#!/bin/sh

LOCK_RESOLUTION="1920x1080"
LOCK_QUALITY=70

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

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

	exit 1
}

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

	err "usage: ${0##*/} [-hqr] [-e RESOLUTION] [-u QUALITY] IMAGE"
	err
	err " -h		show this message and exit"
	err " -q		suppress output and notifications"
	err " -r		restore the previous image as your wallpaper"
	err " -e <RESOLUTION>	override lock screen RESOLUTION"
	err " -u <QUALITY>	override lock screen QUALITY"

	exit 0
}

convert_lock() {
	magick "$1" -resize "$LOCK_RESOLUTION"^ -gravity center -extent "$LOCK_RESOLUTION" -quality "$LOCK_QUALITY" "$XDG_CACHE_HOME/lock.png"
}

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

	previous="$(readlink -f "$XDG_DATA_HOME/wallpaper")"
	case "${previous##*.}" in
		png|jpg|jpeg) ;;
		*) die "$previous: unsupported file type" ;;
	esac

	cmp -s "$previous" "$XDG_CACHE_HOME/lock.png" || convert_lock "$previous" &
	xwallpaper --zoom "$XDG_DATA_HOME/wallpaper"

	exit 0
}

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

shift $((OPTIND - 1))

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

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

case "${image##*.}" in
	png|jpg|jpeg) ;;
	*) die "$image: unsupported file type" ;;
esac

cmp -s "$image" "$XDG_CACHE_HOME/lock.png" || convert_lock "$image" &
ln -sf "$image" "$XDG_DATA_HOME/wallpaper"
xwallpaper --zoom "$XDG_DATA_HOME/wallpaper"

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