#!/bin/sh

bgdpid="${XDG_RUNTIME_DIR:-${TMPDIR:-/tmp}}/swaybg.pid"
bgroot="${XDG_DATA_HOME:-$HOME/.local/share}/wallpaper"
bgdesk="${bgroot}/desktop"
bglock="${bgroot}/lockscreen"

die()
{
	printf "\033[31;1merr: %b\033[0m\n" "${1:-no args for die()}" 1>&2
	exit "${2:-1}"
}

usage()
{
	cat <<- EOF
	Usage: ${0##*/} [wallpaper.img|directory]
	A helper script for swaybg

	EOF
}

dep_check()
{
	# usage: cmd_check cmd_1 ...
	: "${1:?}"

	for dep; do
		command -v "$dep" 1>/dev/null ||
			die "${dep}: command not found" 127
	done

	unset dep
}

mimetype()
{
	file --brief --dereference --mime-type "$1"
}

randimg()
{
	# usage: randbg dir
	: "${1:?}"
	maxattempts=10
	attempt=0

	img=
	while :; do
		img="$(find "$1" \
			-iname "*.avif" \
			-o -iname "*.heic" \
			-o -iname "*.heif" \
			-o -iname "*.jpeg" \
			-o -iname "*.jpg" \
			-o -iname "*.jxl" \
			-o -iname "*.png" \
			-o -iname "*.webp" | shuf -n1)"

		[ -z "$img" ] &&
			return 1

		# make sure the file is an actual image
		case "$(mimetype "$img")" in
		"image/"*)
			echo "$img"
			break
			;;
		*)
			attempt=$((attempt + 1))
			[ "$attempt" -gt "$maxattempts" ] &&
				return 1
		esac
	done
}

updatewall()
{
	: "${1:?}"

	rm -f "$bgdesk"
	cp  "$1" "$bgdesk"

	[ -s "$bgdpid" ] &&
		kill -9 "$(cat "$bgdpid")"
	swaybg --mode fill --image "$bgdesk" > /dev/null 2>&1 &
	echo $! > "$bgdpid"

	if command -v ffmpeg > /dev/null; then
		rm -f "$bglock"
		ffmpeg -loglevel quiet \
			-i "$bgdesk" -vf "boxblur=50" -f mjpeg "$bglock"
	else
		ln -fs "$bgdesk" "$bglock"
	fi
}

########
# MAIN #
########

[ ! -r "$1" ] && usage && exit 1
[ ! -d "$bgroot" ] && mkdir -p "$bgroot"
dep_check swaybg file

case "$(mimetype "$1")" in
"image/"*) updatewall "$1" ;;
"inode/directory")
	img=$(randimg "$1") ||
		die "no image file in directory"
	updatewall "$img"
	;;
*) die "invalid image file"
esac