TM-SGNL-iOS/SignalUI/ViewControllers/ModalActivityIndicatorViewController.swift

//
// Copyright 2017 Signal Messenger, LLC
// SPDX-License-Identifier: AGPL-3.0-only
//

import MediaPlayer
public import SignalServiceKit

// A modal view that be used during blocking interactions (e.g. waiting on response from
// service or on the completion of a long-running local operation).
public class ModalActivityIndicatorViewController: OWSViewController {
    public enum Constants {
        public static let defaultPresentationDelay: TimeInterval = 0.05
    }

    let canCancel: Bool

    private let isInvisible: Bool

    private let _wasCancelled = AtomicBool(false, lock: .sharedGlobal)
    public var wasCancelled: Bool {
        _wasCancelled.get()
    }
    public let wasCancelledPromise: Promise<Void>
    private let wasCancelledFuture: Future<Void>

    var activityIndicator: UIActivityIndicatorView?

    var presentTimer: Timer?

    var wasDimissed: Bool = false

    private let presentationDelay: TimeInterval

    // MARK: Initializers

    public init(canCancel: Bool, presentationDelay: TimeInterval, isInvisible: Bool = false) {
        self.canCancel = canCancel
        self.presentationDelay = presentationDelay
        self.isInvisible = isInvisible

        let (promise, future) = Promise<Void>.pending()
        self.wasCancelledPromise = promise
        self.wasCancelledFuture = future

        super.init()
    }

    public class func present(
        fromViewController: UIViewController,
        canCancel: Bool,
        presentationDelay: TimeInterval = Constants.defaultPresentationDelay,
        backgroundBlockQueueQos: DispatchQoS = .default,
        backgroundBlock: @escaping (ModalActivityIndicatorViewController) -> Void
    ) {
        present(
            fromViewController: fromViewController,
            canCancel: canCancel,
            presentationDelay: presentationDelay,
            isInvisible: false,
            backgroundBlockQueueQos: backgroundBlockQueueQos,
            backgroundBlock: backgroundBlock
        )
    }

    public class func presentAsInvisible(
        fromViewController: UIViewController,
        backgroundBlock: @escaping (ModalActivityIndicatorViewController) -> Void
    ) {
        present(
            fromViewController: fromViewController,
            canCancel: false,
            presentationDelay: Constants.defaultPresentationDelay,
            isInvisible: true,
            backgroundBlockQueueQos: .default,
            backgroundBlock: backgroundBlock
        )
    }

    private class func present(
        fromViewController: UIViewController,
        canCancel: Bool,
        presentationDelay: TimeInterval,
        isInvisible: Bool,
        backgroundBlockQueueQos: DispatchQoS,
        backgroundBlock: @escaping (ModalActivityIndicatorViewController) -> Void
    ) {
        AssertIsOnMainThread()

        let viewController = ModalActivityIndicatorViewController(
            canCancel: canCancel,
            presentationDelay: presentationDelay,
            isInvisible: isInvisible
        )
        // Present this modal _over_ the current view contents.
        viewController.modalPresentationStyle = .overFullScreen
        fromViewController.present(viewController, animated: false) {
            DispatchQueue.global(qos: backgroundBlockQueueQos.qosClass).async {
                backgroundBlock(viewController)
            }
        }
    }

    public class func present(
        fromViewController: UIViewController,
        canCancel: Bool = false,
        presentationDelay: TimeInterval = Constants.defaultPresentationDelay,
        isInvisible: Bool = false,
        asyncBlock: @escaping @MainActor (ModalActivityIndicatorViewController) async -> Void
    ) {
        AssertIsOnMainThread()

        let viewController = ModalActivityIndicatorViewController(
            canCancel: canCancel,
            presentationDelay: presentationDelay,
            isInvisible: isInvisible
        )
        // Present this modal _over_ the current view contents.
        viewController.modalPresentationStyle = .overFullScreen
        fromViewController.present(viewController, animated: false) {
            Task {
                await asyncBlock(viewController)
            }
        }
    }

    public func dismiss(completion completionParam: (() -> Void)? = nil) {
        AssertIsOnMainThread()

        let completion = {
            completionParam?()
            self.wasCancelledFuture.reject(OWSGenericError("ModalActivityIndicatorViewController was not cancelled."))
        }

        if !wasDimissed {
            // Only dismiss once.
            self.dismiss(animated: false, completion: completion)
            wasDimissed = true
        } else {
            // If already dismissed, wait a beat then call completion.
            DispatchQueue.main.async {
                completion()
            }
        }
    }

    /// A helper for a common dismissal pattern.
    ///
    /// This can be invoked on any queue, and it'll switch to the main queue if
    /// needed. The completion block will be invoked on the main queue.
    ///
    /// - Parameter completionIfNotCanceled:
    ///     If the modal hasn't been canceled, dismiss it and then call this
    ///     block. Note: If the modal was canceled, the block isn't invoked.
    public func dismissIfNotCanceled(completionIfNotCanceled: @escaping () -> Void = {}) {
        if wasCancelled {
            return
        }
        DispatchQueue.main.async {
            self.dismiss(completion: completionIfNotCanceled)
        }
    }

    public override func loadView() {
        super.loadView()

        if isInvisible {
            self.view.backgroundColor = .clear
            self.view.isOpaque = false
        } else {
            self.view.backgroundColor = (Theme.isDarkThemeEnabled
                                            ? UIColor(white: 0.35, alpha: 0.35)
                                            : UIColor(white: 0, alpha: 0.25))
            self.view.isOpaque = false

            let activityIndicator = UIActivityIndicatorView(style: .large)
            self.activityIndicator = activityIndicator
            self.view.addSubview(activityIndicator)
            activityIndicator.autoCenterInSuperview()

            if canCancel {
                let cancelButton = UIButton(type: .custom)
                cancelButton.setTitle(CommonStrings.cancelButton, for: .normal)
                cancelButton.setTitleColor(UIColor.white, for: .normal)
                cancelButton.backgroundColor = UIColor.ows_gray80
                let font = UIFont.dynamicTypeBody.semibold()
                cancelButton.titleLabel?.font = font
                cancelButton.layer.cornerRadius = .scaleFromIPhone5To7Plus(4, 5)
                cancelButton.clipsToBounds = true
                cancelButton.addTarget(self, action: #selector(cancelPressed), for: .touchUpInside)
                let buttonWidth = CGFloat.scaleFromIPhone5To7Plus(140, 160)
                let buttonHeight = OWSFlatButton.heightForFont(font)
                self.view.addSubview(cancelButton)
                cancelButton.autoHCenterInSuperview()
                cancelButton.autoPinEdge(toSuperviewEdge: .bottom, withInset: 50)
                cancelButton.autoSetDimension(.width, toSize: buttonWidth)
                cancelButton.autoSetDimension(.height, toSize: buttonHeight)
            }
        }

        guard presentationDelay > 0 else {
            return
        }

        // Hide the modal until the presentation animation completes.
        self.view.layer.opacity = 0.0
    }

    public override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)

        self.activityIndicator?.startAnimating()

        guard presentationDelay > 0 else {
            return
        }

        // Hide the modal and wait for a second before revealing it,
        // to avoid "blipping" in the modal during short blocking operations.
        //
        // NOTE: It will still intercept user interactions while hidden, as it
        //       should.
        self.presentTimer?.invalidate()
        self.presentTimer = Timer.scheduledTimer(withTimeInterval: presentationDelay, repeats: false) { [weak self] _ in
            self?.presentTimerFired()
        }
    }

    public override func viewWillDisappear(_ animated: Bool) {
        super.viewWillDisappear(animated)

        clearTimer()
    }

    public override func viewDidDisappear(_ animated: Bool) {
        super.viewDidDisappear(animated)

        self.activityIndicator?.stopAnimating()

        clearTimer()
    }

    private func clearTimer() {
        self.presentTimer?.invalidate()
        self.presentTimer = nil
    }

    private func presentTimerFired() {
        AssertIsOnMainThread()

        clearTimer()

        // Fade in the modal.
        UIView.animate(withDuration: 0.35) {
            self.view.layer.opacity = 1.0
        }
    }

    @objc
    private func cancelPressed() {
        AssertIsOnMainThread()

        _wasCancelled.set(true)

        self.wasCancelledFuture.resolve()

        dismiss()
    }
}