#!/usr/bin/env bash

# Wrapper for nitrogen setting the freedesktop.org AccountsService/BackgroundFile so LightDM wallpaper is synced.
# Inspired by <https://rafaelc.org/posts/sync-wm-wallpaper-with-lightdm-on-linux-mint/>

key_value_retriever(){
	KEY="${1}"
	if [[ -z "${KEY}" ]]; then
		printf "ERROR: KEY should not be empty\n"
		return
	fi
	FILE="${2}"
	if [[ ! -f "${FILE}" ]]; then
		printf "ERROR: Cannot find FILE: %s\n" "${FILE}"
		return
	fi
	VALUE_VARNAME="${3}"
	if [[ -z "${VALUE_VARNAME}" ]]; then
		printf "ERROR: VALUE_VARNAME should not be empty\n"
		return
	fi
	MATCH=$(grep -m1 "^[[:space:]]*${KEY}=" "${FILE}")
	INDEX_OF_FIRST_EQUAL=$(expr index "${MATCH}" =)
	VALUE="${MATCH:${INDEX_OF_FIRST_EQUAL}}"
	export "${VALUE_VARNAME}"="${VALUE}"
}

/usr/bin/nitrogen "$@"
if [[ "${1:-}" == "--restore" ]]; then
	exit $?
fi

NITROGEN_BG_SAVED_CFG_FILE="${HOME}/.config/nitrogen/bg-saved.cfg"
if [[ ! -f "${NITROGEN_BG_SAVED_CFG_FILE}" ]]; then
	printf "!ERROR! Cannot find NITROGEN_BG_SAVED_CFG_FILE[%s]\n" "${NITROGEN_BG_SAVED_CFG_FILE}" 1>&2
	exit 1
fi

key_value_retriever "file" "${NITROGEN_BG_SAVED_CFG_FILE}" "NITROGEN_BG_SAVED_CFG_FIRST_BACKGROUND_FILE"

if [[ -z "${NITROGEN_BG_SAVED_CFG_FIRST_BACKGROUND_FILE}" ]]; then
	printf "!ERROR! Cannot retrieve NITROGEN_BG_SAVED_CFG_FIRST_BACKGROUND_FILE from NITROGEN_BG_SAVED_CFG_FILE[%s]\n" "NITROGEN_BG_SAVED_CFG_FIRST_BACKGROUND_FILE" 1>&2
	exit 1
fi

if [[ ! -f "${NITROGEN_BG_SAVED_CFG_FIRST_BACKGROUND_FILE}" ]]; then
	printf "!ERROR! Cannot find NITROGEN_BG_SAVED_CFG_FIRST_BACKGROUND_FILE[%s]\n" "${NITROGEN_BG_SAVED_CFG_FIRST_BACKGROUND_FILE}" 1>&2
	exit 1
fi

printf "Setting nitrogen background into freedesktop.org AccountsService...\n"
printf "NITROGEN_BG_SAVED_CFG_FIRST_BACKGROUND_FILE[%s]\n" "${NITROGEN_BG_SAVED_CFG_FIRST_BACKGROUND_FILE}"

dbus-send \
	--print-reply \
	--system \
	--dest=org.freedesktop.Accounts \
	/org/freedesktop/Accounts/User$(id -u) \
	org.freedesktop.DBus.Properties.Set \
	string:org.freedesktop.DisplayManager.AccountsService \
	string:BackgroundFile \
	variant:string:"${NITROGEN_BG_SAVED_CFG_FIRST_BACKGROUND_FILE}"