using System.Collections;
using Xunit;
using ytLive.Helpers;

namespace ytLive.Tests;

/// <summary>
/// The layer-list drag arithmetic, tested without a mouse. It replaced a test that injected REAL
/// cursor movement into the desktop — which hijacked the machine and failed whenever it was busy
/// (deleted 2026-11-05). Same behaviour covered here, in microseconds, with no input device.
/// </summary>
public class DragReorderMathTests
{
    [Theory]
    [InlineData(0, 0, false)]      // a click, not a drag
    [InlineData(3, 2, false)]      // inside both thresholds (4 px is WPF's default)
    [InlineData(4, 0, true)]       // exactly the threshold counts — WPF's own rule
    [InlineData(0, 4, true)]
    [InlineData(-9, 1, true)]      // direction is irrelevant
    public void Threshold_DecidesDragVersusClick(double dx, double dy, bool dragging)
        => Assert.Equal(dragging, DragReorderMath.ExceededThreshold(dx, dy, 4, 4));

    [Fact]
    public void MovingDown_LandsOnTheTargetsIndex()
    {
        var items = new ArrayList { "A", "B", "C" };

        var landed = DragReorderMath.TryMove(items, 0, 2);

        Assert.Equal(2, landed);
        Assert.Equal(new[] { "B", "C", "A" }, items.Cast<string>());
    }

    [Fact]
    public void MovingUp_LandsOnTheTargetsIndex()
    {
        var items = new ArrayList { "A", "B", "C" };

        var landed = DragReorderMath.TryMove(items, 2, 0);

        Assert.Equal(0, landed);
        Assert.Equal(new[] { "C", "A", "B" }, items.Cast<string>());
    }

    [Fact]
    public void DraggingOntoItself_IsANoOp()
    {
        var items = new ArrayList { "A", "B", "C" };

        Assert.Equal(-1, DragReorderMath.TryMove(items, 1, 1));
        Assert.Equal(new[] { "A", "B", "C" }, items.Cast<string>());
    }

    [Theory]
    [InlineData(-1, 0)]
    [InlineData(0, -1)]
    [InlineData(3, 0)]
    [InlineData(0, 3)]
    public void OutOfRangeIndices_ChangeNothing(int from, int to)
    {
        var items = new ArrayList { "A", "B", "C" };

        Assert.Equal(-1, DragReorderMath.TryMove(items, from, to));
        Assert.Equal(new[] { "A", "B", "C" }, items.Cast<string>());
    }

    [Fact]
    public void EmptyList_IsSafe()
        => Assert.Equal(-1, DragReorderMath.TryMove(new ArrayList(), 0, 0));
}