Load more direction changing

View Controllers/TableViewController.swift

@@ -77,6 +77,22 @@ class TableViewController: UITableViewController {
         viewModel.request(maxID: nil, minID: nil)
     }
 
+    override func scrollViewDidScroll(_ scrollView: UIScrollView) {
+        guard scrollView.isDragging else { return }
+
+        let up = scrollView.panGestureRecognizer.translation(in: scrollView.superview).y > 0
+
+        for loadMoreView in visibleLoadMoreViews {
+            loadMoreView.directionChanged(up: up)
+        }
+    }
+
+    override func scrollViewDidEndDragging(_ scrollView: UIScrollView, willDecelerate decelerate: Bool) {
+        for loadMoreView in visibleLoadMoreViews {
+            loadMoreView.finalizeDirectionChange()
+        }
+    }
+
     override func tableView(_ tableView: UITableView,
                             willDisplay cell: UITableViewCell,
                             forRowAt indexPath: IndexPath) {
@@ -101,6 +117,8 @@ class TableViewController: UITableViewController {
     }
 
     override func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
+        tableView.deselectRow(at: indexPath, animated: true)
+
         guard let item = dataSource.itemIdentifier(for: indexPath) else { return }
 
         viewModel.itemSelected(item)
@@ -160,6 +178,10 @@ extension TableViewController {
 }
 
 private extension TableViewController {
+    var visibleLoadMoreViews: [LoadMoreView] {
+        tableView.visibleCells.compactMap { $0.contentView as? LoadMoreView }
+    }
+
     func setupViewModelBindings() {
         viewModel.title.sink { [weak self] in self?.navigationItem.title = $0 }.store(in: &cancellables)
 

ViewModels/Sources/ViewModels/LoadMoreViewModel.swift

@@ -3,17 +3,16 @@
 import Combine
 import ServiceLayer
 
-public struct LoadMoreViewModel {
-    public let loading: AnyPublisher<Bool, Never>
+final public class LoadMoreViewModel: ObservableObject {
+    public var direction = LoadMore.Direction.up
+    @Published public private(set) var loading = false
     public let events: AnyPublisher<AnyPublisher<CollectionItemEvent, Error>, Never>
 
     private let loadMoreService: LoadMoreService
     private let eventsSubject = PassthroughSubject<AnyPublisher<CollectionItemEvent, Error>, Never>()
-    private let loadingSubject = PassthroughSubject<Bool, Never>()
 
     init(loadMoreService: LoadMoreService) {
         self.loadMoreService = loadMoreService
-        loading = loadingSubject.eraseToAnyPublisher()
         events = eventsSubject.eraseToAnyPublisher()
     }
 }
@@ -21,10 +20,10 @@ public struct LoadMoreViewModel {
 extension LoadMoreViewModel {
     func loadMore() {
         eventsSubject.send(
-            loadMoreService.request(direction: .down)
+            loadMoreService.request(direction: direction)
                 .handleEvents(
-                    receiveSubscription: { _ in loadingSubject.send(true) },
-                    receiveCompletion: { _ in loadingSubject.send(false) })
+                    receiveSubscription: { [weak self] _ in self?.loading = true },
+                    receiveCompletion: { [weak self] _ in self?.loading = false })
                 .map { _ in CollectionItemEvent.ignorableOutput }
                 .eraseToAnyPublisher())
     }

Views/LoadMoreView.swift

@@ -3,11 +3,14 @@
 import Combine
 import UIKit
 
-class LoadMoreView: UIView {
+final class LoadMoreView: UIView {
+    private let leadingArrowImageView = UIImageView()
+    private let trailingArrowImageView = UIImageView()
     private let label = UILabel()
     private let activityIndicatorView = UIActivityIndicatorView()
     private var loadMoreConfiguration: LoadMoreContentConfiguration
     private var loadingCancellable: AnyCancellable?
+    private var directionChange = LoadMoreView.directionChangeMax
 
     init(configuration: LoadMoreContentConfiguration) {
         self.loadMoreConfiguration = configuration
@@ -15,6 +18,7 @@ class LoadMoreView: UIView {
         super.init(frame: .zero)
 
         initialSetup()
+        applyLoadMoreConfiguration()
     }
 
     @available(*, unavailable)
@@ -23,6 +27,26 @@ class LoadMoreView: UIView {
     }
 }
 
+extension LoadMoreView {
+    func directionChanged(up: Bool) {
+        guard !loadMoreConfiguration.viewModel.loading else { return }
+
+        if up, directionChange < Self.directionChangeMax {
+            directionChange += Self.directionChangeIncrement
+        } else if !up, directionChange > -Self.directionChangeMax {
+            directionChange -= Self.directionChangeIncrement
+        }
+
+        updateDirectionChange(animated: false)
+    }
+
+    func finalizeDirectionChange() {
+        directionChange = directionChange > 0 ? Self.directionChangeMax : -Self.directionChangeMax
+
+        updateDirectionChange(animated: true)
+    }
+}
+
 extension LoadMoreView: UIContentView {
     var configuration: UIContentConfiguration {
         get { loadMoreConfiguration }
@@ -37,15 +61,15 @@ extension LoadMoreView: UIContentView {
 }
 
 private extension LoadMoreView {
-    func initialSetup() {
-        let leadingArrowImageView = UIImageView()
-        let trailingArrowImageView = UIImageView()
+    static let directionChangeMax = CGFloat.pi
+    static let directionChangeIncrement = CGFloat.pi / 10
 
+    func initialSetup() {
         for arrowImageView in [leadingArrowImageView, trailingArrowImageView] {
             addSubview(arrowImageView)
             arrowImageView.translatesAutoresizingMaskIntoConstraints = false
             arrowImageView.image = UIImage(
-                systemName: "arrow.up.circle",
+                systemName: "arrow.up",
                 withConfiguration: UIImage.SymbolConfiguration(
                     pointSize: UIFont.preferredFont(forTextStyle: .title2).pointSize))
             arrowImageView.setContentHuggingPriority(.required, for: .horizontal)
@@ -81,11 +105,27 @@ private extension LoadMoreView {
     }
 
     func applyLoadMoreConfiguration() {
-        loadingCancellable = loadMoreConfiguration.viewModel.loading.sink { [weak self] in
+        loadingCancellable = loadMoreConfiguration.viewModel.$loading.sink { [weak self] in
             guard let self = self else { return }
 
             self.label.isHidden = $0
             $0 ? self.activityIndicatorView.startAnimating() : self.activityIndicatorView.stopAnimating()
         }
     }
+
+    func updateDirectionChange(animated: Bool) {
+        if animated {
+            UIView.animate(withDuration: 0.1) {
+                self.performDirectionChangeUpdates()
+            }
+        } else {
+            self.performDirectionChangeUpdates()
+        }
+    }
+
+    func performDirectionChangeUpdates() {
+        loadMoreConfiguration.viewModel.direction = directionChange > 0 ? .up : .down
+        leadingArrowImageView.transform = CGAffineTransform(rotationAngle: .pi / 2 - directionChange / 2)
+        trailingArrowImageView.transform = CGAffineTransform(rotationAngle: -.pi / 2 + directionChange / 2)
+    }
 }