Yattee v2 rewrite

Yattee/Views/Player/Gestures/OverscrollGestureHandler.swift

@@ -0,0 +1,117 @@
+//
+//  OverscrollGestureHandler.swift
+//  Yattee
+//
+//  UIKit gesture handler for detecting overscroll pull-down gestures on UIScrollView.
+//  When user pulls down at scroll top, disables bounce and forwards drag events for smooth
+//  panel collapse animation.
+//
+
+#if os(iOS)
+import UIKit
+
+/// Coordinates overscroll detection on a UIScrollView, calling back during pull-down gestures
+/// when the scroll is at top. Disables bounce during the gesture to allow smooth animation.
+final class OverscrollGestureHandler: NSObject, UIGestureRecognizerDelegate {
+    // MARK: - Properties
+
+    weak var scrollView: UIScrollView?
+    var onDragChanged: ((CGFloat) -> Void)?
+    var onDragEnded: ((CGFloat, CGFloat) -> Void)?
+
+    /// Whether we're currently tracking an overscroll gesture
+    private var isTracking = false
+
+    /// The pan gesture recognizer we add to the scroll view
+    private var panRecognizer: UIPanGestureRecognizer?
+
+    // MARK: - Setup
+
+    /// Attaches the pan gesture recognizer to the scroll view.
+    func attach(to scrollView: UIScrollView) {
+        detach()
+
+        self.scrollView = scrollView
+
+        let pan = UIPanGestureRecognizer(target: self, action: #selector(handlePan(_:)))
+        pan.delegate = self
+        scrollView.addGestureRecognizer(pan)
+        panRecognizer = pan
+    }
+
+    /// Removes the pan gesture recognizer from the scroll view.
+    func detach() {
+        if let recognizer = panRecognizer, let view = recognizer.view {
+            view.removeGestureRecognizer(recognizer)
+        }
+        panRecognizer = nil
+        scrollView = nil
+        isTracking = false
+    }
+
+    // MARK: - Gesture Handling
+
+    @objc private func handlePan(_ gesture: UIPanGestureRecognizer) {
+        guard let scrollView else { return }
+
+        switch gesture.state {
+        case .began:
+            // Start tracking - disable bounce so we can control the movement
+            isTracking = true
+            scrollView.bounces = false
+
+        case .changed:
+            let translation = gesture.translation(in: gesture.view)
+            // Only forward positive (pull down) translations
+            if translation.y > 0 {
+                onDragChanged?(translation.y)
+            }
+
+        case .ended, .cancelled:
+            // Re-enable bounce
+            scrollView.bounces = true
+            isTracking = false
+
+            let translation = gesture.translation(in: gesture.view)
+            let velocity = gesture.velocity(in: gesture.view)
+            // Calculate predicted end position
+            let decelerationTime: CGFloat = 0.3
+            let predicted = translation.y + velocity.y * decelerationTime
+
+            onDragEnded?(translation.y, predicted)
+
+        default:
+            break
+        }
+    }
+
+    // MARK: - UIGestureRecognizerDelegate
+
+    func gestureRecognizerShouldBegin(_ gestureRecognizer: UIGestureRecognizer) -> Bool {
+        guard let pan = gestureRecognizer as? UIPanGestureRecognizer,
+              let scrollView else {
+            return false
+        }
+
+        let velocity = pan.velocity(in: pan.view)
+
+        // Only begin if:
+        // 1. Scroll view is at top (contentOffset.y <= 0)
+        // 2. User is pulling down (velocity.y > 0)
+        // 3. Vertical movement is dominant (to not interfere with horizontal scrolling)
+        let isAtTop = scrollView.contentOffset.y <= 0
+        let isPullingDown = velocity.y > 0
+        let isVerticalDominant = abs(velocity.y) > abs(velocity.x)
+
+        return isAtTop && isPullingDown && isVerticalDominant
+    }
+
+    func gestureRecognizer(
+        _ gestureRecognizer: UIGestureRecognizer,
+        shouldRecognizeSimultaneouslyWith otherGestureRecognizer: UIGestureRecognizer
+    ) -> Bool {
+        // Don't allow simultaneous recognition - we take over when overscrolling
+        false
+    }
+}
+#endif