Fix BatchRemovingTransitionContext completion being called multiple times

Sources/FluidStack/Transition/BatchRemovingTransitionContext.swift

@@ -36,6 +36,7 @@ public final class BatchRemovingTransitionContext: TransitionContext {
 
   private let onCompleted: (BatchRemovingTransitionContext) -> Void
   private var childContexts: [ChildContext] = []
+  private var hasNotifiedCompletion: Bool = false
   private var callbacks: [(CompletionEvent) -> Void] = []
 
   init(
@@ -56,6 +57,7 @@ public final class BatchRemovingTransitionContext: TransitionContext {
 
   public func notifyCompleted() {
     assert(Thread.isMainThread)
+    guard isInvalidated == false, isCompleted == false else { return }
     isCompleted = true
     onCompleted(self)
   }
@@ -91,6 +93,8 @@ public final class BatchRemovingTransitionContext: TransitionContext {
   override func invalidate() {
     assert(Thread.isMainThread)
     isInvalidated = true
+    guard hasNotifiedCompletion == false else { return }
+    hasNotifiedCompletion = true
     callbacks.forEach { $0(.interrupted) }
   }
 
@@ -106,6 +110,8 @@ public final class BatchRemovingTransitionContext: TransitionContext {
    Triggers ``addCompletionEventHandler(_:)`` with ``TransitionContext/CompletionEvent/succeeded``
    */
   func transitionSucceeded() {
-    callbacks.forEach{ $0(.succeeded) }
+    guard hasNotifiedCompletion == false else { return }
+    hasNotifiedCompletion = true
+    callbacks.forEach { $0(.succeeded) }
   }
 }

Sources/FluidStack/Transition/RemovingTransitionContext.swift

@@ -26,6 +26,7 @@ public final class RemovingTransitionContext: TransitionContext {
   private let onRequestedDisplayOnTop:
     (DisplaySource) -> FluidStackController.DisplayingOnTopSubscription
 
+  private var hasNotifiedCompletion: Bool = false
   private var callbacks: [(CompletionEvent) -> Void] = []
 
   init(
@@ -57,6 +58,7 @@ public final class RemovingTransitionContext: TransitionContext {
     assert(Thread.isMainThread)
     guard isInvalidated == false, isCompleted == false else { return }
     isInvalidated = true
+    hasNotifiedCompletion = true
     callbacks.forEach { $0(.cancelled) }
     onAnimationCompleted(self)
   }
@@ -97,6 +99,8 @@ public final class RemovingTransitionContext: TransitionContext {
   override func invalidate() {
     assert(Thread.isMainThread)
     isInvalidated = true
+    guard hasNotifiedCompletion == false else { return }
+    hasNotifiedCompletion = true
     callbacks.forEach { $0(.interrupted) }
   }
 
@@ -115,6 +119,8 @@ public final class RemovingTransitionContext: TransitionContext {
    Triggers ``addCompletionEventHandler(_:)`` with ``TransitionContext/CompletionEvent/succeeded``
    */
   func transitionSucceeded() {
+    guard hasNotifiedCompletion == false else { return }
+    hasNotifiedCompletion = true
     callbacks.forEach { $0(.succeeded) }
   }
 

Sources/FluidStack/ViewController/FluidStackController.swift

@@ -718,13 +718,17 @@ open class FluidStackController: UIViewController {
       fromViewControllers: itemsToRemove.map(\.viewController),
       toViewController: targetTopItem?.viewController,
       onCompleted: { [weak self] context in
-        
+
         assert(Thread.isMainThread)
-        
+
         guard let self = self else {
-          return          
+          return
         }
-
+
+        guard context.isInvalidated == false else {
+          return
+        }
+
         /**
          Completion of transition, cleaning up
          */

Tests/FluidStackTests/FluidStackControllerTests.swift

@@ -565,6 +565,68 @@ final class FluidStackControllerTests: XCTestCase {
 
   }
 
+  /// Tests that batch removing completion is called exactly once.
+  /// When fluidPop triggers batch removing (VC is not on top),
+  /// the completion must fire exactly once after the batch transition completes.
+  func testBatchRemovingCompletionCalledOnce() {
+
+    let window = UIWindow()
+    let stack = FluidStackController()
+    window.rootViewController = stack
+    window.makeKeyAndVisible()
+
+    let vc1 = UIViewController()
+    let vc2 = UIViewController()
+    let vc3 = UIViewController()
+    let vc4 = UIViewController()
+
+    stack.addContentViewController(vc1, transition: .disabled)
+    stack.addContentViewController(vc2, transition: .disabled)
+    stack.addContentViewController(vc3, transition: .disabled)
+    stack.addContentViewController(vc4, transition: .disabled)
+
+    XCTAssertEqual(stack.stackingViewControllers.count, 4)
+
+    let exp = expectation(description: "completion called")
+    exp.assertForOverFulfill = true
+    var completionCallCount = 0
+
+    vc2.fluidPop { _ in
+      completionCallCount += 1
+      exp.fulfill()
+    }
+
+    wait(for: [exp], timeout: 2)
+
+    XCTAssertEqual(stack.stackingViewControllers.count, 1)
+    XCTAssertEqual(completionCallCount, 1, "Completion should be called exactly once")
+  }
+
+  /// Tests that removeAllViewController completion is called exactly once.
+  func testRemoveAllViewControllerCompletionCalledOnce() {
+
+    let stack = FluidStackController()
+
+    stack.addContentViewController(UIViewController(), transition: .disabled)
+    stack.addContentViewController(UIViewController(), transition: .disabled)
+    stack.addContentViewController(UIViewController(), transition: .disabled)
+    stack.addContentViewController(UIViewController(), transition: .disabled)
+
+    XCTAssertEqual(stack.stackingViewControllers.count, 4)
+
+    var completionCallCount = 0
+
+    stack.removeAllViewController(
+      transition: .disabled,
+      completion: { event in
+        completionCallCount += 1
+      }
+    )
+
+    XCTAssertEqual(stack.stackingViewControllers.count, 1)
+    XCTAssertEqual(completionCallCount, 1, "Completion should be called exactly once")
+  }
+
   final class ContentTypeOption: UIViewController {
     init(contentType: FluidStackContentConfiguration.ContentType) {
       super.init(nibName: nil, bundle: nil)