Update bookmarks VC on bookmarked state changes

Closes #318

Tusker/Screens/Bookmarks/BookmarksViewController.swift

@@ -8,6 +8,7 @@
 
 import UIKit
 import Pachyderm
+import CoreData
 
 class BookmarksViewController: UIViewController, CollectionViewController {
     
@@ -83,7 +84,7 @@ class BookmarksViewController: UIViewController, CollectionViewController {
         }
         return UICollectionViewDiffableDataSource(collectionView: collectionView) { collectionView, indexPath, itemIdentifier in
             switch itemIdentifier {
-            case .status(id: let id, state: let state):
+            case .status(id: let id, state: let state, addedLocally: _):
                 return collectionView.dequeueConfiguredReusableCell(using: statusCell, for: indexPath, item: (id, state))
             case .loadingIndicator:
                 return collectionView.dequeueConfiguredReusableCell(using: loadingCell, for: indexPath, item: ())
@@ -93,6 +94,9 @@ class BookmarksViewController: UIViewController, CollectionViewController {
     
     override func viewDidLoad() {
         super.viewDidLoad()
+        
+        NotificationCenter.default.addObserver(self, selector: #selector(handleStatusDeleted), name: .statusDeleted, object: nil)
+        NotificationCenter.default.addObserver(self, selector: #selector(managedObjectsDidChange), name: .NSManagedObjectContextObjectsDidChange, object: mastodonController.persistentContainer.viewContext)
     }
     
     override func viewWillAppear(_ animated: Bool) {
@@ -132,7 +136,7 @@ class BookmarksViewController: UIViewController, CollectionViewController {
             
             var snapshot = NSDiffableDataSourceSnapshot<Section, Item>()
             snapshot.appendSections([.bookmarks])
-            snapshot.appendItems(statuses.map { .status(id: $0.id, state: .unknown) })
+            snapshot.appendItems(statuses.map { .status(id: $0.id, state: .unknown, addedLocally: false) })
             await apply(snapshot: snapshot, animatingDifferences: true)
             
             state = .loaded
@@ -170,7 +174,7 @@ class BookmarksViewController: UIViewController, CollectionViewController {
             await mastodonController.persistentContainer.addAll(statuses: statuses)
             
             snapshot.deleteItems([.loadingIndicator])
-            snapshot.appendItems(statuses.map { .status(id: $0.id, state: .unknown) })
+            snapshot.appendItems(statuses.map { .status(id: $0.id, state: .unknown, addedLocally: false) })
             await apply(snapshot: snapshot, animatingDifferences: true)
             
             state = .loaded
@@ -187,6 +191,63 @@ class BookmarksViewController: UIViewController, CollectionViewController {
             state = .loaded
         }
     }
+    
+    @objc private func handleStatusDeleted(_ notification: Foundation.Notification) {
+        guard let userInfo = notification.userInfo,
+              let accountID = mastodonController.accountInfo?.id,
+              userInfo["accountID"] as? String == accountID,
+              let statusIDs = userInfo["statusIDs"] as? [String] else {
+            return
+        }
+        var snapshot = dataSource.snapshot()
+        let toDelete = statusIDs.map { id in
+            Item.status(id: id, state: .unknown, addedLocally: false)
+        }.filter { item in
+            snapshot.itemIdentifiers.contains(item)
+        }
+        if !toDelete.isEmpty {
+            snapshot.deleteItems(toDelete)
+            Task {
+                await apply(snapshot: snapshot, animatingDifferences: true)
+            }
+        }
+    }
+    
+    @objc private func managedObjectsDidChange(_ notification: Foundation.Notification) {
+        var snapshot = dataSource.snapshot()
+        func prepend(item: Item) {
+            if let first = snapshot.itemIdentifiers.first {
+                snapshot.insertItems([item], beforeItem: first)
+            } else {
+                snapshot.appendItems([item])
+            }
+        }
+        var hasChanges = false
+        if let inserted = notification.userInfo?[NSInsertedObjectsKey] as? Set<NSManagedObject> {
+            for case let status as StatusMO in inserted where status.bookmarked == true {
+                prepend(item: .status(id: status.id, state: .unknown, addedLocally: true))
+                hasChanges = true
+            }
+        }
+        if let updated = notification.userInfo?[NSUpdatedObjectsKey] as? Set<NSManagedObject> {
+            for case let status as StatusMO in updated {
+                let item = Item.status(id: status.id, state: .unknown, addedLocally: true)
+                var exists = snapshot.itemIdentifiers.contains(item)
+                if status.bookmarked == true && !exists {
+                    prepend(item: item)
+                    hasChanges = true
+                } else if status.bookmarked == false && exists {
+                    snapshot.deleteItems([item])
+                    hasChanges = true
+                }
+            }
+        }
+        if hasChanges {
+            Task {
+                await apply(snapshot: snapshot, animatingDifferences: true)
+            }
+        }
+    }
 
 }
 
@@ -195,7 +256,7 @@ extension BookmarksViewController {
         case bookmarks
     }
     enum Item: Equatable, Hashable {
-        case status(id: String, state: CollapseState)
+        case status(id: String, state: CollapseState, addedLocally: Bool)
         case loadingIndicator
         
         var hideIndicators: Bool {
@@ -209,7 +270,7 @@ extension BookmarksViewController {
         
         static func ==(lhs: Item, rhs: Item) -> Bool {
             switch (lhs, rhs) {
-            case (.status(id: let a, state: _), .status(id: let b, state: _)):
+            case (.status(id: let a, _, _), .status(id: let b, _, _)):
                 return a == b
             case (.loadingIndicator, .loadingIndicator):
                 return true
@@ -220,7 +281,7 @@ extension BookmarksViewController {
         
         func hash(into hasher: inout Hasher) {
             switch self {
-            case .status(id: let id, state: _):
+            case .status(id: let id, _, _):
                 hasher.combine(0)
                 hasher.combine(id)
             case .loadingIndicator:
@@ -250,7 +311,7 @@ extension BookmarksViewController: UICollectionViewDelegate {
     }
     
     func collectionView(_ collectionView: UICollectionView, shouldSelectItemAt indexPath: IndexPath) -> Bool {
-        if case .status(id: _, state: _) = dataSource.itemIdentifier(for: indexPath) {
+        if case .status(_, _, _) = dataSource.itemIdentifier(for: indexPath) {
             return true
         } else {
             return false
@@ -258,7 +319,7 @@ extension BookmarksViewController: UICollectionViewDelegate {
     }
     
     func collectionView(_ collectionView: UICollectionView, didSelectItemAt indexPath: IndexPath) {
-        if case .status(id: let id, state: let state) = dataSource.itemIdentifier(for: indexPath) {
+        if case .status(id: let id, state: let state, _) = dataSource.itemIdentifier(for: indexPath) {
             selected(status: id, state: state.copy())
         }
     }