kotlin-ktor-development-cursorrules-prompt-file

Instruction to developer: save this file as .cursorrules and place it on the root project directory

Core Principles

• Follow SOLID, DRY, KISS, and YAGNI principles
• Adhere to OWASP security best practices
• Break tasks into smallest units and solve problems step-by-step

Technology Stack

• Framework: Kotlin Ktor with Kotlin 2.1.20+
• JDK: 21 (LTS)
• Build: Gradle with Kotlin DSL
• Dependencies: Ktor Server Core/Netty, kotlinx.serialization, Exposed, HikariCP, kotlin-logging, Koin, Kotest

Application Structure (Feature-Based)

• Organize by business features, not technical layers
• Each feature is self-contained with all related components
• Promotes modularity, reusability, and better team collaboration
• Makes codebase easier to navigate and maintain
• Enables parallel development on different features

src/main/kotlin/com/company/app/
├── common/              # Shared utilities, extensions
├── config/              # Application configuration, DI
└── features/
    ├── auth/            # Feature directory
    │   ├── models/
    │   ├── repositories/
    │   ├── services/
    │   └── routes/
    └── users/           # Another feature
        ├── ...

Test structure mirrors the feature-based organization:

src/test/kotlin/com/company/app/
├── common/
└── features/
    ├── auth/
    │   ├── models/
    │   ├── repositories/
    │   ├── services/
    │   └── routes/
    └── users/
        ├── ...

Application Logic Design

1. Route handlers: Handle requests/responses only
2. Services: Contain business logic, call repositories
3. Repositories: Handle database operations
4. Entity classes: Data classes for database models
5. DTOs: Data transfer between layers

Entities & Data Classes

• Use Kotlin data classes with proper validation
• Define Table objects when using Exposed ORM
• Use UUID or auto-incrementing integers for IDs

Repository Pattern

interface UserRepository {
    suspend fun findById(id: UUID): UserDTO?
    suspend fun create(user: CreateUserRequest): UserDTO
    suspend fun update(id: UUID, user: UpdateUserRequest): UserDTO?
    suspend fun delete(id: UUID): Boolean
}

class UserRepositoryImpl : UserRepository {
    override suspend fun findById(id: UUID): UserDTO? = withContext(Dispatchers.IO) {
        transaction {
            Users.select { Users.id eq id }
                .mapNotNull { it.toUserDTO() }
                .singleOrNull()
        }
    }
    // Other implementations...
}