Some words about DRY, DIE, KISS, SOLID, YAGNI
Don’t Repeat Youself
Duplication Is Evil
Keep It Simple, Stupid
do not complicate! Create the most understandable solutions, apply design patterns and not reinvent the wheel.
Single responsibility principle
A class should have one and only one reason to change, meaning that a class should have only one job.
Open/closed principle
Objects or entities should be open for extension, but closed for modification
Liskov substitution principle
Let q(x) be a property provable about objects of x of type T. Then q(y) should be provable for objects y of type S where S is a subtype of T.
Interface segregation principle
A client should never be forced to implement an interface that it doesn't use or clients shouldn't be forced to depend on methods they do not use.
Dependency inversion principle
Entities must depend on abstractions not on concretions. It states that the high level module must not depend on the low level module, but they should depend on abstractions.
You Ain’t Gonna Need It
implement only the necessary tasks and abandon the excess functionality
Duplication of the same code should be avoided.