deltachat-ios/DcShare/Controller/SendingController.swift

import UIKit
import DcCore

protocol SendingControllerDelegate: class {
    func onSendingAttemptFinished()
}

class SendingController: UIViewController {

    private let dcMsgs: [DcMsg]
    private let chatId: Int
    private let dcContext: DcContext
    weak var delegate: SendingControllerDelegate?

    private var progressLabel: UILabel = {
        let view = UILabel()
        view.translatesAutoresizingMaskIntoConstraints = false
        /// TODO: translation!
        view.text = "Sending..."
        return view
    }()

    private var activityIndicator: UIActivityIndicatorView = {
        let view: UIActivityIndicatorView
        if #available(iOS 13, *) {
             view = UIActivityIndicatorView(style: .large)
        } else {
            view = UIActivityIndicatorView(style: .whiteLarge)
            view.color = UIColor.gray
        }
        view.startAnimating()
        view.translatesAutoresizingMaskIntoConstraints = false
        return view
    }()

    init(chatId: Int, dcMsgs: [DcMsg], dcContext: DcContext) {
        self.chatId = chatId
        self.dcMsgs = dcMsgs
        self.dcContext = dcContext
        super.init(nibName: nil, bundle: nil)
    }

    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }


    override func viewDidLoad() {
        view.backgroundColor = DcColors.defaultBackgroundColor
        setupViews()
        sendMessage()
    }

    private func setupViews() {
        view.addSubview(progressLabel)
        view.addSubview(activityIndicator)
        view.addConstraints([
            progressLabel.constraintCenterXTo(view),
            progressLabel.constraintAlignTopTo(view, paddingTop: 25),
            activityIndicator.constraintCenterXTo(view),
            activityIndicator.constraintCenterYTo(view)
        ])
        setupNavigationBar()
    }

    private func setupNavigationBar() {
        self.navigationItem.leftBarButtonItem = UIBarButtonItem()
        self.navigationItem.titleView = UIImageView(image: UIImage(named: "ic_chat")?.scaleDownImage(toMax: 26))
    }

    private func sendMessage() {
        DispatchQueue.global(qos: .utility).async {
            for message in self.dcMsgs {
                message.sendInChat(id: self.chatId)
            }
            self.dcContext.performSmtpJobs()
            self.delegate?.onSendingAttemptFinished()
        }
    }
}