Turns a Retrofit service interface into Ktor routing. Very early stage prototype.

You use Retrofit on the client side to access the end points of your server, why not use that same interface to define the routings? The idea is to use an implementation of the interface and add it to Ktor routing which will dynamically construct sub-routings from the annotations and call the implementation when the end point is accessed.

Example

interface Service {
  @GET("string")
  suspend fun getAll(): List<String>

  @GET("string/{id}")
  suspend fun getSingle(@Path("id") id: Long): String
}

fun Application.module() {
  install(ContentNegotiation) {
    jackson { }
  }

  val service = object : Service {
    override suspend fun getAll(): List<String> {
      return listOf("first", "second")
    }

    override suspend fun getSingle(id: Long): String {
      return when (id) {
        0L -> "first"
        1L -> "second"
        else -> throw IndexOutOfBoundsException("id=$id")
      }
    }
  }

  routing { 
    route("api") {
      retrofitService(service = service)
    }
  }
}