type(pinfo) ~= "string" then pinfo = "what the fuck" end
	if string.find(pinfo, "Freescale i.MX6", 1, true) then
		invoker.invoke(invoker.NOSTDIO, "systemctl", "stop", "busyboxdhcpd")
		invoker.invoke(invoker.NOSTDIO, "systemctl", "disable", "busyboxdhcpd")
	end
end

local function fix_debian_lightdm()
	local okay, output = invoker.invoke(invoker.NOSTDIO + invoker.OUTPUT,
		"systemctl", "status", "lightdm")
	if okay ~= 0 then return false end
	if type(output) ~= "string" then output = "" end

	if not string.find(output, "vendor preset: enabled", 1, true) then return false end
	if string.find(output, "indirect;", 1, true) then return false end
	if not string.find(output, "static;", 1, true) then return false end

	io.stdout:write("Restoring lightdm service...\n")
	io.stdout:flush()

	invoker.invoke(invoker.NOSTDIO, "systemctl", "unmask", "lightdm.service")
	invoker.msleep(250)
	invoker.invoke(invoker.NOSTDIO, "systemctl", "daemon-reload")
	invoker.msleep(250)
	invoker.invoke(invoker.NOSTDIO, "dpkg-reconfigure", "lightdm");
	return true
end

local function check_internal_watchdog()
	local okay, output = invoker.invoke(invoker.OUTPUT,
		"sh", "-c", "date '+%s' --date=\"$(uname -v | sed -r -e 's/^#.+SMP //g')\" ; exit 0")
	if okay ~= 0 or type(output) ~= "string" or #output == 0 then
		io.stderr:write("Error, failed to failed to get kernel build date\n")
		io.stderr:flush()
		return false
	end

	local rdate = tonumber(output)
	if not rdate or rdate < 1730267430 then
		io.stdout:write("Error, OLD RK3568 kernel without internal watchdog, do nothing\n")
		io.stdout:flush()
		return false
	end

	okay, output = invoker.invoke(invoker.OUTPUT, "systemctl", "status", "watchdog")
	if type(output) ~= "string" then output = "" end
	if okay == 0 and string.find(output, "active (running)", 1, true) then
		io.stdout:write("Disabling QYWDT...\n")
		io.stdout:flush()
		invoker.invoke(0, "systemctl", "stop", "qywdt")
		invoker.invoke(0, "systemctl", "disable", "qywdt")
	else
		io.stdout:write("Do not stop QYWDT!!!\n")
		io.stdout:flush()
	end
end

local function lsusb_has(usbid)
	local okay, output = invoker.invoke(invoker.OUTPUT, "lsusb")
	if okay == 0 and type(output) == "string" and string.find(output, usbid, 1, true) then
		return true
	end
	return false
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 rk3568_touchscreen_fix()
	local refresh_sh = "/opt/lnxall_app/bin/hdmi-display.sh"
	local calconf = "/etc/X11/xorg.conf.d/99-calibration.conf"

	local uptime = invoker.uptime()
	if uptime < 90 then
		tasklua.delay((90 - uptime) * 1000)
	end

	while not (lsusb_has('222a:0001') or lsusb_has('27c6:0816')) do
		tasklua.delay(600 * 1000)
	end

	invoker.invoke(0, "/bin/bash", refresh_sh)
	local conf_md5 = get_md5sum(calconf)
	local _, hdmi_res = invoker.invoke(invoker.OUTPUT, "bash", "-c", "DISPLAY=:0 xrandr | grep -e 'HDMI-1 connected'")

	while lsusb_has('222a:0001') or lsusb_has('27c6:0816') do
		local _, new_res = invoker.invoke(invoker.OUTPUT, "bash", "-c", "DISPLAY=:0 xrandr | grep -e 'HDMI-1 connected'")
		if new_res ~= hdmi_res then
			io.stderr:write("Updating touchscreen calibration configuration...\n")
			io.stderr:flush()
			invoker.invoke(0, "/bin/bash", refresh_sh)
			conf_md5 = get_md5sum(calconf)
			_, hdmi_res = invoker.invoke(invoker.OUTPUT, "bash", "-c", "DISPLAY=:0 xrandr | grep -e 'HDMI-1 connected'")
		end
		tasklua.delay(120 * 1000)
	end
	return true
end

local function main_func()
	invoker.setname('SYSMONINTOR')

	check_board_name()
	tasklua.taskadd(entry_meminfo, true)
	tasklua.taskadd(entry_netping, true)
	tasklua.taskadd(entry_logremove, true)
	tasklua.taskadd(entry_coredump, true)
	tasklua.taskadd(entry_space_check, true)
	if is_rk3568() then
		tasklua.taskadd(entry_check_ch344, true)
	end
	if posix.access("/usr/share/lnxallinst/electron/electron") == 0  then
		tasklua.taskadd(entry_check_electron, true)
	end
	if posix.access('/sys/class/net/can0') == 0 or
		posix.access('/sys/class/net/can1') == 0 then
		tasklua.taskadd(taskentry_candev, true)
	end

	check_w5500_yt6801()
	fix_debian_ntp()
	disable_busyboxntp()
	if is_rk3568() then
		fix_debian_lightdm()
		check_internal_watchdog()
		tasklua.taskadd(rk3568_touchscreen_fix, true)
	end

	if is_imx6ul() and lsusb_has("1a86:8091") then
		tasklua.taskadd(entry_imx6ul_ch344, true)
	end

	while true do
		if not tasklua.taskloop(900000) then
			break
		end
	end
end

main_func(arg[1])
os.exit(1)