feat: add kotlin commands and skill pack

2026-04-13 13:23:31 +08:00 · 2026-03-10 21:25:52 -07:00
parent 82f9f58d28
commit 135eb4c98d
14 changed files with 3900 additions and 0 deletions
--- a/skills/kotlin-ktor-patterns/SKILL.md
+++ b/skills/kotlin-ktor-patterns/SKILL.md
@@ -0,0 +1,689 @@
+---
+name: kotlin-ktor-patterns
+description: Ktor server patterns including routing DSL, plugins, authentication, Koin DI, kotlinx.serialization, WebSockets, and testApplication testing.
+origin: ECC
+---
+
+# Ktor Server Patterns
+
+Comprehensive Ktor patterns for building robust, maintainable HTTP servers with Kotlin coroutines.
+
+## When to Activate
+
+- Building Ktor HTTP servers
+- Configuring Ktor plugins (Auth, CORS, ContentNegotiation, StatusPages)
+- Implementing REST APIs with Ktor
+- Setting up dependency injection with Koin
+- Writing Ktor integration tests with testApplication
+- Working with WebSockets in Ktor
+
+## Application Structure
+
+### Standard Ktor Project Layout
+
+```text
+src/main/kotlin/
+├── com/example/
+│   ├── Application.kt           # Entry point, module configuration
+│   ├── plugins/
+│   │   ├── Routing.kt           # Route definitions
+│   │   ├── Serialization.kt     # Content negotiation setup
+│   │   ├── Authentication.kt    # Auth configuration
+│   │   ├── StatusPages.kt       # Error handling
+│   │   └── CORS.kt              # CORS configuration
+│   ├── routes/
+│   │   ├── UserRoutes.kt        # /users endpoints
+│   │   ├── AuthRoutes.kt        # /auth endpoints
+│   │   └── HealthRoutes.kt      # /health endpoints
+│   ├── models/
+│   │   ├── User.kt              # Domain models
+│   │   └── ApiResponse.kt       # Response envelopes
+│   ├── services/
+│   │   ├── UserService.kt       # Business logic
+│   │   └── AuthService.kt       # Auth logic
+│   ├── repositories/
+│   │   ├── UserRepository.kt    # Data access interface
+│   │   └── ExposedUserRepository.kt
+│   └── di/
+│       └── AppModule.kt         # Koin modules
+src/test/kotlin/
+├── com/example/
+│   ├── routes/
+│   │   └── UserRoutesTest.kt
+│   └── services/
+│       └── UserServiceTest.kt
+```
+
+### Application Entry Point
+
+```kotlin
+// Application.kt
+fun main() {
+    embeddedServer(Netty, port = 8080, module = Application::module).start(wait = true)
+}
+
+fun Application.module() {
+    configureSerialization()
+    configureAuthentication()
+    configureStatusPages()
+    configureCORS()
+    configureDI()
+    configureRouting()
+}
+```
+
+## Routing DSL
+
+### Basic Routes
+
+```kotlin
+// plugins/Routing.kt
+fun Application.configureRouting() {
+    routing {
+        userRoutes()
+        authRoutes()
+        healthRoutes()
+    }
+}
+
+// routes/UserRoutes.kt
+fun Route.userRoutes() {
+    val userService by inject<UserService>()
+
+    route("/users") {
+        get {
+            val users = userService.getAll()
+            call.respond(users)
+        }
+
+        get("/{id}") {
+            val id = call.parameters["id"]
+                ?: return@get call.respond(HttpStatusCode.BadRequest, "Missing id")
+            val user = userService.getById(id)
+                ?: return@get call.respond(HttpStatusCode.NotFound)
+            call.respond(user)
+        }
+
+        post {
+            val request = call.receive<CreateUserRequest>()
+            val user = userService.create(request)
+            call.respond(HttpStatusCode.Created, user)
+        }
+
+        put("/{id}") {
+            val id = call.parameters["id"]
+                ?: return@put call.respond(HttpStatusCode.BadRequest, "Missing id")
+            val request = call.receive<UpdateUserRequest>()
+            val user = userService.update(id, request)
+                ?: return@put call.respond(HttpStatusCode.NotFound)
+            call.respond(user)
+        }
+
+        delete("/{id}") {
+            val id = call.parameters["id"]
+                ?: return@delete call.respond(HttpStatusCode.BadRequest, "Missing id")
+            val deleted = userService.delete(id)
+            if (deleted) call.respond(HttpStatusCode.NoContent)
+            else call.respond(HttpStatusCode.NotFound)
+        }
+    }
+}
+```
+
+### Route Organization with Authenticated Routes
+
+```kotlin
+fun Route.userRoutes() {
+    route("/users") {
+        // Public routes
+        get { /* list users */ }
+        get("/{id}") { /* get user */ }
+
+        // Protected routes
+        authenticate("jwt") {
+            post { /* create user - requires auth */ }
+            put("/{id}") { /* update user - requires auth */ }
+            delete("/{id}") { /* delete user - requires auth */ }
+        }
+    }
+}
+```
+
+## Content Negotiation & Serialization
+
+### kotlinx.serialization Setup
+
+```kotlin
+// plugins/Serialization.kt
+fun Application.configureSerialization() {
+    install(ContentNegotiation) {
+        json(Json {
+            prettyPrint = true
+            isLenient = false
+            ignoreUnknownKeys = true
+            encodeDefaults = true
+            explicitNulls = false
+        })
+    }
+}
+```
+
+### Serializable Models
+
+```kotlin
+@Serializable
+data class UserResponse(
+    val id: String,
+    val name: String,
+    val email: String,
+    val role: Role,
+    @Serializable(with = InstantSerializer::class)
+    val createdAt: Instant,
+)
+
+@Serializable
+data class CreateUserRequest(
+    val name: String,
+    val email: String,
+    val role: Role = Role.USER,
+)
+
+@Serializable
+data class ApiResponse<T>(
+    val success: Boolean,
+    val data: T? = null,
+    val error: String? = null,
+) {
+    companion object {
+        fun <T> ok(data: T): ApiResponse<T> = ApiResponse(success = true, data = data)
+        fun <T> error(message: String): ApiResponse<T> = ApiResponse(success = false, error = message)
+    }
+}
+
+@Serializable
+data class PaginatedResponse<T>(
+    val data: List<T>,
+    val total: Long,
+    val page: Int,
+    val limit: Int,
+)
+```
+
+### Custom Serializers
+
+```kotlin
+object InstantSerializer : KSerializer<Instant> {
+    override val descriptor = PrimitiveSerialDescriptor("Instant", PrimitiveKind.STRING)
+    override fun serialize(encoder: Encoder, value: Instant) =
+        encoder.encodeString(value.toString())
+    override fun deserialize(decoder: Decoder): Instant =
+        Instant.parse(decoder.decodeString())
+}
+```
+
+## Authentication
+
+### JWT Authentication
+
+```kotlin
+// plugins/Authentication.kt
+fun Application.configureAuthentication() {
+    val jwtSecret = environment.config.property("jwt.secret").getString()
+    val jwtIssuer = environment.config.property("jwt.issuer").getString()
+    val jwtAudience = environment.config.property("jwt.audience").getString()
+    val jwtRealm = environment.config.property("jwt.realm").getString()
+
+    install(Authentication) {
+        jwt("jwt") {
+            realm = jwtRealm
+            verifier(
+                JWT.require(Algorithm.HMAC256(jwtSecret))
+                    .withAudience(jwtAudience)
+                    .withIssuer(jwtIssuer)
+                    .build()
+            )
+            validate { credential ->
+                if (credential.payload.audience.contains(jwtAudience)) {
+                    JWTPrincipal(credential.payload)
+                } else {
+                    null
+                }
+            }
+            challenge { _, _ ->
+                call.respond(HttpStatusCode.Unauthorized, ApiResponse.error<Unit>("Invalid or expired token"))
+            }
+        }
+    }
+}
+
+// Extracting user from JWT
+fun ApplicationCall.userId(): String =
+    principal<JWTPrincipal>()
+        ?.payload
+        ?.getClaim("userId")
+        ?.asString()
+        ?: throw AuthenticationException("No userId in token")
+```
+
+### Auth Routes
+
+```kotlin
+fun Route.authRoutes() {
+    val authService by inject<AuthService>()
+
+    route("/auth") {
+        post("/login") {
+            val request = call.receive<LoginRequest>()
+            val token = authService.login(request.email, request.password)
+                ?: return@post call.respond(
+                    HttpStatusCode.Unauthorized,
+                    ApiResponse.error<Unit>("Invalid credentials"),
+                )
+            call.respond(ApiResponse.ok(TokenResponse(token)))
+        }
+
+        post("/register") {
+            val request = call.receive<RegisterRequest>()
+            val user = authService.register(request)
+            call.respond(HttpStatusCode.Created, ApiResponse.ok(user))
+        }
+
+        authenticate("jwt") {
+            get("/me") {
+                val userId = call.userId()
+                val user = authService.getProfile(userId)
+                call.respond(ApiResponse.ok(user))
+            }
+        }
+    }
+}
+```
+
+## Status Pages (Error Handling)
+
+```kotlin
+// plugins/StatusPages.kt
+fun Application.configureStatusPages() {
+    install(StatusPages) {
+        exception<ContentTransformationException> { call, cause ->
+            call.respond(
+                HttpStatusCode.BadRequest,
+                ApiResponse.error<Unit>("Invalid request body: ${cause.message}"),
+            )
+        }
+
+        exception<IllegalArgumentException> { call, cause ->
+            call.respond(
+                HttpStatusCode.BadRequest,
+                ApiResponse.error<Unit>(cause.message ?: "Bad request"),
+            )
+        }
+
+        exception<AuthenticationException> { call, _ ->
+            call.respond(
+                HttpStatusCode.Unauthorized,
+                ApiResponse.error<Unit>("Authentication required"),
+            )
+        }
+
+        exception<AuthorizationException> { call, _ ->
+            call.respond(
+                HttpStatusCode.Forbidden,
+                ApiResponse.error<Unit>("Access denied"),
+            )
+        }
+
+        exception<NotFoundException> { call, cause ->
+            call.respond(
+                HttpStatusCode.NotFound,
+                ApiResponse.error<Unit>(cause.message ?: "Resource not found"),
+            )
+        }
+
+        exception<Throwable> { call, cause ->
+            call.application.log.error("Unhandled exception", cause)
+            call.respond(
+                HttpStatusCode.InternalServerError,
+                ApiResponse.error<Unit>("Internal server error"),
+            )
+        }
+
+        status(HttpStatusCode.NotFound) { call, status ->
+            call.respond(status, ApiResponse.error<Unit>("Route not found"))
+        }
+    }
+}
+```
+
+## CORS Configuration
+
+```kotlin
+// plugins/CORS.kt
+fun Application.configureCORS() {
+    install(CORS) {
+        allowHost("localhost:3000")
+        allowHost("example.com", schemes = listOf("https"))
+        allowHeader(HttpHeaders.ContentType)
+        allowHeader(HttpHeaders.Authorization)
+        allowMethod(HttpMethod.Put)
+        allowMethod(HttpMethod.Delete)
+        allowMethod(HttpMethod.Patch)
+        allowCredentials = true
+        maxAgeInSeconds = 3600
+    }
+}
+```
+
+## Koin Dependency Injection
+
+### Module Definition
+
+```kotlin
+// di/AppModule.kt
+val appModule = module {
+    // Database
+    single<Database> { DatabaseFactory.create(get()) }
+
+    // Repositories
+    single<UserRepository> { ExposedUserRepository(get()) }
+    single<OrderRepository> { ExposedOrderRepository(get()) }
+
+    // Services
+    single { UserService(get()) }
+    single { OrderService(get(), get()) }
+    single { AuthService(get(), get()) }
+}
+
+// Application setup
+fun Application.configureDI() {
+    install(Koin) {
+        modules(appModule)
+    }
+}
+```
+
+### Using Koin in Routes
+
+```kotlin
+fun Route.userRoutes() {
+    val userService by inject<UserService>()
+
+    route("/users") {
+        get {
+            val users = userService.getAll()
+            call.respond(ApiResponse.ok(users))
+        }
+    }
+}
+```
+
+### Koin for Testing
+
+```kotlin
+class UserServiceTest : FunSpec(), KoinTest {
+    override fun extensions() = listOf(KoinExtension(testModule))
+
+    private val testModule = module {
+        single<UserRepository> { mockk() }
+        single { UserService(get()) }
+    }
+
+    private val repository by inject<UserRepository>()
+    private val service by inject<UserService>()
+
+    init {
+        test("getUser returns user") {
+            coEvery { repository.findById("1") } returns testUser
+            service.getById("1") shouldBe testUser
+        }
+    }
+}
+```
+
+## Request Validation
+
+```kotlin
+// Validate request data in routes
+fun Route.userRoutes() {
+    val userService by inject<UserService>()
+
+    post("/users") {
+        val request = call.receive<CreateUserRequest>()
+
+        // Validate
+        require(request.name.isNotBlank()) { "Name is required" }
+        require(request.name.length <= 100) { "Name must be 100 characters or less" }
+        require(request.email.matches(Regex(".+@.+\\..+"))) { "Invalid email format" }
+
+        val user = userService.create(request)
+        call.respond(HttpStatusCode.Created, ApiResponse.ok(user))
+    }
+}
+
+// Or use a validation extension
+fun CreateUserRequest.validate() {
+    require(name.isNotBlank()) { "Name is required" }
+    require(name.length <= 100) { "Name must be 100 characters or less" }
+    require(email.matches(Regex(".+@.+\\..+"))) { "Invalid email format" }
+}
+```
+
+## WebSockets
+
+```kotlin
+fun Application.configureWebSockets() {
+    install(WebSockets) {
+        pingPeriod = 15.seconds
+        timeout = 15.seconds
+        maxFrameSize = 64 * 1024 // 64 KiB — increase only if your protocol requires larger frames
+        masking = false // Server-to-client frames are unmasked per RFC 6455; client-to-server are always masked by Ktor
+    }
+}
+
+fun Route.chatRoutes() {
+    val connections = Collections.synchronizedSet<Connection>(LinkedHashSet())
+
+    webSocket("/chat") {
+        val thisConnection = Connection(this)
+        connections += thisConnection
+
+        try {
+            send("Connected! Users online: ${connections.size}")
+
+            for (frame in incoming) {
+                frame as? Frame.Text ?: continue
+                val text = frame.readText()
+                val message = ChatMessage(thisConnection.name, text)
+
+                // Snapshot under lock to avoid ConcurrentModificationException
+                val snapshot = synchronized(connections) { connections.toList() }
+                snapshot.forEach { conn ->
+                    conn.session.send(Json.encodeToString(message))
+                }
+            }
+        } catch (e: Exception) {
+            logger.error("WebSocket error", e)
+        } finally {
+            connections -= thisConnection
+        }
+    }
+}
+
+data class Connection(val session: DefaultWebSocketSession) {
+    val name: String = "User-${counter.getAndIncrement()}"
+
+    companion object {
+        private val counter = AtomicInteger(0)
+    }
+}
+```
+
+## testApplication Testing
+
+### Basic Route Testing
+
+```kotlin
+class UserRoutesTest : FunSpec({
+    test("GET /users returns list of users") {
+        testApplication {
+            application {
+                install(Koin) { modules(testModule) }
+                configureSerialization()
+                configureRouting()
+            }
+
+            val response = client.get("/users")
+
+            response.status shouldBe HttpStatusCode.OK
+            val body = response.body<ApiResponse<List<UserResponse>>>()
+            body.success shouldBe true
+            body.data.shouldNotBeNull().shouldNotBeEmpty()
+        }
+    }
+
+    test("POST /users creates a user") {
+        testApplication {
+            application {
+                install(Koin) { modules(testModule) }
+                configureSerialization()
+                configureStatusPages()
+                configureRouting()
+            }
+
+            val client = createClient {
+                install(io.ktor.client.plugins.contentnegotiation.ContentNegotiation) {
+                    json()
+                }
+            }
+
+            val response = client.post("/users") {
+                contentType(ContentType.Application.Json)
+                setBody(CreateUserRequest("Alice", "alice@example.com"))
+            }
+
+            response.status shouldBe HttpStatusCode.Created
+        }
+    }
+
+    test("GET /users/{id} returns 404 for unknown id") {
+        testApplication {
+            application {
+                install(Koin) { modules(testModule) }
+                configureSerialization()
+                configureStatusPages()
+                configureRouting()
+            }
+
+            val response = client.get("/users/unknown-id")
+
+            response.status shouldBe HttpStatusCode.NotFound
+        }
+    }
+})
+```
+
+### Testing Authenticated Routes
+
+```kotlin
+class AuthenticatedRoutesTest : FunSpec({
+    test("protected route requires JWT") {
+        testApplication {
+            application {
+                install(Koin) { modules(testModule) }
+                configureSerialization()
+                configureAuthentication()
+                configureRouting()
+            }
+
+            val response = client.post("/users") {
+                contentType(ContentType.Application.Json)
+                setBody(CreateUserRequest("Alice", "alice@example.com"))
+            }
+
+            response.status shouldBe HttpStatusCode.Unauthorized
+        }
+    }
+
+    test("protected route succeeds with valid JWT") {
+        testApplication {
+            application {
+                install(Koin) { modules(testModule) }
+                configureSerialization()
+                configureAuthentication()
+                configureRouting()
+            }
+
+            val token = generateTestJWT(userId = "test-user")
+
+            val client = createClient {
+                install(io.ktor.client.plugins.contentnegotiation.ContentNegotiation) { json() }
+            }
+
+            val response = client.post("/users") {
+                contentType(ContentType.Application.Json)
+                bearerAuth(token)
+                setBody(CreateUserRequest("Alice", "alice@example.com"))
+            }
+
+            response.status shouldBe HttpStatusCode.Created
+        }
+    }
+})
+```
+
+## Configuration
+
+### application.yaml
+
+```yaml
+ktor:
+  application:
+    modules:
+      - com.example.ApplicationKt.module
+  deployment:
+    port: 8080
+
+jwt:
+  secret: ${JWT_SECRET}
+  issuer: "https://example.com"
+  audience: "https://example.com/api"
+  realm: "example"
+
+database:
+  url: ${DATABASE_URL}
+  driver: "org.postgresql.Driver"
+  maxPoolSize: 10
+```
+
+### Reading Config
+
+```kotlin
+fun Application.configureDI() {
+    val dbUrl = environment.config.property("database.url").getString()
+    val dbDriver = environment.config.property("database.driver").getString()
+    val maxPoolSize = environment.config.property("database.maxPoolSize").getString().toInt()
+
+    install(Koin) {
+        modules(module {
+            single { DatabaseConfig(dbUrl, dbDriver, maxPoolSize) }
+            single { DatabaseFactory.create(get()) }
+        })
+    }
+}
+```
+
+## Quick Reference: Ktor Patterns
+
+| Pattern | Description |
+|---------|-------------|
+| `route("/path") { get { } }` | Route grouping with DSL |
+| `call.receive<T>()` | Deserialize request body |
+| `call.respond(status, body)` | Send response with status |
+| `call.parameters["id"]` | Read path parameters |
+| `call.request.queryParameters["q"]` | Read query parameters |
+| `install(Plugin) { }` | Install and configure plugin |
+| `authenticate("name") { }` | Protect routes with auth |
+| `by inject<T>()` | Koin dependency injection |
+| `testApplication { }` | Integration testing |
+
+**Remember**: Ktor is designed around Kotlin coroutines and DSLs. Keep routes thin, push logic to services, and use Koin for dependency injection. Test with `testApplication` for full integration coverage.