Show number of unread messages in back-button (#2280)

DcCore/DcCore/DC/events.swift

@@ -105,6 +105,7 @@ public class DcEventHandler {
 
             NotificationCenter.default.post(name: Event.messagesNoticed, object: nil, userInfo: [
                 "chat_id": Int(data1),
+                "account_id": accountId
             ])
 
         case DC_EVENT_CHAT_MODIFIED:
@@ -129,7 +130,11 @@ public class DcEventHandler {
 
         case DC_EVENT_INCOMING_MSG:
 
-            NotificationCenter.default.post(name: Event.incomingMessageOnAnyAccount, object: nil)
+            NotificationCenter.default.post(name: Event.incomingMessageOnAnyAccount, object: nil, userInfo: [
+                "chat_id": Int(data1),
+                "account_id": accountId
+            ])
+
             if accountId != dcAccounts.getSelected().id {
                 return
             }
@@ -138,6 +143,7 @@ public class DcEventHandler {
             NotificationCenter.default.post(name: Event.incomingMessage, object: nil, userInfo: [
                 "message_id": Int(data2),
                 "chat_id": Int(data1),
+                "account_id": accountId
             ])
 
         case DC_EVENT_CONTACTS_CHANGED:

deltachat-ios/Chat/ChatViewController.swift

@@ -2784,3 +2784,15 @@ extension ChatViewController: ReactionsOverviewViewControllerDelegate {
         navigationController?.pushViewController(contactDetailController, animated: true)
     }
 }
+
+// MARK: - ChatListViewControllerDataSource
+
+extension ChatViewController: BackButtonUpdateable {
+    func shouldUpdateBackButton(_ viewController: UIViewController, chatId: Int, accountId: Int) -> Bool {
+        if chatId == self.chatId && accountId == dcContext.id {
+            return false
+        } else {
+            return true
+        }
+    }
+}

deltachat-ios/Controller/ChatListViewController.swift

@@ -1,12 +1,17 @@
 import UIKit
 import DcCore
 
+protocol BackButtonUpdateable: AnyObject {
+    func shouldUpdateBackButton(_ viewController: UIViewController, chatId: Int, accountId: Int) -> Bool
+}
+
 class ChatListViewController: UITableViewController {
     var viewModel: ChatListViewModel?
     let dcContext: DcContext
     internal let dcAccounts: DcAccounts
     var isArchive: Bool
     private var accountSwitchTransitioningDelegate: PartialScreenModalTransitioningDelegate!
+    weak var backButtonUpdateableDataSource: BackButtonUpdateable?
 
     private weak var timer: Timer?
 
@@ -206,6 +211,9 @@ class ChatListViewController: UITableViewController {
 
     @objc private func handleMessagesNoticed(_ notification: Notification) {
         refreshInBg()
+        DispatchQueue.main.async { [weak self] in
+            self?.updateNextScreensBackButton()
+        }
     }
 
     @objc private func handleMessagesChanged(_ notification: Notification) {
@@ -227,14 +235,48 @@ class ChatListViewController: UITableViewController {
     }
 
     @objc private func handleIncomingMessageOnAnyAccount(_ notification: Notification) {
+
+        guard let userInfo = notification.userInfo,
+              let chatId = userInfo["chat_id"] as? Int,
+              let accountId = userInfo["account_id"] as? Int
+        else { return }
+
         DispatchQueue.main.async { [weak self] in
             self?.updateAccountButton()
+            self?.updateNextScreensBackButton(accountId: accountId, chatId: chatId)
         }
     }
 
     private func setupSubviews() {
         emptyStateLabel.addCenteredTo(parentView: view)
-        navigationItem.backButtonTitle = isArchive ? String.localized("chat_archived_label") : String.localized("pref_chats")
+        updateNextScreensBackButton()
+    }
+
+    private func updateNextScreensBackButton(accountId: Int? = nil, chatId: Int? = nil) {
+        let numberOfUnreadMessages = DcAccounts.shared.getFreshMessageCount()
+
+        if isArchive {
+            navigationItem.backBarButtonItem = nil
+            navigationItem.backButtonTitle = String.localized("chat_archived_label")
+        } else if numberOfUnreadMessages > 0, #available(iOS 13, *) {
+
+            if let backButtonUpdateableDataSource, let accountId, let chatId,
+               backButtonUpdateableDataSource.shouldUpdateBackButton(self, chatId: chatId, accountId: accountId) == false {
+                return
+            }
+
+            let symbolName: String
+            if numberOfUnreadMessages > 50 {
+                symbolName = "circle.fill"
+            } else {
+                symbolName = "\(numberOfUnreadMessages).circle.fill"
+            }
+
+            navigationItem.backBarButtonItem = UIBarButtonItem(image: UIImage(systemName: symbolName), style: .plain, target: nil, action: nil)
+        } else { // if numberOfUnreadMessages == 0 or iOS 12
+            navigationItem.backBarButtonItem = nil
+            navigationItem.backButtonTitle = String.localized("pref_chats")
+        }
     }
 
     @objc
@@ -823,8 +865,11 @@ class ChatListViewController: UITableViewController {
         if searchController.isActive {
             searchController.searchBar.resignFirstResponder()
         }
-        let chatVC = ChatViewController(dcContext: dcContext, chatId: chatId, highlightedMsg: highlightedMsg)
-        navigationController?.pushViewController(chatVC, animated: animated)
+        let chatViewController = ChatViewController(dcContext: dcContext, chatId: chatId, highlightedMsg: highlightedMsg)
+        backButtonUpdateableDataSource = chatViewController
+        updateNextScreensBackButton(accountId: dcContext.id, chatId: chatId)
+
+        navigationController?.pushViewController(chatViewController, animated: animated)
     }
 
     public func showArchive(animated: Bool) {
@@ -838,7 +883,7 @@ class ChatListViewController: UITableViewController {
     }
 }
 
-// MARK: - uisearchbardelegate
+// MARK: - UISearchBarDelegate
 extension ChatListViewController: UISearchBarDelegate {
     func searchBarShouldBeginEditing(_ searchBar: UISearchBar) -> Bool {
         viewModel?.beginSearch()
@@ -860,6 +905,7 @@ extension ChatListViewController: UISearchBarDelegate {
     }
 }
 
+// MARK: - ContactCellDelegate
 extension ChatListViewController: ContactCellDelegate {
     func onLongTap(at indexPath: IndexPath) {
         if let searchActive = viewModel?.searchActive,
@@ -875,6 +921,7 @@ extension ChatListViewController: ContactCellDelegate {
     }
 }
 
+// MARK: - ChatListEditingBarDelegate
 extension ChatListViewController: ChatListEditingBarDelegate {
     func onPinButtonPressed() {
         viewModel?.pinChatsToggle(indexPaths: tableView.indexPathsForSelectedRows)

deltachat-ios/Controller/ContactDetailViewController.swift

@@ -534,8 +534,9 @@ class ContactDetailViewController: UITableViewController {
 
     // MARK: - coordinator
     private func showChat(chatId: Int) {
-        if let chatlistViewController = navigationController?.viewControllers[0] {
+        if let chatlistViewController = navigationController?.viewControllers[0] as? ChatListViewController {
             let chatViewController = ChatViewController(dcContext: viewModel.context, chatId: chatId)
+            chatlistViewController.backButtonUpdateableDataSource = chatViewController
             navigationController?.setViewControllers([chatlistViewController, chatViewController], animated: true)
         }
     }

deltachat-ios/Controller/NewChatViewController.swift

@@ -318,9 +318,11 @@ class NewChatViewController: UITableViewController {
     }
 
     private func showChat(chatId: Int) {
-        let chatViewController = ChatViewController(dcContext: dcContext, chatId: chatId)
-        navigationController?.pushViewController(chatViewController, animated: true)
-        navigationController?.viewControllers.remove(at: 1)
+        if let chatlistViewController = navigationController?.viewControllers[0] as? ChatListViewController {
+            let chatViewController = ChatViewController(dcContext: dcContext, chatId: chatId)
+            chatlistViewController.backButtonUpdateableDataSource = chatViewController
+            navigationController?.setViewControllers([chatlistViewController, chatViewController], animated: true)
+        }
     }
 
     private func showContactDetail(contactId: Int) {

deltachat-ios/Controller/NewContactController.swift

@@ -119,8 +119,9 @@ class NewContactController: UITableViewController {
 
     // MARK: - coordinator
     private func showChat(chatId: Int) {
-        if let chatlistViewController = navigationController?.viewControllers[0] {
+        if let chatlistViewController = navigationController?.viewControllers[0] as? ChatListViewController {
             let chatViewController = ChatViewController(dcContext: dcContext, chatId: chatId)
+            chatlistViewController.backButtonUpdateableDataSource = chatViewController
             navigationController?.setViewControllers([chatlistViewController, chatViewController], animated: true)
         }
     }

deltachat-ios/Controller/NewGroupController.swift

@@ -305,8 +305,9 @@ class NewGroupController: UITableViewController, MediaPickerDelegate {
 
     // MARK: - coordinator
     private func showGroupChat(chatId: Int) {
-        if let chatlistViewController = navigationController?.viewControllers[0] {
+        if let chatlistViewController = navigationController?.viewControllers[0] as? ChatListViewController {
             let chatViewController = ChatViewController(dcContext: dcContext, chatId: chatId)
+            chatlistViewController.backButtonUpdateableDataSource = chatViewController
             navigationController?.setViewControllers([chatlistViewController, chatViewController], animated: true)
         }
     }

deltachat-ios/Coordinator/AppCoordinator.swift

@@ -121,9 +121,10 @@ class AppCoordinator: NSObject {
            let chatListViewController = rootController.viewControllers.first as? ChatListViewController {
             if let msgId = msgId, openHighlightedMsg {
                 let dcContext = dcAccounts.getSelected()
-                let chatVC = ChatViewController(dcContext: dcContext, chatId: chatId, highlightedMsg: msgId)
+                let chatViewController = ChatViewController(dcContext: dcContext, chatId: chatId, highlightedMsg: msgId)
+                chatListViewController.backButtonUpdateableDataSource = chatViewController
                 let webxdcVC = WebxdcViewController(dcContext: dcContext, messageId: msgId)
-                let controllers: [UIViewController] = [chatListViewController, chatVC, webxdcVC]
+                let controllers: [UIViewController] = [chatListViewController, chatViewController, webxdcVC]
                 rootController.setViewControllers(controllers, animated: animated)
             } else {
                 if clearViewControllerStack {