namespace VoiceCat.Dsp;

public sealed class EnergyVadProcessor
{
    private readonly TimeProvider timeProvider;
    private long lastVoiceTimestamp;
    private bool hasVoice;
    private float threshold;

    public float Threshold
    {
        get => Volatile.Read(ref threshold);
        set
        {
            if (!float.IsFinite(value) || value is < 0 or > 1) throw new ArgumentOutOfRangeException(nameof(value));
            Volatile.Write(ref threshold, value);
        }
    }
    public TimeSpan HangTime { get; }

    public EnergyVadProcessor(float threshold = 0.02f, TimeSpan? hangTime = null, TimeProvider? timeProvider = null)
    {
        Threshold = threshold;
        HangTime = hangTime ?? TimeSpan.FromMilliseconds(300);
        if (HangTime < TimeSpan.Zero) throw new ArgumentOutOfRangeException(nameof(hangTime));
        this.timeProvider = timeProvider ?? TimeProvider.System;
    }

    public bool Process(ReadOnlySpan<short> pcm)
    {
        long now = timeProvider.GetTimestamp();
        if (!pcm.IsEmpty)
        {
            double sum = 0;
            foreach (short sample in pcm)
            {
                double normalized = sample / 32768.0;
                sum += normalized * normalized;
            }
            if (Math.Sqrt(sum / pcm.Length) >= Threshold)
            {
                lastVoiceTimestamp = now;
                hasVoice = true;
            }
        }
        return hasVoice && timeProvider.GetElapsedTime(lastVoiceTimestamp, now) < HangTime;
    }
}