# no need for shebang - this file is included from other scripts

# this function is used to sleep a fraction of a second
# it calculates the difference between every time is called
# and tries to align the sleep time to give you exactly the
# loop you need.

LOOPSLEEP_DATE="$(which date)"
if [ -z "$LOOPSLEEP_DATE" ]
    then
    echo >&2 "$0: ERROR: Cannot find the command 'date' in the system path."
    exit 1
fi

LOOPSLEEPMS_LASTRUN=0
LOOPSLEEPMS_LASTSLEEP=0
LOOPSLEEPMS_LASTWORK=0

LOOPSLEEPMS_HIGHRES=1
test "$($LOOPSLEEP_DATE +%N)" = "%N" && LOOPSLEEPMS_HIGHRES=0

now_ms=
current_time_ms() {
    # if high resolution is not supported
    # just sleep the time requested, in seconds
    if [ $LOOPSLEEPMS_HIGHRES -eq 0 ]
    then
        now_ms="$($LOOPSLEEP_DATE +'%s')000"
    else
        now_ms="$(( $( $LOOPSLEEP_DATE +'%s * 1000 + %-N / 1000000' ) ))"
    fi
}

loopsleepms() {
    local tellwork=0 t="$1" div s m now mstosleep

    if [ "$t" = "tellwork" ]
    then
        tellwork=1
        shift
        t="$1"
    fi
    div="${2-100}"

    # $t = the time in seconds to wait

    # if high resolution is not supported
    # just sleep the time requested, in seconds
    if [ $LOOPSLEEPMS_HIGHRES -eq 0 ]
    then
        sleep $t
        return
    fi

    # get the current time, in ms
    # milliseconds since epoch (1-1-1970)
    now="$(( $( $LOOPSLEEP_DATE +'%s * 1000 + %-N / 1000000' ) ))"

    # calculate required sleep in ms
    t=$((t * 1000 * div / 100))

    # this is our first run
    # just wait the requested time
    test $LOOPSLEEPMS_LASTRUN -eq 0 && LOOPSLEEPMS_LASTRUN=$now

    # calculate ms since last run
    LOOPSLEEPMS_LASTWORK=$((now - LOOPSLEEPMS_LASTRUN - LOOPSLEEPMS_LASTSLEEP))
    # echo "# last loop's work took $LOOPSLEEPMS_LASTWORK ms"

    # calculate ms to sleep
    mstosleep=$(( t - LOOPSLEEPMS_LASTWORK ))
    # echo "# mstosleep is $mstosleep ms"

    # if we are too slow, sleep some time
    test $mstosleep -lt 200 && mstosleep=200

    s=$((mstosleep / 1000))
    m=$((mstosleep - (s * 1000)))

    test $tellwork -eq 1 && echo >&2 " >>> PERFORMANCE >>> WORK TOOK $LOOPSLEEPMS_LASTWORK ms ( $((LOOPSLEEPMS_LASTWORK * 100 / 1000)).$((LOOPSLEEPMS_LASTWORK % 10))% cpu ) >>> SLEEPING $mstosleep ms"

    # echo "# sleeping $s.$m"
    # echo
    sleep $s.$m

    # keep the values we need
    # for our next run
    LOOPSLEEPMS_LASTRUN=$now
    LOOPSLEEPMS_LASTSLEEP=$mstosleep
}
