woocommerce gateway process payment

1public function process_payment( $order_id ) {
2    
3    $order = wc_get_order( $order_id );
4            
5    // Mark as on-hold (we're awaiting the payment)
6    $order->update_status( 'on-hold', __( 'Awaiting offline payment', 'wc-gateway-offline' ) );
7            
8    // Reduce stock levels
9    $order->reduce_order_stock();
10            
11    // Remove cart
12    WC()->cart->empty_cart();
13            
14    // Return thankyou redirect
15    return array(
16        'result'    => 'success',
17        'redirect'  => $this->get_return_url( $order )
18    );
19}
20