Code review/issues found

[shukebeta]

Main issues found:

• Shape class has too much responsibility, while Order class is too simple
• Magic number and hard-coded strings everywhere
• Inconsistent / unclear method names
• Too many public methods, even they are only used internal
• Too much duplicate code between classes
• Using int type to save price is not wise
• If you want to define a custom ToString method for a class, it should be an override one
• No unit test to ensure the correctness of code

Though the project is programmed in OOP style, but the code mainly violates the following two design principals:

• Single responsibility principle (good code should be high cohesion, lower coupling)
  • Shape class has too much responsibility, while Order class is too simple
• Open/Close principle: When we add a new shape, we have to modify many places.