Add load more

Author: longkimhoang

UI/Sources/UI/Resources/Localizable.xcstrings

@@ -48,6 +48,9 @@
     },
     "Latest updates" : {
 
+    },
+    "Load more" : {
+
     },
     "Logged in as %@" : {
 

UI/Sources/UI/Updates/ViewController/UpdatesViewController+DataSource.swift

@@ -72,6 +72,33 @@ extension UpdatesViewController {
                 )
             }
         }
+
+        let loadMoreButtonRegistration = UICollectionView.SupplementaryRegistration<UICollectionViewCell>(
+            elementKind: SupplementaryElementKind.loadMore
+        ) { [unowned viewModel] cell, _, _ in
+            cell.contentConfiguration = UIHostingConfiguration {
+                Button(String(localized: "Load more", bundle: .module)) {
+                    Task {
+                        try await viewModel.fetchFollowedFeed()
+                    }
+                }
+                .buttonStyle(.borderedProminent)
+                .buttonBorderShape(.capsule)
+                .frame(maxWidth: .infinity)
+            }
+            .margins(.vertical, 16)
+        }
+
+        dataSource.supplementaryViewProvider = { collectionView, elementKind, indexPath in
+            if elementKind == SupplementaryElementKind.loadMore {
+                return collectionView.dequeueConfiguredReusableSupplementary(
+                    using: loadMoreButtonRegistration,
+                    for: indexPath
+                )
+            }
+
+            return nil
+        }
     }
 
     func updateDataSource(animated: Bool = true) {

UI/Sources/UI/Updates/ViewController/UpdatesViewController+Layout.swift

@@ -8,16 +8,37 @@
 import UIKit
 
 extension UpdatesViewController {
+    enum SupplementaryElementKind {
+        static let loadMore = "loadMore"
+    }
+
     func makeCollectionViewLayout() -> UICollectionViewLayout {
-        let sectionProvider: UICollectionViewCompositionalLayoutSectionProvider = { _, layoutEnvironment in
+        let sectionProvider: UICollectionViewCompositionalLayoutSectionProvider = {
+            [unowned self] sectionIndex, layoutEnvironment in
+
             var listConfig = UICollectionLayoutListConfiguration(appearance: .plain)
             listConfig.headerMode = .firstItemInSection
             listConfig.separatorConfiguration.topSeparatorVisibility = .visible
             listConfig.separatorConfiguration.bottomSeparatorVisibility = .hidden
 
-            return NSCollectionLayoutSection.list(using: listConfig, layoutEnvironment: layoutEnvironment)
+            let section = NSCollectionLayoutSection.list(using: listConfig, layoutEnvironment: layoutEnvironment)
+            let sectionsCount = dataSource.numberOfSections(in: collectionView)
+            if sectionIndex == sectionsCount - 1 {
+                section.boundarySupplementaryItems.append(makeLoadMoreItem())
+            }
+
+            return section
         }
 
         return UICollectionViewCompositionalLayout(sectionProvider: sectionProvider)
     }
+
+    private func makeLoadMoreItem() -> NSCollectionLayoutBoundarySupplementaryItem {
+        let itemSize = NSCollectionLayoutSize(widthDimension: .fractionalWidth(1), heightDimension: .estimated(60))
+        return NSCollectionLayoutBoundarySupplementaryItem(
+            layoutSize: itemSize,
+            elementKind: SupplementaryElementKind.loadMore,
+            alignment: .bottom
+        )
+    }
 }

ViewModels/Sources/ViewModels/Updates/UpdatesViewModel.swift

@@ -25,7 +25,7 @@ public final class UpdatesViewModel: ObservableObject {
 
     public func loadFollowedFeedFromStorage() throws {
         let context = modelContainer.mainContext
-        let chapterEntities = try context.fetch(ChapterEntity.followedFeed(limit: 32))
+        let chapterEntities = try context.fetch(ChapterEntity.followedFeed(limit: 32, offset: offset))
         let chaptersGroupedByMangaID: OrderedDictionary<UUID, [ChapterEntity]> =
             chapterEntities.reduce(into: [:]) { result, chapterEntity in
                 guard let manga = chapterEntity.manga else {
@@ -48,8 +48,21 @@ public final class UpdatesViewModel: ObservableObject {
             return Section(mangaInfo: manga, chapters: IdentifiedArray(uniqueElements: chapters))
         }
 
-        offset = chapterEntities.count
-        self.sections = IdentifiedArray(uniqueElements: sections)
+        offset += chapterEntities.count
+
+        for section in sections {
+            if let existingSection = self.sections[id: section.id] {
+                // If section already exists, append its chapters
+                // and use new manga info (since it's more up-to-date)
+                let newSection = Section(
+                    mangaInfo: section.mangaInfo,
+                    chapters: IdentifiedArray(existingSection.chapters + section.chapters) { $1 }
+                )
+                self.sections[id: section.id] = newSection
+            } else {
+                self.sections.append(section)
+            }
+        }
     }
 
     public func fetchFollowedFeed(resetsOffset: Bool = false) async throws {