.swift

struct Session {
    let messageFeed = PassthroughSubject<Message, Never>()
    
    func send(_ message: Message) {
        DispatchQueue.main.asyncAfter(deadline: .now() + .milliseconds(100)) {
            self.messageFeed.send(message)
            self.simulateReceivingMessages()
        }
    }
    
    private func simulateReceivingMessages() {
        DispatchQueue.main.asyncAfter(deadline: .now() + .milliseconds(200)) {
            let receivedMessage = Message(sender: "Person B", text: UUID().uuidString)
            self.messageFeed.send(receivedMessage)
        }
    }
}