How to modify correctly: calculate and add to the data received from the model?

Question

Software design

It is necessary to display goods at a discount. Data for products and given discounts is stored in different tables: 'products' and 'discounts' are many-to-many related.

When displaying a list of goods and a detailed page of goods, it is necessary to obtain modified data of goods already calculated based on the parameter of the base price of the goods and the discount - data located in different tables:

• discount percentage, old and new price, benefit - the difference between the old and new prices etc.
• that discounted products received from the model already contain the specified data in the form of a collection or array.

I don't think this should be done in a controller. What is the best approach to take? Where to look?

Answer 1

Look in the direction of "make a service that will accept data as input, process it and return it."