[breaking change] Update propagation of stack action

Sources/FluidStack/Helper/UIViewController+.swift

@@ -151,16 +151,23 @@ extension UIViewController {
   func propagateStackAction(_ action: FluidStackAction) {
 
     func _propagateRecursively(viewController: UIViewController) {
-
-      guard (viewController is FluidStackController) == false else {
+
+      if let stackController = viewController as? FluidStackController {
+
+        for handler in stackController.fluidStackActionHandlers {
+          handler(action)
+        }
+
+        stackController.topViewController?.propagateStackAction(action)
+
         return
       }
-      
+
       // call all of handlers
-      viewController.fluidStackActionHandlers.forEach {
-        $0(action)
+      for handler in viewController.fluidStackActionHandlers {
+        handler(action)
       }
-      
+
       // propagates to children
       for viewController in viewController.children {
         // recursive

Sources/FluidStack/ViewController/FluidStackController.swift

@@ -6,8 +6,8 @@ import FluidPortal
 /// Actions that comes from ``FluidStackController``
 public enum FluidStackAction {
 
-  /// on started push operation in the stack
-  /// dispatches after viewDidLoad, added in hierarchy, before transitioning
+  /// It will appear on a stack.
+  /// Emits before the transition starts but after viewDidLoad and inserted into the stack.
   case willPush
 
   /// Potentially it won't be emmited after ``FluidStackAction/willPush``
@@ -18,10 +18,6 @@ public enum FluidStackAction {
 
   /// Potentially it won't be emmited after ``FluidStackAction/willPop``
   case didPop
-
-  /// will become currenty top view controller on the stack.
-  /// that happens on push and pop higher view controller.
-  case willBecomeTop
 }
 
 /// A struct that configures how to display in ``FluidStackController``
@@ -304,8 +300,7 @@ open class FluidStackController: UIViewController {
 
     // propagate after `viewDidLoad`
     viewControllerToAdd.propagateStackAction(.willPush)
-    viewControllerToAdd.propagateStackAction(.willBecomeTop)
-
+
     // take before modifying.
     let currentTop = stackingItems.last
 
@@ -462,7 +457,7 @@ open class FluidStackController: UIViewController {
     }()
 
     platterView.viewController.propagateStackAction(.willPop)
-    backView?.viewController.propagateStackAction(.willBecomeTop)
+    backView?.viewController.propagateStackAction(.willPush)
 
     let newTransitionContext = RemovingTransitionContext(
       contentView: platterView,

Tests/FluidStackTests/FluidStackControllerTests.swift

@@ -445,8 +445,15 @@ final class FluidStackControllerTests: XCTestCase {
 
     let childStack = FluidStackController(configuration: .init(retainsRootViewController: false))
 
+    let childExp = expectation(description: "child")
+
     childStack.addFluidStackActionHandler { action in
-      XCTFail("Never gets any actions on child")
+
+      if case .willPush = action {
+        // child will get an event that happens in the higher layer.
+        childExp.fulfill()
+      }
+
     }
 
     let expWillPop = expectation(description: "called")
@@ -466,8 +473,6 @@ final class FluidStackControllerTests: XCTestCase {
         break
       case .didPop:
         expDidPop.fulfill()
-      case .willBecomeTop:
-        break
       }
     }
 
@@ -481,7 +486,7 @@ final class FluidStackControllerTests: XCTestCase {
 
     stack.topViewController?.fluidPop()
 
-    wait(for: [expWillPop, expDidPop], timeout: 1)
+    wait(for: [expWillPop, expDidPop, childExp], timeout: 1)
   }
 
   func testPropagationActions_willBecomeTop() {
@@ -495,15 +500,13 @@ final class FluidStackControllerTests: XCTestCase {
     controller_1.addFluidStackActionHandler { action in
       switch action {
       case .willPush:
-        break
+        expWillBecomeTop.fulfill()
       case .willPop:
         break
       case .didPush:
         break
       case .didPop:
         break
-      case .willBecomeTop:
-        expWillBecomeTop.fulfill()
       }
     }