feat: add HighlightEvent and UnhighlightEvent

Sources/KarrotListKit/Adapter/CollectionViewAdapter.swift

@@ -484,6 +484,40 @@ extension CollectionViewAdapter: UICollectionViewDelegate {
       return
     }
   }
+
+  public func collectionView(
+    _ collectionView: UICollectionView,
+    didHighlightItemAt indexPath: IndexPath
+  ) {
+    guard let item = item(at: indexPath) else {
+      return
+    }
+
+    item.event(for: HighlightEvent.self)?.handler(
+      .init(
+        indexPath: indexPath,
+        anyComponent: item.component,
+        content: (collectionView.cellForItem(at: indexPath) as? ComponentRenderable)?.renderedContent
+      )
+    )
+  }
+
+  public func collectionView(
+    _ collectionView: UICollectionView,
+    didUnhighlightItemAt indexPath: IndexPath
+  ) {
+    guard let item = item(at: indexPath) else {
+      return
+    }
+
+    item.event(for: UnhighlightEvent.self)?.handler(
+      .init(
+        indexPath: indexPath,
+        anyComponent: item.component,
+        content: (collectionView.cellForItem(at: indexPath) as? ComponentRenderable)?.renderedContent
+      )
+    )
+  }
 }
 
 // MARK: - UIScrollViewDelegate

Sources/KarrotListKit/Cell.swift

@@ -67,6 +67,22 @@ extension Cell {
   public func didEndDisplay(_ handler: @escaping (DidEndDisplayingEvent.EventContext) -> Void) -> Self {
     registerEvent(DidEndDisplayingEvent(handler: handler))
   }
+
+  /// Register a callback handler that will be called when the cell was highlighted.
+  ///
+  /// - Parameters:
+  ///  - handler: The callback handler for highlight event
+  public func onHighlight(_ handler: @escaping (HighlightEvent.EventContext) -> Void) -> Self {
+    registerEvent(HighlightEvent(handler: handler))
+  }
+
+  /// Register a callback handler that will be called when the cell was unhighlight.
+  ///
+  /// - Parameters:
+  ///  - handler: The callback handler for unhighlight event
+  public func onUnhighlight(_ handler: @escaping (UnhighlightEvent.EventContext) -> Void) -> Self {
+    registerEvent(UnhighlightEvent(handler: handler))
+  }
 }
 
 // MARK: - Hashable

Sources/KarrotListKit/Event/Cell/HighlightEvent.swift

@@ -0,0 +1,24 @@
+//
+//  Copyright (c) 2024 Danggeun Market Inc.
+//
+
+import UIKit
+
+/// This structure encapsulates the highlight event information and contains a closure object for handling the highlight event.
+public struct HighlightEvent: ListingViewEvent {
+
+  public struct EventContext {
+
+    /// The index path of the view that was highlighted.
+    public let indexPath: IndexPath
+
+    /// The component owned by the view that was highlighted.
+    public let anyComponent: AnyComponent
+
+    /// The content owned by the view that was highlighted.
+    public let content: UIView?
+  }
+
+  /// A closure that's called when the cell was highlighted
+  let handler: (EventContext) -> Void
+}

Sources/KarrotListKit/Event/Cell/UnhighlightEvent.swift

@@ -0,0 +1,25 @@
+//
+//  Copyright (c) 2024 Danggeun Market Inc.
+//
+
+import UIKit
+
+/// This structure encapsulates the unhighlight event information and contains a closure object for handling the unhighlight event.
+public struct UnhighlightEvent: ListingViewEvent {
+
+  public struct EventContext {
+
+    /// The index path of the view that was unhighlight.
+    public let indexPath: IndexPath
+
+    /// The component owned by the view that was unhighlight.
+    public let anyComponent: AnyComponent
+
+    /// The content owned by the view that was unhighlight.
+    public let content: UIView?
+  }
+
+  /// A closure that's called when the cell was unhighlight
+  let handler: (EventContext) -> Void
+}
+

Tests/KarrotListKitTests/CollectionViewAdapterTests.swift

@@ -634,6 +634,60 @@ extension CollectionViewAdapterTests {
     // then
     XCTAssertEqual(eventContext.indexPath, IndexPath(item: 0, section: 0))
   }
+
+  func test_given_highlightHandler_when_highlightCell_then_handleEvent() {
+    // given
+    var eventContext: HighlightEvent.EventContext!
+    let collectionView = UICollectionView(layoutAdapter: CollectionViewLayoutAdapter())
+    let component = DummyComponent()
+    let sut = sut(collectionView: collectionView)
+    sut.list = List {
+      Section(id: UUID()) {
+        Cell(id: UUID(), component: component)
+          .onHighlight { context in
+            eventContext = context
+          }
+      }
+    }
+
+    // when
+    collectionView
+      .delegate?
+      .collectionView?(
+        collectionView,
+        didHighlightItemAt: IndexPath(item: 0, section: 0)
+      )
+
+    // then
+    XCTAssertEqual(eventContext.indexPath, IndexPath(item: 0, section: 0))
+  }
+
+  func test_given_unhighlightHandler_when_unhighlightCell_then_handleEvent() {
+    // given
+    var eventContext: UnhighlightEvent.EventContext!
+    let collectionView = UICollectionView(layoutAdapter: CollectionViewLayoutAdapter())
+    let component = DummyComponent()
+    let sut = sut(collectionView: collectionView)
+    sut.list = List {
+      Section(id: UUID()) {
+        Cell(id: UUID(), component: component)
+          .onUnhighlight { context in
+            eventContext = context
+          }
+      }
+    }
+
+    // when
+    collectionView
+      .delegate?
+      .collectionView?(
+        collectionView,
+        didUnhighlightItemAt: IndexPath(item: 0, section: 0)
+      )
+
+    // then
+    XCTAssertEqual(eventContext.indexPath, IndexPath(item: 0, section: 0))
+  }
 }
 
 // MARK: - UIScrollViewDelegate