#!/bin/bash

# Exit out if the same script is already running in the background
pidof -sq -o %PPID -x "$(basename "$0")" && exit

# Set the directory/file paths
declare -r flatpak_themes_dir="$HOME/.themes"
declare -r config_dir="${XDG_CONFIG_HOME:-$HOME/.config}"
declare -r profile="$HOME/.profile"

# Create directories if they don't exist
mkdir -p "$flatpak_themes_dir" "$config_dir" ||
	{ echo "failed to make directories $flatpak_themes_dir & $config_dir"; exit 1; }

# Enable option for syncing the current theme with XFWM theme if not already enabled
[ "$(xfconf-query -c xsettings -p /Xfce/SyncThemes)" != 'true' ] &&
	xfconf-query -c xsettings -p /Xfce/SyncThemes -n -t bool -s true

xdg_directory_lookup() {
	# Go through each item in $XDG_DATA_DIRS and find the subdirectory $1
	while read -r dir; do
		local subdir="${dir%/}/$1"
		if [ -d "$subdir" ]; then
			echo "$subdir"
			break
		fi
	done < <(printf '%s:%s\n' "$HOME/.local/share" "$XDG_DATA_DIRS" | tr ':' '\n')
}

theme_exists() {
	local -r theme_dir=$(xdg_directory_lookup "themes/$1")
	[ -d "$theme_dir" ]
}

# Function for setting variables in ~/.profile
profile_set_variable() {
	# Return if the variable is already set to the correct value
	grep -xq "\s*export\s\+$1=$2\s*" "$profile" && return

	# If the variable is set to a different value then remove that line
	grep -q "^\s*export\s\+$1=" "$profile" && sed -i "/^\s*export\s\+$1=/d" "$profile"

	# Set the variable to the correct value under a comment mentioning this script
	if grep -xq '\s*#\s*Values set by the fix-theming script\s*' "$profile"; then
		sed -i "/^\s*#\s*Values set by the fix-theming script\s*$/a export $1=$2" "$profile"
	elif grep -q '\s' "$profile"; then
		# shellcheck disable=SC2015
		tail -n1 "$profile" | grep -qx '\s*' &&
			local -r begin='' || local -r begin='\n'
		printf '%b# Values set by the fix-theming script\nexport %s=%s\n' "$begin" "$1" "$2" >> "$profile"
	else
		printf '# Values set by the fix-theming script\nexport %s=%s\n' "$1" "$2" > "$profile"
	fi

	logout_required='true'
}

set_QT_scaling() {
	for var in QT_SCALE_FACTOR QT_AUTO_SCREEN_SCALE_FACTOR QT_ENABLE_HIGHDPI_SCALING; do
		profile_set_variable "$var" "$1"
	done
}

set_cursor_size() {
	xfconf-query -c xsettings -p /Gtk/CursorThemeSize -s "$1"
}

set_xfwm_theme() {
	xfconf-query -c xfwm4 -p /general/theme -n -t string -s "$1"
}

# Use the highDPI variant of the XFWM theme
use_hdpi_theme_variant() {
	# shellcheck disable=SC2015
	[ -n "$1" ] && local -r xfwm_theme="$1" ||
		local -r xfwm_theme=$(xfconf-query -c xfwm4 -p /general/theme)

	for variant in xhdpi hdpi; do
		# If this variant of the theme is already enabled then break out of the loop
		[ "${xfwm_theme##*-}" = "$variant" ] && break

		# Store the name for this variant of the theme in highDPI_theme variable
		local highDPI_theme=$xfwm_theme-$variant

		if theme_exists "$highDPI_theme"; then
			set_xfwm_theme "$highDPI_theme"
			[ -z "$1" ] &&
				notify-send "XFWM theme changed to $highDPI_theme" "Changed to the highDPI variant of your chosen theme because you've enabled highDPI on your system"
			break
		fi
	done
	if ! theme_exists "$highDPI_theme"; then
		[ -n "$1" ] && theme_exists "$1" && set_xfwm_theme "$1"
	fi
}

# Use the normal variant of the XFWM theme
use_normal_theme_variant() {
	local -r current_xfwm_theme=$(xfconf-query -c xfwm4 -p /general/theme)

	for variant in xhdpi hdpi; do
		# Continue looping if this (highDPI) variant of the theme is not enabled
		[ "${current_xfwm_theme##*-}" != "$variant" ] && continue

		# Store the name for the normal variant of this theme in normal_theme variable
		local normal_theme=${current_xfwm_theme%-"$variant"}

		if theme_exists "$normal_theme"; then
			set_xfwm_theme "$normal_theme"
			notify-send "XFWM theme changed to $normal_theme" "Changed to the normal variant of your chosen theme because you've disabled highDPI on your system"
			break
		fi
	done
}

# Change XFWM theme, QT apps scaling, and mouse cursor size according to
# the user's current window scaling (highDPI setting)
hdpi_theme_fix() {
	local -r current_window_scaling=$(xfconf-query -c xsettings -p /Gdk/WindowScalingFactor)
	local -r current_cursor_size=$(xfconf-query -c xsettings -p /Gtk/CursorThemeSize)

	unset logout_required

	if [ "$current_window_scaling" -eq '2' ]; then
		# Increase scaling for QT apps
		set_QT_scaling 2
		# Use the highDPI variant of the XFWM theme
		use_hdpi_theme_variant
		if [ "$current_cursor_size" -eq 25 ]; then
			set_cursor_size '45'
			notify-send 'Mouse cursor size increased to 45' "Changed to a larger mouse cursor because you've enabled highDPI on your system"
		fi
	else
		# Decrease scaling for QT apps
		set_QT_scaling 1
		# Use the normal variant of the XFWM theme
		use_normal_theme_variant
		if [ "$current_cursor_size" -eq 45 ]; then
			set_cursor_size '25'
			notify-send 'Mouse cursor size decreased to 25' "Changed to a smaller mouse cursor because you've disabled highDPI on your system"
		fi
	fi

	# Show popup menu about logout if it's required
	[ "$logout_required" = 'true' ] &&
		yad  --image "dialog-question" --title "Alert" --buttons-layout=center --text-align=center --button=yad-yes:0 --button=yad-no:1 --text 'Logout is required in order to apply your DPI preferences to QT apps.\nWould you like to logout now?' &&
		xfce4-session-logout --logout
}

sync_theme() {
	# Get the current system theme
	local -r current_theme=$(xfconf-query -c xsettings -p /Net/ThemeName)
	# Get the current window scaling factor (highDPI setting)
	local -r current_window_scaling=$(xfconf-query -c xsettings -p /Gdk/WindowScalingFactor)

	# Apply the current theme with gsettings
	gsettings set org.gnome.desktop.interface gtk-theme "$current_theme"

	# Apply the current theme for GTK and Libadwaita apps on flatpak
	flatpak override --user --env=GTK_THEME="$current_theme"

	# Apply the current theme for XFWM unless it's initial_sync on system reboot
	if [ "$1" != 'initial_sync' ]; then
		# Use the highDPI variant of the XFWM theme if the current_window_scaling factor is 2
		if [ "$current_window_scaling" -eq '2' ]; then
			use_hdpi_theme_variant "$current_theme"
		else
			set_xfwm_theme "$current_theme"
		fi
	fi

	# Cleanup flatpak_themes_dir and remove ~/.config/gtk-4.0
	rm -rf "${flatpak_themes_dir:?}"/{*,.*} "$config_dir/gtk-4.0"

	# Find the directory where the current theme is stored
	local -r current_theme_dir=$(xdg_directory_lookup "themes/$current_theme")

	if [ -d "$current_theme_dir" ]; then
		# Copy/sync current_theme_dir to flatpak_themes_dir
		rsync -av --delete --progress "$current_theme_dir" "$flatpak_themes_dir"
		# Create symlink for gtk-4.0 directory
		ln -s "$current_theme_dir/gtk-4.0" "$config_dir"
	fi
}

sync_font() {
	# Get the current system font
	local -r current_font=$(xfconf-query -c xsettings -p /Gtk/FontName)
	# Apply the same font for the title of XFCE windows
	xfconf-query -c xfwm4 -p /general/title_font -n -t string -s "$current_font"
}

# Initial synchronization
sync_theme 'initial_sync'
sync_font

# Monitor when the user changes their system theme/icons/font in XFCE and sync them as needed
while read -r line; do
	case "$line" in
		'set: /Net/ThemeName') sync_theme ;;
		'set: /Gdk/WindowScalingFactor') hdpi_theme_fix ;;
		'set: /Gtk/FontName') sync_font ;;
	esac
done < <(xfconf-query -c xsettings -m)