#!/bin/bash
pidof -sq -o %PPID -x "$(basename "$0")" && exit
data="$HOME"/.local/share/applications/tweaked-desktop-files
data2="$HOME"/.local/share/applications/bakkedup-desktop-files

# Directories where desktop files are stored
user="$HOME"/.local/share/applications
flatpak_local="$HOME"/.local/share/flatpak/exports/share/applications
flatpak_global=/var/lib/flatpak/exports/share/applications
pacman_local=/usr/local/share/applications
pacman_global=/usr/share/applications
snap=/var/lib/snapd/desktop/applications

detectfiles() {
	for file in "$user"/*.desktop; do
		name=$(basename "$file") || continue
		[ -d "$file" ] || grep -xq "\(flatpak-local\|flatpak-global\|pacman-local\|pacman-global\|snap\)/$name" "$data" && continue
		if [ -f "$flatpak_local/$name" ]; then
			echo "flatpak-local/$name" >> "$data"
		elif [ -f "$flatpak_global/$name" ]; then
			echo "flatpak-global/$name" >> "$data"
		elif [ -f "$pacman_local/$name" ]; then
			echo "pacman-local/$name" >> "$data"
		elif [ -f "$pacman_global/$name" ]; then
			echo "pacman-global/$name" >> "$data"
		elif [ -f "$snap/$name" ]; then
			echo "snap/$name" >> "$data"
		fi
	done
}

fixfiles() {
	lastmod=$(stat -c "%Y" "$data")
	tmp="$(mktemp)"
	trap 'rm $tmp' EXIT
	[ -f "$data" ] && cp "$data" "$tmp" && copied='true'
	lineno=0
	[ "$copied" = 'true' ] && while IFS= read -r line; do
		((lineno++))
		name=${line#*/}
		file="$user/$name"
		# shellcheck disable=2015 # To disable shellcheck error here, line below is intended to work this way
		echo "$line" | grep -xq '\(flatpak-local\|flatpak-global\|pacman-local\|pacman-global\|snap\)/.\+' && [ -f "$file" ] || { sed -i "${lineno}d" "$tmp" && ((lineno--)) ; continue; }
		[ -f "$flatpak_local/$name" ] ||
			[ -f "$flatpak_global/$name" ] ||
			[ -f "$pacman_local/$name" ] ||
			[ -f "$pacman_global/$name" ] ||
			[ -f "$snap/$name" ] ||
			{ mv "$file" "$file.bak" && echo "$line" >> "$data2"; }
	done < "$data"

	[ "$copied" = 'true' ] && [ "$(stat -c '%Y' "$data")" = "$lastmod" ] && sort "$tmp" | uniq > "$data"

	[ -n "$(sort "$data2" | uniq -d)" ] && cp "$data2" "$tmp" && sort "$tmp" | uniq > "$data2"

	for bakfile in "$user"/*.desktop.bak; do
		origfile="${bakfile%.bak}"
		[ -f "$origfile" ] && continue
		name=$(basename "$origfile") || continue
		[ -f "$flatpak_local/$name" ] ||
			[ -f "$flatpak_global/$name" ] ||
			[ -f "$pacman_local/$name" ] ||
			[ -f "$pacman_global/$name" ] ||
			[ -f "$snap/$name" ] &&
			mv "$bakfile" "$origfile"
	done
}

while :; do
	user_new=$(ls -ad "$user"/*.desktop 2>/dev/null)
	flatpak_local_new=$(ls -ad "$flatpak_local"/*.desktop 2>/dev/null)
	flatpak_global_new=$(ls -ad "$flatpak_global"/*.desktop 2>/dev/null)
	pacman_local_new=$(ls -ad "$pacman_local"/*.desktop 2>/dev/null)
	pacman_global_new=$(ls -ad "$pacman_global"/*.desktop 2>/dev/null)
	snap_new=$(ls -ad "$snap"/*.desktop 2>/dev/null)
	[ "$user_new" != "$user_old" ] && detectfiles
	[ "$flatpak_local_new" != "$flatpak_local_old" ] ||
		[ "$flatpak_global_new" != "$flatpak_global_old" ] ||
		[ "$pacman_local_new" != "$pacman_local_old" ] ||
		[ "$pacman_global_new" != "$pacman_global_old" ] ||
		[ "$snap_new" != "$snap_old" ] && fixfiles
	user_old=$user_new
	flatpak_local_old=$flatpak_local_new
	flatpak_global_old=$flatpak_global_new
	pacman_local_old=$pacman_local_new
	pacman_global_old=$pacman_global_new
	snap_old=$snap_new
	sleep 5
done