#!/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