#!/bin/sh

name=`basename "$0"`

isInstalled() {
	type "$1" > /dev/null
}

mustHaveInstalled() {
	if ! isInstalled "$1"; then
		echo "$name: $1 is not installed" >&2
		exit 1
	fi
}

usage() {
	echo "Usage: $name day | night | daemon" >&2
	exit 2
}

dayTemp=6500
nightTemp=4000
sunset=17
sunrise=7

if   isInstalled xsct
then SCT=xsct
elif isInstalled sct
then SCT=sct
fi

case "$1" in
"day" | "night" | "daemon")
	mode="$1"
	shift 1
	;;
*)
	usage
	;;
esac

[ "$#" -gt 0 ] && usage

case "$mode" in
"day")
	$SCT "$dayTemp"
	;;
"night")
	$SCT "$nightTemp"
	;;
"daemon")
	while
		hour=`date +%H`
		if [ "$hour" -gt "$sunset" ] || [ "$hour" -lt "$sunrise" ]
		then temp="$nightTemp"
		else temp="$dayTemp"
		fi
		$SCT "$temp"
	do sleep 4; done
	;;
esac