A 0 dependency replacement for Hoverfly, WireMock and MockServer. Simple stupid and extendable

MockHttpServer.kt

package net.arhipov

import com.sun.net.httpserver.Headers
import com.sun.net.httpserver.HttpServer
import java.net.InetSocketAddress
import java.net.URI
import java.util.Collections.synchronizedList

class MockHttpServer(
    port: Int = 0
) : AutoCloseable {
    data class Capture(
        val request: Request,
        val response: Response
    )

    class Request(
        val uri: URI,
        val method: String,
        val body: ByteArray,
        val headers: Headers
    )

    class Response(
        val body: ByteArray,
        val status: Int,
        val headers: Headers
    )

    private val httpServer: HttpServer = HttpServer.create(InetSocketAddress(port), 0)
        .apply {
            start()
            createContext("/") { ctx ->
                val request = Request(
                    uri = ctx.requestURI,
                    method = ctx.requestMethod,
                    body = ctx.requestBody.readAllBytes(),
                    headers = ctx.requestHeaders
                )
                val response = matchers
                    .asSequence()
                    .map { it(request) }
                    .firstOrNull { it != null }
                    ?: Response("".toByteArray(), 500, Headers())

                captures.add(response)


                ctx.responseHeaders.putAll(response.headers)
                ctx.sendResponseHeaders(response.status, response.body.size.toLong())
                ctx.responseBody.write(response.body)
            }
        }

    val captures: MutableList<Response> = synchronizedList(mutableListOf())
    val matchers: MutableList<(request: Request) -> Response?> = synchronizedList(mutableListOf())

    val port: Int get() = httpServer.address.port

    fun reset() {
        captures.clear()
        matchers.clear()
    }

    override fun close() {
        httpServer.stop(0)
    }
}

fun MockHttpServer.addHandler(
    matcher: (request: MockHttpServer.Request) -> Boolean,
    responseWriter: (request: MockHttpServer.Request) -> MockHttpServer.Response
) {
    matchers.add {
        if (matcher(it)) responseWriter(it)
        else null
    }
}