MessageKit/Example/Sources/Views/SwiftUI/MessagesView.swift

// MIT License
//
// Copyright (c) 2017-2020 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 InputBarAccessoryView
import MessageKit
import SwiftUI

// MARK: - MessageSwiftUIVC

final class MessageSwiftUIVC: MessagesViewController {
  override func viewDidAppear(_ animated: Bool) {
    super.viewDidAppear(animated)
    // Because SwiftUI wont automatically make our controller the first responder, we need to do it on viewDidAppear
    becomeFirstResponder()
    messagesCollectionView.scrollToLastItem(animated: true)
  }
}

// MARK: - MessagesView

struct MessagesView: UIViewControllerRepresentable {
  // MARK: Internal

  final class Coordinator {
    // MARK: Lifecycle

    init(messages: Binding<[MessageType]>) {
      self.messages = messages
    }

    // MARK: Internal

    let formatter: DateFormatter = {
      let formatter = DateFormatter()
      formatter.dateStyle = .medium
      return formatter
    }()

    var messages: Binding<[MessageType]>
  }

  @State var initialized = false
  @Binding var messages: [MessageType]

  func makeUIViewController(context: Context) -> MessagesViewController {
    let messagesVC = MessageSwiftUIVC()

    messagesVC.messagesCollectionView.messagesDisplayDelegate = context.coordinator
    messagesVC.messagesCollectionView.messagesLayoutDelegate = context.coordinator
    messagesVC.messagesCollectionView.messagesDataSource = context.coordinator
    messagesVC.messageInputBar.delegate = context.coordinator
    messagesVC.scrollsToLastItemOnKeyboardBeginsEditing = true // default false
    messagesVC.maintainPositionOnInputBarHeightChanged = true // default false
    messagesVC.showMessageTimestampOnSwipeLeft = true // default false

    return messagesVC
  }

  func updateUIViewController(_ uiViewController: MessagesViewController, context _: Context) {
    uiViewController.messagesCollectionView.reloadData()
    scrollToBottom(uiViewController)
  }

  func makeCoordinator() -> Coordinator {
    Coordinator(messages: $messages)
  }

  // MARK: Private

  private func scrollToBottom(_ uiViewController: MessagesViewController) {
    DispatchQueue.main.async {
      // The initialized state variable allows us to start at the bottom with the initial messages without seeing the initial scroll flash by
      uiViewController.messagesCollectionView.scrollToLastItem(animated: self.initialized)
      self.initialized = true
    }
  }
}

// MARK: - MessagesView.Coordinator + MessagesDataSource

extension MessagesView.Coordinator: MessagesDataSource {
  var currentSender: SenderType {
    SampleData.shared.currentSender
  }

  func messageForItem(at indexPath: IndexPath, in _: MessagesCollectionView) -> MessageType {
    messages.wrappedValue[indexPath.section]
  }

  func numberOfSections(in _: MessagesCollectionView) -> Int {
    messages.wrappedValue.count
  }

  func messageTopLabelAttributedText(for message: MessageType, at _: IndexPath) -> NSAttributedString? {
    let name = message.sender.displayName
    return NSAttributedString(
      string: name,
      attributes: [NSAttributedString.Key.font: UIFont.preferredFont(forTextStyle: .caption1)])
  }

  func messageBottomLabelAttributedText(for message: MessageType, at _: IndexPath) -> NSAttributedString? {
    let dateString = formatter.string(from: message.sentDate)
    return NSAttributedString(
      string: dateString,
      attributes: [NSAttributedString.Key.font: UIFont.preferredFont(forTextStyle: .caption2)])
  }

  func messageTimestampLabelAttributedText(for message: MessageType, at _: IndexPath) -> NSAttributedString? {
    let sentDate = message.sentDate
    let sentDateString = MessageKitDateFormatter.shared.string(from: sentDate)
    let timeLabelFont: UIFont = .boldSystemFont(ofSize: 10)
    let timeLabelColor: UIColor = .systemGray
    return NSAttributedString(
      string: sentDateString,
      attributes: [NSAttributedString.Key.font: timeLabelFont, NSAttributedString.Key.foregroundColor: timeLabelColor])
  }
}

// MARK: - MessagesView.Coordinator + InputBarAccessoryViewDelegate

extension MessagesView.Coordinator: InputBarAccessoryViewDelegate {
  func inputBar(_ inputBar: InputBarAccessoryView, didPressSendButtonWith text: String) {
    let message = MockMessage(text: text, user: SampleData.shared.currentSender, messageId: UUID().uuidString, date: Date())
    messages.wrappedValue.append(message)
    inputBar.inputTextView.text = ""
  }
}

// MARK: - MessagesView.Coordinator + MessagesLayoutDelegate, MessagesDisplayDelegate

extension MessagesView.Coordinator: MessagesLayoutDelegate, MessagesDisplayDelegate {
  func configureAvatarView(_ avatarView: AvatarView, for message: MessageType, at _: IndexPath, in _: MessagesCollectionView) {
    let avatar = SampleData.shared.getAvatarFor(sender: message.sender)
    avatarView.set(avatar: avatar)
  }

  func messageTopLabelHeight(for _: MessageType, at _: IndexPath, in _: MessagesCollectionView) -> CGFloat {
    20
  }

  func messageBottomLabelHeight(for _: MessageType, at _: IndexPath, in _: MessagesCollectionView) -> CGFloat {
    16
  }
}