Fix MultiSelect bulk selection and Paginator previous item navigation

src/Sharprompt/Forms/MultiSelectForm.cs

@@ -124,32 +124,45 @@ private bool HandleSpacebar()
 
     private bool HandleCtrlA()
     {
-        if (_selectedItems.Count == Paginator.TotalCount)
+        // Bulk operations only apply to the currently filtered items, so selections
+        // hidden by the filter are preserved.
+        var selectedItems = new HashSet<T>(_selectedItems);
+
+        if (Paginator.All(_selectedItems.Contains))
         {
-            _selectedItems.Clear();
+            selectedItems.ExceptWith(Paginator);
         }
         else
         {
-            foreach (var item in Paginator)
-            {
-                _selectedItems.Add(item);
-            }
+            selectedItems.UnionWith(Paginator);
         }
 
+        UpdateSelectedItems(selectedItems);
+
         return true;
     }
 
     private bool HandleCtrlI()
     {
-        var invertedItems = Paginator.Except(_selectedItems).ToArray();
+        var selectedItems = new HashSet<T>(_selectedItems);
 
-        _selectedItems.Clear();
+        selectedItems.SymmetricExceptWith(Paginator);
+
+        UpdateSelectedItems(selectedItems);
 
-        foreach (var item in invertedItems)
+        return true;
+    }
+
+    private void UpdateSelectedItems(HashSet<T> selectedItems)
+    {
+        if (selectedItems.Count > _options.Maximum)
         {
-            _selectedItems.Add(item);
+            SetError(string.Format(Resource.Validation_Maximum_SelectionRequired, _options.Maximum));
+
+            return;
         }
 
-        return true;
+        _selectedItems.Clear();
+        _selectedItems.UnionWith(selectedItems);
     }
 }

src/Sharprompt/Internal/Paginator.cs

@@ -93,7 +93,9 @@ public void PreviousItem()
     {
         if (_selectedIndex <= 0)
         {
-            if (!LoopingSelection)
+            // With nothing selected, select the last item on the current page
+            // instead of moving to the previous page, mirroring NextItem.
+            if (!LoopingSelection && _selectedIndex == 0)
             {
                 PreviousPage();
             }

tests/Sharprompt.Tests/Forms/FormInteractionTests.cs

@@ -123,6 +123,170 @@ public void MultiSelectForm_SpacebarToggle_ReturnsCheckedItems()
         Assert.Equal(new[] { "apple", "banana" }, form.Start());
     }
 
+    [Fact]
+    public void MultiSelectForm_CtrlA_SelectsAllItems()
+    {
+        var (driver, configuration) = CreateTestContext();
+
+        driver.EnqueueKey(ConsoleKey.A, ConsoleModifiers.Control, '\x01');
+        driver.EnqueueEnter();
+
+        var options = new MultiSelectOptions<string>
+        {
+            Message = "message",
+            Items = ["apple", "banana", "cherry"]
+        };
+
+        using var form = new MultiSelectForm<string>(options, configuration);
+
+        Assert.Equal(new[] { "apple", "banana", "cherry" }, form.Start());
+    }
+
+    [Fact]
+    public void MultiSelectForm_CtrlA_AllSelected_DeselectsAllItems()
+    {
+        var (driver, configuration) = CreateTestContext();
+
+        driver.EnqueueKey(ConsoleKey.A, ConsoleModifiers.Control, '\x01');
+        driver.EnqueueEnter();
+
+        var options = new MultiSelectOptions<string>
+        {
+            Message = "message",
+            Items = ["apple", "banana", "cherry"],
+            DefaultValues = ["apple", "banana", "cherry"],
+            Minimum = 0
+        };
+
+        using var form = new MultiSelectForm<string>(options, configuration);
+
+        Assert.Empty(form.Start());
+    }
+
+    [Fact]
+    public void MultiSelectForm_CtrlA_ExceedingMaximum_KeepsSelection()
+    {
+        var (driver, configuration) = CreateTestContext();
+
+        driver.EnqueueKey(ConsoleKey.A, ConsoleModifiers.Control, '\x01');
+        driver.EnqueueEnter();
+
+        var options = new MultiSelectOptions<string>
+        {
+            Message = "message",
+            Items = ["apple", "banana", "cherry"],
+            DefaultValues = ["apple"],
+            Maximum = 2
+        };
+
+        using var form = new MultiSelectForm<string>(options, configuration);
+
+        Assert.Equal(new[] { "apple" }, form.Start());
+    }
+
+    [Fact]
+    public void MultiSelectForm_CtrlA_WithFilter_SelectsOnlyFilteredItems()
+    {
+        var (driver, configuration) = CreateTestContext();
+
+        driver.EnqueueText("b");
+        driver.EnqueueKey(ConsoleKey.A, ConsoleModifiers.Control, '\x01');
+        driver.EnqueueEnter();
+
+        var options = new MultiSelectOptions<string>
+        {
+            Message = "message",
+            Items = ["apple", "banana", "cherry", "blueberry"]
+        };
+
+        using var form = new MultiSelectForm<string>(options, configuration);
+
+        Assert.Equal(new[] { "banana", "blueberry" }, form.Start());
+    }
+
+    [Fact]
+    public void MultiSelectForm_CtrlA_WithFilter_DeselectsOnlyFilteredItems()
+    {
+        var (driver, configuration) = CreateTestContext();
+
+        driver.EnqueueText("b");
+        driver.EnqueueKey(ConsoleKey.A, ConsoleModifiers.Control, '\x01');
+        driver.EnqueueEnter();
+
+        var options = new MultiSelectOptions<string>
+        {
+            Message = "message",
+            Items = ["apple", "banana", "cherry", "blueberry"],
+            DefaultValues = ["apple", "banana", "blueberry"]
+        };
+
+        using var form = new MultiSelectForm<string>(options, configuration);
+
+        Assert.Equal(new[] { "apple" }, form.Start());
+    }
+
+    [Fact]
+    public void MultiSelectForm_CtrlI_InvertsSelection()
+    {
+        var (driver, configuration) = CreateTestContext();
+
+        driver.EnqueueKey(ConsoleKey.I, ConsoleModifiers.Control, '\t');
+        driver.EnqueueEnter();
+
+        var options = new MultiSelectOptions<string>
+        {
+            Message = "message",
+            Items = ["apple", "banana", "cherry"],
+            DefaultValues = ["apple"]
+        };
+
+        using var form = new MultiSelectForm<string>(options, configuration);
+
+        Assert.Equal(new[] { "banana", "cherry" }, form.Start());
+    }
+
+    [Fact]
+    public void MultiSelectForm_CtrlI_WithFilter_PreservesHiddenSelections()
+    {
+        var (driver, configuration) = CreateTestContext();
+
+        driver.EnqueueText("b");
+        driver.EnqueueKey(ConsoleKey.I, ConsoleModifiers.Control, '\t');
+        driver.EnqueueEnter();
+
+        var options = new MultiSelectOptions<string>
+        {
+            Message = "message",
+            Items = ["apple", "banana", "cherry", "blueberry"],
+            DefaultValues = ["apple", "banana"]
+        };
+
+        using var form = new MultiSelectForm<string>(options, configuration);
+
+        Assert.Equal(new[] { "apple", "blueberry" }, form.Start());
+    }
+
+    [Fact]
+    public void MultiSelectForm_CtrlI_ExceedingMaximum_KeepsSelection()
+    {
+        var (driver, configuration) = CreateTestContext();
+
+        driver.EnqueueKey(ConsoleKey.I, ConsoleModifiers.Control, '\t');
+        driver.EnqueueEnter();
+
+        var options = new MultiSelectOptions<string>
+        {
+            Message = "message",
+            Items = ["apple", "banana", "cherry"],
+            DefaultValues = ["apple"],
+            Maximum = 1
+        };
+
+        using var form = new MultiSelectForm<string>(options, configuration);
+
+        Assert.Equal(new[] { "apple" }, form.Start());
+    }
+
     [Fact]
     public void InputForm_TypedText_ReturnsConvertedValue()
     {

tests/Sharprompt.Tests/Internal/PaginatorTests.cs

@@ -103,6 +103,39 @@ public void PreviousItem()
         Assert.Equal(0, selectedItem);
     }
 
+    [Fact]
+    public void PreviousItem_NotSelected_SelectsLastItemOnCurrentPage()
+    {
+        var paginator = new Paginator<int>(Enumerable.Range(0, 20), 5, Optional<int>.Empty, x => x.ToString());
+        paginator.LoopingSelection = false;
+
+        paginator.NextPage();
+        paginator.PreviousItem();
+
+        var selected = paginator.TryGetSelectedItem(out var selectedItem);
+
+        Assert.True(selected);
+        Assert.Equal(9, selectedItem);
+        Assert.Equal(1, paginator.CurrentPage);
+    }
+
+    [Fact]
+    public void PreviousItem_FirstItem_MovesToPreviousPage()
+    {
+        var paginator = new Paginator<int>(Enumerable.Range(0, 20), 5, Optional<int>.Empty, x => x.ToString());
+        paginator.LoopingSelection = false;
+
+        paginator.NextPage();
+        paginator.NextItem();
+        paginator.PreviousItem();
+
+        var selected = paginator.TryGetSelectedItem(out var selectedItem);
+
+        Assert.True(selected);
+        Assert.Equal(4, selectedItem);
+        Assert.Equal(0, paginator.CurrentPage);
+    }
+
     [Fact]
     public void PreviousPage()
     {