Ktor Server Core JVM

import io.ktor.server.application.*
import io.ktor.server.routing.*
import io.ktor.server.request.*
import io.ktor.server.response.*
import io.ktor.server.plugins.*
import io.ktor.server.engine.*

import io.ktor.server.application.*
import io.ktor.server.response.*
import io.ktor.server.routing.*

fun Application.module() {
    routing {
        get("/") {
            call.respondText("Hello, World!")
        }
        
        post("/api/users") {
            val user = call.receive<User>()
            // Process user
            call.respond(HttpStatusCode.Created, user)
        }
    }
}

abstract class Application {
    abstract val environment: ApplicationEnvironment
    abstract val attributes: Attributes
    abstract val monitor: Events
    
    fun plugin(plugin: Plugin<*, *, *>): PluginInstance
}

interface ApplicationEnvironment {
    val config: ApplicationConfig
    val log: Logger
    val monitor: Events
    val developmentMode: Boolean
    val rootPath: String
    val classLoader: ClassLoader
}

suspend fun ApplicationCall.application(): Application

interface ApplicationRequest {
    val call: ApplicationCall
    val pipeline: ApplicationReceivePipeline
    val queryParameters: Parameters
    val headers: Headers
    val local: RequestConnectionPoint
    val cookies: RequestCookies
    val httpMethod: HttpMethod
    val uri: String
}

suspend inline fun <reified T : Any> ApplicationCall.receive(): T
suspend inline fun <reified T : Any> ApplicationCall.receiveNullable(): T?
suspend fun ApplicationCall.receiveText(): String
suspend fun ApplicationCall.receiveParameters(): Parameters

interface ApplicationResponse {
    val call: ApplicationCall
    val pipeline: ApplicationSendPipeline
    val status: HttpStatusCode?
    val headers: ResponseHeaders
    val cookies: ResponseCookies
    val isCommitted: Boolean
    val isSent: Boolean
    
    fun status(value: HttpStatusCode)
}

suspend fun ApplicationCall.respond(message: Any)
suspend fun ApplicationCall.respond(status: HttpStatusCode, message: Any = "")
suspend fun ApplicationCall.respondText(text: String, contentType: ContentType? = null, status: HttpStatusCode? = null)
suspend fun ApplicationCall.respondBytes(bytes: ByteArray, contentType: ContentType? = null, status: HttpStatusCode? = null)
suspend fun ApplicationCall.respondRedirect(url: String, permanent: Boolean = false)

class Route(
    val parent: Route?,
    val selector: RouteSelector,
    val developmentMode: Boolean = false,
    val environment: ApplicationEnvironment
) : ApplicationCallPipeline()

fun Route.get(path: String = "", body: PipelineInterceptor<Unit, ApplicationCall>): Route
fun Route.post(path: String = "", body: PipelineInterceptor<Unit, ApplicationCall>): Route
fun Route.put(path: String = "", body: PipelineInterceptor<Unit, ApplicationCall>): Route
fun Route.delete(path: String = "", body: PipelineInterceptor<Unit, ApplicationCall>): Route
fun Route.patch(path: String = "", body: PipelineInterceptor<Unit, ApplicationCall>): Route
fun Route.head(path: String = "", body: PipelineInterceptor<Unit, ApplicationCall>): Route
fun Route.options(path: String = "", body: PipelineInterceptor<Unit, ApplicationCall>): Route

fun Route.route(path: String, build: Route.() -> Unit): Route
fun Application.routing(configuration: Routing.() -> Unit): Routing

interface ApplicationPlugin<out TConfiguration : Any> {
    val key: AttributeKey<*>
    fun install(pipeline: ApplicationCallPipeline, configure: TConfiguration.() -> Unit): Any
}

interface RouteScopedPlugin<TConfiguration : Any, TPlugin : Any> {
    val key: AttributeKey<TPlugin>
    fun install(pipeline: ApplicationCallPipeline, configure: TConfiguration.() -> Unit): TPlugin
}

fun <P : Any, B : Any, F : Any> createApplicationPlugin(
    name: String,
    createConfiguration: () -> B,
    body: PluginBuilder<P>.() -> Unit
): ApplicationPlugin<B, P, F>

fun <TConfiguration : Any> Application.install(
    plugin: ApplicationPlugin<TConfiguration, *, *>,
    configure: TConfiguration.() -> Unit = {}
)

interface ApplicationConfig {
    fun property(path: String): ApplicationConfigValue
    fun propertyOrNull(path: String): ApplicationConfigValue?
    fun config(path: String): ApplicationConfig
    fun configList(path: String): List<ApplicationConfig>
    fun keys(): Set<String>
    fun toMap(): Map<String, Any?>
}

interface ApplicationConfigValue {
    fun getString(): String
    fun getList(): List<String>
}

class MapApplicationConfig : ApplicationConfig
class MergedApplicationConfig(vararg sources: ApplicationConfig) : ApplicationConfig

interface ApplicationEngine {
    val environment: ApplicationEngineEnvironment
    fun start(wait: Boolean = true): ApplicationEngine
    fun stop(gracePeriodMillis: Long, timeoutMillis: Long)
}

interface ApplicationEngineEnvironment {
    val application: Application
    val log: Logger
    val config: ApplicationConfig
    val monitor: Events
    val developmentMode: Boolean
    val connectors: List<EngineConnectorConfig>
    val modules: List<Application.() -> Unit>
}

abstract class BaseApplicationEngine(
    final override val environment: ApplicationEngineEnvironment,
    val pipeline: EnginePipeline = defaultEnginePipeline(environment)
) : ApplicationEngine

interface ApplicationCall {
    val application: Application
    val request: ApplicationRequest
    val response: ApplicationResponse
    val parameters: Parameters
    val attributes: Attributes
}

interface PipelineInterceptor<TSubject : Any, TContext : Any> : 
    suspend PipelineContext<TSubject, TContext>.(TSubject) -> Unit

interface Parameters {
    operator fun get(name: String): String?
    fun getAll(name: String): List<String>?
    fun names(): Set<String>
    fun isEmpty(): Boolean
    fun contains(name: String): Boolean
    fun contains(name: String, value: String): Boolean
    fun forEach(body: (String, List<String>) -> Unit)
}

enum class HttpStatusCode(val value: Int, val description: String) {
    OK(200, "OK"),
    Created(201, "Created"),
    NotFound(404, "Not Found"),
    InternalServerError(500, "Internal Server Error")
    // ... more status codes
}

interface Attributes {
    operator fun <T : Any> get(key: AttributeKey<T>): T
    operator fun <T : Any> set(key: AttributeKey<T>, value: T)
    fun <T : Any> getOrNull(key: AttributeKey<T>): T?
    operator fun <T : Any> contains(key: AttributeKey<T>): Boolean
    fun <T : Any> remove(key: AttributeKey<T>)
    fun <T : Any> put(key: AttributeKey<T>, value: T): T?
}

data class AttributeKey<T>(val name: String)

interface Events {  
    fun <T> subscribe(definition: EventDefinition<T>, handler: (T) -> Unit)
    fun <T> unsubscribe(definition: EventDefinition<T>, handler: (T) -> Unit)
    fun <T> raise(definition: EventDefinition<T>, value: T)
}

data class EventDefinition<T>(val name: String)