namespace Nonemm.Recorder;

/// A capture device in use: takes its interleaved samples apart and hands each
/// one to the channel that records it.
internal sealed class OpenDevice
{
    private readonly float[] scratch = new float[RecorderEngine.SampleRate];
    private volatile RecorderChannel?[] byDeviceChannel;

    public OpenDevice(AudioDeviceInfo info)
    {
        Info = info;
        byDeviceChannel = new RecorderChannel?[Math.Max(1, info.Channels)];
    }

    public AudioDeviceInfo Info { get; }

    public IDisposable Handle { get; set; } = null!; // set right after the device opens

    /// Sets which channel gets which of the device's channels.
    public void Route(IEnumerable<RecorderChannel> users)
    {
        RecorderChannel?[] routing = new RecorderChannel?[byDeviceChannel.Length];
        foreach (RecorderChannel user in users)
        {
            if (user.Source.Channel < routing.Length)
            {
                routing[user.Source.Channel] = user;
            }
        }
        byDeviceChannel = routing;
    }

    public void OnSamples(ReadOnlySpan<float> interleaved)
    {
        RecorderChannel?[] routing = byDeviceChannel;
        int width = routing.Length;
        int frames = Math.Min(interleaved.Length / width, scratch.Length);
        for (int index = 0; index < width; index++)
        {
            if (routing[index] is not { } channel)
            {
                continue;
            }
            float level = 0;
            for (int frame = 0; frame < frames; frame++)
            {
                float sample = interleaved[frame * width + index];
                scratch[frame] = sample;
                level = Math.Max(level, Math.Abs(sample));
            }
            channel.Add(scratch.AsSpan(0, frames), level);
        }
    }
}