update_export_percentage_complete( $report_type, $export_id, $percentage ) {
		$exports_status = get_option( self::EXPORT_STATUS_OPTION, array() );
		$status_key     = self::get_status_key( $report_type, $export_id );

		$exports_status[ $status_key ] = $percentage;

		update_option( self::EXPORT_STATUS_OPTION, $exports_status );
	}

	/**
	 * Get the completion percentage of a report export.
	 *
	 * @param string $report_type Report type. E.g. 'customers'.
	 * @param string $export_id Unique ID for report (timestamp expected).
	 * @return bool|int Completion percentage, or false if export not found.
	 */
	public static function get_export_percentage_complete( $report_type, $export_id ) {
		$exports_status = get_option( self::EXPORT_STATUS_OPTION, array() );
		$status_key     = self::get_status_key( $report_type, $export_id );

		if ( isset( $exports_status[ $status_key ] ) ) {
			return $exports_status[ $status_key ];
		}

		return false;
	}

	/**
	 * Serve the export file.
	 */
	public static function download_export_file() {
		// @todo - add nonce? (nonces are good for 24 hours)
		if (
			isset( $_GET['action'] ) &&
			! empty( $_GET['filename'] ) &&
			self::DOWNLOAD_EXPORT_ACTION === wp_unslash( $_GET['action'] ) && // WPCS: input var ok, sanitization ok.
			current_user_can( 'view_woocommerce_reports' )
		) {
			$exporter = new ReportCSVExporter();
			$exporter->set_filename( wp_unslash( $_GET['filename'] ) ); // WPCS: input var ok, sanitization ok.
			$exporter->export();
		}
	}

	/**
	 * Process a report export email action.
	 *
	 * @param int    $user_id User ID that requested the email.
	 * @param string $export_id Unique ID for report (timestamp expected).
	 * @param string $report_type Report type. E.g. 'customers'.
	 * @return void
	 */
	public static function email_report_download_link( $user_id, $export_id, $report_type ) {
		$percent_complete = self::get_export_percentage_complete( $report_type, $export_id );

		if ( 100 === $percent_complete ) {
			$query_args   = array(
				'action'   => self::DOWNLOAD_EXPORT_ACTION,
				'filename' => "wc-{$report_type}-report-export-{$export_id}",
			);
			$download_url = add_query_arg( $query_args, admin_url() );

			\WC_Emails::instance();
			$email = new ReportCSVEmail();
			$email->trigger( $user_id, $report_type, $download_url );
		}
	}
}