MessageKit/Sources/Controllers/MessagesViewController.swift

/*
 MIT License

 Copyright (c) 2017-2022 MessageKit

 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal
 in the Software without restriction, including without limitation the rights
 to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 copies of the Software, and to permit persons to whom the Software is
 furnished to do so, subject to the following conditions:

 The above copyright notice and this permission notice shall be included in all
 copies or substantial portions of the Software.

 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 SOFTWARE.
 */

import Foundation
import UIKit
import Combine
import InputBarAccessoryView

/// A subclass of `UIViewController` with a `MessagesCollectionView` object
/// that is used to display conversation interfaces.
open class MessagesViewController: UIViewController, UICollectionViewDelegateFlowLayout, UICollectionViewDataSource {

    /// The `MessagesCollectionView` managed by the messages view controller object.
    open var messagesCollectionView = MessagesCollectionView()

    /// The `InputBarAccessoryView` used as the `inputAccessoryView` in the view controller.
    open lazy var messageInputBar = InputBarAccessoryView()

    /// Display the date of message by swiping left.
    /// The default value of this property is `false`.
    open var showMessageTimestampOnSwipeLeft: Bool = false {
        didSet {
            messagesCollectionView.showMessageTimestampOnSwipeLeft = showMessageTimestampOnSwipeLeft
            if showMessageTimestampOnSwipeLeft {
                addPanGesture()
            } else {
                removePanGesture()
            }
        }
    }

    /// A CGFloat value that adds to (or, if negative, subtracts from) the automatically
    /// computed value of `messagesCollectionView.contentInset.bottom`. Meant to be used
    /// as a measure of last resort when the built-in algorithm does not produce the right
    /// value for your app. Please let us know when you end up having to use this property.
    open var additionalBottomInset: CGFloat = 0 {
        didSet {
            updateMessageCollectionViewBottomInset()
        }
    }

    public var selectedIndexPathForMenu: IndexPath?

    // MARK: - Internal properties

    internal let state: State = .init()

    // MARK: - Lifecycle

    open override func viewDidLoad() {
        super.viewDidLoad()
        setupDefaults()
        setupSubviews()
        setupConstraints()
        setupInputBar(for: inputBarType)
        setupDelegates()
        addObservers()
        addKeyboardObservers()
        addMenuControllerObservers()
        /// Layout input container view and update messagesCollectionViewInsets
        view.layoutIfNeeded()
    }
    
    open override func viewSafeAreaInsetsDidChange() {
        super.viewSafeAreaInsetsDidChange()
        updateMessageCollectionViewBottomInset()
    }

    deinit {
        removeMenuControllerObservers()
        clearMemoryCache()
    }

    // MARK: - Private methods

    private func setupDefaults() {
        extendedLayoutIncludesOpaqueBars = true
        view.backgroundColor = .collectionViewBackground
        messagesCollectionView.keyboardDismissMode = .interactive
        messagesCollectionView.alwaysBounceVertical = true
        messagesCollectionView.backgroundColor = .collectionViewBackground
    }

    private func setupSubviews() {
        view.addSubviews(messagesCollectionView, inputContainerView)
    }

    private func setupConstraints() {
        messagesCollectionView.translatesAutoresizingMaskIntoConstraints = false
        /// Constraints of inputContainerView are managed by keyboardManager
        inputContainerView.translatesAutoresizingMaskIntoConstraints = false

        NSLayoutConstraint.activate([
            messagesCollectionView.topAnchor.constraint(equalTo: view.topAnchor),
            messagesCollectionView.bottomAnchor.constraint(equalTo: view.bottomAnchor),
            messagesCollectionView.leadingAnchor.constraint(equalTo: view.safeAreaLayoutGuide.leadingAnchor),
            messagesCollectionView.trailingAnchor.constraint(equalTo: view.safeAreaLayoutGuide.trailingAnchor)
        ])
    }

    private func setupDelegates() {
        messagesCollectionView.delegate = self
        messagesCollectionView.dataSource = self
    }

    private func setupInputBar(for kind: MessageInputBarKind) {
        inputContainerView.subviews.forEach { $0.removeFromSuperview() }

        func pinViewToInputContainer(_ view: UIView) {
            view.translatesAutoresizingMaskIntoConstraints = false
            inputContainerView.addSubviews(view)

            NSLayoutConstraint.activate([
                view.topAnchor.constraint(equalTo: inputContainerView.topAnchor),
                view.bottomAnchor.constraint(equalTo: inputContainerView.bottomAnchor),
                view.leadingAnchor.constraint(equalTo: inputContainerView.leadingAnchor),
                view.trailingAnchor.constraint(equalTo: inputContainerView.trailingAnchor)
            ])
        }

        switch kind {
        case .messageInputBar:
            pinViewToInputContainer(messageInputBar)
        case .custom(let view):
            pinViewToInputContainer(view)
        }
    }

    private func addObservers() {
        NotificationCenter.default
            .publisher(for: UIApplication.didReceiveMemoryWarningNotification)
            .subscribe(on: DispatchQueue.global())
            .receive(on: DispatchQueue.main)
            .sink { [weak self] _ in
                self?.clearMemoryCache()
            }
            .store(in: &disposeBag)

        state.$inputBarType
            .subscribe(on: DispatchQueue.global())
            .dropFirst()
            .removeDuplicates()
            .receive(on: DispatchQueue.main)
            .sink(receiveValue: { [weak self] newType in
                self?.setupInputBar(for: newType)
            })
            .store(in: &disposeBag)
    }

    private func clearMemoryCache() {
        MessageStyle.bubbleImageCache.removeAllObjects()
    }

    // MARK: - UICollectionViewDataSource

    open func numberOfSections(in collectionView: UICollectionView) -> Int {
        guard let collectionView = collectionView as? MessagesCollectionView else {
            fatalError(MessageKitError.notMessagesCollectionView)
        }
        let sections = collectionView.messagesDataSource?.numberOfSections(in: collectionView) ?? 0
        return collectionView.isTypingIndicatorHidden ? sections : sections + 1
    }

    open func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        guard let collectionView = collectionView as? MessagesCollectionView else {
            fatalError(MessageKitError.notMessagesCollectionView)
        }
        if isSectionReservedForTypingIndicator(section) {
            return 1
        }
        return collectionView.messagesDataSource?.numberOfItems(inSection: section, in: collectionView) ?? 0
    }

    /// Notes:
    /// - If you override this method, remember to call MessagesDataSource's customCell(for:at:in:)
    /// for MessageKind.custom messages, if necessary.
    ///
    /// - If you are using the typing indicator you will need to ensure that the section is not
    /// reserved for it with `isSectionReservedForTypingIndicator` defined in
    /// `MessagesCollectionViewFlowLayout`
    open func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {

        guard let messagesCollectionView = collectionView as? MessagesCollectionView else {
            fatalError(MessageKitError.notMessagesCollectionView)
        }

        guard let messagesDataSource = messagesCollectionView.messagesDataSource else {
            fatalError(MessageKitError.nilMessagesDataSource)
        }

        if isSectionReservedForTypingIndicator(indexPath.section) {
            return messagesDataSource.typingIndicator(at: indexPath, in: messagesCollectionView)
        }

        let message = messagesDataSource.messageForItem(at: indexPath, in: messagesCollectionView)

        switch message.kind {
        case .text, .attributedText, .emoji:
            if let cell = messagesDataSource.textCell(for: message, at: indexPath, in: messagesCollectionView) {
                return cell
            } else {
                let cell = messagesCollectionView.dequeueReusableCell(TextMessageCell.self, for: indexPath)
                cell.configure(with: message, at: indexPath, and: messagesCollectionView)
                return cell
            }
        case .photo, .video:
            if let cell = messagesDataSource.photoCell(for: message, at: indexPath, in: messagesCollectionView) {
                return cell
            } else {
                let cell = messagesCollectionView.dequeueReusableCell(MediaMessageCell.self, for: indexPath)
                cell.configure(with: message, at: indexPath, and: messagesCollectionView)
                return cell
            }
        case .location:
            if let cell = messagesDataSource.locationCell(for: message, at: indexPath, in: messagesCollectionView) {
                return cell
            } else {
                let cell = messagesCollectionView.dequeueReusableCell(LocationMessageCell.self, for: indexPath)
                cell.configure(with: message, at: indexPath, and: messagesCollectionView)
                return cell
            }
        case .audio:
            if let cell = messagesDataSource.audioCell(for: message, at: indexPath, in: messagesCollectionView) {
                return cell
            } else {
                let cell = messagesCollectionView.dequeueReusableCell(AudioMessageCell.self, for: indexPath)
                cell.configure(with: message, at: indexPath, and: messagesCollectionView)
                return cell
            }
        case .contact:
            if let cell = messagesDataSource.contactCell(for: message, at: indexPath, in: messagesCollectionView) {
                return cell
            } else {
                let cell = messagesCollectionView.dequeueReusableCell(ContactMessageCell.self, for: indexPath)
                cell.configure(with: message, at: indexPath, and: messagesCollectionView)
                return cell
            }
        case .linkPreview:
            let cell = messagesCollectionView.dequeueReusableCell(LinkPreviewMessageCell.self, for: indexPath)
            cell.configure(with: message, at: indexPath, and: messagesCollectionView)
            return cell
        case .custom:
            return messagesDataSource.customCell(for: message, at: indexPath, in: messagesCollectionView)
        }
    }

    open func collectionView(_ collectionView: UICollectionView, viewForSupplementaryElementOfKind kind: String, at indexPath: IndexPath) -> UICollectionReusableView {

        guard let messagesCollectionView = collectionView as? MessagesCollectionView else {
            fatalError(MessageKitError.notMessagesCollectionView)
        }

        guard let displayDelegate = messagesCollectionView.messagesDisplayDelegate else {
            fatalError(MessageKitError.nilMessagesDisplayDelegate)
        }

        switch kind {
        case UICollectionView.elementKindSectionHeader:
            return displayDelegate.messageHeaderView(for: indexPath, in: messagesCollectionView)
        case UICollectionView.elementKindSectionFooter:
            return displayDelegate.messageFooterView(for: indexPath, in: messagesCollectionView)
        default:
            fatalError(MessageKitError.unrecognizedSectionKind)
        }
    }

    // MARK: - UICollectionViewDelegateFlowLayout

    open func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
        guard let messagesFlowLayout = collectionViewLayout as? MessagesCollectionViewFlowLayout else { return .zero }
        return messagesFlowLayout.sizeForItem(at: indexPath)
    }

    open func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, referenceSizeForHeaderInSection section: Int) -> CGSize {

        guard let messagesCollectionView = collectionView as? MessagesCollectionView else {
            fatalError(MessageKitError.notMessagesCollectionView)
        }
        guard let layoutDelegate = messagesCollectionView.messagesLayoutDelegate else {
            fatalError(MessageKitError.nilMessagesLayoutDelegate)
        }
        if isSectionReservedForTypingIndicator(section) {
            return .zero
        }
        return layoutDelegate.headerViewSize(for: section, in: messagesCollectionView)
    }

    open func collectionView(_ collectionView: UICollectionView, willDisplay cell: UICollectionViewCell, forItemAt indexPath: IndexPath) {
        guard let cell = cell as? TypingIndicatorCell else { return }
        cell.typingBubble.startAnimating()
    }

    open func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, referenceSizeForFooterInSection section: Int) -> CGSize {
        guard let messagesCollectionView = collectionView as? MessagesCollectionView else {
            fatalError(MessageKitError.notMessagesCollectionView)
        }
        guard let layoutDelegate = messagesCollectionView.messagesLayoutDelegate else {
            fatalError(MessageKitError.nilMessagesLayoutDelegate)
        }
        if isSectionReservedForTypingIndicator(section) {
            return .zero
        }
        return layoutDelegate.footerViewSize(for: section, in: messagesCollectionView)
    }

    open func collectionView(_ collectionView: UICollectionView, shouldShowMenuForItemAt indexPath: IndexPath) -> Bool {
        guard let messagesDataSource = messagesCollectionView.messagesDataSource else { return false }

        if isSectionReservedForTypingIndicator(indexPath.section) {
            return false
        }

        let message = messagesDataSource.messageForItem(at: indexPath, in: messagesCollectionView)

        switch message.kind {
        case .text, .attributedText, .emoji, .photo:
            selectedIndexPathForMenu = indexPath
            return true
        default:
            return false
        }
    }

    open func collectionView(_ collectionView: UICollectionView, canPerformAction action: Selector, forItemAt indexPath: IndexPath, withSender sender: Any?) -> Bool {
        if isSectionReservedForTypingIndicator(indexPath.section) {
            return false
        }
        return (action == NSSelectorFromString("copy:"))
    }

    open func collectionView(_ collectionView: UICollectionView, performAction action: Selector, forItemAt indexPath: IndexPath, withSender sender: Any?) {
        guard let messagesDataSource = messagesCollectionView.messagesDataSource else {
            fatalError(MessageKitError.nilMessagesDataSource)
        }
        let pasteBoard = UIPasteboard.general
        let message = messagesDataSource.messageForItem(at: indexPath, in: messagesCollectionView)

        switch message.kind {
        case .text(let text), .emoji(let text):
            pasteBoard.string = text
        case .attributedText(let attributedText):
            pasteBoard.string = attributedText.string
        case .photo(let mediaItem):
            pasteBoard.image = mediaItem.image ?? mediaItem.placeholderImage
        default:
            break
        }
    }
}