Merge pull request #47 from daangn/impl-should-scroll-to-top-modifier

NO-JIRA `scrollViewShouldScrollToTop`event modifier 추가해요.

Sources/KarrotListKit/Adapter/CollectionViewAdapter.swift

@@ -620,6 +620,18 @@ extension CollectionViewAdapter {
       )
     )
   }
+
+  public func scrollViewShouldScrollToTop(_ scrollView: UIScrollView) -> Bool {
+    guard let collectionView else {
+      return true
+    }
+
+    return list?.event(for: ShouldScrollToTopEvent.self)?.handler(
+      .init(
+        collectionView: collectionView
+      )
+    ) ?? true
+  }
 }
 
 // MARK: - UICollectionViewDataSourcePrefetching

Sources/KarrotListKit/Event/List/ShouldScrollToTopEvent.swift

@@ -0,0 +1,16 @@
+//
+//  Copyright (c) 2025 Danggeun Market Inc.
+//
+
+import UIKit
+
+/// This structure encapsulates the shouldScrollToTop event information and contains a closure object for shouldScrollToTop event.
+public struct ShouldScrollToTopEvent: ListingViewEvent {
+  public struct EventContext {
+    /// The collectionView object requesting this information.
+    public let collectionView: UICollectionView
+  }
+
+  /// A closure that's called when if the scroll view should scroll to the top of the content.
+  let handler: (EventContext) -> Bool
+}

Sources/KarrotListKit/List.swift

@@ -120,4 +120,12 @@ extension List {
   public func didEndDecelerating(_ handler: @escaping (DidEndDeceleratingEvent.EventContext) -> Void) -> Self {
     registerEvent(DidEndDeceleratingEvent(handler: handler))
   }
+
+  /// Register a callback handler that will be called when the scroll view should scroll to the top of the content
+  ///
+  /// - Parameters:
+  ///  - handler: The callback handler for shouldScrollToTop event
+  public func shouldScrollToTop(_ handler: @escaping (ShouldScrollToTopEvent.EventContext) -> Bool) -> Self {
+    registerEvent(ShouldScrollToTopEvent(handler: handler))
+  }
 }

Tests/KarrotListKitTests/CollectionViewAdapterTests.swift

@@ -889,6 +889,32 @@ extension CollectionViewAdapterTests {
     // then
     XCTAssertNotNil(eventContext)
   }
+
+  func test_given_scrollToTopValue_when_try_scrollToTop_then_handleShouldScrollToTopEvent() {
+    [true, false].forEach { value in
+      // given
+      var eventContext: ShouldScrollToTopEvent.EventContext!
+      let collectionView = UICollectionView(layoutAdapter: CollectionViewLayoutAdapter())
+      let sut = sut(
+        configuration: .init(),
+        collectionView: collectionView
+      )
+      sut.list = List(
+        sections: []
+      ).shouldScrollToTop { context in
+        eventContext = context
+        return value
+      }
+
+      // when
+      let shouldScrollToTop = collectionView
+        .delegate?.scrollViewShouldScrollToTop?(collectionView)
+
+      // then
+      XCTAssertEqual(shouldScrollToTop, value)
+      XCTAssertNotNil(eventContext)
+    }
+  }
 }
 
 // MARK: - UICollectionViewDataSourcePrefetching