#!/bin/sh

err() {
	echo "$1" >&2
}

die() {
	err "${0##*/}: $1"

	exit 1
}

usage() {
	if [ -n "$1" ]; then
		err "${0##*/}: $1"
		err
	fi

	err "usage: ${0##*/} [-hqrde] SCRIPT"
	err
	err " -h	show this message and exit"
	err " -q	suppress output and notifications"
	err " -r	restore the previous script as your screen layout"
	err " -d	reset screen layout to X default"
	err " -e	edit previous screen layout script in your EDITOR"

	exit 0
}

restore() {
	[ -f "$XDG_DATA_HOME/screenlayout" ] || die "previous script not found"

	. "$XDG_DATA_HOME/screenlayout"

	exit 0
}

default() {
	xrandr --auto

	[ -z "$QUIET" ] && notify-send -u low "System" "Screen layout set to default."

	exit 0
}

edit() {
	[ -z "$EDITOR" ] && die "\$EDITOR is not set"
	[ -f "$XDG_DATA_HOME/screenlayout" ] || die "previous script not found"

	$EDITOR "$XDG_DATA_HOME/screenlayout"
	
	exit 0
}

while getopts ":hqrde" opt; do
	case $opt in
		h) usage ;;
		q) QUIET=1 ;;
		r) restore ;;
		d) default ;;
		e) edit ;;
		\?) usage "invalid option -- '$OPTARG'" ;;
		:) usage "option requires an argument -- '$OPTARG'" ;;
	esac
done

shift $((OPTIND - 1))

if [ "$1" = "-" ]; then
	while IFS= read -r line; do
		script="$line"
	done
else
	script="$1"
fi

[ -n "$script" ] || usage "SCRIPT was not provided"
[ -d "$script" ] && die "$script: is a directory"
[ -f "$script" ] || die "$script: no such file"

case "$(file -b --mime-type "$script")" in
	text/x-shellscript) ;;
	*) die "$script: unsupported file type" ;;
esac

ln -sf "$script" "$XDG_DATA_HOME/screenlayout"
. "$XDG_DATA_HOME/screenlayout"

[ -z "$QUIET" ] && notify-send -u low "System" "Screen layout set to <b>${script##*/}</b>."