using AcDream.UI.Abstractions.Panels.Settings;

namespace AcDream.UI.Abstractions.Tests.Panels.Settings;

/// <summary>
/// L.0: <see cref="DisplaySettings"/> is the immutable record of
/// display-tab preferences. Defaults are pinned here so a regression
/// (e.g. someone changing the default FOV out from under users)
/// surfaces immediately.
/// </summary>
public sealed class DisplaySettingsTests
{
    [Fact]
    public void Default_values_match_pre_L0_runtime_state()
    {
        // Defaults pinned to match the actual pre-L.0 startup state:
        //  · Resolution matches WindowOptions (1280×720 in GameWindow.Run)
        //  · FieldOfView matches camera FovY (60° = π/3)
        //  · VSync matches WindowOptions (false during dev)
        //  · ShowFps true preserves the perf string in the title bar
        // Net effect: opening Display + Save with no edits is a visual
        // no-op (no window resize, no camera FovY change, no title
        // bar change).
        var d = DisplaySettings.Default;
        Assert.Equal("1280x720", d.Resolution);
        Assert.False(d.Fullscreen);
        Assert.False(d.VSync);
        Assert.Equal(60f, d.FieldOfView);
        Assert.Equal(1.0f, d.Gamma);
        Assert.True(d.ShowFps);
    }

    [Fact]
    public void AvailableResolutions_includes_common_16_9_options()
    {
        var list = DisplaySettings.AvailableResolutions;
        Assert.Contains("1280x720", list);
        Assert.Contains("1920x1080", list);
        Assert.Contains("2560x1440", list);
        Assert.Contains("3840x2160", list);
        // List should be ascending so the dropdown reads naturally.
        for (int i = 1; i < list.Count; i++)
        {
            int prevW = ParseWidth(list[i - 1]);
            int curW  = ParseWidth(list[i]);
            Assert.True(curW >= prevW, $"Resolutions not sorted: {list[i - 1]} >= {list[i]}");
        }
    }

    [Fact]
    public void Equality_is_value_based()
    {
        var a = DisplaySettings.Default;
        var b = DisplaySettings.Default with { Fullscreen = true };
        var c = DisplaySettings.Default with { Fullscreen = true };
        Assert.NotEqual(a, b);
        Assert.Equal(b, c);
    }

    [Fact]
    public void With_expression_clones_one_field()
    {
        var d = DisplaySettings.Default with { FieldOfView = 90f };
        Assert.Equal(90f, d.FieldOfView);
        // Other fields untouched.
        Assert.Equal("1280x720", d.Resolution);
        Assert.False(d.VSync);
        Assert.True(d.ShowFps);
    }

    private static int ParseWidth(string res)
    {
        int x = res.IndexOf('x');
        return int.Parse(res.AsSpan(0, x));
    }
}