#!/bin/sh
#
# Returns 0 (true) if on AC power
#         1 (false) if not on AC power
#         255 (false) if can't tell
#
# Example shell script:
#     if on_ac_power; then
#       echo We're on AC power
#     else
#       echo Can't say we're on AC power
#     fi

set -e

# sysfs
#
# This algorithm is complicated by the possibility of multiple AC
# adapters.  We scan the ac_adapter/power_supply directory looking for adapters
# that have known states.  If any adapter is on-line, we return 0.  If
# no adapters are on-line but one or more are off-line, we return 1.
#
OFF_LINE_P=no
USB_IS_SINK=no
USB_IS_SOURCE=no
power_type="Mains"

# USB-C sysfs documentation:
# https://www.kernel.org/doc/Documentation/ABI/testing/sysfs-class-typec
#
# We verify first if there are any USB-C devices in power sink mode to
# check if we should consider USB as a power source.  If no source ports
# are found assume they are sink ports.
#
if [ -d /sys/class/typec/ ]; then
	for FN in /sys/class/typec/*; do
		if test -d "${FN}" && test -r "${FN}/power_role"; then
			power_role="$(cat "${FN}/power_role")"
			if echo $power_role | grep -q '\[source\]'; then
				USB_IS_SOURCE=yes
			elif echo $power_role | grep -q '\[sink\]'; then
				USB_IS_SINK=yes
			fi
		fi
	done
	# Add USB* power type if any USB ports are sink or no source is found
	if [ "${USB_IS_SINK}" = "yes" ] || [ "${USB_IS_SOURCE}" = "no" ]; then
		power_type="USB*"
	fi
fi


if [ -d /sys/class/power_supply/ ]; then
    for FN in /sys/class/power_supply/*; do
	if test -d "${FN}" && test -r "${FN}/type"; then
	    type="$(cat "${FN}/type")"
	    case "${type}" in
	    Mains|$power_type|BrickID|Wireless)
		if [ -r "${FN}/online" ]; then
		    online="$(cat "${FN}/online")"
		    [ "$online" = 1 ] && exit 0
		    [ "$online" = 0 ] && OFF_LINE_P=yes
		fi;;
	    esac
	fi
    done
    [ "${OFF_LINE_P}" = "yes" ] && exit 1
fi

# PMU
if [ -r /proc/pmu/info ]; then
    exec awk </proc/pmu/info '
	BEGIN { FS=":"; ret = 255 }
	/^AC Power.*1$/ { ret = 0; exit }
	/^AC Power.*0$/ { ac = 1 }
        /^Battery.*/ {
                if ($2 ~/0/ && ac == 1)
                        ret = 0
                else
                        ret = 1
                exit }
	END { exit ret }
    '
fi

# APM
if [ -r /proc/apm ]; then
    exec awk </proc/apm '
	BEGIN { ret = 255 }
	/^[0-9.a-zA-Z]* [0-9.]* 0x.. 0x../ {
		if ($4 == "0x01") { ret = 0; exit }
		else if ($4 == "0x00") { ret = 1; exit }
	}
	END { exit ret }
    '
fi

# nothing is available
exit 255