How to set a custom free shipping amount for each quote?

Question

I need to set a custom free-shipping threshold (in config this is carriers/freeshipping/free_shipping_subtotal and can be set in the back-end) for each quote subtotal. So quotes above this subtotal amount will have free shipping applied. The subtotal-amount will change dynamically (by user) and should revert to default value set in back end when user is logged off.

How do I go about doing this?

Answer 1

You can accomplish a free shipping/per customer/per minimum subtotal by :

1. Adding a new customer entity attribute, which will be the place to edit the minimum per order for each customer. Adding custom attribute to Customer
2. After this you will need to rewrite the class Mage_Shipping_Model_Carrier_Freeshipping in app/code/core/Mage/Shipping/Model/Carrier/Freeshipping.php , specifically in the collectRates() method. instead of checking for $this->getConfigData('free_shipping_subtotal') we will check the customer subtotal from the attribute we created in point one.

if(Mage::getSingleton('customer/session')->isLoggedIn()) {
    $minimumOrderAmount = Mage::getSingleton('customer/session')->getCustomer()->getNewAttrubuteYouCreated();
} else {
    $minimumOrderAmount = $this->getConfigData('free_shipping_subtotal');
}

if (($request->getFreeShipping())
    || ($request->getBaseSubtotalInclTax() >= $minimumOrderAmount)
) {
    $method = Mage::getModel('shipping/rate_result_method');

    $method->setCarrier('freeshipping');
    $method->setCarrierTitle($this->getConfigData('title'));

    $method->setMethod('freeshipping');
    $method->setMethodTitle($this->getConfigData('name'));

    $method->setPrice('0.00');
    $method->setCost('0.00');

    $result->append($method);
}

Some links to help: http://inchoo.net/magento/overriding-magento-blocks-models-helpers-and-controllers/