which()
{
	# on some systems 'which' command is considered deprecated and not installed by default
	# 'command -v' replacement does not work exactly the same way. it outputs shell aliases if present
	# $1 - executable name
	local IFS=:
	for p in $PATH; do
	    [ -x "$p/$1" ] && {
		echo "$p/$1"
		return 0
	    }
	done
	return 1
}
exists()
{
	which "$1" >/dev/null 2>/dev/null
}
existf()
{
	type "$1" >/dev/null 2>/dev/null
}
whichq()
{
	which $1 2>/dev/null
}
exist_all()
{
	while [ -n "$1" ]; do
		exists "$1" || return 1
		shift
	done
	return 0
}
on_off_function()
{
	# $1 : function name on
	# $2 : function name off
	# $3 : 0 - off, 1 - on
	local F="$1"
	[ "$3" = "1" ] || F="$2"
	shift
	shift
	shift
	"$F" "$@"
}
contains()
{
	# check if substring $2 contains in $1
	[ "${1#*$2}" != "$1" ]
}
starts_with()
{
	# $1 : what
	# $2 : starts with
	case "$1" in
		"$2"*)
			return 0
			;;
	esac
	return 1
}
find_str_in_list()
{
	# $1 - string
	# $2 - space separated values

	local v
	[ -n "$1" ] && {
		for v in $2; do
			[ "$v" = "$1" ] && return 0
		done
	}
	return 1
}
end_with_newline()
{
	local c="$(tail -c 1)"
	[ "$c" = "" ]
}
trim()
{
	awk '{gsub(/^ +| +$/,"")}1'
}

dir_is_not_empty()
{
	# $1 - directory
	local n
	[ -d "$1" ] || return 1
	n=$(ls "$1" | wc -c | xargs)
	[ "$n" != 0 ]
}

append_separator_list()
{
	# $1 - var name to receive result
	# $2 - separator
	# $3 - quoter
	# $4,$5,... - elements
	local _var="$1" sep="$2" quo="$3" i

	eval i="\$$_var"
	shift; shift; shift
	while [ -n "$1" ]; do
		if [ -n "$i" ] ; then
			i="$i$sep$quo$1$quo"
		else
			i="$quo$1$quo"
		fi
		shift
	done
	eval $_var="\$i"
}
make_separator_list()
{
	eval $1=''
	append_separator_list "$@"
}
make_comma_list()
{
	# $1 - var name to receive result
	# $2,$3,... - elements
	local var="$1"
	shift
	make_separator_list $var , '' "$@"
}
make_quoted_comma_list()
{
	# $1 - var name to receive result
	# $2,$3,... - elements
	local var="$1"
	shift
	make_separator_list $var , '"' "$@"
}
unique()
{
	local i
	for i in "$@"; do echo $i; done | sort -u | xargs
}

is_linked_to_busybox()
{
	local IFS F P
	
	IFS=:
	for path in $PATH; do
		F=$path/$1
		P="$(readlink $F)"
		if [ -z "$P" ] && [ -x $F ] && [ ! -L $F ]; then return 1; fi
		[ "${P%busybox*}" != "$P" ] && return
	done
}
get_dir_inode()
{
	local dir="$1"
	[ -L "$dir" ] && dir=$(readlink "$dir")
	ls -id "$dir" | awk '{print $1}'
}

linux_min_version()
{
	# $1 - major ver
	# $2 - minor ver
	local V1=$(sed -nre 's/^Linux version ([0-9]+)\.[0-9]+.*$/\1/p' /proc/version)
	local V2=$(sed -nre 's/^Linux version [0-9]+\.([0-9]+).*$/\1/p' /proc/version)
	[ -n "$V1" -a -n "$V2" ] && [ "$V1" -gt "$1" -o "$V1" -eq "$1" -a "$V2" -ge "$2" ]
}
linux_get_subsys()
{
	local INIT="$(sed 's/\x0/\n/g' /proc/1/cmdline | head -n 1)"

	[ -L "$INIT" ] && INIT=$(readlink "$INIT")
	INIT="$(basename "$INIT")"
	if [ -f "/etc/openwrt_release" ] && [ "$INIT" = "procd" ] ; then
		SUBSYS=openwrt
	elif [ -x "/bin/ndm" ] ; then
		SUBSYS=keenetic
	else
		# generic linux
		SUBSYS=
	fi
}
openwrt_fw3()
{
	[ ! -x /sbin/fw4 -a -x /sbin/fw3 ]
}
openwrt_fw4()
{
	[ -x /sbin/fw4 ]
}
openwrt_fw3_integration()
{
	[ "$FWTYPE" = iptables ] && openwrt_fw3
}

create_dev_stdin()
{
	[ -e /dev/stdin ] || ln -s /proc/self/fd/0 /dev/stdin
}

call_for_multiple_items()
{
	# $1 - function to get an item
	# $2 - variable name to put result into
	# $3 - space separated parameters to function $1

	local i item items
	for i in $3; do
		$1 item $i
		[ -n "$item" ] && {
			if [ -n "$items" ]; then
				items="$items $item"
			else
				items="$item"
			fi
		}
	done
	eval $2=\"$items\"
}

fix_sbin_path()
{
	local IFS=':'
	printf "%s\n" $PATH | grep -Fxq '/usr/sbin' || PATH="/usr/sbin:$PATH"
	printf "%s\n" $PATH | grep -Fxq '/sbin' || PATH="/sbin:$PATH"
	export PATH
}

# it can calculate floating point expr
calc()
{
	awk "BEGIN { print $*}";
}

fsleep_setup()
{
    [ -n "$FSLEEP" ] || {
	if sleep 0.001 2>/dev/null; then
		FSLEEP=1
	elif busybox usleep 1 2>/dev/null; then
		FSLEEP=2
	else
		local errtext="$(read -t 0.001 2>&1)"
		if [ -z "$errtext" ]; then
			FSLEEP=3
		# newer openwrt has ucode with system function that supports timeout in ms
		elif ucode -e "system(['sleep','1'], 1)" 2>/dev/null; then
			FSLEEP=4
		# older openwrt may have lua and nixio lua module
		elif lua -e 'require "nixio".nanosleep(0,1)' 2>/dev/null ; then
			FSLEEP=5
		else
			FSLEEP=0
		fi
	fi
    }
}
msleep()
{
    # $1 - milliseconds
    case "$FSLEEP" in
	1)
		sleep $(calc $1/1000)
		;;
	2)
		busybox usleep $(calc $1*1000)
		;;
	3)
		read -t $(calc $1/1000)
		;;
	4)
		ucode -e "system(['sleep','2147483647'], $1)"
		;;
	5)
		lua -e "require 'nixio'.nanosleep($(($1/1000)),$(calc $1%1000*1000000))"
		;;
    	*)
		sleep $((($1+999)/1000))
    esac
}
minsleep()
{
	msleep 100
}

replace_char()
{
	local a=$1
	local b=$2
	shift; shift
	echo "$@" | tr $a $b
}

replace_str()
{
	local a=$(echo "$1" | sed 's/\//\\\//g')
	local b=$(echo "$2" | sed 's/\//\\\//g')
	shift; shift
	echo "$@" | sed "s/$a/$b/g"
}

setup_md5()
{
	[ -n "$MD5" ] && return
	MD5=md5sum
	exists $MD5 || MD5=md5
}

random()
{
	# $1 - min, $2 - max
	local r rs
	setup_md5
	if [ -c /dev/urandom ]; then
		read rs </dev/urandom
	else
		rs="$RANDOM$RANDOM$(date)"
	fi
	# shells use signed int64
	r=1$(echo $rs | $MD5 | sed 's/[^0-9]//g' | cut -c 1-17)
	echo $(( ($r % ($2-$1+1)) + $1 ))
}

shell_name()
{
	[ -n "$SHELL_NAME" ] || {
		[ -n "$UNAME" ] || UNAME="$(uname)"

		if [ "$UNAME" = "Linux" ]; then
			SHELL_NAME="$(readlink /proc/$$/exe)"
			SHELL_NAME="$(basename "$SHELL_NAME")"
		else
			SHELL_NAME=$(ps -p $$ -o comm=)
		fi

		[ -n "$SHELL_NAME" ] || SHELL_NAME="$(basename "$SHELL")"
	}
}

process_exists()
{
	if exists pgrep; then
		pgrep ^$1$ >/dev/null
	elif exists pidof; then
		pidof $1 >/dev/null
	else
		return 1
	fi 
}

win_process_exists()
{
	tasklist /NH /FI "IMAGENAME eq ${1}.exe" | grep -q "^${1}.exe"
}

alloc_num()
{
	# $1 - source var name
	# $2 - target var name
	# $3 - min
	# $4 - max
	
	local v
	eval v="\$$2"
	# do not replace existing value
	[ -n "$v" ] && return
	eval v="\$$1"
	[ -n "$v" ] || v=$3
	eval $2="$v"
	v=$((v + 1))
	[ $v -gt $4 ] && v=$3
	eval $1="$v"
}

std_ports()
{
	TPWS_PORTS_IPT=$(replace_char - : $TPWS_PORTS)
	NFQWS_PORTS_TCP_IPT=$(replace_char - : $NFQWS_PORTS_TCP)
	NFQWS_PORTS_TCP_KEEPALIVE_IPT=$(replace_char - : $NFQWS_PORTS_TCP_KEEPALIVE)
	NFQWS_PORTS_UDP_IPT=$(replace_char - : $NFQWS_PORTS_UDP)
	NFQWS_PORTS_UDP_KEEPALIVE_IPT=$(replace_char - : $NFQWS_PORTS_UDP_KEEPALIVE)
}

has_bad_ws_options()
{
	# $1 - nfqws/tpws opts
	# опхлевюмхе дкъ пюяопнярпюмхрекеи йнохоюярш
	# щрнр йнд ядекюм яоежхюкэмн дкъ бюя, врнаш бш ме онярхкх б яерэ окнухе пежеорш
	# еякх бюл унверяъ ецн сдюкхрэ х мюохяюрэ хмярпсйжхч йюй ецн сдюкърэ, бш декюере упемнбсч сяксцс. мюохьхре ксвье custom script.
	# custom script - щрн тюикхй, йнрнпши днярюрнвмн яйнохпнбюрэ б мсфмсч дхпейрнпхч, врнаш нм ядекюк рнфе яюлне, мн щттейрхбмн.
	# тхкэрпюжхъ он IPSET б ъдпе меяпюбмхлн щттейрхбмее, вел оепейхдшбюрэ бяе оюйерш б nfqws х рюл тхкэрпнбюрэ
	# --ipset ясыеярбсер рнкэйн дкъ бхмдш х LINUX яхярел аег ipset (мюопхлеп, Android).
	# х рнкэйн он щрни опхвхме нмн ме бшйхмсрн онкмнярэч хг LINUX бепяхх
	contains "$1" "--ipset"
}
check_bad_ws_options()
{
	# $1 - 0 = stop, 1 = start
	# $2 - nfqws/tpws options
	if [ "$1" = 1 ] && has_bad_ws_options "$2"; then
		echo "!!! REFUSING TO USE BAD OPTIONS : $2"
		return 1
	else
		return 0
	fi
}
help_bad_ws_options()
{
	echo "WARNING ! you have specified --ipset option"
	echo "WARNING ! it would work but on $UNAME it's not the best option"
	echo "WARNING ! you should use kernel mode sets. they are much more efficient."
	echo "WARNING ! to use ipsets you have to write your own custom script"
	echo "WARNING ! installer will stop here to prevent distribution of easy to use but bad copy-paste solutions"
}