Sync active tab and navigation stack between split view/tab bar controllers

Tusker/Screens/Explore/ExploreViewController.swift

@@ -19,6 +19,8 @@ class ExploreViewController: EnhancedTableViewController {
     var resultsController: SearchResultsViewController!
     var searchController: UISearchController!
     
+    var searchControllerStatusOnAppearance: Bool? = nil
+    
     init(mastodonController: MastodonController) {
         self.mastodonController = mastodonController
         
@@ -109,6 +111,18 @@ class ExploreViewController: EnhancedTableViewController {
         reloadLists()
     }
     
+    override func viewDidAppear(_ animated: Bool) {
+        super.viewDidAppear(animated)
+        
+        // this is a workaround for the issue that setting isActive on a search controller that is not visible
+        // does not cause it to automatically become active once it becomes visible
+        // see FB7814561
+        if let active = searchControllerStatusOnAppearance {
+            searchController.isActive = active
+            searchControllerStatusOnAppearance = nil
+        }
+    }
+    
     func reloadLists() {
         let request = Client.getLists()
         mastodonController.run(request) { (response) in

Tusker/Screens/Main/MainSidebarViewController.swift

@@ -18,12 +18,45 @@ protocol MainSidebarViewControllerDelegate: class {
 @available(iOS 14.0, *)
 class MainSidebarViewController: UIViewController {
     
-    weak var mastodonController: MastodonController!
+    private weak var mastodonController: MastodonController!
     
     weak var sidebarDelegate: MainSidebarViewControllerDelegate?
     
-    var collectionView: UICollectionView!
+    private var collectionView: UICollectionView!
-    var dataSource: UICollectionViewDiffableDataSource<Section, Item>!
+    private var dataSource: UICollectionViewDiffableDataSource<Section, Item>!
+    
+    var allItems: [Item] {
+        [
+            .tab(.timelines),
+            .tab(.notifications),
+            .tab(.myProfile),
+        ] + exploreTabItems
+    }
+    
+    var exploreTabItems: [Item] {
+        var items: [Item] = [.search, .bookmarks]
+        let snapshot = dataSource.snapshot()
+        for case let .list(list) in snapshot.itemIdentifiers(inSection: .lists) {
+            items.append(.list(list))
+        }
+        for case let .savedHashtag(hashtag) in snapshot.itemIdentifiers(inSection: .savedHashtags) {
+            items.append(.savedHashtag(hashtag))
+        }
+        for case let .savedInstance(instance) in snapshot.itemIdentifiers(inSection: .savedInstances) {
+            items.append(.savedInstance(instance))
+        }
+        return items
+    }
+    
+    private(set) var previouslySelectedItem: Item?
+    var selectedItem: Item? {
+        guard let indexPath = collectionView.indexPathsForSelectedItems?.first else {
+            return nil
+        }
+        return dataSource.itemIdentifier(for: indexPath)
+    }
+    
+    private(set) var itemLastSelectedTimestamps = [Item: Date]()
 
     init(mastodonController: MastodonController) {
         self.mastodonController = mastodonController
@@ -53,15 +86,16 @@ class MainSidebarViewController: UIViewController {
         
         applyInitialSnapshot()
         
-        select(.tab(.timelines), animated: false)
+        select(item: .tab(.timelines), animated: false)
         
         NotificationCenter.default.addObserver(self, selector: #selector(reloadSavedHashtags), name: .savedHashtagsChanged, object: nil)
         NotificationCenter.default.addObserver(self, selector: #selector(reloadSavedInstances), name: .savedInstancesChanged, object: nil)
     }
     
-    func select(_ item: Item, animated: Bool) {
+    func select(item: Item, animated: Bool) {
         guard let indexPath = dataSource.indexPath(for: item) else { return }
         collectionView.selectItem(at: indexPath, animated: animated, scrollPosition: .top)
+        itemLastSelectedTimestamps[item] = Date()
     }
     
     private func createDataSource() -> UICollectionViewDiffableDataSource<Section, Item> {
@@ -301,34 +335,37 @@ fileprivate extension MainTabBarViewController.Tab {
 @available(iOS 14.0, *)
 extension MainSidebarViewController: UICollectionViewDelegate {
     func collectionView(_ collectionView: UICollectionView, shouldSelectItemAt indexPath: IndexPath) -> Bool {
-        guard let item = dataSource.itemIdentifier(for: indexPath) else {
+        previouslySelectedItem = selectedItem
-            return false
-        }
-        switch item {
-        case .tab(.compose):
-            sidebarDelegate?.sidebarRequestPresentCompose(self)
-            return false
-        case .addList:
-            showAddList()
-            return false
-        case .addSavedHashtag:
-            showAddSavedHashtag()
-            return false
-        case .addSavedInstance:
-            showAddSavedInstance()
-            return false
-        default:
         return true
     }
-    }
+    
     func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
         guard let item = dataSource.itemIdentifier(for: indexPath) else {
             collectionView.deselectItem(at: indexPath, animated: true)
             return
         }
+        itemLastSelectedTimestamps[item] = Date()
+        if [MainSidebarViewController.Item.tab(.compose), .addList, .addSavedHashtag, .addSavedInstance].contains(item) {
+            if let previous = previouslySelectedItem, let indexPath = dataSource.indexPath(for: previous) {
+                collectionView.selectItem(at: indexPath, animated: false, scrollPosition: .centeredVertically)
+            }
+            switch item {
+            case .tab(.compose):
+                sidebarDelegate?.sidebarRequestPresentCompose(self)
+            case .addList:
+                showAddList()
+            case .addSavedHashtag:
+                showAddSavedHashtag()
+            case .addSavedInstance:
+                showAddSavedInstance()
+            default:
+                fatalError("unreachable")
+            }
+        } else {
             sidebarDelegate?.sidebar(self, didSelectItem: item)
         }
     }
+}
 
 @available(iOS 14.0, *)
 extension MainSidebarViewController: InstanceTimelineViewControllerDelegate {

Tusker/Screens/Main/MainSplitViewController.swift

@@ -15,7 +15,10 @@ class MainSplitViewController: UISplitViewController {
     
     private var sidebar: MainSidebarViewController!
     
-    private var detailViewControllers: [MainSidebarViewController.Item: UIViewController] = [:]
+    // Keep track of navigation stacks per-item so that we can only ever use a single navigation controller
+    private var navigationStacks: [MainSidebarViewController.Item: [UIViewController]] = [:]
+    
+    private var tabBarViewController: MainTabBarViewController!
     
     init(mastodonController: MastodonController) {
         self.mastodonController = mastodonController
@@ -34,36 +37,234 @@ class MainSplitViewController: UISplitViewController {
         preferredSplitBehavior = .tile
         presentsWithGesture = false
         showsSecondaryOnlyButton = false
+        delegate = self
         
         sidebar = MainSidebarViewController(mastodonController: mastodonController)
         sidebar.sidebarDelegate = self
         setViewController(sidebar, for: .primary)
+
+        setViewController(EnhancedNavigationViewController(), for: .secondary)
         select(item: .tab(.timelines))
-        setViewController(MainTabBarViewController(mastodonController: mastodonController), for: .compact)
+        
+        tabBarViewController = MainTabBarViewController(mastodonController: mastodonController)
+        setViewController(tabBarViewController, for: .compact)
     }
     
     func select(item: MainSidebarViewController.Item) {
-        let itemController = getOrCreateDetailViewController(item: item)
+        let nav = viewController(for: .secondary) as! UINavigationController
-        setViewController(itemController, for: .secondary)
+        nav.viewControllers = getOrCreateNavigationStack(item: item)
     }
     
-    func getOrCreateDetailViewController(item: MainSidebarViewController.Item) -> UIViewController? {
+    func getOrCreateNavigationStack(item: MainSidebarViewController.Item) -> [UIViewController] {
-        if let existing = detailViewControllers[item] {
+        if let existing = navigationStacks[item], existing.count > 0 {
             return existing
         } else {
-            guard let new = item.createRootViewController(mastodonController) else { return nil }
+            let new = [item.createRootViewController(mastodonController)!]
-            let nav = EnhancedNavigationViewController(rootViewController: new)
+            navigationStacks[item] = new
-            
+            return new
-            // Prevents the navigation bar from going transparent when switching sidebar sections.
-            nav.navigationBar.scrollEdgeAppearance = nav.navigationBar.standardAppearance
-            
-            detailViewControllers[item] = nav
-            return nav
         }
     }
 
 }
 
+@available(iOS 14.0, *)
+extension MainSplitViewController: UISplitViewControllerDelegate {
+    /// Transfer the navigation stack for a sidebar item to a destination navgiation controller.
+    /// - Parameter dropFirst: Remove the first view controller from the item's navigation stack before transferring.
+    /// - Parameter append: Append the item's navigation stack to the destination nav controller's instead of replacing it.
+    private func transferNavigationStack(from item: MainSidebarViewController.Item, to destination: UINavigationController, dropFirst: Bool = false, append: Bool = false) {
+        var itemNavStack: [UIViewController]
+        if item == sidebar.selectedItem {
+            let detailNav = viewController(for: .secondary) as! UINavigationController
+            itemNavStack = detailNav.viewControllers
+        } else {
+            itemNavStack = navigationStacks[item] ?? []
+            navigationStacks.removeValue(forKey: item)
+        }
+        if itemNavStack.isEmpty {
+            itemNavStack = [item.createRootViewController(mastodonController)!]
+        }
+        
+        if dropFirst {
+            itemNavStack.remove(at: 0)
+        }
+        
+        if append {
+            destination.viewControllers += itemNavStack
+        } else {
+            destination.viewControllers = itemNavStack
+        }
+    }
+    
+    func splitViewControllerDidCollapse(_ svc: UISplitViewController) {
+        // Transfer the nav stacks for all the sidebar items that map 1 <-> 1 with tabs
+        for tab in [MainTabBarViewController.Tab.timelines, .notifications, .myProfile] {
+            let tabNav = tabBarViewController.viewController(for: tab) as! UINavigationController
+            transferNavigationStack(from: .tab(tab), to: tabNav)
+        }
+        
+        // Since several sidebar items map to the single Explore tab, we only transfer the
+        // navigation stack of the most-recently used one.
+        let mostRecentExploreItem: (MainSidebarViewController.Item, Date)? =
+            sidebar.exploreTabItems.compactMap {
+                if let timestamp = sidebar.itemLastSelectedTimestamps[$0] {
+                    return ($0, timestamp)
+                } else {
+                    return nil
+                }
+            }.min {
+                $0.1 > $1.1
+            }
+        if let mostRecentExploreItem = mostRecentExploreItem?.0,
+           mostRecentExploreItem != .search {
+            let exploreNav = tabBarViewController.viewController(for: .explore) as! UINavigationController
+            // Pop back to root, so we're appending to the Explore VC instead of some other VC
+            exploreNav.popToRootViewController(animated: false)
+            // Append so we don't replace the Explore VC
+            transferNavigationStack(from: mostRecentExploreItem, to: exploreNav, append: true)
+        }
+        
+        // Switch the tab bar to focus the same item as the sidebar has selected
+        switch sidebar.selectedItem! {
+        case let .tab(tab):
+            // sidebar items that map 1 <-> 1 can be transferred directly
+            tabBarViewController.select(tab: tab)
+            
+        case .search:
+            // Search sidebar item maps to the Explore tab with the search controller/results visible
+            // The nav stack can't be copied directly, since the split VC uses a different SearchViewController
+            // so that explore items aren't shown multiple times.
+            
+            let exploreNav = tabBarViewController.viewController(for: .explore) as! UINavigationController
+            let explore: ExploreViewController
+            if let existing = exploreNav.viewControllers.first as? ExploreViewController {
+                explore = existing
+                exploreNav.popToRootViewController(animated: false)
+            } else {
+                // If the Explore tab hasn't been loaded before, it's root view controller won't be loaded yet, so create and add it manually.
+                explore = ExploreViewController(mastodonController: mastodonController)
+                exploreNav.viewControllers = [explore]
+            }
+            // Make sure viewDidLoad is called so that the searchController/resultsController have been initialized
+            explore.loadViewIfNeeded()
+            
+            let nav = viewController(for: .secondary) as! UINavigationController
+            let search = nav.viewControllers.first as! SearchViewController
+            // Copy the search query from the search VC to the Explore VC's search controller.
+            let query = search.searchController.searchBar.text ?? ""
+            explore.searchController.searchBar.text = query
+            // Instruct the explore controller to show its search controller immediately upon its first appearance.
+            // explore.searchController.isActive can't be set directly, see FB7814561
+            explore.searchControllerStatusOnAppearance = !query.isEmpty
+            // Copy the results from the search VC's results controller to avoid the delay introduced by an extra network request
+            explore.resultsController.loadResults(from: search.resultsController)
+            
+            // Transfer the navigation stack, dropping the search VC, to keep anything the user has opened
+            transferNavigationStack(from: .search, to: exploreNav, dropFirst: true, append: true)
+            
+            tabBarViewController.select(tab: .explore)
+            
+        case .bookmarks, .list(_), .savedHashtag(_), .savedInstance(_):
+            tabBarViewController.select(tab: .explore)
+            // Make sure the Explore VC doesn't show it's search bar when it appears, in case the user was previously
+            // in compact mode and performing a search.
+            let exploreNav = tabBarViewController.viewController(for: .explore) as! UINavigationController
+            let explore = exploreNav.viewControllers.first as! ExploreViewController
+            explore.searchControllerStatusOnAppearance = false
+            
+        case .listsHeader, .addList, .savedHashtagsHeader, .addSavedHashtag, .savedInstancesHeader, .addSavedInstance:
+            // These items are not selectable in the sidebar collection view, so this code is unreachable.
+            fatalError("unreachable")
+        }
+    }
+    
+    /// Transfer a navigation stack from a navigation controller belonging to the tab bar VC to a sidebar item.
+    /// - Parameter skipFirst:The number of view controllers that should be skipped from the source navigation controller.
+    /// - Parameter prepend: An optional view controller to prepend to the beginning of the navigation stack being moved.
+    private func transferNavigationStack(from navController: UINavigationController, to item: MainSidebarViewController.Item, skipFirst: Int = 0, prepend: UIViewController? = nil) {
+        let viewControllersToMove = navController.viewControllers.dropFirst(skipFirst)
+        navController.viewControllers.removeLast(navController.viewControllers.count - skipFirst)
+        
+        if let prepend = prepend {
+            navigationStacks[item] = [prepend] + viewControllersToMove
+        } else {
+            navigationStacks[item] = Array(viewControllersToMove)
+        }
+    }
+    
+    func splitViewControllerDidExpand(_ svc: UISplitViewController) {
+        // For each sidebar item, transfer the existing navigation stasck from the tab bar controller to ourself.
+        var exploreItem: MainSidebarViewController.Item?
+        for tab in MainTabBarViewController.Tab.allCases {
+            guard let tabNavController = tabBarViewController.viewController(for: tab) as? UINavigationController else { continue }
+            let tabNavigationStack = tabNavController.viewControllers
+            
+            switch tab {
+            case .timelines, .notifications, .myProfile:
+                // Items that map 1 <-> 1 to tabs can be transferred directly.
+                let item = MainSidebarViewController.Item.tab(tab)
+                transferNavigationStack(from: tabNavController, to: item)
+                
+            case .explore:
+                // The Explore tab is more complicated since it encapsulates a bunch of screens which have top-level sidebar items.
+                
+                var toPrepend: UIViewController? = nil
+                
+                // If the tab navigation stack has only one item or the search controller is active, it corresponds to the Search item
+                // For other items, the 2nd VC in the nav stack determines which sidebar item they map to.
+                // Search screen has special considerations, all others can be transferred directly.
+                if tabNavigationStack.count == 1 || ((tabNavigationStack.first as? ExploreViewController)?.searchController.isActive ?? false) {
+                    exploreItem = .search
+                    let searchVC = SearchViewController(mastodonController: mastodonController)
+                    searchVC.loadViewIfNeeded()
+                    let explore = tabNavigationStack.first as! ExploreViewController
+                    if let exploreSearchControler = explore.searchController,
+                       let query = exploreSearchControler.searchBar.text {
+                        // Transfer query to search VC
+                        searchVC.searchController.searchBar.text = query
+                        // If there is a query, make the search VC activate itself upon appearing
+                        searchVC.searchControllerStatusOnAppearance = !query.isEmpty
+                        // Transfer the results from the explore VC, to avoid an extra network request
+                        searchVC.resultsController.loadResults(from: explore.resultsController)
+                    }
+                    // Insert the new search VC at the beginning of the new search nav stack
+                    toPrepend = searchVC
+                } else if tabNavigationStack[1] is BookmarksTableViewController {
+                    exploreItem = .bookmarks
+                } else if let listVC = tabNavigationStack[1] as? ListTimelineViewController {
+                    exploreItem = .list(listVC.list)
+                } else if let hashtagVC = tabNavigationStack[1] as? HashtagTimelineViewController {
+                    exploreItem = .savedHashtag(hashtagVC.hashtag)
+                } else if let instanceVC = tabNavigationStack[1] as? InstanceTimelineViewController {
+                    exploreItem = .savedInstance(instanceVC.instanceURL)
+                }
+                transferNavigationStack(from: tabNavController, to: exploreItem!, skipFirst: 1, prepend: toPrepend)
+                
+            case .compose:
+                // The compose tab can't be activated, this is unreachable.
+                fatalError("unreachable")
+            }
+        }
+        
+        // Transfer the selected tab from the tab bar VC to the sidebar
+        switch tabBarViewController.selectedTab {
+        case .timelines, .notifications, .myProfile:
+            // These tabs map 1 <-> 1 with sidebar items
+            let item = MainSidebarViewController.Item.tab(tabBarViewController.selectedTab)
+            sidebar.select(item: item, animated: false)
+            select(item: item)
+            
+        case .explore:
+            // If the explore tab is active, the sidebar item is determined above when transferring the explore VC's nav stack
+            sidebar.select(item: exploreItem!, animated: false)
+            select(item: exploreItem!)
+            
+        default:
+            return
+        }
+    }
+}
+
 @available(iOS 14.0, *)
 extension MainSplitViewController: MainSidebarViewControllerDelegate {
     func sidebarRequestPresentCompose(_ sidebarViewController: MainSidebarViewController) {
@@ -71,6 +272,10 @@ extension MainSplitViewController: MainSidebarViewControllerDelegate {
     }
     
     func sidebar(_ sidebarViewController: MainSidebarViewController, didSelectItem item: MainSidebarViewController.Item) {
+        let nav = viewController(for: .secondary) as! UINavigationController
+        if let previous = sidebar.previouslySelectedItem {
+            navigationStacks[previous] = nav.viewControllers
+        }
         select(item: item)
     }
 }

Tusker/Screens/Main/MainTabBarViewController.swift

@@ -14,6 +14,10 @@ class MainTabBarViewController: UITabBarController, UITabBarControllerDelegate {
     
     private var composePlaceholder: UIViewController!
     
+    var selectedTab: Tab {
+        return Tab(rawValue: selectedIndex)!
+    }
+
     override var supportedInterfaceOrientations: UIInterfaceOrientationMask {
         if UIDevice.current.userInterfaceIdiom == .phone {
             return .portrait
@@ -65,6 +69,14 @@ class MainTabBarViewController: UITabBarController, UITabBarControllerDelegate {
         }
         return true
     }
+    
+    func setViewController(_ viewController: UIViewController, forTab tab: Tab) {
+        viewControllers![tab.rawValue] = viewController
+    }
+    
+    func viewController(for tab: Tab) -> UIViewController {
+        return viewControllers![tab.rawValue]
+    }
 }
 
 extension MainTabBarViewController {
@@ -91,8 +103,6 @@ extension MainTabBarViewController {
         }
     }
     
-    
-    
     func getTabController(tab: Tab) -> UIViewController? {
         if tab == .compose {
             return nil

Tusker/Screens/Profile/MyProfileTableViewController.swift

@@ -17,7 +17,6 @@ class MyProfileTableViewController: ProfileTableViewController {
         title = "My Profile"
         tabBarItem.image = UIImage(systemName: "person.fill")
         
-        
         mastodonController.getOwnAccount { (account) in
             self.accountID = account.id
             
@@ -41,14 +40,6 @@ class MyProfileTableViewController: ProfileTableViewController {
         fatalError("init(coder:) has not been implemented")
     }
     
-    override func viewDidLoad() {
-        super.viewDidLoad()
-    }
-    
-    override func viewDidAppear(_ animated: Bool) {
-        super.viewDidAppear(animated)
-    }
-    
     @objc func preferencesPressed() {
         present(PreferencesNavigationController(mastodonController: mastodonController), animated: true)
     }

Tusker/Screens/Profile/ProfileTableViewController.swift

@@ -31,10 +31,6 @@ class ProfileTableViewController: EnhancedTableViewController {
         self.accountID = accountID
         
         super.init(style: .plain)
-        
-        self.refreshControl = UIRefreshControl()
-        refreshControl!.addTarget(self, action: #selector(refreshStatuses(_:)), for: .valueChanged)
-        navigationItem.rightBarButtonItem = UIBarButtonItem(barButtonSystemItem: .compose, target: self, action: #selector(composePressed(_:)))
     }
     
     required init?(coder aDecoder: NSCoder) {
@@ -52,6 +48,10 @@ class ProfileTableViewController: EnhancedTableViewController {
     override func viewDidLoad() {
         super.viewDidLoad()
         
+        self.refreshControl = UIRefreshControl()
+        refreshControl!.addTarget(self, action: #selector(refreshStatuses(_:)), for: .valueChanged)
+        navigationItem.rightBarButtonItem = UIBarButtonItem(barButtonSystemItem: .compose, target: self, action: #selector(composePressed(_:)))
+
         tableView.rowHeight = UITableView.automaticDimension
         tableView.estimatedRowHeight = 140
         

Tusker/Screens/Search/SearchResultsViewController.swift

@@ -109,6 +109,15 @@ class SearchResultsViewController: EnhancedTableViewController {
         return super.targetViewController(forAction: action, sender: sender)
     }
     
+    func loadResults(from source: SearchResultsViewController) {
+        currentQuery = source.currentQuery
+        if let sourceDataSource = source.dataSource {
+            dataSource.apply(sourceDataSource.snapshot())
+        }
+        // todo: check if the search needs to be performed before searching
+//        performSearch(query: currentQuery)
+    }
+    
     func performSearch(query: String?) {
         guard let query = query, !query.isEmpty else {
             self.dataSource.apply(NSDiffableDataSourceSnapshot<Section, Item>())
@@ -212,6 +221,20 @@ extension SearchResultsViewController {
         case account(String)
         case hashtag(Hashtag)
         case status(String, StatusState)
+        
+        func hash(into hasher: inout Hasher) {
+            switch self {
+            case let .account(id):
+                hasher.combine("account")
+                hasher.combine(id)
+            case let .hashtag(hashtag):
+                hasher.combine("hashtag")
+                hasher.combine(hashtag.url)
+            case let .status(id, _):
+                hasher.combine("status")
+                hasher.combine(id)
+            }
+        }
     }
     
     class DataSource: UITableViewDiffableDataSource<Section, Item> {

Tusker/Screens/Search/SearchViewController.swift

@@ -15,6 +15,8 @@ class SearchViewController: UIViewController {
     var resultsController: SearchResultsViewController!
     var searchController: UISearchController!
     
+    var searchControllerStatusOnAppearance: Bool? = nil
+    
     init(mastodonController: MastodonController) {
         self.mastodonController = mastodonController
         
@@ -42,5 +44,16 @@ class SearchViewController: UIViewController {
         navigationItem.hidesSearchBarWhenScrolling = false
     }
     
+    override func viewDidAppear(_ animated: Bool) {
+        super.viewDidAppear(animated)
+        
+        // this is a workaround for the issue that setting isActive on a search controller that is not visible
+        // does not cause it to automatically become active once it becomes visible
+        // see FB7814561
+        if let active = searchControllerStatusOnAppearance {
+            searchController.isActive = active
+            searchControllerStatusOnAppearance = nil
+        }
+    }
 
 }