#!/bin/sh

fullPage=10 # How many pages before a full refresh?

### Do not edit below this line unless you know what you are doing ###

## Get cvm PID
read cvmPid < /var/run/cvm.pid
if [[ -z "$cvmPid" ]]; then
	echo "cvm isn't running..."
	exit 2
fi

pCount=0
fullPage="$(($fullPage-1))"

if [[ ! -e "/var/run/flashDis.pid" ]]; then
	echo $$ > "/var/run/flashDis.pid"
else
	echo "Flash disabler is already running"
	exit 1
fi

trap "enableFlash ; rm /var/run/flashDis.pid ; exit" SIGINT SIGTERM

update() {
	waitForEink
	## Do some fancy stuff to make the page look decent
	echo 19 0 > /proc/eink_fb/update_display
	echo 0 > /sys/devices/platform/eink_fb.0/override_upd_mode
	echo 18 0 > /proc/eink_fb/update_display
	echo 1 > /sys/devices/platform/eink_fb.0/override_upd_mode
	echo 19 4 > /proc/eink_fb/update_display
	
	## Sets the next page turn to be a full refresh
	let pCount+=1
	if [[ "$pCount" -ge "$fullPage" ]]; then
		echo 0 > /sys/devices/platform/eink_fb.0/override_upd_mode
		echo 19 0 > /proc/eink_fb/update_display
		pCount=0
	fi	
}

enableFlash() {
	echo 0 > /sys/devices/platform/eink_fb.0/override_upd_mode
	echo 19 0 > /proc/eink_fb/update_display
}

## Check if we need to look for a book/check if current book is open
bookCheck() {
	if [[ -n "$fd" -a -n "$book" ]]; then
		if [[ "$(realpath /proc/$cvmPid/fd/$fd 2> /dev/null)" == "$book" ]]; then
			if [[ "$bookType" != "BAD" ]]; then
				update
			else
				enableFlash
			fi
		else
			book=""
			bookType=""
			findBook
		fi
	else
		findBook
	fi
}

## Check if cvm has a file descriptor open in /mnt/us/documents
findBook() {
	enableFlash
	fd="$(ls -l /proc/$cvmPid/fd/ | awk '/\/mnt\/us\/documents\// {print $9}')"
	if [[ -n "$fd" ]]; then
		book="$(realpath /proc/$cvmPid/fd/$fd 2> /dev/null)"
		bookType="${book##*.}"
		case $bookType in
			[Mm][Oo][Bb][Ii]|[Pp][Dd][Ff]|[Pp][Rr][Cc]|[Aa][Zz][Ww]*|[Tt][Xx][Tt])
				update
			;;
			*)
				bookType="BAD"
			;;
		esac
	fi
}

## Check if /var/log/messages has changed within the last second
waitForEink() {
	c=1
	while [[ "$(stat -c %Y /var/log/messages)" -lt "$time" -a "$c" -lt "10" ]]; do
		let c+=1
		usleep 100000
	done
}

## Wait for page turn
while :; do
	case "$(waitforkey)" in	
		191*|109*|104*|193*)
			time="$(($(date +%s)-1))"
			bookCheck
		;;
	esac
	usleep 100000
done