acdream/tests/AcDream.App.Tests/UI/UiScrollbarTests.cs

using AcDream.App.UI;
using Xunit;

namespace AcDream.App.Tests.UI;

/// <summary>
/// Pure unit tests for <see cref="UiScrollbar.ThumbRect"/> — no GL dependency.
/// </summary>
public class UiScrollbarTests
{
    // Model: content=400, view=100, trackLen=200.
    // ThumbRatio = 100/400 = 0.25  →  thumbH = max(8, 200*0.25) = 50.
    // Travel = 200 - 50 = 150.

    [Fact]
    public void ThumbRect_AtStart_HasCorrectSizeAndZeroOffset()
    {
        var m = new UiScrollable { ContentHeight = 400, ViewHeight = 100 };
        // PositionRatio = 0 (start).
        var (y, h) = UiScrollbar.ThumbRect(m, trackTop: 0f, trackLen: 200f);
        Assert.Equal(50f, h, 3f);
        Assert.Equal(0f, y, 3f);
    }

    [Fact]
    public void ThumbRect_AtEnd_PinsToBottomOfTrack()
    {
        var m = new UiScrollable { ContentHeight = 400, ViewHeight = 100 };
        m.ScrollToEnd(); // PositionRatio = 1.
        float trackTop = 16f, trackLen = 200f;
        var (y, h) = UiScrollbar.ThumbRect(m, trackTop, trackLen);
        Assert.Equal(50f, h, 3f);
        // y = trackTop + travel * 1 = 16 + 150 = 166.
        Assert.Equal(166f, y, 3f);
    }

    [Fact]
    public void ThumbRect_WithButtonH_CorrectlyOffsetsFromTrackTop()
    {
        // Matches task spec: content=400, view=100, trackLen=200, PositionRatio=1.
        // thumbH=50; travel=150; y = trackTop + 150 = trackTop + 150.
        var m = new UiScrollable { ContentHeight = 400, ViewHeight = 100 };
        m.ScrollToEnd();
        var (y, h) = UiScrollbar.ThumbRect(m, trackTop: 16f, trackLen: 200f);
        Assert.Equal(50f, h, 3f);
        Assert.Equal(166f, y, 3f); // 16 + 150
    }

    [Fact]
    public void ThumbRect_MidScroll_InterpolatesPosition()
    {
        // content=400 view=100 → MaxScroll=300; ScrollY=150 → PositionRatio=0.5.
        var m = new UiScrollable { ContentHeight = 400, ViewHeight = 100 };
        m.SetScrollY(150);
        Assert.Equal(0.5f, m.PositionRatio, 3);

        var (y, h) = UiScrollbar.ThumbRect(m, trackTop: 0f, trackLen: 200f);
        Assert.Equal(50f, h, 3f);
        // y = 0 + 150 * 0.5 = 75.
        Assert.Equal(75f, y, 3f);
    }

    [Fact]
    public void ThumbRect_SmallContent_EnforcesMinThumb()
    {
        // content=1000, view=10, trackLen=200 → ThumbRatio=0.01 → raw=2 < 8 → clamp to 8.
        var m = new UiScrollable { ContentHeight = 1000, ViewHeight = 10 };
        var (_, h) = UiScrollbar.ThumbRect(m, trackTop: 0f, trackLen: 200f);
        Assert.Equal(8f, h, 3f);
    }

    [Fact]
    public void ThumbRect_NoOverflow_ThumbFillsTrack()
    {
        // content <= view → ThumbRatio = 1 → thumbH = trackLen.
        var m = new UiScrollable { ContentHeight = 50, ViewHeight = 100 };
        var (y, h) = UiScrollbar.ThumbRect(m, trackTop: 16f, trackLen: 100f);
        Assert.Equal(100f, h, 3f);
        Assert.Equal(16f, y, 3f); // travel = 0 → y = trackTop
    }

    [Fact]
    public void HorizontalScalar_clickAndDrag_updatesNormalizedValue()
    {
        float value = 1f;
        var bar = new UiScrollbar
        {
            Width = 90f,
            Height = 14f,
            Horizontal = true,
            ScalarChanged = next => value = next,
        };
        bar.SetScalarPosition(1f);

        Assert.True(bar.OnEvent(new UiEvent(0u, bar, UiEventType.MouseDown, Data1: 8)));
        Assert.Equal(0f, value, 3);
        Assert.Equal(0f, bar.ScalarPosition, 3);

        Assert.True(bar.OnEvent(new UiEvent(0u, bar, UiEventType.MouseMove, Data1: 45)));
        Assert.Equal(0.5f, value, 3);
        Assert.Equal(0.5f, bar.ScalarPosition, 3);

        Assert.True(bar.OnEvent(new UiEvent(0u, bar, UiEventType.MouseUp, Data1: 45)));
    }

    [Theory]
    [InlineData(0f,   0f,   0f)]
    [InlineData(0.5f, 0f,  50f)]
    [InlineData(1f,   0f, 100f)]
    public void ScalarFillRect_CombatPower_GrowsLeftToRight(
        float fill, float expectedX, float expectedWidth)
    {
        var (x, width) = UiScrollbar.ScalarFillRect(100f, fill, fromRight: false);
        Assert.Equal(expectedX, x, 3);
        Assert.Equal(expectedWidth, width, 3);
    }

    [Theory]
    [InlineData(0f,   104f,   0f)]
    [InlineData(0.5f, 104f, 149.5f)]
    [InlineData(1f,   104f, 299f)]
    public void ScalarFillRect_CombatPower_StaysBetweenAuthoredLabels(
        float fill, float expectedX, float expectedWidth)
    {
        var (x, width) = UiScrollbar.ScalarFillRect(
            rangeLeft: 104f, rangeWidth: 299f, fill, fromRight: false);
        Assert.Equal(expectedX, x, 3);
        Assert.Equal(expectedWidth, width, 3);
    }
}