using Xunit;
using ytLive.Services.Audio;

namespace ytLive.Tests;

/// <summary>The dock shows ONE ladder per source, but the creator is profoundly deaf on the right,
/// so the meter has to know which side a signal is on: hard-panned content is inaudible, not merely
/// quieter. These levels drive the imbalance flag, and they must be measured — never decorative.
/// </summary>
public class StereoMeterTests
{
    private const int Rate = 48000;

    private static AudioLevelMeter Pushed(int channels, float left, float right, int frames = 64, int pushes = 12)
    {
        var meter = new AudioLevelMeter();
        var buffer = new float[frames * channels];
        for (var f = 0; f < frames; f++)
        {
            buffer[f * channels] = left;
            if (channels > 1) buffer[f * channels + 1] = right;
        }
        for (var i = 0; i < pushes; i++) meter.Push(new AudioSample(buffer, Rate, channels));
        return meter;
    }

    [Fact]
    public void The_meter_knows_which_side_the_signal_is_on()
    {
        // Hard left: the left side carries it, the right is silent, and the gap is reported.
        var hardLeft = Pushed(channels: 2, left: 0.5f, right: 0f);
        Assert.True(hardLeft.Left > 0.1f, $"left should carry the tone, got {hardLeft.Left}");
        Assert.True(hardLeft.Right < 0.01f, $"right should be silent, got {hardLeft.Right}");
        Assert.True(hardLeft.ImbalanceDb > 20f, "a one-sided signal must report a large imbalance");

        // Hard right is the mirror case — the one this creator cannot hear.
        var hardRight = Pushed(channels: 2, left: 0f, right: 0.5f);
        Assert.True(hardRight.Right > 0.1f);
        Assert.True(hardRight.Left < 0.01f);

        // Balanced stereo reports no imbalance.
        var centred = Pushed(channels: 2, left: 0.5f, right: 0.5f);
        Assert.True(centred.Left > 0.1f && centred.Right > 0.1f);
        Assert.True(centred.ImbalanceDb < 1f, $"balanced audio must not flag, got {centred.ImbalanceDb}");

        // Mono is centred by definition: both sides equal, no flag — never "one-sided".
        var mono = Pushed(channels: 1, left: 0.5f, right: 0f);
        Assert.True(mono.Left > 0.1f);
        Assert.Equal(mono.Left, mono.Right, 5);
        Assert.Equal(0f, mono.ImbalanceDb);

        // Silence on both sides is not an imbalance (nothing to compare).
        var silent = Pushed(channels: 2, left: 0f, right: 0f);
        Assert.Equal(0f, silent.ImbalanceDb);
    }
}