#!/bin/bash

usage() {
	cat <<-EOF
	Usage: ${0##*/} [options]

	Options:
	  -x, --reset    reset display to no redshift
	EOF

	if [[ $# -eq 0 ]] ; then
		exit 0
	else
		printf '\nERROR: %s\n' "$*" >&2
		exit 1
	fi
}

rs() {
	exec redshift -m randr "$@"
}

main() {
	cd /
	export DISPLAY=:0

	local auth="${HOME}/.Xauthority"
	if [[ -e ${auth} ]]; then
		export XAUTHORITY=${auth}
	fi

	while [[ $# -gt 0 ]] ; do
		case $1 in
		-x|--reset) rs -x ;;
		-h|--help) usage ;;
		*) usage "Unknown option: $1" ;;
		esac
	done

	h=$(date +%H)

	declare -A temps
	local min=2000
	temps=(
		[20]=$(( min + 2000 ))
		[21]=$(( min + 1500 ))
		[22]=$(( min + 1000 ))
		[23]=$(( min + 500 ))
		[00]=$(( min ))
		[01]=$(( min ))
		[02]=$(( min ))
		[03]=$(( min ))
		[04]=$(( min ))
		[05]=$(( min ))
		[06]=$(( min + 500 ))
		[07]=$(( min + 1000 ))
		[08]=$(( min + 1500 ))
		[09]=$(( min + 2000 ))
	)

	t=${temps[${h}]}
	if [[ -z ${t} ]]; then
		rs -x
	else
		rs -O ${t}k
	fi
}
main "$@"