Workshop: Creating DSLs in Kotlin by Hadi Hariri

sampleServerDSL.kt

@DslMarker
annotation class CloudProviderDSL

data class Configuration(
        val provider: String,
        val region: String,
        val isActive: Boolean,
        val fallback: Int,
        val servers: List<Server>
)

data class Server(
        val hostname: String,
        val name: String,
        val description: String
)

@CloudProviderDSL
class ConfigurationBuilder {
    var provider: String = ""
    var region: String = ""
    var isActive: Boolean = false
    var fallback: Int = 0
    private var servers = mutableListOf<Server>()

    fun servers(block: SERVERS.() -> Unit) {
        servers.addAll(SERVERS().apply(block))
    }

    fun build(): Configuration =
            Configuration(provider, region, isActive, fallback, servers)

}

@CloudProviderDSL
class SERVERS : ArrayList<Server>() {
    fun server(block: ServerBuilder.() -> Unit) {
        add(ServerBuilder().apply(block).build())
    }
}

@CloudProviderDSL
class ServerBuilder {
    fun build(): Server = Server(hostname, name, description)

    var hostname: String = ""
    var name: String = ""
    var description: String = ""
}

fun configuration(block: ConfigurationBuilder.() -> Unit) = ConfigurationBuilder().apply(block).build()

fun main() {
    val config = configuration {
        provider = "Google"
        region = "eu-west-1"
        isActive = true
        fallback = 10
        servers {
            server {
                hostname = ""
                name = "persistence 1"
                description = "Provides persistence mechanism"
            }
            
            server {

            }
        }
    }
}