#!/bin/sh

# In recent versions of shellcheck, busybox is a valid shell type
# shellcheck shell=busybox

# OpenWrt hotplug script to set permissions on USB serial
# ports to allow NUT to access UPSes attached via
# USB-to-serial cables

# OpenWrt hotplug calls this script with DEVNAME and
# ACTION set in the environment

# IPKG_INSTROOT is intentionally only set when building an image and
# is intentionally empty on a live OpenWrt device

# shellcheck source=net/nut/files/functions.sh.functions
. "${IPKG_INSTROOT}"/lib/functions.sh || {
	# Before our sourcing error logging definitions are sourced
	logger -s -t nut-serial-hotplug "Unable to source 'functions.sh' in 'nut-serial' hotplug. Bailing"
	exit 1
}

# 'shellcheck' complains about nut-common.sh due to a case pattern it does not understand, even
# though it is correctly POSIX compliant
# shellcheck disable=SC1094
# shellcheck source=net/nut/files/nut-common.sh.functions
. "${IPKG_INSTROOT}"/lib/functions/nut/nut-common.sh || {
	# Before our sourcing error logging definitions are sourced
	logger -s -t nut-serial-hotplug "Unable to source 'nut-common.sh' in 'nut-serial' hotplug. Bailing"
	exit 1
}

# shellcheck source=net/nut/files/nut-service.sh.functions
. "${IPKG_INSTROOT}"/lib/functions/nut/nut-service.sh || {
	log_source_error "nut-service.sh" "nut-serial" "nut-serial-hotplug"
	exit 1
}

# 'shellcheck' does not understand config_foreach and therefore treats
# functions and variables referenced only from config_foreach as not reachable,
# or never invoked.
# shellcheck disable=SC2317,SC2329
nut_set_serial_port_permissions() {
	local devname="$1" # Must be full path (e.g. /dev/...)
	local ups="$2"
	local device_group

	# Get group of RUNAS user, to set the group of the hotplugged device node
	# If RUNAS user does not exist, exit with an error.
	device_group="$(id -gn "${RUNAS:-nut}")" || {
		log_error "Unable to find group for '$RUNAS'. Skipping ups '$ups'" nut-serial nut-serial-hotplug
		return 1
	}

	# Guard against disappearing device (e.g. due to 'bouncing' device)
	if [ -e "$devname" ]; then
		if ! chgrp "$device_group" "$devname"; then
			log_error "Unable to set group on '$devname'" nut-serial nut-serial-hotplug
			return 1
		fi
	else
		log_error "'$devname' disappeared before setting group" nut-serial nut-serial-hotplug
		return 1
	fi

	# Device could disappear between chgrp and chmod
	if [ -e "$devname" ]; then
		if ! chmod g+rw "$devname"; then
			log_error "Unable to set permissions on '$devname'" nut-serial nut-serial-hotplug
			return 1
		fi
	else
		log_error "'$devname' disappeared before setting permissions" nut-serial nut-serial-hotplug
		return 1
	fi
	return 0
}

# If enable_usb_serial is set, set the permissions on applicable USB
# serial devices to allow NUT access
# We do not exit with error as that would stop processing of other UPS config
# sections.
# We use 'did_set_perms' as a 'pseudo-global' from nut_on_hotplug_add in order
# to return a value to config_foreach

# 'shellcheck' does not understand config_foreach and therefore treats
# functions and variables referenced only from config_foreach as not reachable,
# or never invoked.
# shellcheck disable=SC2317,SC2329
nut_serial() {
	local ups="$1" # UCI section name is also the UPS configuration name
	local enable_usb_serial port normal_devname

	config_get_bool enable_usb_serial "$ups" enable_usb_serial 0
	config_get port "$ups" port

	[ "$enable_usb_serial" = "1" ] && {
		# If port is specified only change tty's matching port
		if [ -n "$port" ] && [ "${port#/dev/}" = "${port}" ]; then
			port="/dev/$port"
		fi
		# Normalize DEVNAME
		normal_devname="$DEVNAME"
		if [ -n "$DEVNAME" ] && [ "${DEVNAME#/dev/}" = "${DEVNAME}" ]; then
			normal_devname="/dev/$DEVNAME"
		fi
		# Empty port from configuration means match any device.
		if [ "$port" = "$normal_devname" ] || [ "$port" = "" ]; then
			if nut_set_serial_port_permissions "$normal_devname" "$ups"; then
				did_set_perms="true"
			fi
		fi
	}
}

nut_on_hotplug_add() {
	# We use did_set_perms as a 'pseudo-global'. It is visible and can be
	# modified by called functions, but the changes do not propagate up from
	# this function.
	local did_set_perms="false"

	config_load nut_server || {
		log_config_load_error "nut_server" "nut-serial" "nut-serial-hotplug"
		exit 1
	}

	# Only find statepath and runas once per event
	# sets RUNAS
	find_runas "upsd" "nut_server" || {
		log_error_exit "Failed to set RUNAS" nut-serial nut-serial-hotplug
	}

	# Check if serial USB UPS for each NUT driver instance (UPS), and if so
	# configure permissions to allow NUT to access the port
	config_foreach nut_serial driver

	# If we set permissions on a device that may have a UPS attached, run
	# the UPS (NUT) server reload to check for UPS configuration and
	# attempt to reload the driver and/or server
	if [ "$did_set_perms" = "true" ]; then
		# Informational and not an error
		logger -t nut-serial-hotplug "Successfully set permissions for serial device(s)"
		# We shouldn't get here if hotplug is disabled (race condition if we do), so log it as an error
		if ! allow_hotplug_restart; then
			log_error "Did not restart NUT after setting permissions as hotplug restart is disabled" nut-serial nut-serial-hotplug
			# Disabled hotplug is an allowed state
			return 0
		fi
		if ! /etc/init.d/nut-server enabled; then
			# shellcheck disable=SC2153
			log_error "NUT server disabled when processing hotplug event 'add' for '$DEVNAME'." nut-serial nut-serial-hotplug
			# Disabled nut-server is an allowed state
			return 0
		else
			# Initscript should have its own logging
			/etc/init.d/nut-server reload || return 1
		fi
	fi
	return 0
}

# Do not do any hotplug actions if hotplug is disabled. Not an error but log
# for information
if ! allow_hotplug_restart; then
	# Informational and not an error
	logger -t nut-serial-hotplug "Did not set permissions on serial port hotplug as NUT hotplug is disabled"
	exit 0
fi

if ! [ "$(id -u)" = "0" ]; then
	log_error_exit "Cannot set update device node on serial port hotplug. Hotplug not running as root." nut-serial nut-serial-hotplug
fi

# Only act on hotplug events with ACTION 'add' and where
# the hotplugged device is a USB serial port
# shellcheck disable=SC2153
if [ "$ACTION" = "add" ] && [ -n "$DEVNAME" ]; then
	# On add of a USB serial port with name
	# ttyUSB* or ttyAMA* or ttyACM* or ttyGS*
	case "$DEVNAME" in
	ttyUSB* | ttyAMA* | ttyACM* | ttyGS*)
		nut_on_hotplug_add || exit 1
		;;
	esac
fi

exit 0