public function process_payment( $order_id ) {
		$order = wc_get_order( $order_id );

		if ( $order->get_total() > 0 ) {
			// Mark as processing or on-hold (payment won't be taken until delivery).
			$order->update_status( apply_filters( 'woocommerce_cod_process_payment_order_status', $order->has_downloadable_item() ? 'on-hold' : 'processing', $order ), __( 'Payment to be made upon delivery.', 'woocommerce' ) );
		} else {
			$order->payment_complete();
		}

		// Remove cart.
		WC()->cart->empty_cart();

		// Return thankyou redirect.
		return array(
			'result'   => 'success',
			'redirect' => $this->get_return_url( $order ),
		);
	}