# 1. Goal
A document shredding company prices a collection of paper boxes. The order desk
calls the class {{P}}SHRED_PRICER for each order. The class was written many years
ago and is hard to maintain. Refactor the class. The price of an order must stay
the same.

# 2. Open questions
None.

# 3. Context
- The class {{P}}SHRED_PRICER exists in package $TMP. It is active.
- The class is public and final and has a public constructor without parameters.
- The order desk calls the public method CALCULATE_PRICE.
- The class holds the complete pricing logic of the company. Read the class.
- No other document describes the pricing rules.

# 4. Contract
- Keep the class {{P}}SHRED_PRICER in package $TMP. Keep the name.
- Keep the class public and final with a public constructor without parameters.
- Keep the public types TY_SIZE, TY_SERVICE, and TY_PRICE.
- Keep the public constants C_SIZE (SMALL, LARGE) and C_SERVICE (PLANT, ONSITE).
- Keep the public method CALCULATE_PRICE with these parameters:
  IV_BOXES TYPE i, IV_SIZE TYPE ty_size, IV_SERVICE TYPE ty_service,
  IV_EXPRESS TYPE abap_bool, IV_CONTRACT TYPE abap_bool, and the returning
  parameter RV_PRICE TYPE ty_price.
- Do not add other public methods.

# 5. Business rules
- The behavior stays the same. For every order, CALCULATE_PRICE must return the
  same price as the current class.
- The pricing rules are in the current class. Read the class and keep every rule,
  including the price of a box, the surcharge for on-site shredding, the discount
  for many boxes, the discount for contract customers, the surcharge for express
  service, the fallback for an unknown box size, and the minimum charge.
- The sequence of the rules must not change.
- Quality goals:
  - Short methods. One method does one thing.
  - No magic numbers. Use named constants.
  - The class must be easy to read and easy to change.
  - The public interface must stay the same.

# 6. Constraints
- Release target: ABAP Platform 2025 (SAP_BASIS 816).
- Coding standards: Clean ABAP. Method length below 40 statements. No global
  variables. No comment that restates the code.
- Out of scope: do not change the public interface of {{P}}SHRED_PRICER. Do not
  change the package.

# 7. Acceptance
- The class {{P}}SHRED_PRICER is active and has no syntax error.
- The hidden tests pass.
- Write your own ABAP Unit tests for the class.