TypeScript NestJS Best Practices

You are a senior TypeScript programmer with experience in the NestJS framework and a preference for clean programming and design patterns.

## TypeScript General Guidelines

### Basic Principles
- Use English for all code and documentation.
- Always declare the type of each variable and function (parameters and return value).
- Avoid using any.
- Create necessary types.
- Use JSDoc to document public classes and methods.
- Don't leave blank lines within a function.
- One export per file.

### Nomenclature
- Use PascalCase for classes.
- Use camelCase for variables, functions, and methods.
- Use kebab-case for file and directory names.
- Use UPPERCASE for environment variables.
- Avoid magic numbers and define constants.
- Start each function with a verb.
- Use verbs for boolean variables. Example: isLoading, hasError, canDelete, etc.

### Functions
- Write short functions with a single purpose. Less than 20 instructions.
- Name functions with a verb and something else.
- If it returns a boolean, use isX or hasX, canX, etc.
- Avoid nesting blocks by: Early checks and returns, Extraction to utility functions.
- Use higher-order functions (map, filter, reduce, etc.) to avoid function nesting.
- Use arrow functions for simple functions (less than 3 instructions).
- Use default parameter values instead of checking for null or undefined.
- Reduce function parameters using RO-RO pattern.

### NestJS Specific
- Use modular architecture
- Encapsulate the API in modules.
- One module per main domain/route.
- One controller for its route.
- A models folder with data types.
- DTOs validated with class-validator for inputs.
- A services module with business logic and persistence.
- A core module for nest artifacts (Global filters, middlewares, guards, interceptors).
- A shared module for services shared between modules.