Convert TimelineTableViewController to use DiffableTimelineLikeTableViewController

Tusker/Screens/Lists/ListTimelineViewController.swift

@@ -58,7 +58,7 @@ class ListTimelineViewController: TimelineTableViewController {
         dismiss(animated: true)
         
         // todo: show loading indicator
-        reloadInitialItems()
+        reloadInitial()
     }
 
 }

Tusker/Screens/Timeline/TimelineTableViewController.swift

@@ -11,7 +11,7 @@ import Pachyderm
 
 typealias TimelineEntry = (id: String, state: StatusState)
 
-class TimelineTableViewController: TimelineLikeTableViewController<TimelineEntry> {
+class TimelineTableViewController: DiffableTimelineLikeTableViewController<TimelineTableViewController.Section, TimelineTableViewController.Item> {
     
     let timeline: Timeline
     weak var mastodonController: MastodonController!
@@ -44,10 +44,8 @@ class TimelineTableViewController: TimelineLikeTableViewController<TimelineEntry
         // decrement reference counts of any statuses we still have
         // if the app is currently being quit, this will not affect the persisted data because
         // the persistent container would already have been saved in SceneDelegate.sceneDidEnterBackground(_:)
-        for section in sections {
+        for case let .status(id: id, state: _) in dataSource.snapshot().itemIdentifiers {
-            for (id, _) in section {
+            persistentContainer.status(for: id)?.decrementReferenceCount()
-                persistentContainer.status(for: id)?.decrementReferenceCount()
-            }
         }
     }
     
@@ -57,96 +55,125 @@ class TimelineTableViewController: TimelineLikeTableViewController<TimelineEntry
         tableView.register(UINib(nibName: "TimelineStatusTableViewCell", bundle: .main), forCellReuseIdentifier: "statusCell")
     }
     
+    // MARK: - DiffableTimelineLikeTableViewController
+    
     override class func refreshCommandTitle() -> String {
         return NSLocalizedString("Refresh Statuses", comment: "refresh status command discoverability title")
     }
 
-    override func willRemoveRows(at indexPaths: [IndexPath]) {
+    override func cellProvider(_ tableView: UITableView, _ indexPath: IndexPath, _ item: Item) -> UITableViewCell? {
-        for indexPath in indexPaths {
+        guard case let .status(id: id, state: state) = item,
-            let id = item(for: indexPath).id
+              let cell = tableView.dequeueReusableCell(withIdentifier: "statusCell", for: indexPath) as? TimelineStatusTableViewCell else {
-            mastodonController.persistentContainer.status(for: id)?.decrementReferenceCount()
+            return nil
-        }
-    }
-    
-    override func loadInitialItems(completion: @escaping ([TimelineEntry]) -> Void) {
-        let request = Client.getStatuses(timeline: timeline)
-        
-        mastodonController?.run(request) { (response) in
-            guard case let .success(statuses, pagination) = response else {
-                completion([])
-                return
-            }
-            
-            self.newer = pagination?.newer
-            self.older = pagination?.older
-            
-            self.mastodonController?.persistentContainer.addAll(statuses: statuses) {
-                completion(statuses.map { ($0.id, .unknown) })
-            }
-        }
-    }
-    
-    override func loadOlder(completion: @escaping ([TimelineEntry]) -> Void) {
-        guard let older = older else {
-            completion([])
-            return
         }
         
-        let request = Client.getStatuses(timeline: timeline, range: older)
-        
-        mastodonController.run(request) { (response) in
-            guard case let .success(statuses, pagination) = response else {
-                completion([])
-                return
-            }
-            
-            self.older = pagination?.older
-            
-            self.mastodonController?.persistentContainer.addAll(statuses: statuses) {
-                completion(statuses.map { ($0.id, .unknown) })
-            }
-        }
-    }
-    
-    override func loadNewer(completion: @escaping ([TimelineEntry]) -> Void) {
-        guard let newer = newer else {
-            completion([])
-            return
-        }
-        
-        let request = Client.getStatuses(timeline: timeline, range: newer)
-        
-        mastodonController.run(request) { (response) in
-            guard case let .success(statuses, pagination) = response else {
-                completion([])
-                return
-            }
-            
-            // if there are no new statuses, pagination is nil
-            // if we were to then overwrite self.newer, future refreshes would fail
-            if let newer = pagination?.newer {
-                self.newer = newer
-            }
-            
-            self.mastodonController?.persistentContainer.addAll(statuses: statuses) {
-                completion(statuses.map { ($0.id, .unknown) })
-            }
-        }
-    }
-    
-    // MARK: - UITableViewDataSource
-    
-    override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
-        guard let cell = tableView.dequeueReusableCell(withIdentifier: "statusCell", for: indexPath) as? TimelineStatusTableViewCell else { fatalError() }
-
-        let (id, state) = item(for: indexPath)
         cell.delegate = self
-
         cell.updateUI(statusID: id, state: state)
         
         return cell
     }
     
+    override func loadInitialItems(completion: @escaping (LoadResult) -> Void) {
+        guard let mastodonController = mastodonController else {
+            completion(.failure(.noClient))
+            return
+        }
+        
+        let request = Client.getStatuses(timeline: timeline)
+        
+        mastodonController.run(request) { response in
+            switch response {
+            case let .failure(error):
+                completion(.failure(.client(error)))
+                
+            case let .success(statuses, pagination):
+                self.newer = pagination?.newer
+                self.older = pagination?.older
+                
+                self.mastodonController.persistentContainer.addAll(statuses: statuses) {
+                    var snapshot = Snapshot()
+                    snapshot.appendSections([.statuses])
+                    snapshot.appendItems(statuses.map { .status(id: $0.id, state: .unknown) })
+                    completion(.success(snapshot))
+                }
+            }
+        }
+    }
+    
+    override func loadOlderItems(currentSnapshot: Snapshot, completion: @escaping (LoadResult) -> Void) {
+        guard let older = older else {
+            completion(.failure(.noOlder))
+            return
+        }
+        
+        let request = Client.getStatuses(timeline: timeline, range: older)
+        
+        mastodonController.run(request) { response in
+            switch response {
+            case let .failure(error):
+                completion(.failure(.client(error)))
+                
+            case let .success(statuses, pagination):
+                self.older = pagination?.older
+                
+                self.mastodonController.persistentContainer.addAll(statuses: statuses) {
+                    var snapshot = currentSnapshot
+                    snapshot.appendItems(statuses.map { .status(id: $0.id, state: .unknown) }, toSection: .statuses)
+                    completion(.success(snapshot))
+                }
+            }
+        }
+    }
+    
+    override func loadNewerItems(currentSnapshot: Snapshot, completion: @escaping (LoadResult) -> Void) {
+        guard let newer = newer else {
+            completion(.failure(.noNewer))
+            return
+        }
+        
+        let request = Client.getStatuses(timeline: timeline, range: newer)
+        mastodonController.run(request) { response in
+            switch response {
+            case let .failure(error):
+                completion(.failure(.client(error)))
+                
+            case let .success(statuses, pagination):
+                // if there are no new statuses, pagination is nil
+                // if we were to then overwrite self.newer, future refresh would fail
+                if let newer = pagination?.newer {
+                    self.newer = newer
+                }
+                
+                self.mastodonController.persistentContainer.addAll(statuses: statuses) {
+                    var snapshot = currentSnapshot
+                    let identifiers = statuses.map { Item.status(id: $0.id, state: .unknown) }
+                    if let first = snapshot.itemIdentifiers(inSection: .statuses).first {
+                        snapshot.insertItems(identifiers, beforeItem: first)
+                    } else {
+                        snapshot.appendItems(identifiers, toSection: .statuses)
+                    }
+                    completion(.success(snapshot))
+                }
+            }
+        }
+    }
+    
+    override func willRemoveItems(_ items: [Item]) {
+        for case let .status(id: id, state: _) in items {
+            mastodonController.persistentContainer.status(for: id)?.decrementReferenceCount()
+        }
+    }
+    
+}
+
+extension TimelineTableViewController {
+    enum Section: Hashable, CaseIterable {
+        case statuses
+        case footer
+    }
+    enum Item: Hashable {
+        case status(id: String, state: StatusState)
+    }
 }
 
 extension TimelineTableViewController: TuskerNavigationDelegate {
@@ -161,17 +188,23 @@ extension TimelineTableViewController: StatusTableViewCellDelegate {
 
 extension TimelineTableViewController: UITableViewDataSourcePrefetching, StatusTablePrefetching {
     func tableView(_ tableView: UITableView, prefetchRowsAt indexPaths: [IndexPath]) {
-        let ids = indexPaths.map { item(for: $0).id }
+        let ids: [String] = indexPaths.compactMap {
+            if case let .status(id: id, state: _) = dataSource.itemIdentifier(for: $0) {
+                return id
+            } else {
+                return nil
+            }
+        }
         prefetchStatuses(with: ids)
     }
 
     func tableView(_ tableView: UITableView, cancelPrefetchingForRowsAt indexPaths: [IndexPath]) {
         let ids: [String] = indexPaths.compactMap {
-            guard $0.section < sections.count,
+            if case let .status(id: id, state: _) = dataSource.itemIdentifier(for: $0) {
-                  $0.row < sections[$0.section].count else {
+                return id
+            } else {
                 return nil
             }
-            return item(for: $0).id
         }
         cancelPrefetchingStatuses(with: ids)
     }