Add pull to refresh for Subscriptions, Popular and Trending (fixes #31)

Vendor/RefreshControl/ScrollViewMatcher/FramePreferenceKey.swift

@@ -0,0 +1,18 @@
+//
+//  FramePreferenceKey.swift
+//  SwiftUI_Pull_to_Refresh
+//
+//  Created by Geri Borbás on 21/09/2021.
+//
+
+import Foundation
+import SwiftUI
+
+struct FramePreferenceKey: PreferenceKey {
+    typealias Value = CGRect
+    static var defaultValue = CGRect.zero
+
+    static func reduce(value: inout CGRect, nextValue: () -> CGRect) {
+        value = nextValue()
+    }
+}

Vendor/RefreshControl/ScrollViewMatcher/ScrollViewMatcher.swift

@@ -0,0 +1,106 @@
+//
+//  ScrollViewMatcher.swift
+//  SwiftUI_Pull_to_Refresh
+//
+//  Created by Geri Borbás on 17/09/2021.
+//
+
+import Foundation
+import SwiftUI
+
+final class ScrollViewMatcher: UIViewControllerRepresentable {
+    let onMatch: (UIScrollView) -> Void
+    @Binding var geometryReaderFrame: CGRect
+
+    init(onResolve: @escaping (UIScrollView) -> Void, geometryReaderFrame: Binding<CGRect>) {
+        onMatch = onResolve
+        _geometryReaderFrame = geometryReaderFrame
+    }
+
+    func makeUIViewController(context _: Context) -> ScrollViewMatcherViewController {
+        ScrollViewMatcherViewController(onResolve: onMatch, geometryReaderFrame: geometryReaderFrame)
+    }
+
+    func updateUIViewController(_ viewController: ScrollViewMatcherViewController, context _: Context) {
+        viewController.geometryReaderFrame = geometryReaderFrame
+    }
+}
+
+final class ScrollViewMatcherViewController: UIViewController {
+    let onMatch: (UIScrollView) -> Void
+    private var scrollView: UIScrollView? {
+        didSet {
+            if oldValue != scrollView,
+               let scrollView = scrollView
+            {
+                onMatch(scrollView)
+            }
+        }
+    }
+
+    var geometryReaderFrame: CGRect {
+        didSet {
+            match()
+        }
+    }
+
+    init(onResolve: @escaping (UIScrollView) -> Void, geometryReaderFrame: CGRect, debug _: Bool = false) {
+        onMatch = onResolve
+        self.geometryReaderFrame = geometryReaderFrame
+        super.init(nibName: nil, bundle: nil)
+    }
+
+    @available(*, unavailable)
+    required init?(coder _: NSCoder) {
+        fatalError("Use init(onMatch:) to instantiate ScrollViewMatcherViewController.")
+    }
+
+    func match() {
+        // matchUsingHierarchy()
+        matchUsingGeometry()
+    }
+
+    func matchUsingHierarchy() {
+        if parent != nil {
+            // Lookup view ancestry for any `UIScrollView`.
+            view.searchViewAnchestorsFor { (scrollView: UIScrollView) in
+                self.scrollView = scrollView
+            }
+        }
+    }
+
+    func matchUsingGeometry() {
+        if let parent = parent {
+            if let scrollViewsInHierarchy: [UIScrollView] = parent.view.viewsInHierarchy() {
+                // Return first match if only a single scroll view is found in the hierarchy.
+                if scrollViewsInHierarchy.count == 1,
+                   let firstScrollViewInHierarchy = scrollViewsInHierarchy.first
+                {
+                    scrollView = firstScrollViewInHierarchy
+
+                    // Filter by frame origins if multiple matches found.
+                } else {
+                    if let firstMatchingFrameOrigin = scrollViewsInHierarchy.filter({
+                        $0.globalFrame.origin.close(to: geometryReaderFrame.origin)
+                    }).first {
+                        scrollView = firstMatchingFrameOrigin
+                    }
+                }
+            }
+        }
+    }
+
+    override func didMove(toParent parent: UIViewController?) {
+        super.didMove(toParent: parent)
+        match()
+    }
+}
+
+extension CGPoint {
+    /// Returns `true` if this point is close the other point (considering a ~1 pt tolerance).
+    func close(to point: CGPoint) -> Bool {
+        let inset = Double(1)
+        let rect = CGRect(x: x - inset, y: y - inset, width: inset * 2, height: inset * 2)
+        return rect.contains(point)
+    }
+}