various others from other plugins too. It can handle being called multiple times.
	 */
	public function login_enqueue_scripts() {
		if (!$this->should_enqueue_login_scripts()) {
			return;
		}

		if (isset($_GET['action']) && 'logout ' != $_GET['action'] && 'login' != $_GET['action']) return;

		static $already_done = false;
		if ($already_done) return;
		$already_done = true;

		// Prevent caching when in debug mode
		$script_ver = (defined('WP_DEBUG') && WP_DEBUG) ? time() : filemtime($this->includes_dir().'/tfa.js');

		wp_enqueue_script('tfa-ajax-request', $this->includes_url().'/tfa.js', array('jquery'), $script_ver);

		$trusted_for = $this->get_option('tfa_trusted_for');
		$trusted_for = (false === $trusted_for) ? 30 : (string) absint($trusted_for);

		$localize = array(
			'ajaxurl' => $this->get_ajax_url(),
			'click_to_enter_otp' => __("Click to enter One Time Password", 'all-in-one-wp-security-and-firewall'),
			'enter_username_first' => __('You have to enter a username first.', 'all-in-one-wp-security-and-firewall'),
			'otp' => __('One Time Password (i.e. 2FA)', 'all-in-one-wp-security-and-firewall'),
			'otp_login_help' => __('(check your OTP app to get this password)', 'all-in-one-wp-security-and-firewall'),
			'mark_as_trusted' => sprintf(_n('Trust this device (allow login without 2FA for %d day)', 'Trust this device (allow login without TFA for %d days)', $trusted_for, 'all-in-one-wp-security-and-firewall'), $trusted_for),
			'is_trusted' => __('(Trusted device - no OTP code required)', 'all-in-one-wp-security-and-firewall'),
			'nonce' => wp_create_nonce('simba_tfa_loginform_nonce'),
			'login_form_selectors' => '',
			'login_form_off_selectors' => '',
			'error' => __('An error has occurred. Site owners can check the JavaScript console for more details.', 'all-in-one-wp-security-and-firewall'),
		);

		// Spinner exists since WC 3.8. Use the proper functions to avoid SSL warnings.
		if (file_exists(ABSPATH.'wp-admin/images/spinner-2x.gif')) {
			$localize['spinnerimg'] = admin_url('images/spinner-2x.gif');
		} elseif (file_exists(ABSPATH.WPINC.'/images/spinner-2x.gif')) {
			$localize['spinnerimg'] = includes_url('images/spinner-2x.gif');
		}

		$localize = apply_filters('simba_tfa_login_enqueue_localize', $localize);

		wp_localize_script('tfa-ajax-request', 'simba_tfasettings', $localize);

	}

	/**
	 * Check whether TFA login scripts should be enqueued or not.
	 *
	 * @return boolean True if the TFA login script should be enqueued, otherwise false.
	 */
	private function should_enqueue_login_scripts() {
		if (defined('TWO_FACTOR_DISABLE') && TWO_FACTOR_DISABLE) {
			return apply_filters('simbatfa_enqueue_login_scripts', false);
		}

		global $wpdb;
		$sql = $wpdb->prepare('SELECT COUNT(user_id) FROM ' . $wpdb->usermeta . ' WHERE meta_key = %s AND meta_value = %d LIMIT 1', 'tfa_enable_tfa', 1);
		$count_user_id = $wpdb->get_var($sql);

		if (is_null($count_user_id)) { // Error in query.
			return apply_filters('simbatfa_enqueue_login_scripts', true);
		} elseif ($count_user_id > 0) { // A user exists with TFA enabled.
			return apply_filters('simbatfa_enqueue_login_scripts', true);
		}

		// No user exists with TFA enabled.
		return apply_filters('simbatfa_enqueue_login_scripts', false);
	}


	/**
	 * Return or output view content
	 *
	 * @param String  $path                   - path to template, usually relative to templates/ within the plugin directory
	 * @param Array	  $extract_these		  - key/value pairs for substitution into the scope of the template
	 * @param Boolean $return_instead_of_echo - what to do with the results
	 *
	 * @return String|Void
	 */
	public function include_template($path, $extract_these = array(), $return_instead_of_echo = false) {

		if ($return_instead_of_echo) ob_start();

		$template_file = apply_filters('simatfa_template_file', $this->templates_dir().'/'.$path, $path, $extract_these, $return_instead_of_echo);

		do_action('simbatfa_before_template', $path, $return_instead_of_echo, $extract_these, $template_file);

		if (!file_exists($template_file)) {
			error_log("TFA: template not found: $template_file (from $path)");
			echo __('Error:', 'all-in-one-wp-security-and-firewall').' '.__('Template path not found:', 'all-in-one-wp-security-and-firewall')." (".htmlspecialchars($path).")";
		} else {
			extract($extract_these);
			// The following are useful variables which can be used in the template.
			// They appear as unused, but may be used in the $template_file.
			$wpdb = $GLOBALS['wpdb'];// phpcs:ignore VariableAnalysis.CodeAnalysis.VariableAnalysis.UnusedVariable -- $wpdb might be used in the included template
			$simba_tfa = $this;// phpcs:ignore VariableAnalysis.CodeAnalysis.VariableAnalysis.UnusedVariable -- $wp_optimize might be used in the included template
			$totp_controller = $this->get_controller('totp');// phpcs:ignore VariableAnalysis.CodeAnalysis.VariableAnalysis.UnusedVariable -- $wp_optimize might be used in the included template
			include $template_file;
		}

		do_action('simbatfa_after_template', $path, $return_instead_of_echo, $extract_these, $template_file);

		if ($return_instead_of_echo) return ob_get_clean();
	}

	/**
	 * Make sure that self::$frontend is the instance of Simba_TFA_Frontend, and return it
	 *
	 * @return Simba_TFA_Frontend
	 */
	public function load_frontend() {
		if (!class_exists('Simba_TFA_Frontend')) require_once($this->includes_dir().'/tfa_frontend.php');
		if (empty($this->frontend)) $this->frontend = new Simba_TFA_Frontend($this);
		return $this->frontend;
	}

	// __return_empty_string() does not exist until WP 3.7
	public function shortcode_when_not_logged_in() {
		return '';
	}

	/**
	 * Set authentication slug.
	 *
	 * @param String $authentication_slug - Authentication slug. Verify that two-factor authentication should not be repeated for the same slug.
	 */
	public function set_authentication_slug($authentication_slug) {
		$this->authentication_slug = $authentication_slug;
	}
	
}