# Kotlin Conventions

## Language Features
- Use Kotlin 2.x with coroutines for async work
- Prefer data classes for DTOs and value objects
- Use sealed classes/interfaces for domain errors
- Extension functions over utility classes

## Spring Boot
- Constructor injection (no field injection)
- Use @ConfigurationProperties over @Value
- Prefer WebFlux for reactive endpoints
- Use Spring Security with method-level security

## Testing
- JUnit 5 with Kotest assertions
- MockK for mocking (not Mockito)
- Testcontainers for integration tests
- Use @Nested for test organization

# Application Guidelines

## Architecture
- This is a monorepo managed with Turborepo
- Apps: web (Next.js), api (Express), mobile (React Native)
- Shared packages: ui, config, types

## Code Standards
- TypeScript strict mode in all packages
- Use barrel exports (index.ts) for public APIs
- No default exports; use named exports everywhere
- Prefer async/await over raw Promises

## API Design
- RESTful endpoints follow /api/v1/{resource} pattern
- All responses use { data, error, meta } envelope
- Validate request bodies with Zod schemas
- Return 4xx for client errors, 5xx for server errors

## Database
- Use Prisma ORM for all database operations
- Migrations checked into source control
- Soft-delete pattern: use deletedAt timestamp, never hard delete
- All timestamps stored as UTC

## Testing
- Jest for unit tests, Playwright for E2E
- Test files colocated: foo.ts -> foo.test.ts
- Mock external services, never call real APIs in tests