Magento – AJAX Auto Update on One Step Checkout

The first way that comes to mind is:

To create a new first step in the checkout process that would be called each time. When you are returned from the 3rd party page this would have a URL param set so we know to do something. This requires:

Updating: public/app/code/core/Mage/Checkout/Block/Onepage/Abstract.php

protected function _getStepCodes()
{
    return array('login', 'billing', 'shipping', 'shipping_method', 'payment', 'review');
}

This block gets the available checkout steps. We would include a new one at the beginning for API or whatever make sense to what you are doing.

Then in OnePageController.php ( All should be changed in your own module ) we would need a new step:

public function saveAPIAction()
{
  $this->_expireAjax();
  if ($this->getRequest()->getParam('returned')) {
     $result['goto_section'] = 'review';          
  } else {
     $result['goto_section'] = 'login';
  }
}

Next up would be to change the JS OpCheckout.js this file will need:

this.steps = ['login', 'billing', 'shipping', 'shipping_method', 'payment', 'review'];

Updating to reflect the new step. As well as a full new class adding for API

var Billing = Class.create();
Billing.prototype = {
initialize: function(form, addressUrl, saveUrl){
    this.form = form;
    if ($(this.form)) {
        $(this.form).observe('submit', function(event){this.save();Event.stop(event);}.bind(this));
    }
    this.saveUrl = saveUrl;
    this.onSave = this.nextStep.bindAsEventListener(this);
    this.onComplete = this.resetLoadWaiting.bindAsEventListener(this);
    // would need to add forcing payment save or success redirect 
}
}

Complexity when it comes to all of the above is ensuring that all the options throughout your checkout journey are set. If when the current implementation returns to the current checkout it just calls payment.save then it should be ok as adding to what I have provided will get you going with a new checkout step that does implement almost the same as the current but in a more modular means. You could add more functionality if required.

Please change code in file : HusseyCoding_AjaxCartPopup_Block_Popup

Find bellow function

public function getCheckoutUrl()
{
  return $this->_getCheckoutUrl();      
}

And replace below function

 public function getCheckoutUrl()
        {
//Make sure please put your One step checkout extension module enable or disable condition here
            if (!$this->helper('onestepcheckout')->isRewriteCheckoutLinksEnabled()){
                return $this->_getCheckoutUrl();
            }
            return $this->getUrl('onestepcheckout', array('_secure'=>true));
        }