# Connection to a remote server
class RemoteServer

	# `RemoteServerConfig` used to initiate connection to the server
	var config: RemoteServerConfig

	# Communication socket with the server
	var socket: nullable TCPStream = null

	# Is this connection connected?
	fun connected: Bool
	do
		var socket = socket
		return socket != null and socket.connected
	end

	# `MsgPackSerializer` used to send data to this client through `socket`
	var writer: MsgPackSerializer is noinit

	# `MsgPackDeserializer` used to receive data from this client through `socket`
	var reader: MsgPackDeserializer is noinit

	# Attempt connection with the remote server
	fun connect: Bool
	do
		print "Connecting to {config.address}:{config.port}..."
		var socket = new TCPStream.connect(config.address.to_s, config.port)
		self.socket = socket

		if not socket.connected then
			print "Connection failed: {socket.last_error or else "Internal error"}"
			return false
		end

		# Setup serialization
		writer = new MsgPackSerializer(socket)
		writer.cache = new AsyncCache(false)
		reader = new MsgPackDeserializer(socket)
		writer.link reader

		return true
	end

	# Attempt handshake with server
	#
	# Validates compatibility between `handshake_app_name` and `handshake_app_version`.
	#
	# On error, close `socket`.
	fun handshake: Bool
	do
		# The client goes first so that the server doesn't show its hand
		var socket = socket
		assert socket != null

		# App name
		var app_name = sys.handshake_app_name
		socket.serialize_msgpack app_name

		var server_app = socket.deserialize_msgpack("String")
		if server_app != app_name then
			print_error "Handshake Error: server app name is '{server_app or else "<invalid>"}'"
			socket.close
			return false
		end

		# App version
		socket.serialize_msgpack sys.handshake_app_version

		var server_version = socket.deserialize_msgpack("String")
		if server_version != sys.handshake_app_version then
			print_error "Handshake Error: server version is different '{server_version or else "<invalid>"}'"
			socket.close
			return false
		end

		return true
	end
end