/*

    Copyright (C) 2018 Apple Inc. All Rights Reserved.

    See LICENSE.txt for this sample’s licensing information

    Abstract:

    Binds a conversation view controller to its transport.

 */

import UIKit

/// Binds a conversation view controller to its transport.  This is a controller

/// that the app delegate creates to move the details of running a conversation

/// off into a separate entity.  The app controller managers a single instance

/// of this but you could imagine a more complex app, where multiple

/// conversations can be on screen at a time, having multiple instances.

class ActiveConversation : ConversationViewController.Delegate {

    /// Creates the object with the specified view controller and transport.

    ///

    /// The created object becomes the delegate for the view controller.

    ///

    /// - Parameters:

    ///   - viewController: The view controller being displayed.

    ///   - transport: The transport which updates that controller.

    init(viewController: ConversationViewController, transport: ConversationTransport) {

        self.viewController = viewController

        self.transport = transport

        self.viewController.delegate = self

    }

    /// The value passed to the initialiser.

    let viewController: ConversationViewController

    /// The value passed to the initialiser.

    let transport: ConversationTransport

    typealias Delegate = ActiveConversationDelegate

    weak var delegate: Delegate? = nil

    /// The client calls this when everything is set up and it wants the object

    /// to start the transport and routing updates between it and the

    /// conversation view controller.

    func start() {

        self.viewController.conversation = self.transport.conversation

        NotificationCenter.default.addObserver(

            self,

            selector: #selector(conversationDidChange(note:)),

            name: ConversationTransport.conversationDidChange,

            object: self.transport

        )

        self.transport.start()

    }

    /// The client calls this when it wants the object to stop the transport and

    /// to stop routing updates between that and the conversation view

    /// controller.

    func stop() {

        NotificationCenter.default.removeObserver(self)

        self.transport.stop()

    }

    func send(message: String, conversationViewController: ConversationViewController) {

        self.transport.send(message: message)

    }

    func close(conversationViewController: ConversationViewController) {

        self.delegate?.close(activeConversation: self)

    }

    /// Updates the conversation view controller with the latest conversatino

    /// from the transport; call in response to the

    /// `ConversationTransport.conversationDidChange` notification.

    @objc

    private func conversationDidChange(note: Notification) {

        self.viewController.conversation = self.transport.conversation

    }

}

/// Delegate protocol for `ActiveConversation`.

protocol ActiveConversationDelegate : AnyObject {

    /// Called when the user indicates that they want to close the conversation.

    ///

    /// - Parameter activeConversation: The sender.

    func close(activeConversation: ActiveConversation)

}