Add support for System Messages

Example/Sources/Data Generation/SampleData.swift

@@ -45,6 +45,7 @@ final internal class SampleData {
     case Phone
     case Custom
     case ShareContact
+    case System
   }
 
   static let shared = SampleData()
@@ -234,6 +235,11 @@ final internal class SampleData {
       return MockMessage(custom: "Someone left the conversation", user: system, messageId: uniqueID, date: date)
     case .ShareContact:
       return MockMessage(contact: contactsToShare.random()!, user: user, messageId: uniqueID, date: date)
+    case .System:
+      let message = NSAttributedString(string: "John Doe entered the conversation", attributes: [
+        .font: UIFont.preferredFont(forTextStyle: .footnote)
+      ])
+      return MockMessage(system: message, user: system, messageId: uniqueID, date: date)
     }
   }
 

Example/Sources/Models/MockMessage.swift

@@ -122,6 +122,10 @@ internal struct MockMessage: MessageType {
     self.init(kind: .text(text), user: user, messageId: messageId, date: date)
   }
 
+  init(system: NSAttributedString, user: MockUser, messageId: String, date: Date) {
+    self.init(kind: .system(system), user: user, messageId: messageId, date: date)
+  }
+
   init(attributedText: NSAttributedString, user: MockUser, messageId: String, date: Date) {
     self.init(kind: .attributedText(attributedText), user: user, messageId: messageId, date: date)
   }

Example/Sources/View Controllers/SettingsViewController.swift

@@ -53,6 +53,7 @@ final internal class SettingsViewController: UITableViewController {
     "Url Messages",
     "Phone Messages",
     "ShareContact Messages",
+    "System Messages"
   ]
 
   var messagesPicker = UIPickerView()

Sources/Controllers/MessagesViewController.swift

@@ -174,6 +174,10 @@ open class MessagesViewController: UIViewController, UICollectionViewDelegateFlo
       return cell
     case .custom:
       return messagesDataSource.customCell(for: message, at: indexPath, in: messagesCollectionView)
+    case .system:
+      let cell = messagesCollectionView.dequeueReusableCell(SystemMessageCell.self, for: indexPath)
+      cell.configure(with: message, at: indexPath, and: messagesCollectionView)
+      return cell
     }
   }
 

Sources/Layout/MessagesCollectionViewFlowLayout.swift

@@ -70,6 +70,7 @@ open class MessagesCollectionViewFlowLayout: UICollectionViewFlowLayout {
   lazy open var contactMessageSizeCalculator = ContactMessageSizeCalculator(layout: self)
   lazy open var typingIndicatorSizeCalculator = TypingCellSizeCalculator(layout: self)
   lazy open var linkPreviewMessageSizeCalculator = LinkPreviewMessageSizeCalculator(layout: self)
+  lazy open var systemMessageSizeCalculator = SystemMessageSizeCalculator(layout: self)
 
   /// A method that by default checks if the section is the last in the
   /// `messagesCollectionView` and that `isTypingIndicatorViewHidden`
@@ -161,6 +162,8 @@ open class MessagesCollectionViewFlowLayout: UICollectionViewFlowLayout {
       return linkPreviewMessageSizeCalculator
     case .custom:
       return messagesLayoutDelegate.customCellSizeCalculator(for: message, at: indexPath, in: messagesCollectionView)
+    case .system:
+      return systemMessageSizeCalculator
     }
   }
 
@@ -181,6 +184,7 @@ open class MessagesCollectionViewFlowLayout: UICollectionViewFlowLayout {
       audioMessageSizeCalculator,
       contactMessageSizeCalculator,
       linkPreviewMessageSizeCalculator,
+      systemMessageSizeCalculator
     ]
   }
 

Sources/Layout/SystemMessageSizeCalculator.swift.swift

@@ -0,0 +1,53 @@
+/*
+ MIT License
+
+ Copyright (c) 2017-2019 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
+
+open class SystemMessageSizeCalculator: MessageSizeCalculator {
+
+  public override init(layout: MessagesCollectionViewFlowLayout? = nil) {
+    super.init()
+    self.layout = layout
+  }
+
+  open override func sizeForItem(at indexPath: IndexPath) -> CGSize {
+    guard let layout = layout else { return .zero }
+
+    let collectionViewWidth = layout.collectionView?.bounds.width ?? 0
+    let contentInset = layout.collectionView?.contentInset ?? .zero
+    let inset = layout.sectionInset.left + layout.sectionInset.right + contentInset.left + contentInset.right
+
+    guard let messagesCollectionViewFlowLayout = layout as? MessagesCollectionViewFlowLayout else { return .zero }
+    guard let messagesCollectionView = layout.collectionView as? MessagesCollectionView else { return .zero }
+
+    let message = messagesCollectionViewFlowLayout.messagesDataSource.messageForItem(at: indexPath, in: messagesCollectionView)
+    guard case .system = message.kind else { return .zero }
+
+    return CGSize(width: collectionViewWidth - inset, height: 44)
+  }
+
+  open override func cellContentHeight(for message: MessageType, at indexPath: IndexPath) -> CGFloat {
+    return 44
+  }
+}

Sources/Models/MessageKind.swift

@@ -63,6 +63,9 @@ public enum MessageKind {
   ///   - MessagesLayoutDelegate: customCellSizeCalculator(for message: MessageType, at indexPath: IndexPath, in messagesCollectionView: MessagesCollectionView) -> CellSizeCalculator
   case custom(Any?)
 
+  /// A system message.
+  case system(NSAttributedString)
+
   // MARK: - Not supported yet
 
 //    case system(String)

Sources/Views/Cells/SystemMessageCell.swift

@@ -0,0 +1,86 @@
+/*
+ MIT License
+
+ Copyright (c) 2017-2019 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 UIKit
+
+/// A subclass of `MessageContentCell` used to display system messages.
+open class SystemMessageCell: MessageCollectionViewCell {
+
+  /// The label used to display the message's text.
+  open var label = UILabel()
+
+  /// The `MessageCellDelegate` for the cell.
+  open weak var delegate: MessageCellDelegate?
+
+  // MARK: - Lifecycle
+
+  public override init(frame: CGRect) {
+    super.init(frame: frame)
+    contentView.autoresizingMask = [.flexibleWidth, .flexibleHeight]
+    setupSubviews()
+  }
+
+  required public init?(coder aDecoder: NSCoder) {
+    super.init(coder: aDecoder)
+    contentView.autoresizingMask = [.flexibleWidth, .flexibleHeight]
+    setupSubviews()
+  }
+
+  // MARK: - Methods
+
+  open func setupSubviews() {
+    contentView.addSubview(label)
+    label.textColor = .gray
+    label.textAlignment = .center
+    label.numberOfLines = 0
+    if #available(iOS 10.0, *) {
+      label.adjustsFontForContentSizeCategory = true
+    }
+  }
+
+  open override func layoutSubviews() {
+    super.layoutSubviews()
+    label.frame = contentView.bounds
+  }
+
+  open override func prepareForReuse() {
+    super.prepareForReuse()
+    label.attributedText = nil
+    label.text = nil
+  }
+
+  open func configure(with message: MessageType, at indexPath: IndexPath, and messagesCollectionView: MessagesCollectionView) {
+    guard case let .system(systemMessage) = message.kind else {
+      fatalError("Message must be of kind .system to be displayed in SystemMessageCell")
+    }
+
+    delegate = messagesCollectionView.messageCellDelegate
+
+    label.attributedText = systemMessage
+  }
+
+  open override func handleTapGesture(_: UIGestureRecognizer) {
+    delegate?.didTapMessage(in: self)
+  }
+}

Sources/Views/MessagesCollectionView.swift

@@ -213,6 +213,7 @@ open class MessagesCollectionView: UICollectionView {
     register(ContactMessageCell.self)
     register(TypingIndicatorCell.self)
     register(LinkPreviewMessageCell.self)
+    register(SystemMessageCell.self)
     register(MessageReusableView.self, forSupplementaryViewOfKind: UICollectionView.elementKindSectionHeader)
     register(MessageReusableView.self, forSupplementaryViewOfKind: UICollectionView.elementKindSectionFooter)
   }