clean-code

Apply the extract method refactoring: identify each distinct responsibility in the function (validation, calculation, persistence, notification) and move each into its own named function. The original function then orchestrates calls, keeping each unit single-purpose and testable.

Replace nested if-blocks with early returns that handle failure cases first. Each guard clause returns immediately when a precondition fails, leaving the happy path at the top indentation level and eliminating arrow-shaped code.

Do not DRY code used in only one place, since premature abstraction is worse than duplication. Inline trivial one-liners when the operation is self-documenting, and only extract shared functions when duplication represents the same concept changing together.

Good comments explain why a decision was made, such as business rules, performance constraints, or external system behavior. Bad comments restate what the code already says, like "increment i by 1", and should be removed in favor of clearer naming.

No, it applies where variation is expected, such as discount types or payment providers. Define a strategy interface so new variants are added as new classes without modifying existing code, but avoid abstracting stable single-implementation logic.