Display groups and feeds

Reader/CoreData/PersistentContainer.swift

@@ -17,6 +17,7 @@ class PersistentContainer: NSPersistentContainer {
     
     private(set) lazy var backgroundContext: NSManagedObjectContext = {
         let context = NSManagedObjectContext(concurrencyType: .privateQueueConcurrencyType)
+        // todo: should the background context really be parented to the view context, or should they both be direct children of the PSC?
         context.parent = self.viewContext
         return context
     }()
@@ -58,6 +59,7 @@ class PersistentContainer: NSPersistentContainer {
             
             if self.backgroundContext.hasChanges {
                 try self.backgroundContext.save()
+                try self.viewContext.save()
             }
         }
     }

Reader/SceneDelegate.swift

@@ -45,12 +45,6 @@ class SceneDelegate: UIResponder, UIWindowSceneDelegate {
         // Use this method to restart any tasks that were paused (or not yet started) when the scene was inactive.
     }
 
-    @MainActor
-    private func fetchFeeds() async {
-        let feeds = try! self.fervorController.persistentContainer.viewContext.fetch(Feed.fetchRequest())
-        print(feeds)
-    }
-
     func sceneWillResignActive(_ scene: UIScene) {
         // Called when the scene will move from an active state to an inactive state.
         // This may occur due to temporary interruptions (ex. an incoming phone call).
@@ -81,6 +75,12 @@ class SceneDelegate: UIResponder, UIWindowSceneDelegate {
         }
     }
     
+    @MainActor
+    private func fetchFeeds() async {
+        let feeds = try! self.fervorController.persistentContainer.viewContext.fetch(Feed.fetchRequest())
+        print(feeds)
+    }
+
 }
 
 extension SceneDelegate: LoginViewControllerDelegate {

Reader/Screens/Home/HomeViewController.swift

@@ -6,11 +6,17 @@
 //
 
 import UIKit
+import CoreData
 
-class HomeViewController: UIViewController {
+class HomeViewController: UIViewController, UICollectionViewDelegate {
     
     let fervorController: FervorController
     
+    private var collectionView: UICollectionView!
+    private var dataSource: UICollectionViewDiffableDataSource<Section, Item>!
+    private var groupResultsController: NSFetchedResultsController<Group>!
+    private var feedResultsController: NSFetchedResultsController<Feed>!
+    
     init(fervorController: FervorController) {
         self.fervorController = fervorController
         
@@ -26,14 +32,105 @@ class HomeViewController: UIViewController {
         
         view.backgroundColor = .systemBackground
         
-        let label = UILabel()
-        label.translatesAutoresizingMaskIntoConstraints = false
-        label.text = "Logged in to \(fervorController.instanceURL.host!)"
-        view.addSubview(label)
-        NSLayoutConstraint.activate([
-            label.centerXAnchor.constraint(equalTo: view.centerXAnchor),
-            label.centerYAnchor.constraint(equalTo: view.centerYAnchor),
-        ])
+//        let label = UILabel()
+//        label.translatesAutoresizingMaskIntoConstraints = false
+//        label.text = "Logged in to \(fervorController.instanceURL.host!)"
+//        view.addSubview(label)
+//        NSLayoutConstraint.activate([
+//            label.centerXAnchor.constraint(equalTo: view.centerXAnchor),
+//            label.centerYAnchor.constraint(equalTo: view.centerYAnchor),
+//        ])
+        
+        let configuration = UICollectionLayoutListConfiguration(appearance: .insetGrouped)
+        let layout = UICollectionViewCompositionalLayout.list(using: configuration)
+        collectionView = UICollectionView(frame: view.bounds, collectionViewLayout: layout)
+        collectionView.autoresizingMask = [.flexibleWidth, .flexibleHeight]
+        collectionView.delegate = self
+        view.addSubview(collectionView)
+        
+        dataSource = createDataSource()
+        
+        // todo: maybe NSFetchedResultsController to automatically update when the database changes?
+//        applyInitialSnapshot()
+        var snapshot = NSDiffableDataSourceSnapshot<Section, Item>()
+        snapshot.appendSections([.groups, .feeds])
+        dataSource.apply(snapshot, animatingDifferences: false)
+        
+        let groupReq = Group.fetchRequest()
+        groupReq.sortDescriptors = [NSSortDescriptor(key: "title", ascending: true)]
+        groupResultsController = NSFetchedResultsController(fetchRequest: groupReq, managedObjectContext: fervorController.persistentContainer.viewContext, sectionNameKeyPath: nil, cacheName: nil)
+        groupResultsController.delegate = self
+        try! groupResultsController.performFetch()
+        
+        let feedReq = Feed.fetchRequest()
+        feedReq.sortDescriptors = [NSSortDescriptor(key: "title", ascending: true)]
+        feedResultsController = NSFetchedResultsController(fetchRequest: feedReq, managedObjectContext: fervorController.persistentContainer.viewContext, sectionNameKeyPath: nil, cacheName: nil)
+        feedResultsController.delegate = self
+        try! feedResultsController.performFetch()
     }
     
+    private func createDataSource() -> UICollectionViewDiffableDataSource<Section, Item> {
+        let listCell = UICollectionView.CellRegistration<UICollectionViewListCell, Item> { cell, indexPath, item in
+            var config = cell.defaultContentConfiguration()
+            config.text = item.title
+            cell.contentConfiguration = config
+            
+            cell.accessories = [.disclosureIndicator()]
+        }
+        let dataSource = UICollectionViewDiffableDataSource<Section, Item>(collectionView: collectionView) { collectionView, indexPath, item in
+            return collectionView.dequeueConfiguredReusableCell(using: listCell, for: indexPath, item: item)
+        }
+        return dataSource
+    }
+    
+//    private func applyInitialSnapshot() {
+//        let groups = try! fervorController.persistentContainer.viewContext.fetch(Group.fetchRequest())
+//        let feeds = try! fervorController.persistentContainer.viewContext.fetch(Feed.fetchRequest())
+//
+//        var snapshot = NSDiffableDataSourceSnapshot<Section, Item>()
+//        snapshot.appendSections([.groups, .feeds])
+//        snapshot.appendItems(groups.map { .group($0) }, toSection: .groups)
+//        snapshot.appendItems(feeds.map { .feed($0) }, toSection: .feeds)
+//        dataSource.apply(snapshot, animatingDifferences: false)
+//    }
+    
+}
+
+extension HomeViewController {
+    enum Section: Hashable {
+        case groups
+        case feeds
+    }
+    enum Item: Hashable {
+        case group(Group)
+        case feed(Feed)
+        
+        var title: String {
+            switch self {
+            case let .group(group):
+                // todo: manual codegen for models so this force unwrap isn't necessary
+                return group.title!
+            case let .feed(feed):
+                return feed.title!
+            }
+        }
+    }
+}
+
+extension HomeViewController: NSFetchedResultsControllerDelegate {
+    func controller(_ controller: NSFetchedResultsController<NSFetchRequestResult>, didChangeContentWith snapshot: NSDiffableDataSourceSnapshotReference) {
+        var snapshot = dataSource.snapshot()
+        if controller == groupResultsController {
+            if snapshot.sectionIdentifiers.contains(.groups) {
+                snapshot.deleteItems(snapshot.itemIdentifiers(inSection: .groups))
+            }
+            snapshot.appendItems(controller.fetchedObjects!.map { .group($0 as! Group) }, toSection: .groups)
+        } else if controller == feedResultsController {
+            if snapshot.sectionIdentifiers.contains(.feeds) {
+                snapshot.deleteItems(snapshot.itemIdentifiers(inSection: .feeds))
+            }
+            snapshot.appendItems(controller.fetchedObjects!.map { .feed($0 as! Feed) }, toSection: .feeds)
+        }
+        dataSource.apply(snapshot, animatingDifferences: false)
+    }
 }