swift MessageKitについて

MessageKitのサンプルコードで勉強しているのですが、
ザーっとでいいのでここはこういう働きをしていると教えていただけると嬉しいです。

swift
1import UIKit
2import MessageKit
3import MessageInputBar
4
5class ViewController: MessagesViewController {
6    
7    var messageList: [MockMessage] = []
8    
9    lazy var formatter: DateFormatter = {
10        let formatter = DateFormatter()
11        formatter.dateStyle = .medium
12        return formatter
13    }()
14    
15    override func viewDidLoad() {
16        super.viewDidLoad()
17        
18        DispatchQueue.main.async {
19            // messageListにメッセージの配列をいれて
20            self.messageList = self.getMessages()
21            // messagesCollectionViewをリロードして
22            self.messagesCollectionView.reloadData()
23            // 一番下までスクロールする
24            self.messagesCollectionView.scrollToBottom()
25        }
26        
27        messagesCollectionView.messagesDataSource = self
28        messagesCollectionView.messagesLayoutDelegate = self
29        messagesCollectionView.messagesDisplayDelegate = self
30        messagesCollectionView.messageCellDelegate = self
31        
32        messageInputBar.delegate = self
33        messageInputBar.sendButton.tintColor = UIColor.lightGray
34        
35        
36       
37        
38        // メッセージ入力時に一番下までスクロール
39        scrollsToBottomOnKeyboardBeginsEditing = true // default false
40        maintainPositionOnKeyboardFrameChanged = true // default false
41    }
42    
43    
44   //サンプルメッセージ
45    func getMessages() -> [MockMessage] {
46        return [
47            createMessage(text: "あ"),
48            createMessage(text: "い"),
49            createMessage(text: "う"),
50            createMessage(text: "え"),
51            createMessage(text: "お"),
52            createMessage(text: "か"),
53            createMessage(text: "き"),
54            createMessage(text: "く"),
55            createMessage(text: "け"),
56            createMessage(text: "こ"),
57            createMessage(text: "さ"),
58            createMessage(text: "し"),
59            createMessage(text: "すせそたちつてとなにぬねのはひふへほまみむめもやゆよらりるれろわをん"),
60        ]
61    }
62    
63    func createMessage(text: String) -> MockMessage {
64        let attributedText = NSAttributedString(string: text, attributes: [.font: UIFont.systemFont(ofSize: 15),
65                                                                           .foregroundColor: UIColor.black])
66        return MockMessage(attributedText: attributedText, sender: otherSender(), messageId: UUID().uuidString, date: Date())
67    }
68    
69    override func didReceiveMemoryWarning() {
70        super.didReceiveMemoryWarning()
71    }
72}
73
74extension ViewController: MessagesDataSource {
75    
76    func currentSender() -> Sender {
77        return Sender(id: "123", displayName: "自分")
78    }
79    
80    func otherSender() -> Sender {
81        return Sender(id: "456", displayName: "知らない人")
82    }
83    
84    func numberOfSections(in messagesCollectionView: MessagesCollectionView) -> Int {
85        return messageList.count
86    }
87    
88    func messageForItem(at indexPath: IndexPath, in messagesCollectionView: MessagesCollectionView) -> MessageType {
89        return messageList[indexPath.section]
90    }
91    
92    // メッセージの上に文字を表示
93    func cellTopLabelAttributedText(for message: MessageType, at indexPath: IndexPath) -> NSAttributedString? {
94        if indexPath.section % 3 == 0 {
95            return NSAttributedString(
96                string: MessageKitDateFormatter.shared.string(from: message.sentDate),
97                attributes: [NSAttributedString.Key.font: UIFont.boldSystemFont(ofSize: 10),
98                             NSAttributedString.Key.foregroundColor: UIColor.darkGray]
99            )
100        }
101        return nil
102    }
103    
104    // メッセージの上に文字を表示（名前）
105    func messageTopLabelAttributedText(for message: MessageType, at indexPath: IndexPath) -> NSAttributedString? {
106        let name = message.sender.displayName
107        return NSAttributedString(string: name, attributes: [NSAttributedString.Key.font: UIFont.preferredFont(forTextStyle: .caption1)])
108    }
109    
110    // メッセージの下に文字を表示（日付）
111    func messageBottomLabelAttributedText(for message: MessageType, at indexPath: IndexPath) -> NSAttributedString? {
112        let dateString = formatter.string(from: message.sentDate)
113        return NSAttributedString(string: dateString, attributes: [NSAttributedString.Key.font: UIFont.preferredFont(forTextStyle: .caption2)])
114    }
115}
116
117// メッセージのdelegate
118extension ViewController: MessagesDisplayDelegate {
119    
120    // メッセージの色を変更（デフォルトは自分：白、相手：黒）
121    func textColor(for message: MessageType, at indexPath: IndexPath, in messagesCollectionView: MessagesCollectionView) -> UIColor {
122        return isFromCurrentSender(message: message) ? .white : .darkText
123    }
124    
125    // メッセージの背景色を変更している（デフォルトは自分：緑、相手：グレー）
126    func backgroundColor(for message: MessageType, at indexPath: IndexPath, in messagesCollectionView: MessagesCollectionView) -> UIColor {
127        return isFromCurrentSender(message: message) ?
128            UIColor(red: 69/255, green: 193/255, blue: 89/255, alpha: 1) :
129            UIColor(red: 230/255, green: 230/255, blue: 230/255, alpha: 1)
130    }
131    
132    // メッセージの枠にしっぽを付ける
133    func messageStyle(for message: MessageType, at indexPath: IndexPath, in messagesCollectionView: MessagesCollectionView) -> MessageStyle {
134        let corner: MessageStyle.TailCorner = isFromCurrentSender(message: message) ? .bottomRight : .bottomLeft
135        return .bubbleTail(corner, .curved)
136    }
137    
138    // アイコンをセット
139    func configureAvatarView(_ avatarView: AvatarView, for message: MessageType, at indexPath: IndexPath, in messagesCollectionView: MessagesCollectionView) {
140        // message.sender.displayNameとかで送信者の名前を取得できるので
141        // そこからイニシャルを生成するとよい
142        let avatar = Avatar(initials: "人")
143        avatarView.set(avatar: avatar)
144    }
145}
146
147
148// 各ラベルの高さを設定（デフォルト0なので必須）
149extension ViewController: MessagesLayoutDelegate {
150    
151    func cellTopLabelHeight(for message: MessageType, at indexPath: IndexPath, in messagesCollectionView: MessagesCollectionView) -> CGFloat {
152        if indexPath.section % 3 == 0 { return 10 }
153        return 0
154    }
155    
156    func messageTopLabelHeight(for message: MessageType, at indexPath: IndexPath, in messagesCollectionView: MessagesCollectionView) -> CGFloat {
157        return 16
158    }
159    
160    func messageBottomLabelHeight(for message: MessageType, at indexPath: IndexPath, in messagesCollectionView: MessagesCollectionView) -> CGFloat {
161        return 16
162    }
163}
164
165extension ViewController: MessageCellDelegate {
166    // メッセージをタップした時の挙動
167    func didTapMessage(in cell: MessageCollectionViewCell) {
168        print("Message tapped")
169    }
170}
171
172extension ViewController: MessageInputBarDelegate {
173    // メッセージ送信ボタンをタップした時の挙動
174    func messageInputBar(_ inputBar: MessageInputBar, didPressSendButtonWith text: String) {
175        for component in inputBar.inputTextView.components {
176            if let image = component as? UIImage {
177                
178                let imageMessage = MockMessage(image: image, sender: currentSender(), messageId: UUID().uuidString, date: Date())
179                messageList.append(imageMessage)
180                messagesCollectionView.insertSections([messageList.count - 1])
181                
182            } else if let text = component as? String {
183                
184                let attributedText = NSAttributedString(string: text, attributes: [.font: UIFont.systemFont(ofSize: 15),
185                                                                                   .foregroundColor: UIColor.white])
186                let message = MockMessage(attributedText: attributedText, sender: currentSender(), messageId: UUID().uuidString, date: Date())
187                messageList.append(message)
188                messagesCollectionView.insertSections([messageList.count - 1])
189            }
190        }
191        inputBar.inputTextView.text = String()
192        messagesCollectionView.scrollToBottom()
193    }
194}