#!/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"

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