#!/bin/sh

set -eu

DEFAULT_POLL_TIME=5

debug=0

err()
{
	local fmt="${1}"
	shift 1

	printf "Error: ${fmt}\n" "${@}" 1>&2
	return 0
}

dbg()
{
	local fmt="${1}"
	shift 1

	case "${debug}" in '1')
		printf "DEBUG: ${fmt}\n" "${@}" 1>&2
	esac

	return 0
}

enable_devices()
{
	local device=

	dbg 'Enabling devices:'
	for device in "${@}"; do
		dbg '  %s' "${device}"
		xinput --enable "${device}"
	done
}

disable_devices()
{
	local device=

	dbg 'Disabling devices:'
	for device in "${@}"; do
		dbg '  %s' "${device}"
		xinput --disable "${device}"
	done
}

poll()
{
	local poll_time=${1}
	shift 1
	local displays=
	local prev_state=
	local displays_on=
	local displays_off=
	local display=
	local status=
	local dpms=
	local state=

	displays="$(printf '%s ' \
		/sys/devices/pci????:??/????:??:??.?/drm/card*/card*-*/ \
		/sys/devices/pci????:??/????:??:??.?/????:??:??.?/drm/card*/card*-*/)"

	prev_state=''
	while :; do
		displays_on=0
		displays_off=0
		for display in ${displays}; do
			[ -f "${display}/status" ] || continue
			read status 0<"${display}/status"
			case "${status}" in 'disconnected')
				continue
			esac
			read dpms 0<"${display}/dpms"
			case "${dpms}" in
				'On')  displays_on=1;;
				'Off') displays_off=1;;
			esac
		done

		state='enable_devices'
		case ${displays_on} in 0)
			case ${displays_off} in 1)
				state='disable_devices'
			esac
		esac

		case "${state}" in
			"${prev_state}");;
			*)
				"${state}" "${@}"
				prev_state="${state}"
				;;
		esac

		sleep ${poll_time}
	done
}

usage()
{
	printf 'Usage: %s [<options>] <device> [<device> ...]\n' "${0}"
	printf '\n'
	printf 'Options:\n'
	printf '  -p <secs>  Poll at least every <secs> seconds\n'
	printf '  -d         Enable debugging output\n'
}

main()
{
	local move_win=
	local opt=
	local dir=
	local dx=
	local dy=
	local cur_dt=
	local new_dt=

	poll_time=${DEFAULT_POLL_TIME}

	while getopts 'p:d' opt "${@}"; do
		case "${opt}" in
			'p')
				case "${OPTARG}" in *[!0-9]* | '')
					usage 1>&2
					return 1
				esac
				poll_time="${OPTARG}"
				;;
			'd') debug=1;;
			'?')
				usage 1>&2
				return 1
				;;
		esac
	done
	shift $((${OPTIND} - 1))

	if [ ${#} -lt 1 ]; then
		usage 1>&2
		return 1
	fi

	poll ${poll_time} "${@}"

	return 0
}

main "${@}"