#!/bin/sh
# SPDX-License-Identifier: MIT

umask 077

# A nonblocking kernel lock covers all rpcd clients and is released on exit,
# including forced termination. Keep the lock file in place to preserve its inode.
probe_neighbors() (
	set -f
	command -v ping >/dev/null 2>&1 && command -v flock >/dev/null 2>&1 || exit 2
	flock -n 9 || exit 0

	read -r uptime rest < /proc/uptime
	now="${uptime%%.*}"
	last=""; cursor=""
	read -r last cursor < /tmp/luci-device-manager-probe.state 2>/dev/null
	case "$last" in ''|*[!0-9]*) last=0 ;; esac
	case "$cursor" in ''|*[!0-9]*) cursor=0 ;; esac
	if [ "$last" -gt 0 ] && [ "$now" -ge "$last" ] && [ "$((now-last))" -lt 30 ]; then
		exit 0
	fi

	# Resolve only explicitly selected logical LAN interfaces through netifd.
	# Never infer a LAN from connected routes or invent a /24 fallback.
	interfaces="$(uci -q get device_manager.settings.scan_interface 2>/dev/null || printf lan)"
	lan_subnets="$(
		selected=0
		for interface in $interfaces; do
			case "$interface" in ''|*[!a-zA-Z0-9_]*) continue ;; esac
			selected=$((selected+1))
			[ "$selected" -le 8 ] || break
			status="$(ubus call "network.interface.$interface" status 2>/dev/null)" || continue
			json_load "$status" || continue
			json_get_var device l3_device
			case "$device" in ''|*[!a-zA-Z0-9_.:-]*) continue ;; esac
			ip -o -4 addr show dev "$device" 2>/dev/null |
				awk -v dev="$device" '$3=="inet" {print $4, dev}'
		done | sort -u
	)"
	[ -n "$lan_subnets" ] || exit 2
	# Bind every target to its LAN device. Exclude router/network/broadcast
	# addresses. Subnets exceeding 4096 addresses use known hosts only.
	targets="$(
		{
			printf '%s\n' "$lan_subnets" | awk '{print "N", $1, $2}'
			awk '{print "H", $1, $6}' /proc/net/arp 2>/dev/null
			ip neigh show 2>/dev/null | awk '{dev=""; for(i=2;i<NF;i++) if($i=="dev") dev=$(i+1); print "H", $1, dev}'
			awk '{print "H", $3}' /tmp/dhcp.leases /var/dhcp.leases 2>/dev/null
		} | awk '
			function number(ip, a,n,i,v) {
				n=split(ip,a,"."); if(n!=4) return -1
				v=0; for(i=1;i<=4;i++) {if(a[i]!~/^[0-9]+$/ || a[i]>255) return -1; v=v*256+a[i]}
				if(a[1]==0 || a[1]==127 || a[1]>=224) return -1
				return v
			}
			function literal(v, a,b,c) {
				a=int(v/16777216); b=int(v/65536)%256; c=int(v/256)%256
				return a "." b "." c "." v%256
			}
			function emit(v,i, key) {
				key=v SUBSEP dev[i]
				if(!own[v] && !seen[key]++) print literal(v), dev[i]
			}
			$1=="N" {
				split($2,a,"/"); v=number(a[1]); p=a[2]
				if(v<0 || p!~/^[0-9]+$/ || p>32 || count>=64) next
				count++; size[count]=1; for(j=0;j<32-p;j++) size[count]*=2
				lo[count]=int(v/size[count])*size[count]
				hi[count]=lo[count]+size[count]-1; dev[count]=$3; own[v]=1
				if(p<31) {lo[count]++; hi[count]--}
				next
			}
			$1=="H" {
				v=number($2); if(v<0) next
				for(i=1;i<=count;i++) if(v>=lo[i] && v<=hi[i] && ($3=="" || $3==dev[i])) emit(v,i)
			}
			END {
				for(i=1;i<=count;i++) if(size[i]<=4096) for(v=lo[i];v<=hi[i];v++) emit(v,i)
			}'
	)" || exit 2
	[ -n "$targets" ] || exit 0
	count="$(printf '%s\n' "$targets" | awk 'END {print NR}')"
	[ "$cursor" -lt "$count" ] || cursor=0
	targets="$(printf '%s\n' "$targets" | awk -v offset="$cursor" '
		{ips[NR-1]=$0}
		END {for (i=0; i<NR; i++) print ips[(offset+i)%NR]}
	')"

	processed=0; pending=0
	while read -r address device; do
		# At most 16 children, 128 addresses and about 8 seconds of probing.
		# The cursor resumes the remaining addresses on a later eligible request.
		[ "$processed" -lt 128 ] || break
		if [ "$pending" -eq 0 ]; then
			read -r uptime rest < /proc/uptime
			[ "$((${uptime%%.*}-now))" -lt 8 ] || break
		fi
		ping -c 1 -w 1 -W 1 -q -I "$device" "$address" >/dev/null 2>&1 &
		processed=$((processed+1))
		pending=$((pending+1))
		if [ "$pending" -ge 16 ]; then
			wait 2>/dev/null
			pending=0
		fi
	done <<EOF
$targets
EOF
	wait 2>/dev/null
	read -r uptime rest < /proc/uptime
	printf '%s %s\n' "${uptime%%.*}" "$(((cursor+processed)%count))" > /tmp/luci-device-manager-probe.state
) 9>/tmp/luci-device-manager-probe.lock 2>/dev/null

ping_error() {
	json_init
	json_add_boolean ok 0
	json_add_string error "$1"
	json_dump
}

# Resolve the target on the router; callers provide a MAC, never a shell command
# or an arbitrary destination. One global lock bounds simultaneous detail probes.
ping_device() (
	command -v flock >/dev/null 2>&1 || { ping_error 'Ping is unavailable'; exit 0; }
	flock -n 9 || { ping_error 'Another device is being probed. Please retry.'; exit 0; }
	json_load "$(cat)" || { ping_error 'Enter a valid MAC address'; exit 0; }
	json_get_var mac mac
	mac="$(printf '%s' "$mac" | tr 'A-F' 'a-f')"
	if ! printf '%s\n' "$mac" | awk -F: '
		NF != 6 {exit 1}
		{for (i=1; i<=6; i++) if ($i !~ /^[0-9a-f][0-9a-f]$/) exit 1}
		$0 == "00:00:00:00:00:00" || $0 == "ff:ff:ff:ff:ff:ff" {exit 1}
	'; then
		ping_error 'Enter a valid MAC address'; exit 0
	fi
	neighbors="$(ip neigh show 2>/dev/null)" || { ping_error 'Unable to read the kernel neighbor table'; exit 0; }
	candidates="$(
		{
			printf '%s\n' "$neighbors" | awk -v mac="$mac" '
				{
					owner=""; dev=""; active=0
					for (i=2; i<=NF; i++) {
						if ($i=="lladdr") owner=tolower($(i+1))
						if ($i=="dev") dev=$(i+1)
						if ($i=="REACHABLE") active=1
					}
					if (owner==mac) {
						priority=($1 ~ /:/) ? (tolower($1) ~ /^fe80:/ ? 4 : 3) : (active ? 0 : 2)
						print priority, $1, dev
					}
				}'
			awk -v mac="$mac" 'tolower($2)==mac {print 1, $3}' /tmp/dhcp.leases /var/dhcp.leases 2>/dev/null
		} | sort -n -k1,1
	)"
	address=""; iface=""
	while read -r priority candidate candidate_iface; do
		# Only numeric IP literals and kernel interface names reach ping.
		if printf '%s\n' "$candidate" | awk '
			/^[0-9]+\.[0-9]+\.[0-9]+\.[0-9]+$/ {split($0,a,"."); for(i=1;i<=4;i++) if(a[i]>255) exit 1; exit 0}
			/^[0-9a-fA-F:]+$/ && /:/ {exit 0}
			{exit 1}'; then
			case "$candidate_iface" in *[!a-zA-Z0-9_.:-]*) continue ;; esac
			# A stale lease must not cause another device at a reassigned IP to
			# be reported as this MAC. Scope link-local ownership by interface.
			if ! printf '%s\n' "$neighbors" | awk -v address="$candidate" -v mac="$mac" -v iface="$candidate_iface" '
				$1==address {
					owner=""; dev=""
					for(i=2;i<=NF;i++) {
						if($i=="lladdr") owner=tolower($(i+1))
						if($i=="dev") dev=$(i+1)
					}
					if(owner!="" && owner!=mac && (iface=="" || iface==dev)) exit 1
				}'; then
				continue
			fi
			address="$candidate"; iface="$candidate_iface"; break
		fi
	done <<EOF
$candidates
EOF
	[ -n "$address" ] || { ping_error 'No known IP address for this device'; exit 0; }
	set -- -c 1 -w 3 -W 2
	[ -z "$iface" ] || set -- "$@" -I "$iface"
	case "$address" in
		*:*)
			if command -v ping6 >/dev/null 2>&1; then
				ping_command=ping6
			else
				ping_command=ping
				set -- -6 "$@"
			fi ;;
		*) ping_command=ping ;;
	esac
	command -v "$ping_command" >/dev/null 2>&1 || { ping_error 'Ping is unavailable'; exit 0; }
	output="$("$ping_command" "$@" "$address" 2>&1)"
	result=$?
	json_init
	json_add_string ip "$address"
	json_add_string interface "$iface"
	json_add_string output "$output"
	if [ "$result" -eq 0 ] || [ "$result" -eq 1 ]; then
		json_add_boolean ok 1
		json_add_boolean reachable "$((1-result))"
	else
		json_add_boolean ok 0
		json_add_string error 'Ping could not be completed'
	fi
	json_dump
) 9>/tmp/luci-device-manager-single-ping.lock 2>/dev/null

case "$1:$2" in
	list:*)
		printf '{"get_online_status":{},"scan_devices":{},"ping_device":{"mac":"string"}}\n'
		;;
	call:ping_device)
		. /usr/share/libubox/jshn.sh
		ping_device
		;;
	call:scan_devices)
		. /usr/share/libubox/jshn.sh
		probe_neighbors
		result=$?
		json_init
		if [ "$result" -eq 0 ]; then
			json_add_boolean ok 1
		else
			json_add_boolean ok 0
			json_add_string error 'LAN scanning is unavailable. Check the selected interfaces and probe dependencies.'
		fi
		json_dump
		;;
	call:get_online_status)
		. /usr/share/libubox/jshn.sh
		json_init
		if ! neighbors="$(ip neigh show 2>/dev/null)"; then
			json_add_boolean ok 0
			json_add_string error 'Unable to read the kernel neighbor table'
			json_dump
			exit 0
		fi
		json_add_boolean ok 1
		json_add_array neighbors
		# A here document keeps parsing in this shell. jshn escapes all JSON strings.
		while read -r address rest; do
			[ -n "$address" ] || continue
			mac=""; state=""; device=""; previous=""
			set -f
			for word in $rest; do
				case "$previous" in
					dev) device="$word" ;;
					lladdr) mac="$word" ;;
				esac
				case "$word" in
					REACHABLE|DELAY|PROBE|STALE|FAILED|INCOMPLETE|PERMANENT|NOARP|NONE) state="$word" ;;
				esac
				previous="$word"
			done
			[ -n "$device" ] || continue
			# FAILED and INCOMPLETE commonly have no lladdr. Preserve their IP/state.
			json_add_object ''
			json_add_string ip "$address"
			json_add_string mac "$mac"
			json_add_string dev "$device"
			json_add_string state "$state"
			json_close_object
		done <<EOF
$neighbors
EOF
		json_close_array
		json_dump
		;;
	*) exit 1 ;;
esac