#!/bin/sh

# Establish an epoch time for Victor.  Our clock should never be set to a value before this.
EPOCH="2018-05-10 12:34:56"
SAVEDTIME="${EPOCH}"

# Try to use the timestamp file to update the SAVEDTIME
TIMESTAMP="/etc/timestamp"
if [ -f "${TIMESTAMP}" ]; then
    ETIME=$(date -u -D '%Y%m%d%H%M%S' -d `cat ${TIMESTAMP}` +'%Y-%m-%d %H:%M:%S')

    if expr "${ETIME}" \> "${SAVEDTIME}" > /dev/null ; then
	SAVEDTIME=${ETIME}
    fi
fi

# Get the Current UTC Time
CTIME=$(date -u +'%Y-%m-%d %H:%M:%S')
# Get the current value in seconds for the hardware clock
HWCLOCK=$(date -u -D '%a %b %d %T %Y' -d "`hwclock`" +'%s')
FHWCLOCK=${HWCLOCK}

# If we have a saved time and hardware clock value, load them
CLOCKFILE="/data/opt/fake-hwclock/fake-hwclock.data"
if [ -f "${CLOCKFILE}" ]; then
    FTIME=$(grep TIME "${CLOCKFILE}" | awk -F= '{print $2;}')
    FHWCLOCK=$(grep HWCLOCK "${CLOCKFILE}" | awk -F= '{print $2;}')

    if expr "${FTIME}" \> "${SAVEDTIME}" > /dev/null ; then
	SAVEDTIME=${FTIME}
    fi
fi


# if the file time is in the future, use that
setclock() {
    CLOCK_OFFSET=0
    if [ -f "${CLOCKFILE}" ]; then
	# Only add in hwclock seconds if we have a saved fake-hwclock.data file
	# Otherwise, we don't want to add a potentially large number of seconds
	# to the saved time from the OS build timestamp.  Could cause us to
	# set the clock forward of the true wall clock time if the robot hasn't
	# been power cycled in a long time.
	CLOCK_OFFSET=${HWCLOCK}
	if expr "${HWCLOCK}" \> "${FHWCLOCK}" > /dev/null ; then
	    # If the RTC clock has continued to advance since our last boot
	    # then only use the difference here
	    CLOCK_OFFSET=$(expr "${HWCLOCK}" - "${FHWCLOCK}")
	fi
	SAVEDTIME_SECS=$(date -u -D '%Y-%m-%d %H:%M:%S' -d "${SAVEDTIME}" +'%s')
	SAVEDTIME_SECS=$(expr "${SAVEDTIME_SECS}" + "${CLOCK_OFFSET}")
	SAVEDTIME=$(date -u -D '%s' -d "${SAVEDTIME_SECS}" +'%Y-%m-%d %H:%M:%S')
    fi

    if expr "${SAVEDTIME}" \> "${CTIME}" > /dev/null ; then
	echo -e "loading saved time ${SAVEDTIME} over ${CTIME}\nClock Offset = ${CLOCK_OFFSET} seconds"
	date -u --set="${SAVEDTIME}"
    else
	echo "ignoring saved time ${SAVEDTIME} over ${CTIME}"
    fi
}


# if current time is greater than what is in the file, save it
saveclock() {
	if expr "${CTIME}" \> "${SAVEDTIME}" > /dev/null ; then
		mkdir -p `dirname "${CLOCKFILE}"`
		echo "saving time ${CTIME} over ${SAVEDTIME}"
		echo "TIME=${CTIME}" > "${CLOCKFILE}.tmp"
		echo "HWCLOCK=${HWCLOCK}" >> "${CLOCKFILE}.tmp"
		mv "${CLOCKFILE}.tmp" "${CLOCKFILE}"
	else
		echo "not saving time ${CTIME} over ${SAVEDTIME}"
	fi
}


# The format expected is "<CMD>\n"
# Read line from stdin with 1 second timeout.
# If run from systemd the FIFO socket will be read
CMD=$1
if [ -z $CMD ] || [ "$CMD" = "stdin" ]
then
    read -r -t 1 CMD
fi

case "$CMD" in
	load)
		setclock
		;;
	save)
		saveclock
		;;
	tick)
		saveclock
		;;
	*)
		echo "Usage: $0 {load|save|tick}"
		exit 1
		;;
esac