#!/bin/sh

main()
{
	# Load custom configuration if available
	if [ -f "$HOME/.local/etc/x/chwp" ]
	then
		log main "Sourcing $HOME/.local/etc/x/chwp"
		. "$HOME/.local/etc/x/chwp"
	fi

	directory=${CHWP_BASEDIR:-$HOME/pictures/wallpapers}
	size=${CHWP_SIZE:-1920x1080}
	timeout=${1:-0}
	walldir="$directory/$size"

	log main "Checking $walldir for wallpapers"

	# Fail early if there's no wallpaper directory
	if [ ! -d "$walldir" ]
	then
		log main "No such directory: $walldir"
		exit 1
	fi

	CACHEFILE="$(mktemp)"

	log main "Using $CACHEFILE as CACHEFILE"

	find "${walldir}" -type f > "$CACHEFILE"

	log main "Found $(wc -l "$CACHEFILE" | awk '{ print $1 }') wallpapers"

	# If no timeout was set, just change it once
	if [ "$timeout" -eq 0 ]
	then
		log main "No timeout set, only updating once"
		set_papes
		exit
	fi

	# Otherwise, change it every so often
	while :
	do
		set_papes
		sleep "${timeout}"
	done
}

set_papes()
{
	log set_papes "Gathering wallpapers"

	pape="$(make_pape)"

	log set_papes "Setting wallpaper to $pape"

	feh --bg-fill "$pape" 2>&1 | log_pipe "feh"

	log set_papes "Cleaning up temporary wallpaper image"

	rm -f -- "$pape"
}

make_pape()
{
	log make_pape "Creating wallpaper"

	output="$(mktemp)"
	imagelist="$(mktemp)"
	monitorlist="$(mktemp)"

	if [ -z "$CHWP_MONITORS" ]
	then
		log make_pape "Trying to determine screens"

		xrandr -q \
			| grep -F ' connected ' \
			| grep -Eo '[[:digit:]]+x[[:digit:]]+' \
			> "$monitorlist"
	else
		log make_pape "Using \$CHWP_MONITORS for monitorlist"

		printf "%s" "$CHWP_MONITORS" \
			| tr " " "\n" \
			| grep -v "^$" \
			> "$monitorlist"
	fi

	log make_pape "Found $(wc -l "$monitorlist" | awk '{ print $1 }') screen(s)"

	while read -r resolution
	do
		log make_pape "Adding wallpaper for $resolution sized screen"

		current_pape=$(get_pape "$resolution")

		if [ "$current_pape" = "" ]
		then
			log make_pape "No wallpapers for $resolution"

			current_pape="$(mktemp --tmpdir XXXXX.png)"
			convert -size "$resolution" canvas:gray "$current_pape"
		else
			log make_pape "Using $current_pape"
		fi

		printf '"%s"\n' "$current_pape" >> "$imagelist"

		unset resolution
		unset current_pape
	done < "$monitorlist"

	# shellcheck disable=SC2046
	# shellcheck disable=SC2086
	log make_pape "Combine all resolutions into a single image"

	eval convert +append $(cat $imagelist) "$output" 2>&1 | log_pipe "convert"

	printf "%s" "$output"

	rm -f -- "$imagelist"
}

get_pape()
{
	if [ ! -d "$directory/$1" ]
	then
		log get_pape "$directory/$1 does not exist"
		return 1
	fi

	printf "%s\n" "$(find "$directory/$1" -type f | shuf | head -n 1)"
}

log()
{
	printf "[%s] %s: %s\n" "$(date +%FT%T)" "$1" "$2" >&2
}

log_pipe()
{
	pipe_log="$(mktemp)"

	cat - > "$pipe_log"

	while read -r line
	do
		log "$1" "$line"
	done < "$pipe_log"

	rm -fr -- "$pipe_log"
	unset pipe_log
}

main "$@"