Connection.kt

interface Buffer {
    fun clear(): Buffer

    fun flip(): Buffer

    fun index(): Long

    //Read a number of bits(or 8) from a value as a Number at the current index.
    fun <Type : Number> next(bits: Number = 8): Type

    //Write a number of bits(or 8) from a value into the buffer at the current index.
    fun next(value: Long, bits: Number = 8): Buffer
}

class Address(val hostname: String, val port: Short)

//Basic send and receive, semi compatible with any protocol.
expect class Socket(local: Address) {
    suspend fun receive(packet: Buffer): Address

    suspend fun send(packet: Buffer, to: Address)

    fun isOpen(): Boolean
}

class TestSocket(private val input: Buffer,
                 private val output: Buffer,
                 local: Address) {

    private val socket = Socket(local)
    private val outputLock = Mutex()
    private val inputLock = Mutex()

    fun receive(receiver: Buffer.(Address) -> Unit) = launch {
        inputLock.withLock {
            val address = socket.receive(input.clear())
            receiver(input.flip(), address)
        }
    }

    //Receive a packet from an address.
    fun receive(from: Address, receiver: Buffer.() -> Unit) = launch {
        //FIXME obviously restructure this class to handle explicit receives.
        //As well as full implementation of coroutines.
    }

    //Send a packet to an address.
    fun send(to: Address, sender: Buffer.() -> Unit) = launch {
        outputLock.withLock {
            val address = sender(output.clear())
            socket.send(output.flip(), to)
        }
    }

    //Receive a packet from an address, then send a result to the same address.
    fun respond(from: Address, request: Buffer.() -> Buffer.() -> Unit) {
        receive(from) {
            send(from, request(this))
        }
    }

    //Send a packet to an address, then receive a packet from the same address.
    fun request(to: Address, request: Buffer.() -> Buffer.() -> Unit) {
        send(to) {
            receive(to, request(this))
        }
    }
}