Avalonia/tests/Avalonia.Controls.UnitTests/PullToRefresh/RefreshInfoProviderTests.cs

using Avalonia.Controls.PullToRefresh;
using Avalonia.Input;
using Avalonia.UnitTests;
using Xunit;

namespace Avalonia.Controls.UnitTests.PullToRefresh
{
    public class RefreshInfoProviderTests : ScopedTestBase
    {
        // Repro for the "_entered desync" bug.
        //
        // Real-world flow that triggers it:
        //   1. User starts pulling.   ScrollablePullGestureRecognizer raises PullGestureEvent
        //                             -> InteractingStateEntered sets IsInteractingForRefresh = true
        //                                and _entered = true.
        //   2. The pull motion produces a small ScrollChanged that pushes the scroll offset
        //      past the threshold. ScrollViewerIRefreshInfoProviderAdapter.ScrollViewer_ScrollChanged
        //      writes IsInteractingForRefresh = false directly, bypassing PullGestureEnded.
        //      (ScrollViewer_PointerReleased does the same.)
        //   3. _entered stays true.
        //   4. The user is still pulling, more PullGestureEvents arrive.
        //      InteractingStateEntered short-circuits because _entered is already true,
        //      so IsInteractingForRefresh is NOT reasserted.
        //   5. RefreshVisualizer never re-enters the Interacting state -> spinner does not appear.
        [Fact]
        public void IsInteractingForRefresh_is_reasserted_after_being_cleared_externally()
        {
            var provider = new RefreshInfoProvider(
                PullDirection.TopToBottom,
                new Size(100, 100),
                visual: null);

            var pullArgs = new PullGestureEventArgs(0, new Vector(0, 50), PullDirection.TopToBottom);

            // 1. First PullGestureEvent of a gesture
            provider.InteractingStateEntered(this, pullArgs);
            Assert.True(provider.IsInteractingForRefresh,
                "IsInteractingForRefresh should be true after the first PullGestureEvent");

            // 2. Adapter clears the flag directly (simulating ScrollViewer_ScrollChanged
            //    or ScrollViewer_PointerReleased)
            provider.IsInteractingForRefresh = false;
            Assert.False(provider.IsInteractingForRefresh);

            // 3. Pull is still in progress, the next PullGestureEvent arrives
            provider.InteractingStateEntered(this, pullArgs);

            // BUG: stays false because _entered short-circuits the assignment.
            // After the fix this assertion must pass.
            Assert.True(provider.IsInteractingForRefresh,
                "PullGestureEvent must re-assert IsInteractingForRefresh after it was cleared by something other than PullGestureEnded");
        }

        // Repro for the typo where horizontal pulls checked Height==0 instead of Width==0.
        // With Width==0, value.X / Width produces +Infinity / NaN, which then breaks every
        // downstream consumer of InteractionRatio (Math.Min(1, NaN) returns NaN).
        [Fact]
        public void Horizontal_pull_with_zero_width_produces_safe_InteractionRatio()
        {
            var provider = new RefreshInfoProvider(
                PullDirection.LeftToRight,
                new Size(0, 100),
                visual: null);

            provider.ValuesChanged(new Vector(50, 0));

            Assert.False(double.IsNaN(provider.InteractionRatio));
            Assert.False(double.IsInfinity(provider.InteractionRatio));
        }

        // Sanity check for the existing happy-path: a complete gesture lifecycle
        // (Entered -> Exited -> Entered) must toggle IsInteractingForRefresh correctly.
        [Fact]
        public void Normal_gesture_lifecycle_toggles_IsInteractingForRefresh_correctly()
        {
            var provider = new RefreshInfoProvider(
                PullDirection.TopToBottom,
                new Size(100, 100),
                visual: null);

            var pullArgs = new PullGestureEventArgs(0, new Vector(0, 50), PullDirection.TopToBottom);
            var endArgs = new PullGestureEndedEventArgs(0, PullDirection.TopToBottom);

            provider.InteractingStateEntered(this, pullArgs);
            Assert.True(provider.IsInteractingForRefresh);

            provider.InteractingStateExited(this, endArgs);
            Assert.False(provider.IsInteractingForRefresh);

            // Next gesture should work
            provider.InteractingStateEntered(this, pullArgs);
            Assert.True(provider.IsInteractingForRefresh);
        }
    }
}