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

//
//  MessagesView.swift
//  ChatExample
//
//  Created by Kino Roy on 2020-07-18.
//  Copyright © 2020 MessageKit. All rights reserved.
//

import SwiftUI
import MessageKit
import InputBarAccessoryView

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.scrollToBottom(animated: true)
    }
}

@available(iOS 13.0.0, *)
struct MessagesView: UIViewControllerRepresentable {
    
    @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.scrollsToBottomOnKeyboardBeginsEditing = true // default false
        messagesVC.maintainPositionOnKeyboardFrameChanged = true // default false
        
        return messagesVC
    }
    
    func updateUIViewController(_ uiViewController: MessagesViewController, context: Context) {
        uiViewController.messagesCollectionView.reloadData()
        scrollToBottom(uiViewController)
    }
    
    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 inital scroll flash by
            uiViewController.messagesCollectionView.scrollToBottom(animated: self.initialized)
            self.initialized = true
        }
    }
    
    func makeCoordinator() -> Coordinator {
        return Coordinator(messages: $messages)
    }
    
    final class Coordinator {
        
        let formatter: DateFormatter = {
            let formatter = DateFormatter()
            formatter.dateStyle = .medium
            return formatter
        }()
        
        var messages: Binding<[MessageType]>
        init(messages: Binding<[MessageType]>) {
            self.messages = messages
        }
        
    }

}

@available(iOS 13.0.0, *)
extension MessagesView.Coordinator: MessagesDataSource {
    func currentSender() -> SenderType {
        return SampleData.shared.currentSender
    }
    
    func messageForItem(at indexPath: IndexPath, in messagesCollectionView: MessagesCollectionView) -> MessageType {
        return messages.wrappedValue[indexPath.section]
    }
    
    func numberOfSections(in messagesCollectionView: MessagesCollectionView) -> Int {
        return messages.wrappedValue.count
    }
    
    func messageTopLabelAttributedText(for message: MessageType, at indexPath: 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: IndexPath) -> NSAttributedString? {
        let dateString = formatter.string(from: message.sentDate)
        return NSAttributedString(string: dateString, attributes: [NSAttributedString.Key.font: UIFont.preferredFont(forTextStyle: .caption2)])
    }
}

@available(iOS 13.0.0, *)
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 = ""
    }
}

@available(iOS 13.0.0, *)
extension MessagesView.Coordinator: MessagesLayoutDelegate, MessagesDisplayDelegate {
    func configureAvatarView(_ avatarView: AvatarView, for message: MessageType, at indexPath: IndexPath, in messagesCollectionView: MessagesCollectionView) {
        let avatar = SampleData.shared.getAvatarFor(sender: message.sender)
        avatarView.set(avatar: avatar)
    }
    func messageTopLabelHeight(for message: MessageType, at indexPath: IndexPath, in messagesCollectionView: MessagesCollectionView) -> CGFloat {
        return 20
    }
    
    func messageBottomLabelHeight(for message: MessageType, at indexPath: IndexPath, in messagesCollectionView: MessagesCollectionView) -> CGFloat {
        return 16
    }
}