Add validation for server opening handshake response in Ember WebSocket client

[danghieutrung]

This is part of the Ember WebSocket client implementation. This validates the opening handshake response from the server.
http://rfc-editor.org/rfc/rfc6455#page-6

[armanbilge]

Thanks! I retargeted to a new ember-wsclient branch. You can continue making small PRs to that branch and when it's ready we can merge into into series/0.23.

[armanbilge]

This looks great! Can we add a WebSocketHelpersSuite that validates a successful response, and also one response for each of the different failure kinds?

[armanbilge]

I think this all looks great! Just a couple optimization ideas.

[armanbilge]

Adding final makes it a constant that will be inlined, because the right-hand-side is known at compile-time.

Suggested change

	private[internal] val supportedWebSocketVersion = 13L
	private[internal] final val supportedWebSocketVersion = 13L

[armanbilge]

This way each check evaluates lazily and will short-circuit immediately if there is an error.

Suggested change

	private def serverHandshake[F[_]](res: Response[F]): Either[ServerHandshakeError, ByteVector] = {
	val status = res.status match {
	case Status.SwitchingProtocols => Either.unit
	case _ => Left(InvalidStatus)
	}
	val connection = res.headers.get[Connection] match {
	case Some(header) if header.hasUpgrade => Either.unit
	case _ => Left(UpgradeRequired)
	}
	val upgrade = res.headers.get[Upgrade] match {
	case Some(header) if header.values.contains_(webSocketProtocol) => Either.unit
	case _ => Left(UpgradeRequired)
	}
	val secWebSocketAcceptKey = res.headers.get[`Sec-WebSocket-Accept`] match {
	case Some(header) => Right(header.hashedKey)
	case None => Left(SecWebSocketAcceptNotFound)
	}
	(status, connection, upgrade, secWebSocketAcceptKey).mapN {
	case (_, _, _, secWebSocketAcceptKey) =>
	secWebSocketAcceptKey
	}
	private def serverHandshake[F[_]](res: Response[F]): Either[ServerHandshakeError, ByteVector] = {
	def status = res.status match {
	case Status.SwitchingProtocols => Either.unit
	case _ => Left(InvalidStatus)
	}
	def connection = res.headers.get[Connection] match {
	case Some(header) if header.hasUpgrade => Either.unit
	case _ => Left(UpgradeRequired)
	}
	def upgrade = res.headers.get[Upgrade] match {
	case Some(header) if header.values.contains_(webSocketProtocol) => Either.unit
	case _ => Left(UpgradeRequired)
	}
	def secWebSocketAcceptKey = res.headers.get[`Sec-WebSocket-Accept`] match {
	case Some(header) => Right(header.hashedKey)
	case None => Left(SecWebSocketAcceptNotFound)
	}
	status >> connection >> upgrade >> secWebSocketAcceptKey

[ChristopherDavenport]

This is fantastic! Glad to see the effort you are putting in!

[armanbilge]

I'll merge, we can do optimizations later 😁 correctness first!