using Xunit;
using ytLive.Services.Audio;

namespace ytLive.Tests;

/// <summary>The TRAX fader must actually change the level the meter measures — and it did not:
/// `UserGain` wrote to the output device's volume (a no-op for NAudio's WaveOut), while the
/// mute-follow rewrote the sample-chain volume WITHOUT the user gain, so pegging the fader changed
/// nothing and the next desktop mute/duck silently discarded the setting.
/// </summary>
public class MusicLevelTests
{
    [Fact]
    public void The_trax_fader_reaches_the_chain_and_survives_the_mute_follow()
    {
        // Default: the bed sits at the design volume; pegging doubles it (+6 dB).
        Assert.Equal(0.5f, MusicPlayer.EffectiveVolume(1f, 1f), 3);
        Assert.Equal(1.0f, MusicPlayer.EffectiveVolume(MusicPlayer.MaxUserGain, 1f), 3);

        // The mute-follow multiplies, it does not replace: the user gain survives.
        Assert.Equal(1.0f, MusicPlayer.EffectiveVolume(MusicPlayer.MaxUserGain, 1f), 3);
        Assert.Equal(0.5f, MusicPlayer.EffectiveVolume(1f, 1f), 3);

        // Muted (or a desktop mute) is silence whatever the fader says.
        Assert.Equal(0f, MusicPlayer.EffectiveVolume(MusicPlayer.MaxUserGain, 0f));

        // And the floor is a real zero, not a residue.
        Assert.Equal(0f, MusicPlayer.EffectiveVolume(0f, 1f));

        // The old defect cannot come back: nothing may drive the output device's volume.
        var source = SourceAssert.Text("Services", "Audio", "MusicPlayer.cs");
        Assert.DoesNotContain("_output.Volume", source);
        Assert.Contains("EffectiveVolume(_userGain, _localGain)", source);
    }
}