Where/How to re-order collection before pagination but after f.x Price

Question

I'm trying to achieve so that products with specific Manufacturer should be the first in the collection (for example, user wants to sort by price, so it should show all the products by Manufacturer X sorted by the price and then rest of the products like normally).

My idea was to hook somewhere between when the collection is being sorted by those attributes, but before it is "paginated". But I have trouble finding the place for it...

Of course if someone has a better idea, I'd love to hear it :)

Answer 1

Okay, so thanks to @Marius, I kinda figured it out:

<?php
class One_Two_Model_Resource_Product_Collection extends Mage_Catalog_Model_Resource_Product_Collection
{
public function addAttributeToSort($attribute, $dir = self::SORT_ORDER_ASC)
{
    if (Mage::app()->getStore()->getId() == Mage_Core_Model_App::ADMIN_STORE_ID){
        return parent::addAttributeToSort($attribute, $dir);
    }

    if ($attribute == 'position' || $attribute == 'name' || $attribute == 'price') {
        // We need to have the ocean wheel products as the first ones.
        // First get the ids
        $ids = $this->_getIdsIWantFirst();

        // Create sorting sql
        $order = new Zend_Db_Expr("CASE WHEN e.entity_id IN ('" . implode("', '", $ids) . "') THEN 0 ELSE 1 END");

        // Work the magic
        $this
            ->getSelect()
            ->order($order);

        return $this;
    }

    else {
        return parent::addAttributeToSort($attribute, $dir);
    }
}

Now I just need to figure out how to still include the original sorting within those wanted ids...