Complete phase H8: Undo functionality (unbegrenzt)

- Add UndoButton.razor as reusable component
- Refactor GameInputPanel to use UndoButton component
- Enhance GameEffects with proper UndoThrowAction handler
- IState injection for state access in effects

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

docs/IMPLEMENTATION_PLAN.md

@@ -955,7 +955,7 @@ Web:        Store/GameState/, Components/Game/, Hubs/GameHub
 | ✓ | H5 | Games | Scheiss-Spiel + Trigger-Integration | 6 |
 | ✓ | H6 | UI | Game Setup Dialog | 4 |
 | ✓ | H7 | Integration | DayDetails Tabs | 3 |
-| ☐ | H8 | Features | Undo (unbegrenzt, ohne Redo) | 2 |
+| ✓ | H8 | Features | Undo (unbegrenzt, ohne Redo) | 2 |
 | ☐ | H9 | Persistenz | DB Persistence & Recovery | 4 |
 | ☐ | H9b | Sync | SignalR komplett + Auto-Reconnect | 5 |
 | ☐ | H10 | Testing | Kern-Logik Tests | 2 |

src/Koogle.Web/Components/Game/GameInputPanel.razor

@@ -51,18 +51,9 @@
     </div>
 
     @* Undo button *@
-    @if (GameState.Value.UndoStack.Count > 0)
-    {
     <div class="undo-section">
-            <MudButton Variant="Variant.Outlined"
-                       Color="Color.Secondary"
-                       FullWidth="true"
-                       OnClick="HandleUndo"
-                       StartIcon="@Icons.Material.Filled.Undo">
-                Letzten Wurf rückgängig (@GameState.Value.UndoStack.Count)
-            </MudButton>
+        <UndoButton />
     </div>
-    }
 
     @* Error display *@
     @if (!string.IsNullOrEmpty(GameState.Value.Error))
@@ -271,18 +262,6 @@
         await OnThrowCompleted.InvokeAsync(result);
     }
 
-    private void HandleUndo()
-    {
-        if (GameState.Value.UndoStack.Count > 0)
-        {
-            var lastSnapshot = GameState.Value.UndoStack[^1];
-            Dispatcher.Dispatch(new UndoThrowSuccessAction(
-                lastSnapshot.ThrowPanel,
-                lastSnapshot.Participants,
-                lastSnapshot.GameModel));
-        }
-    }
-
     private async Task ShowPlayerSelector()
     {
         await OnShowPlayerSelector.InvokeAsync();

src/Koogle.Web/Components/Game/UndoButton.razor

@@ -0,0 +1,103 @@
+@using Koogle.Web.Store.GameState
+@inherits FluxorComponent
+
+@inject IState<GameState> GameState
+@inject IDispatcher Dispatcher
+
+@* Only show when undo is available *@
+@if (CanUndo)
+{
+    <MudButton Variant="@Variant"
+               Color="Color.Secondary"
+               FullWidth="@FullWidth"
+               Size="@Size"
+               Disabled="@IsDisabled"
+               OnClick="HandleUndo"
+               StartIcon="@Icons.Material.Filled.Undo"
+               Class="@Class">
+        @ButtonText
+    </MudButton>
+}
+
+@code {
+    /// <summary>
+    /// Whether to show the button even when no undo is available.
+    /// </summary>
+    [Parameter]
+    public bool AlwaysShow { get; set; }
+
+    /// <summary>
+    /// Button variant (default: Outlined).
+    /// </summary>
+    [Parameter]
+    public Variant Variant { get; set; } = Variant.Outlined;
+
+    /// <summary>
+    /// Whether button should be full width.
+    /// </summary>
+    [Parameter]
+    public bool FullWidth { get; set; } = true;
+
+    /// <summary>
+    /// Button size.
+    /// </summary>
+    [Parameter]
+    public Size Size { get; set; } = Size.Medium;
+
+    /// <summary>
+    /// Additional CSS classes.
+    /// </summary>
+    [Parameter]
+    public string? Class { get; set; }
+
+    /// <summary>
+    /// Optional custom button text. If not set, shows count.
+    /// </summary>
+    [Parameter]
+    public string? CustomText { get; set; }
+
+    /// <summary>
+    /// Whether to show the undo count in the button text.
+    /// </summary>
+    [Parameter]
+    public bool ShowCount { get; set; } = true;
+
+    /// <summary>
+    /// Callback when undo is triggered.
+    /// </summary>
+    [Parameter]
+    public EventCallback OnUndoTriggered { get; set; }
+
+    private int UndoCount => GameState.Value.UndoStack.Count;
+    private bool CanUndo => UndoCount > 0 || AlwaysShow;
+    private bool IsDisabled => UndoCount == 0 || GameState.Value.IsSaving;
+
+    private string ButtonText
+    {
+        get
+        {
+            if (!string.IsNullOrEmpty(CustomText))
+                return CustomText;
+
+            var baseText = "Letzten Wurf rückgängig";
+            return ShowCount && UndoCount > 0
+                ? $"{baseText} ({UndoCount})"
+                : baseText;
+        }
+    }
+
+    private async Task HandleUndo()
+    {
+        if (UndoCount == 0)
+            return;
+
+        var lastSnapshot = GameState.Value.UndoStack[^1];
+
+        Dispatcher.Dispatch(new UndoThrowSuccessAction(
+            lastSnapshot.ThrowPanel,
+            lastSnapshot.Participants,
+            lastSnapshot.GameModel));
+
+        await OnUndoTriggered.InvokeAsync();
+    }
+}

src/Koogle.Web/Store/GameState/GameEffects.cs

@@ -10,24 +10,44 @@ namespace Koogle.Web.Store.GameState;
 public class GameEffects
 {
     private readonly ILogger<GameEffects> _logger;
+    private readonly IState<GameState> _gameState;
 
     /// <summary>
     /// Initializes a new instance of the GameEffects class.
     /// </summary>
-    public GameEffects(ILogger<GameEffects> logger)
+    public GameEffects(ILogger<GameEffects> logger, IState<GameState> gameState)
     {
         _logger = logger;
+        _gameState = gameState;
     }
 
     /// <summary>
-    /// Handles UndoThrowAction - pops last snapshot from stack.
+    /// Handles UndoThrowAction - pops last snapshot from stack and restores state.
     /// </summary>
     [EffectMethod]
     public Task HandleUndoThrow(UndoThrowAction action, IDispatcher dispatcher)
     {
-        // Note: Actual state access will be handled via IState injection in later phases
-        // For now, this is a placeholder that the reducer handles directly
-        _logger.LogDebug("Undo throw action received");
+        var state = _gameState.Value;
+
+        if (state.UndoStack.Count == 0)
+        {
+            _logger.LogWarning("Undo requested but undo stack is empty");
+            dispatcher.Dispatch(new UndoThrowFailureAction("Keine Würfe zum Rückgängigmachen vorhanden"));
+            return Task.CompletedTask;
+        }
+
+        var lastSnapshot = state.UndoStack[^1];
+
+        _logger.LogDebug(
+            "Undoing throw. Stack size before: {StackSize}, Restoring to throw counter: {ThrowCounter}",
+            state.UndoStack.Count,
+            lastSnapshot.ThrowPanel.TotalThrowCounter);
+
+        dispatcher.Dispatch(new UndoThrowSuccessAction(
+            lastSnapshot.ThrowPanel,
+            lastSnapshot.Participants,
+            lastSnapshot.GameModel));
+
         return Task.CompletedTask;
     }