#!/bin/sh

# General constants declaration
THRESHOLD_PERCENT_LOW_BAT=5
THRESHOLD_PERCENT_EXTREMELY_LOW_BAT=2
MAX_EXTREMELY_LOW_BAT_BEFORE_SHUTDOWN=5
SLEEP_SECS=2
RESCALE_MAX_PERCENTAGE=120

# Blink Low bat constants declaration
BLINK_ICON=0
LOW_BAT_SECS_DISPLAYED=5
LOW_BAT_SECS_NOT_DISPLAYED=5

# Files and commands declaration
USB_PRESENT_FILE=/sys/class/power_supply/axp20x-usb/present
#USB_PRESENT_FILE=/sys/class/power_supply/axp20x-ac/present # Cheat for no USB present simulation when debugging
BAT_PRESENT_FILE=/sys/class/power_supply/axp20x-battery/present
BAT_PERCENT_FILE=/sys/class/power_supply/axp20x-battery/capacity
BAT_PERCENT_RESCALED_FILE=/tmp/current_battery_percentage
LOW_BAT_ICON=/sys/class/graphics/fb0/low_battery
SCHEDULE_SHUTDOWN_CMD=sched_shutdown
SIGNAL_URS1_TO_EMULATORS_CMD=signal_usr1_to_emulators

# Variables declaration
low_bat_status=0
low_bat_displayed=0
cur_secs_disp=0
cur_nb_extremely_low_bat_before_shutdown=0

# Default: Hide Low Bat Icon
echo 0 > ${LOW_BAT_ICON}

# Check low bat #
while true; do
    #echo "Bat present: $(cat ${BAT_PRESENT_FILE})"
    #echo "USB present: $(cat ${USB_PRESENT_FILE})"
    #echo "Bat percentage: $(cat ${BAT_PERCENT_FILE})"

    # Get current bat percentage here once
    cur_bat_percent=$(cat ${BAT_PERCENT_FILE})
    #echo "cur_bat_percent = ${cur_bat_percent}"

    # Rescale bat percentage between 0 and RESCALE_MAX_PERCENTAGE
    bat_percent_rescaled=$(printf "%.f" $(echo $cur_bat_percent $RESCALE_MAX_PERCENTAGE | awk '{print $1*$2/100}'))
    #echo "bat_percent_rescaled = ${bat_percent_rescaled}"

    # Re-maximize to 100%
    bat_percent_rescaled_maxed=$(( bat_percent_rescaled < 100 ? bat_percent_rescaled : 100 ))
    #echo "bat_percent_rescaled_maxed = ${bat_percent_rescaled_maxed}"

    # Save in file
    echo ${bat_percent_rescaled_maxed} > ${BAT_PERCENT_RESCALED_FILE}

    # Low bat status detection
    if [ "$(cat ${USB_PRESENT_FILE})" -eq "0" ]; then
			
		# Value of 0 means wrong i2c reading
		if [ "${cur_bat_percent}" -ne "0" ]; then

		    # Check if we must change state
		    if [ ${cur_bat_percent} -le ${THRESHOLD_PERCENT_LOW_BAT} -a ${low_bat_status} -eq 0 ]; then

				# Set Low Bat status
				low_bat_status=1
				low_bat_displayed=1
				cur_secs_disp=0
				echo 1 > ${LOW_BAT_ICON}

		    elif [ ${cur_bat_percent} -gt ${THRESHOLD_PERCENT_LOW_BAT} -a ${low_bat_status} -eq 1 ]; then

				# Reset status
				low_bat_status=0
				cur_nb_extremely_low_bat_before_shutdown=0
				echo 0 > ${LOW_BAT_ICON}
		    fi
		fi
    else
		if [ ${low_bat_status} -eq 1 ]; then

		    # Reset status
		    low_bat_status=0
		    cur_nb_extremely_low_bat_before_shutdown=0
		    echo 0 > ${LOW_BAT_ICON}
		fi
    fi

    # Low bat processing
    if [ ${low_bat_status} -eq 1 ]; then

		# Check extremely low bat for clean shutdown
		if [ ${cur_bat_percent} -le ${THRESHOLD_PERCENT_EXTREMELY_LOW_BAT} ]; then
		    let cur_nb_extremely_low_bat_before_shutdown++
		    echo "cur_nb_extremely_low_bat_before_shutdown = ${cur_nb_extremely_low_bat_before_shutdown}"

		    # Clean shutdown
		    if [ ${cur_nb_extremely_low_bat_before_shutdown} -ge  ${MAX_EXTREMELY_LOW_BAT_BEFORE_SHUTDOWN} ]; then
				echo "Battery extremely low, shutting down now..."
				sched_shutdown 1 & signal_usr1_to_emulators
				exit 0
		    fi
		fi

		# Blinking process
		if [ ${BLINK_ICON} -eq 1 ]; then
		    if [ ${low_bat_displayed} -eq 1 -a ${cur_secs_disp} -ge ${LOW_BAT_SECS_DISPLAYED} ]; then
				low_bat_displayed=0
				cur_secs_disp=0
				echo 0 > ${LOW_BAT_ICON}
		    elif [ ${low_bat_displayed} -eq 0 -a ${cur_secs_disp} -ge ${LOW_BAT_SECS_NOT_DISPLAYED} ]; then
				low_bat_displayed=1
				cur_secs_disp=0
				echo 1 > ${LOW_BAT_ICON}
		    fi
		fi
    fi

    # Sleep before next check
    sleep ${SLEEP_SECS}

    # Increase vars
    let cur_secs_disp+=${SLEEP_SECS}
done
exit 0
