session-ios/Session/Conversations/ConversationVC.swift

import SessionUIKit
import SessionMessagingKit

// TODO:
// • Slight paging glitch when scrolling up and loading more content
// • Photo rounding (the small corners don't have the correct rounding)
// • Remaining search glitchiness

final class ConversationVC : BaseVC, ConversationViewModelDelegate, OWSConversationSettingsViewDelegate, ConversationSearchControllerDelegate, UITableViewDataSource, UITableViewDelegate {
    let thread: TSThread
    let threadStartedAsMessageRequest: Bool
    let focusedMessageID: String? // This is used for global search
    var focusedMessageIndexPath: IndexPath?
    var initialUnreadCount: UInt = 0
    var unreadViewItems: [ConversationViewItem] = []
    var scrollButtonBottomConstraint: NSLayoutConstraint?
    var scrollButtonMessageRequestsBottomConstraint: NSLayoutConstraint?
    var messageRequestsViewBotomConstraint: NSLayoutConstraint?
    // Search
    var isShowingSearchUI = false
    var lastSearchedText: String?
    // Audio playback & recording
    var audioPlayer: OWSAudioPlayer?
    var audioRecorder: AVAudioRecorder?
    var audioTimer: Timer?
    // Context menu
    var contextMenuWindow: ContextMenuWindow?
    var contextMenuVC: ContextMenuVC?
    // Mentions
    var oldText = ""
    var currentMentionStartIndex: String.Index?
    var mentions: [Mention] = []
    // Scrolling & paging
    var isUserScrolling = false
    var didFinishInitialLayout = false
    var isLoadingMore = false
    var scrollDistanceToBottomBeforeUpdate: CGFloat?
    var baselineKeyboardHeight: CGFloat = 0

    var audioSession: OWSAudioSession { Environment.shared.audioSession }
    var dbConnection: YapDatabaseConnection { OWSPrimaryStorage.shared().uiDatabaseConnection }
    var viewItems: [ConversationViewItem] { viewModel.viewState.viewItems }
    override var canBecomeFirstResponder: Bool { true }
    
    override var inputAccessoryView: UIView? {
        if let thread = thread as? TSGroupThread, thread.groupModel.groupType == .closedGroup && !thread.isCurrentUserMemberInGroup() {
            return nil
        } else {
            return isShowingSearchUI ? searchController.resultsBar : snInputView
        }
    }

    /// The height of the visible part of the table view, i.e. the distance from the navigation bar (where the table view's origin is)
    /// to the top of the input view (`messagesTableView.adjustedContentInset.bottom`).
    var tableViewUnobscuredHeight: CGFloat {
        let bottomInset = messagesTableView.adjustedContentInset.bottom
        return messagesTableView.bounds.height - bottomInset
    }

    /// The offset at which the table view is exactly scrolled to the bottom.
    var lastPageTop: CGFloat {
        return messagesTableView.contentSize.height - tableViewUnobscuredHeight
    }
    
    var isCloseToBottom: Bool {
        let margin = (self.lastPageTop - self.messagesTableView.contentOffset.y)
        return margin <= ConversationVC.scrollToBottomMargin
    }
    
    lazy var mnemonic: String = {
        let identityManager = OWSIdentityManager.shared()
        let databaseConnection = identityManager.value(forKey: "dbConnection") as! YapDatabaseConnection
        var hexEncodedSeed: String! = databaseConnection.object(forKey: "LKLokiSeed", inCollection: OWSPrimaryStorageIdentityKeyStoreCollection) as! String?
        if hexEncodedSeed == nil {
            hexEncodedSeed = identityManager.identityKeyPair()!.hexEncodedPrivateKey // Legacy account
        }
        return Mnemonic.encode(hexEncodedString: hexEncodedSeed)
    }()
    
    lazy var viewModel = ConversationViewModel(thread: thread, focusMessageIdOnOpen: focusedMessageID, delegate: self)
    
    lazy var mediaCache: NSCache<NSString, AnyObject> = {
        let result = NSCache<NSString, AnyObject>()
        result.countLimit = 40
        return result
    }()

    lazy var recordVoiceMessageActivity = AudioActivity(audioDescription: "Voice message", behavior: .playAndRecord)
    
    lazy var searchController: ConversationSearchController = {
        let result = ConversationSearchController(thread: thread)
        result.delegate = self
        if #available(iOS 13, *) {
            result.uiSearchController.obscuresBackgroundDuringPresentation = false
        } else {
            result.uiSearchController.dimsBackgroundDuringPresentation = false
        }
        return result
    }()
    
    // MARK: - UI
    
    private static let messageRequestButtonHeight: CGFloat = 34
    
    lazy var titleView: ConversationTitleView = {
        let result = ConversationTitleView(thread: thread)
        result.delegate = self
        return result
    }()

    lazy var messagesTableView: MessagesTableView = {
        let result: MessagesTableView = MessagesTableView()
        result.dataSource = self
        result.delegate = self
        result.contentInsetAdjustmentBehavior = .never
        result.contentInset = UIEdgeInsets(
            top: 0,
            leading: 0,
            bottom: Values.mediumSpacing,
            trailing: 0
        )
        
        return result
    }()
    
    lazy var snInputView: InputView = InputView(delegate: self)
    
    lazy var unreadCountView: UIView = {
        let result = UIView()
        result.backgroundColor = Colors.text.withAlphaComponent(Values.veryLowOpacity)
        let size = ConversationVC.unreadCountViewSize
        result.set(.width, greaterThanOrEqualTo: size)
        result.set(.height, to: size)
        result.layer.masksToBounds = true
        result.layer.cornerRadius = size / 2
        return result
    }()
    
    lazy var unreadCountLabel: UILabel = {
        let result = UILabel()
        result.font = .boldSystemFont(ofSize: Values.verySmallFontSize)
        result.textColor = Colors.text
        result.textAlignment = .center
        return result
    }()
    
    lazy var blockedBanner: InfoBanner = {
        let name: String
        if let thread = thread as? TSContactThread {
            let publicKey = thread.contactSessionID()
            let context = Contact.context(for: thread)
            name = Storage.shared.getContact(with: publicKey)?.displayName(for: context) ?? publicKey
        } else {
            name = "Thread"
        }
        let message = "\(name) is blocked. Unblock them?"
        let result = InfoBanner(message: message, backgroundColor: Colors.destructive)
        let tapGestureRecognizer = UITapGestureRecognizer(target: self, action: #selector(unblock))
        result.addGestureRecognizer(tapGestureRecognizer)
        return result
    }()
    
    lazy var footerControlsStackView: UIStackView = {
        let result: UIStackView = UIStackView()
        result.translatesAutoresizingMaskIntoConstraints = false
        result.axis = .vertical
        result.alignment = .trailing
        result.distribution = .equalSpacing
        result.spacing = 10
        result.layoutMargins = UIEdgeInsets(top: 0, left: 20, bottom: 0, right: 20)
        result.isLayoutMarginsRelativeArrangement = true
        
        return result
    }()
    
    lazy var scrollButton = ScrollToBottomButton(delegate: self)
    
    lazy var messageRequestView: UIView = {
        let result: UIView = UIView()
        result.translatesAutoresizingMaskIntoConstraints = false
        result.isHidden = !thread.isMessageRequest()
        result.setGradient(Gradients.defaultBackground)
        
        return result
    }()
    
    private let messageRequestDescriptionLabel: UILabel = {
        let result: UILabel = UILabel()
        result.translatesAutoresizingMaskIntoConstraints = false
        result.font = UIFont.systemFont(ofSize: 12)
        result.text = NSLocalizedString("MESSAGE_REQUESTS_INFO", comment: "")
        result.textColor = Colors.sessionMessageRequestsInfoText
        result.textAlignment = .center
        result.numberOfLines = 2
        
        return result
    }()
    
    private let messageRequestAcceptButton: UIButton = {
        let result: UIButton = UIButton()
        result.translatesAutoresizingMaskIntoConstraints = false
        result.clipsToBounds = true
        result.titleLabel?.font = UIFont.boldSystemFont(ofSize: 18)
        result.setTitle(NSLocalizedString("TXT_DELETE_ACCEPT", comment: ""), for: .normal)
        result.setTitleColor(Colors.sessionHeading, for: .normal)
        result.setBackgroundImage(
            Colors.sessionHeading
                .withAlphaComponent(isDarkMode ? 0.2 : 0.06)
                .toImage(isDarkMode: isDarkMode),
            for: .highlighted
        )
        result.layer.cornerRadius = (ConversationVC.messageRequestButtonHeight / 2)
        result.layer.borderColor = {
            if #available(iOS 13.0, *) {
                return Colors.sessionHeading
                    .resolvedColor(
                        // Note: This is needed for '.cgColor' to support dark mode
                        with: UITraitCollection(userInterfaceStyle: isDarkMode ? .dark : .light)
                    ).cgColor
            }
            
            return Colors.sessionHeading.cgColor
        }()
        result.layer.borderWidth = 1
        result.addTarget(self, action: #selector(acceptMessageRequest), for: .touchUpInside)
        
        return result
    }()
    
    private let messageRequestDeleteButton: UIButton = {
        let result: UIButton = UIButton()
        result.translatesAutoresizingMaskIntoConstraints = false
        result.clipsToBounds = true
        result.titleLabel?.font = UIFont.boldSystemFont(ofSize: 18)
        result.setTitle(NSLocalizedString("TXT_DELETE_TITLE", comment: ""), for: .normal)
        result.setTitleColor(Colors.destructive, for: .normal)
        result.setBackgroundImage(
            Colors.destructive
                .withAlphaComponent(isDarkMode ? 0.2 : 0.06)
                .toImage(isDarkMode: isDarkMode),
            for: .highlighted
        )
        result.layer.cornerRadius = (ConversationVC.messageRequestButtonHeight / 2)
        result.layer.borderColor = {
            if #available(iOS 13.0, *) {
                return Colors.destructive
                    .resolvedColor(
                        // Note: This is needed for '.cgColor' to support dark mode
                        with: UITraitCollection(userInterfaceStyle: isDarkMode ? .dark : .light)
                    ).cgColor
            }
            
            return Colors.destructive.cgColor
        }()
        result.layer.borderWidth = 1
        result.addTarget(self, action: #selector(deleteMessageRequest), for: .touchUpInside)
        
        return result
    }()
    
    // MARK: Settings
    static let unreadCountViewSize: CGFloat = 20
    /// The table view's bottom inset (content will have this distance to the bottom if the table view is fully scrolled down).
    static let bottomInset = Values.mediumSpacing
    /// The table view will start loading more content when the content offset becomes less than this.
    static let loadMoreThreshold: CGFloat = 120
    /// The button will be fully visible once the user has scrolled this amount from the bottom of the table view.
    static let scrollButtonFullVisibilityThreshold: CGFloat = 80
    /// The button will be invisible until the user has scrolled at least this amount from the bottom of the table view.
    static let scrollButtonNoVisibilityThreshold: CGFloat = 20
    /// Automatically scroll to the bottom of the conversation when sending a message if the scroll distance from the bottom is less than this number.
    static let scrollToBottomMargin: CGFloat = 60
    
    // MARK: Lifecycle
    init(thread: TSThread, focusedMessageID: String? = nil) {
        self.thread = thread
        self.threadStartedAsMessageRequest = thread.isMessageRequest()
        self.focusedMessageID = focusedMessageID
        super.init(nibName: nil, bundle: nil)
        Storage.read { transaction in
            self.initialUnreadCount = self.thread.unreadMessageCount(transaction: transaction)
        }
        let clampedUnreadCount = min(self.initialUnreadCount, UInt(kConversationInitialMaxRangeSize), UInt(viewItems.endIndex))
        unreadViewItems = clampedUnreadCount != 0 ? [ConversationViewItem](viewItems[viewItems.endIndex - Int(clampedUnreadCount) ..< viewItems.endIndex]) : []
    }
    
    required init?(coder: NSCoder) {
        preconditionFailure("Use init(thread:) instead.")
    }
    
    override func viewDidLoad() {
        SNLog("Ryan: Conversation VC starts loading at \(NSDate.ows_millisecondTimeStamp())")
        super.viewDidLoad()
        // Gradient
        setUpGradientBackground()
        // Nav bar
        setUpNavBarStyle()
        navigationItem.titleView = titleView
        updateNavBarButtons()
        // Constraints
        view.addSubview(messagesTableView)
        messagesTableView.pin(to: view)
        
        // Blocked banner
        addOrRemoveBlockedBanner()
        
        // Message requests view & scroll to bottom
        view.addSubview(scrollButton)
        view.addSubview(messageRequestView)
        
        messageRequestView.addSubview(messageRequestDescriptionLabel)
        messageRequestView.addSubview(messageRequestAcceptButton)
        messageRequestView.addSubview(messageRequestDeleteButton)
        
        scrollButton.pin(.right, to: .right, of: view, withInset: -20)
        messageRequestView.pin(.left, to: .left, of: view)
        messageRequestView.pin(.right, to: .right, of: view)
        self.messageRequestsViewBotomConstraint = messageRequestView.pin(.bottom, to: .bottom, of: view, withInset: -16)
        self.scrollButtonBottomConstraint = scrollButton.pin(.bottom, to: .bottom, of: view, withInset: -16)
        self.scrollButtonBottomConstraint?.isActive = false // Note: Need to disable this to avoid a conflict with the other bottom constraint
        self.scrollButtonMessageRequestsBottomConstraint = scrollButton.pin(.bottom, to: .top, of: messageRequestView, withInset: -16)
        self.scrollButtonMessageRequestsBottomConstraint?.isActive = thread.isMessageRequest()
        self.scrollButtonBottomConstraint?.isActive = !thread.isMessageRequest()
        
        messageRequestDescriptionLabel.pin(.top, to: .top, of: messageRequestView, withInset: 10)
        messageRequestDescriptionLabel.pin(.left, to: .left, of: messageRequestView, withInset: 40)
        messageRequestDescriptionLabel.pin(.right, to: .right, of: messageRequestView, withInset: -40)
        
        messageRequestAcceptButton.pin(.top, to: .bottom, of: messageRequestDescriptionLabel, withInset: 20)
        messageRequestAcceptButton.pin(.left, to: .left, of: messageRequestView, withInset: 20)
        messageRequestAcceptButton.pin(.bottom, to: .bottom, of: messageRequestView)
        messageRequestAcceptButton.set(.height, to: ConversationVC.messageRequestButtonHeight)
        
        messageRequestAcceptButton.pin(.top, to: .bottom, of: messageRequestDescriptionLabel, withInset: 20)
        messageRequestAcceptButton.pin(.left, to: .left, of: messageRequestView, withInset: 20)
        messageRequestAcceptButton.pin(.bottom, to: .bottom, of: messageRequestView)
        messageRequestAcceptButton.set(.height, to: ConversationVC.messageRequestButtonHeight)
        
        messageRequestDeleteButton.pin(.top, to: .bottom, of: messageRequestDescriptionLabel, withInset: 20)
        messageRequestDeleteButton.pin(.left, to: .right, of: messageRequestAcceptButton, withInset: 20)
        messageRequestDeleteButton.pin(.right, to: .right, of: messageRequestView, withInset: -20)
        messageRequestDeleteButton.pin(.bottom, to: .bottom, of: messageRequestView)
        messageRequestDeleteButton.set(.width, to: .width, of: messageRequestAcceptButton)
        messageRequestDeleteButton.set(.height, to: ConversationVC.messageRequestButtonHeight)
        
        // Unread count view
        view.addSubview(unreadCountView)
        unreadCountView.addSubview(unreadCountLabel)
        unreadCountLabel.pin(.top, to: .top, of: unreadCountView)
        unreadCountLabel.pin(.bottom, to: .bottom, of: unreadCountView)
        unreadCountView.pin(.leading, to: .leading, of: unreadCountLabel, withInset: -4)
        unreadCountView.pin(.trailing, to: .trailing, of: unreadCountLabel, withInset: 4)
        unreadCountView.centerYAnchor.constraint(equalTo: scrollButton.topAnchor).isActive = true
        unreadCountView.center(.horizontal, in: scrollButton)
        updateUnreadCountView()
        
        // Notifications
        let notificationCenter = NotificationCenter.default
        notificationCenter.addObserver(self, selector: #selector(handleKeyboardWillChangeFrameNotification(_:)), name: UIResponder.keyboardWillChangeFrameNotification, object: nil)
        notificationCenter.addObserver(self, selector: #selector(handleKeyboardWillHideNotification(_:)), name: UIResponder.keyboardWillHideNotification, object: nil)
        notificationCenter.addObserver(self, selector: #selector(handleAudioDidFinishPlayingNotification(_:)), name: .SNAudioDidFinishPlaying, object: nil)
        notificationCenter.addObserver(self, selector: #selector(addOrRemoveBlockedBanner), name: NSNotification.Name(rawValue: kNSNotificationName_BlockListDidChange), object: nil)
        notificationCenter.addObserver(self, selector: #selector(handleGroupUpdatedNotification), name: .groupThreadUpdated, object: nil)
        notificationCenter.addObserver(self, selector: #selector(sendScreenshotNotificationIfNeeded), name: UIApplication.userDidTakeScreenshotNotification, object: nil)
        notificationCenter.addObserver(self, selector: #selector(handleMessageSentStatusChanged), name: .messageSentStatusDidChange, object: nil)
        // Mentions
        MentionsManager.populateUserPublicKeyCacheIfNeeded(for: thread.uniqueId!)
        // Draft
        var draft = ""
        Storage.read { transaction in
            draft = self.thread.currentDraft(with: transaction)
        }
        if !draft.isEmpty {
            snInputView.text = draft
        }
        
        // Update the input state if this is a contact thread
        if let contactThread: TSContactThread = thread as? TSContactThread {
            let contact: Contact? = Storage.shared.getContact(with: contactThread.contactSessionID())
            
            // If the contact doesn't exist yet then it's a message request without the first message sent
            // so only allow text-based messages
            self.snInputView.setEnabledMessageTypes(
                (thread.isNoteToSelf() || contact?.didApproveMe == true || thread.isMessageRequest() ?
                    .all : .textOnly
                ),
                message: nil
            )
        }
        
        // Update member count if this is a V2 open group
        if let v2OpenGroup = Storage.shared.getV2OpenGroup(for: thread.uniqueId!) {
            OpenGroupAPIV2.getMemberCount(for: v2OpenGroup.room, on: v2OpenGroup.server).retainUntilComplete()
        }
        
        SNLog("Ryan: Conversation VC ends loading at \(NSDate.ows_millisecondTimeStamp())")
    }
    
    override func viewDidLayoutSubviews() {
        super.viewDidLayoutSubviews()
        if !didFinishInitialLayout {
            // Scroll to the last unread message if possible; otherwise scroll to the bottom.
            // When the unread message count is more than the number of view items of a page,
            // the screen will scroll to the bottom instead of the first unread message.
            // unreadIndicatorIndex is calculated during loading of the viewItems, so it's
            // supposed to be accurate.
            DispatchQueue.main.async {
                SNLog("Ryan: Conversation VC starts layout subviews at \(NSDate.ows_millisecondTimeStamp())")
                if let focusedMessageID = self.focusedMessageID {
                    self.scrollToInteraction(with: focusedMessageID, isAnimated: false, highlighted: true)
                } else {
                    let firstUnreadMessageIndex = self.viewModel.viewState.unreadIndicatorIndex?.intValue
                        ?? (self.viewItems.count - self.unreadViewItems.count)
                    if self.initialUnreadCount > 0, let viewItem = self.viewItems[ifValid: firstUnreadMessageIndex], let interactionID = viewItem.interaction.uniqueId {
                        self.scrollToInteraction(with: interactionID, position: .top, isAnimated: false)
                        self.unreadCountView.alpha = self.scrollButton.alpha
                    } else {
                        self.scrollToBottom(isAnimated: false)
                    }
                }
                self.scrollButton.alpha = self.getScrollButtonOpacity()
                SNLog("Ryan: Conversation VC ends layout subviews at \(NSDate.ows_millisecondTimeStamp())")
            }
        }
    }
    
    override func viewDidAppear(_ animated: Bool) {
        SNLog("Ryan: Conversation VC did appear at \(NSDate.ows_millisecondTimeStamp())")
        super.viewDidAppear(animated)
        highlightFocusedMessageIfNeeded()
        didFinishInitialLayout = true
        markAllAsRead()
    }
    
    override func viewWillDisappear(_ animated: Bool) {
        super.viewWillDisappear(animated)
        let text = snInputView.text
        Storage.write { transaction in
            self.thread.setDraft(text, transaction: transaction)
        }
        inputAccessoryView?.resignFirstResponder()
    }
    
    override func viewDidDisappear(_ animated: Bool) {
        super.viewDidDisappear(animated)
        mediaCache.removeAllObjects()
    }
    
    deinit {
        NotificationCenter.default.removeObserver(self)
    }
    
    // MARK: Table View Data Source
    func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return viewItems.count
    }
    
    func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let viewItem = viewItems[indexPath.row]
        let cell = tableView.dequeueReusableCell(withIdentifier: MessageCell.getCellType(for: viewItem).identifier) as! MessageCell
        cell.delegate = self
        cell.thread = thread
        cell.viewItem = viewItem
        return cell
    }
    
    // MARK: Updating
    
    func updateNavBarButtons() {
        if isShowingSearchUI {
            navigationItem.leftBarButtonItem = nil
            navigationItem.rightBarButtonItems = []
        } else {
            navigationItem.leftBarButtonItem = UIViewController.createOWSBackButton(withTarget: self, selector: #selector(handleBackPressed))
            
            let rightBarButtonItem: UIBarButtonItem
            if thread is TSContactThread {
                let size = Values.verySmallProfilePictureSize
                let profilePictureView = ProfilePictureView()
                profilePictureView.accessibilityLabel = "Settings button"
                profilePictureView.size = size
                profilePictureView.update(for: thread)
                profilePictureView.set(.width, to: size)
                profilePictureView.set(.height, to: size)
                let tapGestureRecognizer = UITapGestureRecognizer(target: self, action: #selector(openSettings))
                profilePictureView.addGestureRecognizer(tapGestureRecognizer)
                rightBarButtonItem = UIBarButtonItem(customView: profilePictureView)
            } else {
                rightBarButtonItem = UIBarButtonItem(image: UIImage(named: "Gear"), style: .plain, target: self, action: #selector(openSettings))
            }
            rightBarButtonItem.accessibilityLabel = "Settings button"
            rightBarButtonItem.isAccessibilityElement = true
            navigationItem.rightBarButtonItem = rightBarButtonItem
        }
    }
    
    private func highlightFocusedMessageIfNeeded() {
        if let indexPath = focusedMessageIndexPath, let cell = messagesTableView.cellForRow(at: indexPath) as? VisibleMessageCell {
            cell.highlight()
            focusedMessageIndexPath = nil
        }
    }
    
    @objc func handleKeyboardWillChangeFrameNotification(_ notification: Notification) {
        // Please refer to https://github.com/mapbox/mapbox-navigation-ios/issues/1600
        // and https://stackoverflow.com/a/25260930 to better understand what we are
        // doing with the UIViewAnimationOptions
        let userInfo: [AnyHashable: Any] = (notification.userInfo ?? [:])
        let duration = ((userInfo[UIResponder.keyboardAnimationDurationUserInfoKey] as? TimeInterval) ?? 0)
        let curveValue: Int = ((userInfo[UIResponder.keyboardAnimationCurveUserInfoKey] as? Int) ?? Int(UIView.AnimationOptions.curveEaseInOut.rawValue))
        let options: UIView.AnimationOptions = UIView.AnimationOptions(rawValue: UInt(curveValue << 16))
        let keyboardRect: CGRect = ((userInfo[UIResponder.keyboardFrameEndUserInfoKey] as? CGRect) ?? CGRect.zero)
        
        // Calculate new positions (Need the ensure the 'messageRequestView' has been layed out as it's
        // needed for proper calculations, so force an initial layout if it doesn't have a size)
        var hasDoneLayout: Bool = true
        
        if messageRequestView.bounds.height <= CGFloat.leastNonzeroMagnitude {
            hasDoneLayout = false
            
            UIView.performWithoutAnimation {
                self.view.layoutIfNeeded()
            }
        }
        
        let keyboardTop = (UIScreen.main.bounds.height - keyboardRect.minY)
        let messageRequestsOffset: CGFloat = (messageRequestView.isHidden ? 0 : messageRequestView.bounds.height + 16)
        let oldContentInset: UIEdgeInsets = messagesTableView.contentInset
        let newContentInset: UIEdgeInsets = UIEdgeInsets(
            top: 0,
            leading: 0,
            bottom: (Values.mediumSpacing + keyboardTop + messageRequestsOffset),
            trailing: 0
        )
        let newContentOffsetY: CGFloat = (messagesTableView.contentOffset.y + (newContentInset.bottom - oldContentInset.bottom))
        let changes = { [weak self] in
            self?.scrollButtonBottomConstraint?.constant = -(keyboardTop + 16)
            self?.messageRequestsViewBotomConstraint?.constant = -(keyboardTop + 16)
            self?.messagesTableView.contentInset = newContentInset
            self?.messagesTableView.contentOffset.y = newContentOffsetY
            
            let scrollButtonOpacity: CGFloat = (self?.getScrollButtonOpacity() ?? 0)
            self?.scrollButton.alpha = scrollButtonOpacity
            
            self?.view.setNeedsLayout()
            self?.view.layoutIfNeeded()
        }
        
        // Perform the changes (don't animate if the initial layout hasn't been completed)
        guard hasDoneLayout else {
            UIView.performWithoutAnimation {
                changes()
            }
            return
        }
        
        UIView.animate(
            withDuration: duration,
            delay: 0,
            options: options,
            animations: changes,
            completion: nil
        )
    }
    
    @objc func handleKeyboardWillHideNotification(_ notification: Notification) {
        // Please refer to https://github.com/mapbox/mapbox-navigation-ios/issues/1600
        // and https://stackoverflow.com/a/25260930 to better understand what we are
        // doing with the UIViewAnimationOptions
        let userInfo: [AnyHashable: Any] = (notification.userInfo ?? [:])
        let duration = ((userInfo[UIResponder.keyboardAnimationDurationUserInfoKey] as? TimeInterval) ?? 0)
        let curveValue: Int = ((userInfo[UIResponder.keyboardAnimationCurveUserInfoKey] as? Int) ?? Int(UIView.AnimationOptions.curveEaseInOut.rawValue))
        let options: UIView.AnimationOptions = UIView.AnimationOptions(rawValue: UInt(curveValue << 16))
        
        let keyboardRect: CGRect = ((userInfo[UIResponder.keyboardFrameEndUserInfoKey] as? CGRect) ?? CGRect.zero)
        let keyboardTop = (UIScreen.main.bounds.height - keyboardRect.minY)
        
        UIView.animate(
            withDuration: duration,
            delay: 0,
            options: options,
            animations: { [weak self] in
                self?.scrollButtonBottomConstraint?.constant = -(keyboardTop + 16)
                self?.messageRequestsViewBotomConstraint?.constant = -(keyboardTop + 16)
                
                let scrollButtonOpacity: CGFloat = (self?.getScrollButtonOpacity() ?? 0)
                self?.scrollButton.alpha = scrollButtonOpacity
                self?.unreadCountView.alpha = scrollButtonOpacity
                
                self?.view.setNeedsLayout()
                self?.view.layoutIfNeeded()
            },
            completion: nil
        )
    }
    
    func conversationViewModelWillUpdate() {
        // Not currently in use
    }
    
    func conversationViewModelDidUpdate(_ conversationUpdate: ConversationUpdate) {
        guard self.isViewLoaded else { return }
        let updateType = conversationUpdate.conversationUpdateType
        guard updateType != .minor else { return } // No view items were affected
        if updateType == .reload {
            return messagesTableView.reloadData()
        }
        var shouldScrollToBottom = false
        let batchUpdates: () -> Void = {
            for update in conversationUpdate.updateItems! {
                switch update.updateItemType {
                case .delete:
                    self.messagesTableView.deleteRows(at: [ IndexPath(row: Int(update.oldIndex), section: 0) ], with: .none)
                case .insert:
                    // Perform inserts before updates
                    self.messagesTableView.insertRows(at: [ IndexPath(row: Int(update.newIndex), section: 0) ], with: .none)
                    if update.viewItem?.interaction is TSOutgoingMessage {
                        shouldScrollToBottom = true
                    } else {
                        shouldScrollToBottom = self.isCloseToBottom
                    }
                case .update:
                    self.messagesTableView.reloadRows(at: [ IndexPath(row: Int(update.oldIndex), section: 0) ], with: .none)
                default: preconditionFailure()
                }
            }
        }
        UIView.performWithoutAnimation {
            messagesTableView.performBatchUpdates(batchUpdates) { _ in
                if shouldScrollToBottom {
                    self.scrollToBottom(isAnimated: false)
                }
                self.markAllAsRead()
            }
            if shouldScrollToBottom {
                self.scrollToBottom(isAnimated: false)
            }
        }
        
        // Update the input state if this is a contact thread
        if let contactThread: TSContactThread = thread as? TSContactThread {
            let contact: Contact? = Storage.shared.getContact(with: contactThread.contactSessionID())
            
            // If the contact doesn't exist yet then it's a message request without the first message sent
            // so only allow text-based messages
            self.snInputView.setEnabledMessageTypes(
                (thread.isNoteToSelf() || contact?.didApproveMe == true || thread.isMessageRequest() ?
                    .all : .textOnly
                ),
                message: nil
            )
        }
    }
    
    func conversationViewModelWillLoadMoreItems() {
        view.layoutIfNeeded()
        // The scroll distance to bottom will be restored in conversationViewModelDidLoadMoreItems
        scrollDistanceToBottomBeforeUpdate = messagesTableView.contentSize.height - messagesTableView.contentOffset.y
    }
    
    func conversationViewModelDidLoadMoreItems() {
        guard let scrollDistanceToBottomBeforeUpdate = scrollDistanceToBottomBeforeUpdate else { return }
        view.layoutIfNeeded()
        messagesTableView.contentOffset.y = messagesTableView.contentSize.height - scrollDistanceToBottomBeforeUpdate
        isLoadingMore = false
    }
    
    func conversationViewModelDidLoadPrevPage() {
        // Not currently in use
    }
    
    func conversationViewModelRangeDidChange() {
        // Not currently in use
    }
    
    func conversationViewModelDidReset() {
        // Not currently in use
    }
    
    @objc private func handleGroupUpdatedNotification() {
        thread.reload() // Needed so that thread.isCurrentUserMemberInGroup() is up to date
        reloadInputViews()
    }
    
    @objc private func handleMessageSentStatusChanged() {
        DispatchQueue.main.async {
            guard let indexPaths = self.messagesTableView.indexPathsForVisibleRows else { return }
            var indexPathsToReload: [IndexPath] = []
            for indexPath in indexPaths {
                guard let cell = self.messagesTableView.cellForRow(at: indexPath) as? VisibleMessageCell else { continue }
                let isLast = (indexPath.item == (self.messagesTableView.numberOfRows(inSection: 0) - 1))
                guard !isLast else { continue }
                if !cell.messageStatusImageView.isHidden {
                    indexPathsToReload.append(indexPath)
                }
            }
            UIView.performWithoutAnimation {
                self.messagesTableView.reloadRows(at: indexPathsToReload, with: .none)
            }
        }
    }
    
    // MARK: General
    @objc func addOrRemoveBlockedBanner() {
        func detach() {
            blockedBanner.removeFromSuperview()
        }
        guard let thread = thread as? TSContactThread else { return detach() }
        if OWSBlockingManager.shared().isRecipientIdBlocked(thread.contactSessionID()) {
            view.addSubview(blockedBanner)
            blockedBanner.pin([ UIView.HorizontalEdge.left, UIView.VerticalEdge.top, UIView.HorizontalEdge.right ], to: view)
        } else {
            detach()
        }
    }
    
    func markAllAsRead() {
        guard !thread.isMessageRequest() else { return }
        guard let lastSortID = viewItems.last?.interaction.sortId else { return }
        OWSReadReceiptManager.shared().markAsReadLocally(beforeSortId: lastSortID, thread: thread)
        SSKEnvironment.shared.disappearingMessagesJob.cleanupMessagesWhichFailedToStartExpiringFromNow()
    }
    
    func tableView(_ tableView: UITableView, estimatedHeightForRowAt indexPath: IndexPath) -> CGFloat {
        return UITableView.automaticDimension
    }

    func tableView(_ tableView: UITableView, heightForRowAt indexPath: IndexPath) -> CGFloat {
        return UITableView.automaticDimension
    }

    func getMediaCache() -> NSCache<NSString, AnyObject> {
        return mediaCache
    }
    
    func scrollToBottom(isAnimated: Bool) {
        guard !isUserScrolling else { return }
        if let interactionID = viewItems.last?.interaction.uniqueId {
            self.scrollToInteraction(with: interactionID, position: .top, isAnimated: isAnimated)
            return
        }
        // Ensure the view is fully up to date before we try to scroll to the bottom, since
        // we use the table view's bounds to determine where the bottom is.
        view.layoutIfNeeded()
        let firstContentPageTop: CGFloat = 0
        let contentOffsetY = max(firstContentPageTop, lastPageTop)
        messagesTableView.setContentOffset(CGPoint(x: 0, y: contentOffsetY), animated: isAnimated)
    }
    
    func scrollViewWillBeginDragging(_ scrollView: UIScrollView) {
        isUserScrolling = true
    }
    
    func scrollViewDidEndDragging(_ scrollView: UIScrollView, willDecelerate decelerate: Bool) {
        isUserScrolling = false
    }
    
    func scrollViewDidScroll(_ scrollView: UIScrollView) {
        scrollButton.alpha = getScrollButtonOpacity()
        unreadCountView.alpha = scrollButton.alpha
        autoLoadMoreIfNeeded()
        updateUnreadCountView()
    }
    
    func updateUnreadCountView() {
        let visibleViewItems = (messagesTableView.indexPathsForVisibleRows ?? []).map { viewItems[ifValid: $0.row] }
        for visibleItem in visibleViewItems {
            guard let index = unreadViewItems.firstIndex(where: { $0 === visibleItem }) else { continue }
            unreadViewItems.remove(at: index)
        }
        let unreadCount = unreadViewItems.count
        unreadCountLabel.text = unreadCount < 10000 ? "\(unreadCount)" : "9999+"
        let fontSize = (unreadCount < 10000) ? Values.verySmallFontSize : 8
        unreadCountLabel.font = .boldSystemFont(ofSize: fontSize)
        unreadCountView.isHidden = (unreadCount == 0)
    }
    
    func autoLoadMoreIfNeeded() {
        let isMainAppAndActive = CurrentAppContext().isMainAppAndActive
        guard isMainAppAndActive && didFinishInitialLayout && viewModel.canLoadMoreItems() && !isLoadingMore
            && messagesTableView.contentOffset.y < ConversationVC.loadMoreThreshold else { return }
        isLoadingMore = true
        viewModel.loadAnotherPageOfMessages()
    }
    
    func getScrollButtonOpacity() -> CGFloat {
        let contentOffsetY = messagesTableView.contentOffset.y
        let x = (lastPageTop - ConversationVC.bottomInset - contentOffsetY).clamp(0, .greatestFiniteMagnitude)
        let a = 1 / (ConversationVC.scrollButtonFullVisibilityThreshold - ConversationVC.scrollButtonNoVisibilityThreshold)
        return a * x
    }
    
    func groupWasUpdated(_ groupModel: TSGroupModel) {
        // Not currently in use
    }
    
    // MARK: Search
    func conversationSettingsDidRequestConversationSearch(_ conversationSettingsViewController: OWSConversationSettingsViewController) {
        showSearchUI()
        popAllConversationSettingsViews {
            DispatchQueue.main.asyncAfter(deadline: .now() + 0.5) { // Without this delay the search bar doesn't show
                self.searchController.uiSearchController.searchBar.becomeFirstResponder()
            }
        }
    }
    
    func popAllConversationSettingsViews(completion completionBlock: (() -> Void)? = nil) {
        if presentedViewController != nil {
            dismiss(animated: true) {
                self.navigationController!.popToViewController(self, animated: true, completion: completionBlock)
            }
        } else {
            navigationController!.popToViewController(self, animated: true, completion: completionBlock)
        }
    }
    
    func showSearchUI() {
        isShowingSearchUI = true
        // Search bar
        // FIXME: This code is duplicated with SearchBar
        let searchBar = searchController.uiSearchController.searchBar
        searchBar.searchBarStyle = .minimal
        searchBar.barStyle = .black
        searchBar.tintColor = Colors.accent
        let searchIcon = UIImage(named: "searchbar_search")!.asTintedImage(color: Colors.searchBarPlaceholder)
        searchBar.setImage(searchIcon, for: .search, state: UIControl.State.normal)
        let clearIcon = UIImage(named: "searchbar_clear")!.asTintedImage(color: Colors.searchBarPlaceholder)
        searchBar.setImage(clearIcon, for: .clear, state: UIControl.State.normal)
        let searchTextField: UITextField
        if #available(iOS 13, *) {
            searchTextField = searchBar.searchTextField
        } else {
            searchTextField = searchBar.value(forKey: "_searchField") as! UITextField
        }
        searchTextField.backgroundColor = Colors.searchBarBackground
        searchTextField.textColor = Colors.text
        searchTextField.attributedPlaceholder = NSAttributedString(string: "Search", attributes: [ .foregroundColor : Colors.searchBarPlaceholder ])
        searchTextField.keyboardAppearance = isLightMode ? .default : .dark
        searchBar.setPositionAdjustment(UIOffset(horizontal: 4, vertical: 0), for: .search)
        searchBar.searchTextPositionAdjustment = UIOffset(horizontal: 2, vertical: 0)
        searchBar.setPositionAdjustment(UIOffset(horizontal: -4, vertical: 0), for: .clear)
        navigationItem.titleView = searchBar
        // Nav bar buttons
        updateNavBarButtons()
        // Hack so that the ResultsBar stays on the screen when dismissing the search field
        // keyboard.
        //
        // Details:
        //
        // When the search UI is activated, both the SearchField and the ConversationVC
        // have the resultsBar as their inputAccessoryView.
        //
        // So when the SearchField is first responder, the ResultsBar is shown on top of the keyboard.
        // When the ConversationVC is first responder, the ResultsBar is shown at the bottom of the
        // screen.
        //
        // When the user swipes to dismiss the keyboard, trying to see more of the content while
        // searching, we want the ResultsBar to stay at the bottom of the screen - that is, we
        // want the ConversationVC to becomeFirstResponder.
        //
        // If the SearchField were a subview of ConversationVC.view, this would all be automatic,
        // as first responder status is percolated up the responder chain via `nextResponder`, which
        // basically travereses each superView, until you're at a rootView, at which point the next
        // responder is the ViewController which controls that View.
        //
        // However, because SearchField lives in the Navbar, it's "controlled" by the
        // NavigationController, not the ConversationVC.
        //
        // So here we stub the next responder on the navBar so that when the searchBar resigns
        // first responder, the ConversationVC will be in it's responder chain - keeeping the
        // ResultsBar on the bottom of the screen after dismissing the keyboard.
        let navBar = navigationController!.navigationBar as! OWSNavigationBar
        navBar.stubbedNextResponder = self
    }
    
    func hideSearchUI() {
        isShowingSearchUI = false
        navigationItem.titleView = titleView
        updateNavBarButtons()
        let navBar = navigationController!.navigationBar as! OWSNavigationBar
        navBar.stubbedNextResponder = nil
        becomeFirstResponder()
        reloadInputViews()
    }
    
    func didDismissSearchController(_ searchController: UISearchController) {
        hideSearchUI()
    }
    
    func conversationSearchController(_ conversationSearchController: ConversationSearchController, didUpdateSearchResults resultSet: ConversationScreenSearchResultSet?) {
        lastSearchedText = resultSet?.searchText
        messagesTableView.reloadRows(at: messagesTableView.indexPathsForVisibleRows ?? [], with: UITableView.RowAnimation.none)
    }
    
    func conversationSearchController(_ conversationSearchController: ConversationSearchController, didSelectMessageId interactionID: String) {
        scrollToInteraction(with: interactionID)
    }
    
    func scrollToInteraction(with interactionID: String, position: UITableView.ScrollPosition = .middle, isAnimated: Bool = true, highlighted: Bool = false) {
        guard let indexPath = viewModel.ensureLoadWindowContainsInteractionId(interactionID) else { return }
        messagesTableView.scrollToRow(at: indexPath, at: position, animated: isAnimated)
        if highlighted {
            focusedMessageIndexPath = indexPath
        }
    }
}