session-ios/SignalMessaging/attachments/AttachmentApprovalViewController.swift

//
//  Copyright (c) 2018 Open Whisper Systems. All rights reserved.
//

import Foundation
import AVFoundation
import MediaPlayer

@objc
public protocol AttachmentApprovalViewControllerDelegate: class {
    func attachmentApproval(_ attachmentApproval: AttachmentApprovalViewController, didApproveAttachment attachment: SignalAttachment)
    func attachmentApproval(_ attachmentApproval: AttachmentApprovalViewController, didCancelAttachment attachment: SignalAttachment)
}

@objc
public class AttachmentApprovalViewController: OWSViewController, CaptioningToolbarDelegate, PlayerProgressBarDelegate, OWSVideoPlayerDelegate {

    let TAG = "[AttachmentApprovalViewController]"
    weak var delegate: AttachmentApprovalViewControllerDelegate?

    // We sometimes shrink the attachment view so that it remains somewhat visible
    // when the keyboard is presented.
    enum AttachmentViewScale {
        case fullsize, compact
    }

    // MARK: Properties

    let attachment: SignalAttachment
    private var videoPlayer: OWSVideoPlayer?

    private(set) var bottomToolbar: UIView!
    private(set) var mediaMessageView: MediaMessageView!
    private(set) var scrollView: UIScrollView!
    private(set) var contentContainer: UIView!
    private(set) var playVideoButton: UIView?

    // MARK: Initializers

    @available(*, unavailable, message:"use attachment: constructor instead.")
    required public init?(coder aDecoder: NSCoder) {
        fatalError("unimplemented")
    }

    @objc
    required public init(attachment: SignalAttachment, delegate: AttachmentApprovalViewControllerDelegate) {
        assert(!attachment.hasError)
        self.attachment = attachment
        self.delegate = delegate

        super.init(nibName: nil, bundle: nil)
    }

    // MARK: View Lifecycle

    override public func viewDidLoad() {
        super.viewDidLoad()
        self.navigationItem.title = dialogTitle()
    }

    override public func viewWillLayoutSubviews() {
        Logger.debug("\(logTag) in \(#function)")
        super.viewWillLayoutSubviews()

        // e.g. if flipping to/from landscape
        updateMinZoomScaleForSize(view.bounds.size)
    }

    private func dialogTitle() -> String {
        guard let filename = mediaMessageView.formattedFileName() else {
            return NSLocalizedString("ATTACHMENT_APPROVAL_DIALOG_TITLE",
                                     comment: "Title for the 'attachment approval' dialog.")
        }
        return filename
    }

    override public func viewWillAppear(_ animated: Bool) {
        Logger.debug("\(logTag) in \(#function)")
        super.viewWillAppear(animated)

        CurrentAppContext().setStatusBarHidden(true, animated: animated)
    }

    override public func viewDidAppear(_ animated: Bool) {
        Logger.debug("\(logTag) in \(#function)")
        super.viewDidAppear(animated)
    }

    override public func viewWillDisappear(_ animated: Bool) {
        Logger.debug("\(logTag) in \(#function)")
        super.viewWillDisappear(animated)

        // Since this VC is being dismissed, the "show status bar" animation would feel like
        // it's occuring on the presenting view controller - it's better not to animate at all.
        CurrentAppContext().setStatusBarHidden(false, animated: false)
    }

    // MARK: - Create Views

    public override func loadView() {

        self.view = UIView()

        self.mediaMessageView = MediaMessageView(attachment: attachment, mode: .attachmentApproval)

        // Anything that should be shrunk when user pops keyboard lives in the contentContainer.
        let contentContainer = UIView()
        self.contentContainer = contentContainer
        view.addSubview(contentContainer)
        contentContainer.autoPinEdgesToSuperviewEdges()

        // Scroll View - used to zoom/pan on images and video
        scrollView = UIScrollView()
        contentContainer.addSubview(scrollView)
        scrollView.delegate = self
        scrollView.showsHorizontalScrollIndicator = false
        scrollView.showsVerticalScrollIndicator = false

        // Panning should stop pretty soon after the user stops scrolling
        scrollView.decelerationRate = UIScrollViewDecelerationRateFast

        // We want scroll view content up and behind the system status bar content
        // but we want other content (e.g. bar buttons) to respect the top layout guide.
        self.automaticallyAdjustsScrollViewInsets = false

        scrollView.autoPinEdgesToSuperviewEdges()

        let backgroundColor = UIColor.black
        self.view.backgroundColor = backgroundColor

        // Create full screen container view so the scrollView
        // can compute an appropriate content size in which to center
        // our media view.
        let containerView = UIView.container()
        scrollView.addSubview(containerView)
        containerView.autoPinEdgesToSuperviewEdges()
        containerView.autoMatch(.height, to: .height, of: self.view)
        containerView.autoMatch(.width, to: .width, of: self.view)

        containerView.addSubview(mediaMessageView)
        mediaMessageView.autoPinEdgesToSuperviewEdges()

        if isZoomable {
            // Add top and bottom gradients to ensure toolbar controls are legible
            // when placed over image/video preview which may be a clashing color.
            let topGradient = GradientView(from: backgroundColor, to: UIColor.clear)
            self.view.addSubview(topGradient)
            topGradient.autoPinWidthToSuperview()
            topGradient.autoPinEdge(toSuperviewEdge: .top)
            topGradient.autoSetDimension(.height, toSize: ScaleFromIPhone5(60))
        }

        // Top Toolbar
        let topToolbar = makeClearToolbar()

        self.view.addSubview(topToolbar)
        topToolbar.autoPinWidthToSuperview()
        topToolbar.autoPin(toTopLayoutGuideOf: self, withInset: 0)
        topToolbar.setContentHuggingVerticalHigh()
        topToolbar.setCompressionResistanceVerticalHigh()

        let cancelButton = UIBarButtonItem(barButtonSystemItem: .stop, target: self, action: #selector(cancelPressed))
        cancelButton.tintColor = UIColor.white
        topToolbar.items = [cancelButton]

        // Bottom Toolbar
        let captioningToolbar = CaptioningToolbar()
        captioningToolbar.captioningToolbarDelegate = self
        self.bottomToolbar = captioningToolbar

        // Hide the play button embedded in the MediaView and replace it with our own.
        // This allows us to zoom in on the media view without zooming in on the button
        if attachment.isVideo {

            guard let videoURL = attachment.dataUrl else {
                owsFail("Missing videoURL")
                return
            }

            let player = OWSVideoPlayer(url: videoURL)
            self.videoPlayer = player
            player.delegate = self

            let playerView = VideoPlayerView()
            playerView.player = player.avPlayer
            self.mediaMessageView.addSubview(playerView)
            playerView.autoPinEdgesToSuperviewEdges()

            let pauseGesture = UITapGestureRecognizer(target: self, action: #selector(didTapPlayerView(_:)))
            playerView.addGestureRecognizer(pauseGesture)

            let progressBar = PlayerProgressBar()
            progressBar.player = player.avPlayer
            progressBar.delegate = self

            // we don't want the progress bar to zoom during "pinch-to-zoom"
            // but we do want it to shrink with the media content when the user
            // pops the keyboard.
            contentContainer.addSubview(progressBar)

            progressBar.autoPinEdge(.top, to: .bottom, of: topToolbar)
            progressBar.autoPinWidthToSuperview()
            progressBar.autoSetDimension(.height, toSize: 44)

            self.mediaMessageView.videoPlayButton?.isHidden = true
            let playButton = UIButton()
            self.playVideoButton = playButton
            playButton.accessibilityLabel = NSLocalizedString("PLAY_BUTTON_ACCESSABILITY_LABEL", comment: "Accessibility label for button to start media playback")
            playButton.setBackgroundImage(#imageLiteral(resourceName: "play_button"), for: .normal)
            playButton.contentMode = .scaleAspectFit

            let playButtonWidth = ScaleFromIPhone5(70)
            playButton.autoSetDimensions(to: CGSize(width: playButtonWidth, height: playButtonWidth))
            self.contentContainer.addSubview(playButton)

            playButton.addTarget(self, action: #selector(playButtonTapped), for: .touchUpInside)
            playButton.autoCenterInSuperview()
        }
    }

    public func didTapPlayerView(_ gestureRecognizer: UIGestureRecognizer) {
        assert(self.videoPlayer != nil)
        self.pauseVideo()
    }

    override public var inputAccessoryView: UIView? {
        self.bottomToolbar.layoutIfNeeded()
        return self.bottomToolbar
    }

    override public var canBecomeFirstResponder: Bool {
        return true
    }

    private func makeClearToolbar() -> UIToolbar {
        let toolbar = UIToolbar()

        toolbar.backgroundColor = UIColor.clear

        // Making a toolbar transparent requires setting an empty uiimage
        toolbar.setBackgroundImage(UIImage(), forToolbarPosition: .any, barMetrics: .default)

        // hide 1px top-border
        toolbar.clipsToBounds = true

        return toolbar
    }

    // MARK: - Event Handlers

    @objc
    public func playButtonTapped() {
        self.playVideo()
    }

    func cancelPressed(sender: UIButton) {
        self.delegate?.attachmentApproval(self, didCancelAttachment: attachment)
    }

    // MARK: CaptioningToolbarDelegate

    func captioningToolbarDidBeginEditing(_ captioningToolbar: CaptioningToolbar) {
        self.scaleAttachmentView(.compact)
    }

    func captioningToolbarDidEndEditing(_ captioningToolbar: CaptioningToolbar) {
        self.scaleAttachmentView(.fullsize)
    }

    func captioningToolbarDidTapSend(_ captioningToolbar: CaptioningToolbar, captionText: String?) {
        self.approveAttachment(captionText: captionText)
    }

    // MARK: Video

    private func playVideo() {
        Logger.info("\(TAG) in \(#function)")

        guard let videoPlayer = self.videoPlayer else {
            owsFail("\(TAG) video player was unexpectedly nil")
            return
        }

        guard let playVideoButton = self.playVideoButton else {
            owsFail("\(TAG) playVideoButton was unexpectedly nil")
            return
        }
        UIView.animate(withDuration: 0.1) {
            playVideoButton.alpha = 0.0
        }
        videoPlayer.play()
    }

    private func pauseVideo() {
        guard let videoPlayer = self.videoPlayer else {
            owsFail("\(TAG) video player was unexpectedly nil")
            return
        }

        videoPlayer.pause()
        guard let playVideoButton = self.playVideoButton else {
            owsFail("\(TAG) playVideoButton was unexpectedly nil")
            return
        }
        UIView.animate(withDuration: 0.1) {
            playVideoButton.alpha = 1.0
        }
    }

    @objc
    public func videoPlayerDidPlayToCompletion(_ videoPlayer: OWSVideoPlayer) {
        guard let playVideoButton = self.playVideoButton else {
            owsFail("\(TAG) playVideoButton was unexpectedly nil")
            return
        }

        UIView.animate(withDuration: 0.1) {
            playVideoButton.alpha = 1.0
        }
    }

    public func playerProgressBarDidStartScrubbing(_ playerProgressBar: PlayerProgressBar) {
        //  [self.videoPlayer pause];
        guard let videoPlayer = self.videoPlayer else {
            owsFail("\(TAG) video player was unexpectedly nil")
            return
        }
        videoPlayer.pause()
    }

    public func playerProgressBar(_ playerProgressBar: PlayerProgressBar, scrubbedToTime time: CMTime) {
        guard let videoPlayer = self.videoPlayer else {
            owsFail("\(TAG) video player was unexpectedly nil")
            return
        }

        videoPlayer.seek(to: time)
    }

    public func playerProgressBar(_ playerProgressBar: PlayerProgressBar, didFinishScrubbingAtTime time: CMTime, shouldResumePlayback: Bool) {
        guard let videoPlayer = self.videoPlayer else {
            owsFail("\(TAG) video player was unexpectedly nil")
            return
        }

        videoPlayer.seek(to: time)
        if (shouldResumePlayback) {
            videoPlayer.play()
        }
    }

    // MARK: Helpers

    var isZoomable: Bool {
        return attachment.isImage || attachment.isVideo
    }

    private func approveAttachment(captionText: String?) {
        // Toolbar flickers in and out if there are errors
        // and remains visible momentarily after share extension is dismissed.
        // It's easiest to just hide it at this point since we're done with it.
        shouldAllowAttachmentViewResizing = false
        bottomToolbar.isUserInteractionEnabled = false
        bottomToolbar.isHidden = true

        attachment.captionText = captionText
        delegate?.attachmentApproval(self, didApproveAttachment: attachment)
    }

    // When the keyboard is popped, it can obscure the attachment view.
    // so we sometimes allow resizing the attachment.
    private var shouldAllowAttachmentViewResizing: Bool = true

    private func scaleAttachmentView(_ fit: AttachmentViewScale) {
        guard shouldAllowAttachmentViewResizing else {
            if self.contentContainer.transform != CGAffineTransform.identity {
                UIView.animate(withDuration: 0.2) {
                    self.contentContainer.transform = CGAffineTransform.identity
                }
            }
            return
        }

        switch fit {
        case .fullsize:
            UIView.animate(withDuration: 0.2) {
                self.contentContainer.transform = CGAffineTransform.identity
            }
        case .compact:
            UIView.animate(withDuration: 0.2) {
                let kScaleFactor: CGFloat = 0.7
                let scale = CGAffineTransform(scaleX: kScaleFactor, y: kScaleFactor)

                let originalHeight = self.scrollView.bounds.size.height

                // Position the new scaled item to be centered with respect
                // to it's new size.
                let heightDelta = originalHeight * (1 - kScaleFactor)
                let translate = CGAffineTransform(translationX: 0, y: -heightDelta / 2)

                self.contentContainer.transform = scale.concatenating(translate)
            }
        }
    }
}

extension AttachmentApprovalViewController: UIScrollViewDelegate {

    public func viewForZooming(in scrollView: UIScrollView) -> UIView? {
        if isZoomable {
            return mediaMessageView
        } else {
            // don't zoom for audio or generic attachments.
            return nil
        }
    }

    fileprivate func updateMinZoomScaleForSize(_ size: CGSize) {
        Logger.debug("\(logTag) in \(#function)")

        // Ensure bounds have been computed
        mediaMessageView.layoutIfNeeded()
        guard mediaMessageView.bounds.width > 0, mediaMessageView.bounds.height > 0 else {
            Logger.warn("\(logTag) bad bounds in \(#function)")
            return
        }

        let widthScale = size.width / mediaMessageView.bounds.width
        let heightScale = size.height / mediaMessageView.bounds.height
        let minScale = min(widthScale, heightScale)
        scrollView.maximumZoomScale = minScale * 5.0
        scrollView.minimumZoomScale = minScale
        scrollView.zoomScale = minScale
    }

    // Keep the media view centered within the scroll view as you zoom
    public func scrollViewDidZoom(_ scrollView: UIScrollView) {
        // The scroll view has zoomed, so you need to re-center the contents
        let scrollViewSize = self.scrollViewVisibleSize

        // First assume that mediaMessageView center coincides with the contents center
        // This is correct when the mediaMessageView is bigger than scrollView due to zoom
        var contentCenter = CGPoint(x: (scrollView.contentSize.width / 2), y: (scrollView.contentSize.height / 2))

        let scrollViewCenter = self.scrollViewCenter

        // if mediaMessageView is smaller than the scrollView visible size - fix the content center accordingly
        if self.scrollView.contentSize.width < scrollViewSize.width {
            contentCenter.x = scrollViewCenter.x
        }

        if self.scrollView.contentSize.height < scrollViewSize.height {
            contentCenter.y = scrollViewCenter.y
        }

        self.mediaMessageView.center = contentCenter
    }

    // return the scroll view center
    private var scrollViewCenter: CGPoint {
        let size = scrollViewVisibleSize
        return CGPoint(x: (size.width / 2), y: (size.height / 2))
    }

    // Return scrollview size without the area overlapping with tab and nav bar.
    private var scrollViewVisibleSize: CGSize {
        let contentInset = scrollView.contentInset
        let scrollViewSize = scrollView.bounds.standardized.size
        let width = scrollViewSize.width - (contentInset.left + contentInset.right)
        let height = scrollViewSize.height - (contentInset.top + contentInset.bottom)
        return CGSize(width: width, height: height)
    }
}

protocol CaptioningToolbarDelegate: class {
    func captioningToolbarDidTapSend(_ captioningToolbar: CaptioningToolbar, captionText: String?)
    func captioningToolbarDidBeginEditing(_ captioningToolbar: CaptioningToolbar)
    func captioningToolbarDidEndEditing(_ captioningToolbar: CaptioningToolbar)
}

class CaptioningToolbar: UIView, UITextViewDelegate {

    weak var captioningToolbarDelegate: CaptioningToolbarDelegate?
    private let sendButton: UIButton
    private let textView: UITextView
    private let bottomGradient: GradientView
    private let lengthLimitLabel: UILabel

    // Layout Constants

    let kMinTextViewHeight: CGFloat = 38
    var maxTextViewHeight: CGFloat {
        // About ~4 lines in portrait and ~3 lines in landscape.
        // Otherwise we risk obscuring too much of the content.
        return UIDevice.current.orientation.isPortrait ? 160 : 100
    }
    var textViewHeightConstraint: NSLayoutConstraint!
    var textViewHeight: CGFloat

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

    class MessageTextView: UITextView {
        // When creating new lines, contentOffset is animated, but because because
        // we are simultaneously resizing the text view, this can cause the
        // text in the textview to be "too high" in the text view.
        // Solution is to disable animation for setting content offset.
        override func setContentOffset(_ contentOffset: CGPoint, animated: Bool) {
            super.setContentOffset(contentOffset, animated: false)
        }
    }

    override var intrinsicContentSize: CGSize {
        get {
            // Since we have `self.autoresizingMask = UIViewAutoresizingFlexibleHeight`, we must specify
            // an intrinsicContentSize. Specifying CGSize.zero causes the height to be determined by autolayout.
            return CGSize.zero
        }
    }

    init() {
        self.sendButton = UIButton(type: .system)
        self.bottomGradient = GradientView(from: UIColor.clear, to: UIColor.black)
        self.textView =  MessageTextView()
        self.textViewHeight = kMinTextViewHeight
        self.lengthLimitLabel = UILabel()

        super.init(frame: CGRect.zero)

        // Specifying autorsizing mask and an intrinsic content size allows proper
        // sizing when used as an input accessory view.
        self.autoresizingMask = .flexibleHeight
        self.translatesAutoresizingMaskIntoConstraints = false
        self.backgroundColor = UIColor.clear

        textView.delegate = self
        textView.backgroundColor = UIColor.white
        textView.layer.cornerRadius = 4.0
        textView.addBorder(with: UIColor.lightGray)
        textView.font = UIFont.ows_dynamicTypeBody
        textView.returnKeyType = .done

        let sendTitle = NSLocalizedString("ATTACHMENT_APPROVAL_SEND_BUTTON", comment: "Label for 'send' button in the 'attachment approval' dialog.")
        sendButton.setTitle(sendTitle, for: .normal)
        sendButton.addTarget(self, action: #selector(didTapSend), for: .touchUpInside)

        sendButton.titleLabel?.font = UIFont.ows_mediumFont(withSize: 16)
        sendButton.titleLabel?.textAlignment = .center
        sendButton.tintColor = UIColor.white
        sendButton.backgroundColor = UIColor.ows_systemPrimaryButton
        sendButton.layer.cornerRadius = 4

        // Send Button Shadow - without this the send button bottom doesn't feel aligned with the toolbar.
        let kSendButtonShadowOffset: CGFloat = 1
        sendButton.layer.shadowColor = UIColor.darkGray.cgColor
        sendButton.layer.shadowOffset = CGSize(width: 0, height: kSendButtonShadowOffset)
        sendButton.layer.shadowOpacity = 0.8
        sendButton.layer.shadowRadius = 0.0
        sendButton.layer.masksToBounds = false

        // Increase hit area of send button
        sendButton.contentEdgeInsets = UIEdgeInsets(top: 6, left: 8, bottom: 6, right: 8)

        // Length Limit Label shown when the user inputs too long of a message
        lengthLimitLabel.textColor = .white
        lengthLimitLabel.text = NSLocalizedString("ATTACHMENT_APPROVAL_CAPTION_LENGTH_LIMIT_REACHED", comment: "One line label indicating the user can add no more text to the attachment caption.")
        lengthLimitLabel.textAlignment = .center

        // Add shadow in case overlayed on white content
        lengthLimitLabel.layer.shadowColor = UIColor.black.cgColor
        lengthLimitLabel.layer.shadowOffset = CGSize(width: 0.0, height: 0.0)
        lengthLimitLabel.layer.shadowOpacity = 0.8
        self.lengthLimitLabel.isHidden = true

        let contentView = UIView()
        addSubview(contentView)
        contentView.autoPinEdgesToSuperviewEdges()
        contentView.addSubview(bottomGradient)
        contentView.addSubview(sendButton)
        contentView.addSubview(textView)
        contentView.addSubview(lengthLimitLabel)

        // Layout
        let kToolbarMargin: CGFloat = 8

        // We have to wrap the toolbar items in a content view because iOS (at least on iOS10.3) assigns the inputAccessoryView.layoutMargins
        // when resigning first responder (verified by auditing with `layoutMarginsDidChange`).
        // The effect of this is that if we were to assign these margins to self.layoutMargins, they'd be blown away if the
        // user dismisses the keyboard, giving the input accessory view a wonky layout.
        contentView.layoutMargins = UIEdgeInsets(top: kToolbarMargin, left: kToolbarMargin, bottom: kToolbarMargin, right: kToolbarMargin)

        self.textViewHeightConstraint = textView.autoSetDimension(.height, toSize: kMinTextViewHeight)

        // We pin all three edges explicitly rather than doing something like:
        //  textView.autoPinEdges(toSuperviewMarginsExcludingEdge: .right)
        // because that method uses `leading` / `trailing` rather than `left` vs. `right`.
        // So it doesn't work as expected with RTL layouts when we explicitly want something
        // to be on the right side for both RTL and LTR layouts, like with the send button.
        // I believe this is a bug in PureLayout. Filed here: https://github.com/PureLayout/PureLayout/issues/209
        textView.autoPinEdge(toSuperviewMargin: .left)
        textView.autoPinEdge(toSuperviewMargin: .top)
        textView.autoPinEdge(toSuperviewMargin: .bottom)

        sendButton.autoPinEdge(.left, to: .right, of: textView, withOffset: kToolbarMargin)

        // Because the textview has a border, the sendButton feels unaligned without this shadow and offset
        sendButton.autoPinEdge(.bottom, to: .bottom, of: textView, withOffset: -kSendButtonShadowOffset)

        sendButton.autoPinEdge(toSuperviewMargin: .right)
        sendButton.setContentHuggingHigh()
        sendButton.setCompressionResistanceHigh()

        lengthLimitLabel.autoPinEdge(toSuperviewMargin: .left)
        lengthLimitLabel.autoPinEdge(toSuperviewMargin: .right)
        lengthLimitLabel.autoPinEdge(.bottom, to: .top, of: textView, withOffset: -6)
        lengthLimitLabel.setContentHuggingHigh()
        lengthLimitLabel.setCompressionResistanceHigh()

        let bottomGradientHeight = ScaleFromIPhone5(100)
        bottomGradient.autoSetDimension(.height, toSize: bottomGradientHeight)
        bottomGradient.autoPinEdgesToSuperviewEdges(with: .zero, excludingEdge: .top)
    }

    func didTapSend() {
        self.captioningToolbarDelegate?.captioningToolbarDidTapSend(self, captionText: self.textView.text)
    }

    // MARK: - UITextViewDelegate

    public func textViewDidChange(_ textView: UITextView) {
        updateHeight(textView: textView)
    }

    public func textView(_ textView: UITextView, shouldChangeTextIn range: NSRange, replacementText text: String) -> Bool {

        let existingText: String = textView.text ?? ""
        let proposedText: String = (existingText as NSString).replacingCharacters(in: range, with: text)

        guard proposedText.utf8.count <= kOversizeTextMessageSizeThreshold else {
            Logger.debug("\(self.logTag) in \(#function) long text was truncated")
            self.lengthLimitLabel.isHidden = false

            // `range` represents the section of the existing text we will replace. We can re-use that space.
            // Range is in units of NSStrings's standard UTF-16 characters. Since some of those chars could be
            // represented as single bytes in utf-8, while others may be 8 or more, the only way to be sure is
            // to just measure the utf8 encoded bytes of the replaced substring.
            let bytesAfterDelete: Int = (existingText as NSString).replacingCharacters(in: range, with: "").utf8.count

            // Accept as much of the input as we can
            let byteBudget: Int = Int(kOversizeTextMessageSizeThreshold) - bytesAfterDelete
            if byteBudget >= 0, let acceptableNewText = text.truncated(toByteCount: UInt(byteBudget)) {
                textView.text = (existingText as NSString).replacingCharacters(in: range, with: acceptableNewText)
            }

            return false
        }
        self.lengthLimitLabel.isHidden = true

        // Though we can wrap the text, we don't want to encourage multline captions, plus a "done" button
        // allows the user to get the keyboard out of the way while in the attachment approval view.
        if text == "\n" {
            textView.resignFirstResponder()
            return false
        } else {
            return true
        }
    }

    public func textViewDidBeginEditing(_ textView: UITextView) {
        self.captioningToolbarDelegate?.captioningToolbarDidBeginEditing(self)
    }

    public func textViewDidEndEditing(_ textView: UITextView) {
        self.captioningToolbarDelegate?.captioningToolbarDidEndEditing(self)
    }

    // MARK: - Helpers

    private func updateHeight(textView: UITextView) {
        // compute new height assuming width is unchanged
        let currentSize = textView.frame.size
        let newHeight = clampedTextViewHeight(fixedWidth: currentSize.width)

        if newHeight != self.textViewHeight {
            Logger.debug("\(self.logTag) TextView height changed: \(self.textViewHeight) -> \(newHeight)")
            self.textViewHeight = newHeight
            self.textViewHeightConstraint?.constant = textViewHeight
            self.invalidateIntrinsicContentSize()
        }
    }

    private func clampedTextViewHeight(fixedWidth: CGFloat) -> CGFloat {
        let contentSize = textView.sizeThatFits(CGSize(width: fixedWidth, height: CGFloat.greatestFiniteMagnitude))
        return CGFloatClamp(contentSize.height, kMinTextViewHeight, maxTextViewHeight)
    }
}