How to book purchase discount for special product discounts

We need help with how to book purchase discount in the following two situations:

1. Suppliers will offer a 25% (for example) discount if we agree to take a large amount of product.  We want to book this special discount as “purchase discount”. How do we do it.  
    
2. Suppliers will offer us a 50% discount on freight charges if we pay the product invoice within X days.  We want to book this 50% freight discount as purchase discount.  How do we do it? (We use landed cost to compute cost.)

Your suggestions are greatly appreciated.