Rewrite TrendingStatusesViewController to use collection view

Can happen if the network is slow and the user closes the profile screen before the header loads

Tusker/Screens/Explore/TrendingStatusesViewController.swift

@@ -9,77 +9,163 @@
 import UIKit
 import Pachyderm
 
-class TrendingStatusesViewController: EnhancedTableViewController {
+class TrendingStatusesViewController: UIViewController {
     
     weak var mastodonController: MastodonController!
     
-    private var dataSource: UITableViewDiffableDataSource<Section, Item>!
+    private var collectionView: UICollectionView {
+        view as! UICollectionView
+    }
+    private var dataSource: UICollectionViewDiffableDataSource<Section, Item>!
     
     init(mastodonController: MastodonController) {
         self.mastodonController = mastodonController
         
-        super.init(style: .grouped)
+        super.init(nibName: nil, bundle: nil)
         
-        dragEnabled = true
+        title = NSLocalizedString("Trending Posts", comment: "trending posts screen title")
     }
     
     required init?(coder: NSCoder) {
         fatalError("init(coder:) has not been implemented")
     }
     
-    override func viewDidLoad() {
-        super.viewDidLoad()
+    override func loadView() {
+        var config = UICollectionLayoutListConfiguration(appearance: .plain)
+        config.leadingSwipeActionsConfigurationProvider = { [unowned self] in
+            (collectionView.cellForItem(at: $0) as? TimelineStatusCollectionViewCell)?.leadingSwipeActions()
+        }
+        config.trailingSwipeActionsConfigurationProvider = { [unowned self] in
+            (collectionView.cellForItem(at: $0) as? TimelineStatusCollectionViewCell)?.trailingSwipeActions()
+        }
+        config.itemSeparatorHandler = { [unowned self] indexPath, sectionSeparatorConfiguration in
+            guard let item = self.dataSource.itemIdentifier(for: indexPath) else {
+                return sectionSeparatorConfiguration
+            }
+            var config = sectionSeparatorConfiguration
+            if item.hideSeparators {
+                config.topSeparatorVisibility = .hidden
+                config.bottomSeparatorVisibility = .hidden
+            }
+            if case .status(_, _) = item {
+                config.topSeparatorInsets = TimelineStatusCollectionViewCell.separatorInsets
+                config.bottomSeparatorInsets = TimelineStatusCollectionViewCell.separatorInsets
+            }
+            return config
+        }
+        let layout = UICollectionViewCompositionalLayout.list(using: config)
+        view = UICollectionView(frame: .zero, collectionViewLayout: layout)
+        collectionView.delegate = self
+        collectionView.dragDelegate = self
         
-        title = NSLocalizedString("Trending Posts", comment: "trending posts screen title")
+        dataSource = createDataSource()
+    }
     
-        tableView.register(UINib(nibName: "TimelineStatusTableViewCell", bundle: .main), forCellReuseIdentifier: "statusCell")
-        tableView.estimatedRowHeight = 144
-        
-        dataSource = UITableViewDiffableDataSource(tableView: tableView, cellProvider: { tableView, indexPath, item in
-            let cell = tableView.dequeueReusableCell(withIdentifier: "statusCell", for: indexPath) as! TimelineStatusTableViewCell
+    private func createDataSource() -> UICollectionViewDiffableDataSource<Section, Item> {
+        let statusCell = UICollectionView.CellRegistration<TimelineStatusCollectionViewCell, (String, StatusState)> { [unowned self] cell, indexPath, item in
             cell.delegate = self
-            cell.updateUI(statusID: item.id, state: item.state)
-            return cell
-        })
+            cell.updateUI(statusID: item.0, state: item.1)
+        }
+        let loadingCell = UICollectionView.CellRegistration<LoadingCollectionViewCell, Void> { cell, _, _ in
+            cell.indicator.startAnimating()
+        }
+        return UICollectionViewDiffableDataSource(collectionView: collectionView) { collectionView, indexPath, itemIdentifier in
+            switch itemIdentifier {
+            case .status(id: let id, state: let state):
+                return collectionView.dequeueConfiguredReusableCell(using: statusCell, for: indexPath, item: (id, state))
+            case .loadingIndicator:
+                return collectionView.dequeueConfiguredReusableCell(using: loadingCell, for: indexPath, item: ())
+            }
+        }
     }
 
     override func viewWillAppear(_ animated: Bool) {
         super.viewWillAppear(animated)
         
-        let request = Client.getTrendingStatuses()
-        Task {
-            guard let (statuses, _) = try? await mastodonController.run(request) else {
-                return
-            }
-            mastodonController.persistentContainer.addAll(statuses: statuses) {
         var snapshot = NSDiffableDataSourceSnapshot<Section, Item>()
         snapshot.appendSections([.statuses])
-                snapshot.appendItems(statuses.map { Item(id: $0.id, state: .unknown) })
-                self.dataSource.apply(snapshot)
-            }
+        snapshot.appendItems([.loadingIndicator])
+        dataSource.apply(snapshot, animatingDifferences: false)
+        
+        Task {
+            await loadTrendingStatuses()
         }
     }
     
-    // MARK: - Table View Delegate
+    private func loadTrendingStatuses() async {
+        let statuses: [Status]
+        do {
+            statuses = try await mastodonController.run(Client.getTrendingStatuses()).0
+        } catch {
+            var snapshot = NSDiffableDataSourceSnapshot<Section, Item>()
+            await dataSource.apply(snapshot)
+            let config = ToastConfiguration(from: error, with: "Loading Trending Posts", in: self) { toast in
+                toast.dismissToast(animated: true)
+                await self.loadTrendingStatuses()
+            }
+            showToast(configuration: config, animated: true)
+            return
+        }
+        await mastodonController.persistentContainer.addAll(statuses: statuses)
+        var snapshot = NSDiffableDataSourceSnapshot<Section, Item>()
+        snapshot.appendSections([.statuses])
+        snapshot.appendItems(statuses.map { .status(id: $0.id, state: .unknown) })
+        await dataSource.apply(snapshot)
+    }
 }
 
 extension TrendingStatusesViewController {
     enum Section {
         case statuses
     }
-    struct Item: Hashable {
-        let id: String
-        let state: StatusState
+    enum Item: Hashable {
+        case status(id: String, state: StatusState)
+        case loadingIndicator
         
-        static func ==(lhs: Item, rhs: Item) -> Bool {
-            return lhs.id == rhs.id
+        var hideSeparators: Bool {
+            if case .loadingIndicator = self {
+                return true
+            } else {
+                return false
+            }
         }
         
-        func hash(into hasher: inout Hasher) {
-            hasher.combine(id)
+        var isSelectable: Bool {
+            if case .status(id: _, state: _) = self {
+                return true
+            } else {
+                return false
             }
         }
     }
+}
+
+extension TrendingStatusesViewController: UICollectionViewDelegate {
+    func collectionView(_ collectionView: UICollectionView, shouldSelectItemAt indexPath: IndexPath) -> Bool {
+        return dataSource.itemIdentifier(for: indexPath)?.isSelectable ?? false
+    }
+    
+    func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
+        guard case .status(id: let id, state: let state) = dataSource.itemIdentifier(for: indexPath) else {
+            return
+        }
+        selected(status: id, state: state.copy())
+    }
+    
+    func collectionView(_ collectionView: UICollectionView, contextMenuConfigurationForItemAt indexPath: IndexPath, point: CGPoint) -> UIContextMenuConfiguration? {
+        return (collectionView.cellForItem(at: indexPath) as? TimelineStatusCollectionViewCell)?.contextMenuConfiguration()
+    }
+    
+    func collectionView(_ collectionView: UICollectionView, willPerformPreviewActionForMenuWith configuration: UIContextMenuConfiguration, animator: UIContextMenuInteractionCommitAnimating) {
+        MenuPreviewHelper.willPerformPreviewAction(animator: animator, presenter: self)
+    }
+}
+
+extension TrendingStatusesViewController: UICollectionViewDragDelegate {
+    func collectionView(_ collectionView: UICollectionView, itemsForBeginning session: UIDragSession, at indexPath: IndexPath) -> [UIDragItem] {
+        (collectionView.cellForItem(at: indexPath) as? TimelineStatusCollectionViewCell)?.dragItemsForBeginning(session: session) ?? []
+    }
+}
 
 extension TrendingStatusesViewController: TuskerNavigationDelegate {
     var apiController: MastodonController! { mastodonController }
@@ -91,9 +177,19 @@ extension TrendingStatusesViewController: ToastableViewController {
 extension TrendingStatusesViewController: MenuActionProvider {
 }
 
-extension TrendingStatusesViewController: StatusTableViewCellDelegate {
-    func statusCellCollapsedStateChanged(_ cell: BaseStatusTableViewCell) {
-        tableView.beginUpdates()
-        tableView.endUpdates()
+extension TrendingStatusesViewController: StatusCollectionViewCellDelegate {
+    func statusCellNeedsReconfigure(_ cell: StatusCollectionViewCell, animated: Bool, completion: (() -> Void)?) {
+        if let indexPath = collectionView.indexPath(for: cell) {
+            var snapshot = dataSource.snapshot()
+            snapshot.reconfigureItems([dataSource.itemIdentifier(for: indexPath)!])
+            dataSource.apply(snapshot, animatingDifferences: animated, completion: completion)
+        }
+    }
+}
+
+extension TrendingStatusesViewController: StatusBarTappableViewController {
+    func handleStatusBarTapped(xPosition: CGFloat) -> StatusBarTapActionResult {
+        collectionView.scrollToTop()
+        return .stop
     }
 }

Tusker/Views/Profile Header/ProfileHeaderView.swift

@@ -86,6 +86,11 @@ class ProfileHeaderView: UIView {
     }
     
     private func createObservers() {
+        // mastodonController may be nil if the ProfileViewController is deinit'd before the header is even created
+        guard let mastodonController else {
+            return
+        }
+        
         cancellables = []
         
         mastodonController.persistentContainer.accountSubject