#!/bin/sh /etc/rc.common
# Copyright 2019-2020 Stan Grishin (stangri@melmac.net)
# shellcheck disable=SC2039,SC3043,SC3060
PKG_VERSION='dev-test'

# shellcheck disable=SC2034
START=80
# shellcheck disable=SC2034
USE_PROCD=1

if type extra_command 1>/dev/null 2>&1; then
	extra_command 'version' 'Show version information'
else
# shellcheck disable=SC2034
	EXTRA_COMMANDS='version'
fi

readonly PROG=/usr/sbin/https-dns-proxy
readonly DEFAULT_BOOTSTRAP='1.1.1.1,1.0.0.1,2606:4700:4700::1111,2606:4700:4700::1001,8.8.8.8,8.8.4.4,2001:4860:4860::8888,2001:4860:4860::8844'
dnsmasqConfig=''; forceDNS=''; forceDNSPorts='';

str_contains() { [ -n "$2" ] && [ "${1//$2}" != "$1" ]; }
is_mac_address() { expr "$1" : '[0-9A-F][0-9A-F]:[0-9A-F][0-9A-F]:[0-9A-F][0-9A-F]:[0-9A-F][0-9A-F]:[0-9A-F][0-9A-F]:[0-9A-F][0-9A-F]$' >/dev/null; }
is_ipv4() { expr "$1" : '[0-9][0-9]*\.[0-9][0-9]*\.[0-9][0-9]*\.[0-9][0-9]*$' >/dev/null; }
is_ipv6() { ! is_mac_address "$1" && str_contains "$1" ":"; }

version() { echo "$PKG_VERSION"; }

xappend() { param="$param $1"; }

append_bool() {
	local section="$1"
	local option="$2"
	local value="$3"
	local default="${4:-0}"
	local _loctmp
	config_get_bool _loctmp "$section" "$option" "$default"
	[ "$_loctmp" -ne 0 ] && xappend "$value"
}

append_parm() {
	local section="$1"
	local option="$2"
	local switch="$3"
	local default="$4"
	local _loctmp
	config_get _loctmp "$section" "$option" "$default"
	[ -n "$_loctmp" ] && xappend "$switch $_loctmp"
}

append_counter() {
	local section="$1"
	local option="$2"
	local switch="$3"
	local default="${4:-0}"
	local _loctmp i
	config_get _loctmp "$section" "$option" "$default"
# shellcheck disable=SC2086,SC2154
	for i in $(seq 1 $_loctmp); do
		xappend '-v'
	done
}

append_bootstrap() {
	local section="$1"
	local option="$2"
	local switch="$3"
	local default="$4"
	local _old_ifs="$IFS"
	local _loctmp _newtmp i
	config_get _loctmp "$section" "$option" "$default"
	[ -z "$_loctmp" ] && return 0
	IFS=" ,"
	for i in $_loctmp; do
		if { [ "$ipv6_resolvers_only" -eq 0 ] && is_ipv4 "$i"; } || \
			{ [ "$ipv6_resolvers_only" -ne 0 ] && is_ipv6 "$i"; }; then
			[ -z "$_newtmp" ] && _newtmp="$i" || _newtmp="${_newtmp},${i}"
		fi
	done
	IFS="$_old_ifs"
	[ -n "$_newtmp" ] && xappend "$switch $_newtmp"
	[ "$ipv6_resolvers_only" -eq 0 ] && xappend '-4'
}

start_instance() {
	local cfg="$1" param listen_addr listen_port i ipv6_resolvers_only
	config_get_bool ipv6_resolvers_only "$cfg" 'use_ipv6_resolvers_only' '0'
	append_parm "$cfg" 'resolver_url' '-r'
	append_parm "$cfg" 'polling_interval' '-i'
	append_parm "$cfg" 'listen_addr' '-a' '127.0.0.1'
	append_parm "$cfg" 'listen_port' '-p' "$p"
	append_parm "$cfg" 'dscp_codepoint' '-c'
	append_bootstrap "$cfg" 'bootstrap_dns' '-b' "$DEFAULT_BOOTSTRAP"
	append_parm "$cfg" 'user' '-u' 'nobody'
	append_parm "$cfg" 'group' '-g' 'nogroup'
	append_parm "$cfg" 'proxy_server' '-t'
	append_parm "$cfg" 'logfile' '-l'
	append_bool "$cfg" 'use_http1' '-x'
	append_counter "$cfg" 'verbosity' '-v' '0'

	procd_open_instance
# shellcheck disable=SC2086
	procd_set_param command $PROG $param
	procd_set_param stderr 1
	procd_set_param stdout 1
	procd_set_param respawn
	if [ "$forceDNS" -ne 0 ]; then
		procd_open_data
		json_add_array firewall
		for c in $forceDNSPorts; do
			if netstat -tuln | grep 'LISTEN' | grep ":${c}" >/dev/null 2>&1 || [ "$c" = "53" ]; then
				json_add_object ""
				json_add_string type redirect
				json_add_string target DNAT
				json_add_string src lan
				json_add_string proto "tcp udp"
				json_add_string src_dport "$c"
				json_add_string dest_port "$c"
				json_add_boolean reflection 0
				json_close_object
			else
				json_add_object ""
				json_add_string type rule
				json_add_string src lan
				json_add_string dest "*"
				json_add_string proto "tcp udp"
				json_add_string dest_port "$c"
				json_add_string target REJECT
				json_close_object
			fi
		done
		json_close_array
		procd_close_data
		forceDNS='0'
	fi
	procd_close_instance

	config_get listen_addr "$cfg" 'listen_addr' '127.0.0.1'
	config_get listen_port "$cfg" 'listen_port' "$p"

	if [ "$dnsmasqConfig" = "*" ]; then
		config_load 'dhcp'
		config_foreach dnsmasq_add_doh_server 'dnsmasq' "${listen_addr}" "${listen_port}"
	elif [ -n "$dnsmasqConfig" ]; then
		for i in $dnsmasqConfig; do
			dnsmasq_add_doh_server "@dnsmasq[${i}]" "${listen_addr}" "${listen_port}"
		done
	fi
	p="$((p+1))"
}

is_force_dns_active() { iptables-save | grep -q -w -- '--dport 53'; }

start_service() {
	local p=5053 c
	config_load 'https-dns-proxy'
	config_get dnsmasqConfig	'config' 'update_dnsmasq_config' '*'
	config_get_bool forceDNS	'config' 'force_dns' '1'
	config_get forceDNSPorts	'config' 'force_dns_port' '53 853'
	dhcp_backup 'create'
	config_load 'https-dns-proxy'
	config_foreach start_instance 'https-dns-proxy'
	if [ -n "$(uci -q changes dhcp)" ]; then
		uci -q commit dhcp
		[ -x /etc/init.d/dnsmasq ] && /etc/init.d/dnsmasq restart >/dev/null 2>&1
	fi
}

stop_service() {
	config_load 'https-dns-proxy'
	config_get dnsmasqConfig 'config' 'update_dnsmasq_config' '*'
	dhcp_backup 'restore'
	if [ -n "$(uci -q changes dhcp)" ]; then
		uci -q commit dhcp
		[ -x /etc/init.d/dnsmasq ] && /etc/init.d/dnsmasq restart >/dev/null 2>&1
	fi
}

service_triggers() {
	procd_add_config_trigger "config.change" "https-dns-proxy" /etc/init.d/https-dns-proxy reload
}

service_started() { procd_set_config_changed firewall; }
service_stopped() { procd_set_config_changed firewall; }

dnsmasq_add_doh_server() {
	local cfg="$1" address="$2" port="$3"
	case $address in
		0.0.0.0|::ffff:0.0.0.0) address='127.0.0.1';;
		::) address='::1';;
	esac
	uci -q del_list "dhcp.${cfg}.server=${address}#${port}"
	uci -q add_list "dhcp.${cfg}.server=${address}#${port}"
}

dnsmasq_create_server_backup() {
	local cfg="$1"
	local i
	uci -q get "dhcp.${cfg}" >/dev/null || return 1
	if ! uci -q get "dhcp.${cfg}.doh_backup_noresolv" >/dev/null; then
		if [ -z "$(uci -q get "dhcp.${cfg}.noresolv")" ]; then
			uci -q set "dhcp.${cfg}.noresolv=1"
			uci -q set "dhcp.${cfg}.doh_backup_noresolv=-1"
		elif [ "$(uci -q get "dhcp.${cfg}.noresolv")" != "1" ]; then
			uci -q set "dhcp.${cfg}.noresolv=1"
			uci -q set "dhcp.${cfg}.doh_backup_noresolv=0"
		fi
	fi
	if ! uci -q get "dhcp.${cfg}.doh_backup_server" >/dev/null; then
		if [ -z "$(uci -q get "dhcp.${cfg}.server")" ]; then
			uci -q add_list "dhcp.${cfg}.doh_backup_server="
		fi
		for i in $(uci -q get "dhcp.${cfg}.server"); do
			uci -q add_list "dhcp.${cfg}.doh_backup_server=$i"
			if [ "$i" = "$(echo "$i" | tr -d /\#)" ]; then
				uci -q del_list "dhcp.${cfg}.server=$i"
			fi
		done
	fi
	return 0
}

dnsmasq_restore_server_backup() {
	local cfg="$1"
	local i
	uci -q get "dhcp.${cfg}" >/dev/null || return 0
	if uci -q get "dhcp.${cfg}.doh_backup_noresolv" >/dev/null; then
		if [ "$(uci -q get "dhcp.${cfg}.doh_backup_noresolv")" = "0" ]; then
			uci -q set "dhcp.${cfg}.noresolv=0"
		else 
			uci -q del "dhcp.${cfg}.noresolv"
		fi
		uci -q del "dhcp.${cfg}.doh_backup_noresolv"
	fi
	if uci -q get "dhcp.${cfg}.doh_backup_server" >/dev/null; then
		uci -q del "dhcp.${cfg}.server"
		for i in $(uci -q get "dhcp.${cfg}.doh_backup_server"); do
			uci -q add_list "dhcp.${cfg}.server=$i"
		done
	uci -q del "dhcp.${cfg}.doh_backup_server"
	fi
}

dhcp_backup() {
	local i
	config_load 'dhcp'
	case "$1" in
		create)
			if [ "$dnsmasqConfig" = "*" ]; then
				config_foreach dnsmasq_create_server_backup 'dnsmasq'
			elif [ -n "$dnsmasqConfig" ]; then
				for i in $dnsmasqConfig; do
					dnsmasq_create_server_backup "@dnsmasq[${i}]" || \
						dnsmasq_create_server_backup "$i"
				done
			fi
			;;
		restore)
			config_foreach dnsmasq_restore_server_backup 'dnsmasq'
			;;
	esac
}