feat: add Kotlin, Android, and KMP rules, agent, skills, and command

2026-04-12 12:43:32 +08:00 · 2026-03-06 23:01:39 +01:00
parent 2b8eca3ae9
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+---
+name: android-clean-architecture
+description: Clean Architecture patterns for Android and Kotlin Multiplatform projects — module structure, dependency rules, UseCases, Repositories, and data layer patterns.
+origin: ECC
+---
+
+# Android Clean Architecture
+
+Clean Architecture patterns for Android and KMP projects. Covers module boundaries, dependency inversion, UseCase/Repository patterns, and data layer design with Room, SQLDelight, and Ktor.
+
+## When to Activate
+
+- Structuring Android or KMP project modules
+- Implementing UseCases, Repositories, or DataSources
+- Designing data flow between layers (domain, data, presentation)
+- Setting up dependency injection with Koin or Hilt
+- Working with Room, SQLDelight, or Ktor in a layered architecture
+
+## Module Structure
+
+### Recommended Layout
+
+```
+project/
+├── app/                  # Android entry point, DI wiring, Application class
+├── core/                 # Shared utilities, base classes, error types
+├── domain/               # UseCases, domain models, repository interfaces (pure Kotlin)
+├── data/                 # Repository implementations, DataSources, DB, network
+├── presentation/         # Screens, ViewModels, UI models, navigation
+├── design-system/        # Reusable Compose components, theme, typography
+└── feature/              # Feature modules (optional, for larger projects)
+    ├── auth/
+    ├── settings/
+    └── profile/
+```
+
+### Dependency Rules
+
+```
+app → presentation, domain, data, core
+presentation → domain, design-system, core
+data → domain, core
+domain → core (or no dependencies)
+core → (nothing)
+```
+
+**Critical**: `domain` must NEVER depend on `data`, `presentation`, or any framework. It contains pure Kotlin only.
+
+## Domain Layer
+
+### UseCase Pattern
+
+Each UseCase represents one business operation. Use `operator fun invoke` for clean call sites:
+
+```kotlin
+class GetItemsByCategoryUseCase(
+    private val repository: ItemRepository
+) {
+    suspend operator fun invoke(category: String): Result<List<Item>> {
+        return repository.getItemsByCategory(category)
+    }
+}
+
+// Flow-based UseCase for reactive streams
+class ObserveUserProgressUseCase(
+    private val repository: UserRepository
+) {
+    operator fun invoke(userId: String): Flow<UserProgress> {
+        return repository.observeProgress(userId)
+    }
+}
+```
+
+### Domain Models
+
+Domain models are plain Kotlin data classes — no framework annotations:
+
+```kotlin
+data class Item(
+    val id: String,
+    val title: String,
+    val description: String,
+    val tags: List<String>,
+    val status: Status
+)
+
+enum class Status { DRAFT, ACTIVE, ARCHIVED }
+```
+
+### Repository Interfaces
+
+Defined in domain, implemented in data:
+
+```kotlin
+interface ItemRepository {
+    suspend fun getItemsByCategory(category: String): Result<List<Item>>
+    suspend fun saveItem(item: Item): Result<Unit>
+    fun observeItems(): Flow<List<Item>>
+}
+```
+
+## Data Layer
+
+### Repository Implementation
+
+Coordinates between local and remote data sources:
+
+```kotlin
+class ItemRepositoryImpl(
+    private val localDataSource: ItemLocalDataSource,
+    private val remoteDataSource: ItemRemoteDataSource
+) : ItemRepository {
+
+    override suspend fun getItemsByCategory(category: String): Result<List<Item>> {
+        return runCatching {
+            val remote = remoteDataSource.fetchItems(category)
+            localDataSource.insertItems(remote.map { it.toEntity() })
+            localDataSource.getItemsByCategory(category).map { it.toDomain() }
+        }
+    }
+
+    override fun observeItems(): Flow<List<Item>> {
+        return localDataSource.observeAll().map { entities ->
+            entities.map { it.toDomain() }
+        }
+    }
+}
+```
+
+### Mapper Pattern
+
+Keep mappers as extension functions near the data models:
+
+```kotlin
+// In data layer
+fun ItemEntity.toDomain() = Item(
+    id = id,
+    title = title,
+    description = description,
+    tags = tags.split("|"),
+    status = Status.valueOf(status)
+)
+
+fun ItemDto.toEntity() = ItemEntity(
+    id = id,
+    title = title,
+    description = description,
+    tags = tags.joinToString("|"),
+    status = status
+)
+```
+
+### Room Database (Android)
+
+```kotlin
+@Entity(tableName = "items")
+data class ItemEntity(
+    @PrimaryKey val id: String,
+    val title: String,
+    val description: String,
+    val tags: String,
+    val status: String
+)
+
+@Dao
+interface ItemDao {
+    @Query("SELECT * FROM items WHERE category = :category")
+    suspend fun getByCategory(category: String): List<ItemEntity>
+
+    @Upsert
+    suspend fun upsert(items: List<ItemEntity>)
+
+    @Query("SELECT * FROM items")
+    fun observeAll(): Flow<List<ItemEntity>>
+}
+```
+
+### SQLDelight (KMP)
+
+```sql
+-- Item.sq
+CREATE TABLE ItemEntity (
+    id TEXT NOT NULL PRIMARY KEY,
+    title TEXT NOT NULL,
+    description TEXT NOT NULL,
+    tags TEXT NOT NULL,
+    status TEXT NOT NULL
+);
+
+getByCategory:
+SELECT * FROM ItemEntity WHERE category = ?;
+
+upsert:
+INSERT OR REPLACE INTO ItemEntity (id, title, description, tags, status)
+VALUES (?, ?, ?, ?, ?);
+
+observeAll:
+SELECT * FROM ItemEntity;
+```
+
+### Ktor Network Client (KMP)
+
+```kotlin
+class ItemRemoteDataSource(private val client: HttpClient) {
+
+    suspend fun fetchItems(category: String): List<ItemDto> {
+        return client.get("api/items") {
+            parameter("category", category)
+        }.body()
+    }
+}
+
+// HttpClient setup with content negotiation
+val httpClient = HttpClient {
+    install(ContentNegotiation) { json(Json { ignoreUnknownKeys = true }) }
+    install(Logging) { level = LogLevel.HEADERS }
+    defaultRequest { url("https://api.example.com/") }
+}
+```
+
+## Dependency Injection
+
+### Koin (KMP-friendly)
+
+```kotlin
+// Domain module
+val domainModule = module {
+    factory { GetItemsByCategoryUseCase(get()) }
+    factory { ObserveUserProgressUseCase(get()) }
+}
+
+// Data module
+val dataModule = module {
+    single<ItemRepository> { ItemRepositoryImpl(get(), get()) }
+    single { ItemLocalDataSource(get()) }
+    single { ItemRemoteDataSource(get()) }
+}
+
+// Presentation module
+val presentationModule = module {
+    viewModelOf(::ItemListViewModel)
+    viewModelOf(::DashboardViewModel)
+}
+```
+
+### Hilt (Android-only)
+
+```kotlin
+@Module
+@InstallIn(SingletonComponent::class)
+abstract class RepositoryModule {
+    @Binds
+    abstract fun bindItemRepository(impl: ItemRepositoryImpl): ItemRepository
+}
+
+@HiltViewModel
+class ItemListViewModel @Inject constructor(
+    private val getItems: GetItemsByCategoryUseCase
+) : ViewModel()
+```
+
+## Error Handling
+
+### Result/Try Pattern
+
+Use `Result<T>` or a custom sealed type for error propagation:
+
+```kotlin
+sealed interface Try<out T> {
+    data class Success<T>(val value: T) : Try<T>
+    data class Failure(val error: AppError) : Try<Nothing>
+}
+
+sealed interface AppError {
+    data class Network(val message: String) : AppError
+    data class Database(val message: String) : AppError
+    data object Unauthorized : AppError
+}
+
+// In ViewModel — map to UI state
+viewModelScope.launch {
+    when (val result = getItems(category)) {
+        is Try.Success -> _state.update { it.copy(items = result.value, isLoading = false) }
+        is Try.Failure -> _state.update { it.copy(error = result.error.toMessage(), isLoading = false) }
+    }
+}
+```
+
+## Convention Plugins (Gradle)
+
+For KMP projects, use convention plugins to reduce build file duplication:
+
+```kotlin
+// build-logic/src/main/kotlin/kmp-library.gradle.kts
+plugins {
+    id("org.jetbrains.kotlin.multiplatform")
+}
+
+kotlin {
+    androidTarget()
+    iosX64(); iosArm64(); iosSimulatorArm64()
+    sourceSets {
+        commonMain.dependencies { /* shared deps */ }
+        commonTest.dependencies { implementation(kotlin("test")) }
+    }
+}
+```
+
+Apply in modules:
+
+```kotlin
+// domain/build.gradle.kts
+plugins { id("kmp-library") }
+```
+
+## Anti-Patterns to Avoid
+
+- Importing Android framework classes in `domain` — keep it pure Kotlin
+- Exposing database entities or DTOs to the UI layer — always map to domain models
+- Putting business logic in ViewModels — extract to UseCases
+- Using `GlobalScope` or unstructured coroutines — use `viewModelScope` or structured concurrency
+- Fat repository implementations — split into focused DataSources
+- Circular module dependencies — if A depends on B, B must not depend on A
+
+## References
+
+See skill: `compose-multiplatform-patterns` for UI patterns.
+See skill: `kotlin-coroutines-flows` for async patterns.