using Xunit;
using ytLive.Helpers;

namespace ytLive.Tests;

/// <summary>A segment ladder is only useful if the band it paints is the level it measured. The
/// thresholds are DESIGN.md's (nominal / caution / peak), and peak-hold is what makes clipping
/// visible — a bar that follows the moment hides the one audio fault that cannot be fixed later.
/// </summary>
public class MeterScaleTests
{
    [Fact]
    public void Bands_peak_hold_and_the_display_scale_follow_the_standard()
    {
        // Bands at the documented thresholds.
        Assert.Equal(MeterBand.Nominal, MeterScale.BandFor(-30f));
        Assert.Equal(MeterBand.Nominal, MeterScale.BandFor(-12.1f));
        Assert.Equal(MeterBand.Caution, MeterScale.BandFor(-12f));
        Assert.Equal(MeterBand.Caution, MeterScale.BandFor(-6f));
        Assert.Equal(MeterBand.Peak, MeterScale.BandFor(-3f));
        Assert.Equal(MeterBand.Peak, MeterScale.BandFor(0f));

        // Display fraction: −60 dBFS is empty, 0 dBFS is full, −30 is halfway, and nothing escapes.
        Assert.Equal(0f, MeterScale.ToFraction(-60f));
        Assert.Equal(1f, MeterScale.ToFraction(0f));
        Assert.Equal(0.5f, MeterScale.ToFraction(-30f), 4);
        Assert.Equal(1f, MeterScale.ToFraction(+12f));
        Assert.Equal(0f, MeterScale.ToFraction(-120f));

        // Peak hold rises instantly, then decays at the stated rate.
        Assert.Equal(0.8f, MeterScale.NextPeak(0.2f, 0.8f, 0.05f));
        Assert.Equal(0.7f, MeterScale.NextPeak(0.8f, 0.1f, 0.1f / 0.35f), 3);   // 0.1 fall at 0.35/s
        Assert.Equal(0f, MeterScale.NextPeak(0.1f, 0f, 10f));   // never negative
    }
}