using NAudio.Wave;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Projector
{
    // Custom ISampleProvider to mix 4 channels to stereo
    public class FourChannelToStereoSampleProvider : ISampleProvider
    {
        private readonly ISampleProvider _source;
        private float offTransition = 1f;
        private float _voiceVolume = 0f;
        private bool goingOff = false;

        public WaveFormat WaveFormat { get; }

        public void SetOff()
        {
            goingOff = true;
        }

        public bool IsOff => goingOff && offTransition == 0f;

        public float VoiceVolume
        {
            get
            {
                return _voiceVolume;
            } 
            set
            {
                _voiceVolume = Math.Clamp(value, 0f, 1f);
            }
        }

        public FourChannelToStereoSampleProvider(ISampleProvider source)
        {
            if (source.WaveFormat.Channels != 4)
                throw new ArgumentException("Source must have 4 channels");
            if (source.WaveFormat.Encoding != WaveFormatEncoding.IeeeFloat)
                throw new ArgumentException("Source must be IEEE float format");

            _source = source;
            WaveFormat = WaveFormat.CreateIeeeFloatWaveFormat(source.WaveFormat.SampleRate, 2);
        }

        public int Read(float[] buffer, int offset, int count)
        {
            int samplesNeeded = (count / 2) * 4;
            float[] sourceBuffer = new float[samplesNeeded];
            int samplesRead = _source.Read(sourceBuffer, 0, samplesNeeded);

            int stereoSamples = samplesRead / 4 * 2;
            int outIndex = offset;

            if (goingOff && offTransition > 0f)
            {
                offTransition -= 0.2f;
                if (offTransition <= 0f)
                {
                    offTransition = 0f;
                }
            }

            float musicVolume = 1f - VoiceVolume;
            float voiceVolume = VoiceVolume;

            for (int i = 0; i < samplesRead; i += 4)
            {
                // Mix channel 0 and 2 to left, 1 and 3 to right
                float left = (sourceBuffer[i] * musicVolume) + (sourceBuffer[i + 2] * voiceVolume);
                float right = (sourceBuffer[i + 1] * musicVolume) + (sourceBuffer[i + 3] * voiceVolume);
                buffer[outIndex++] = left * offTransition;
                buffer[outIndex++] = right * offTransition;
            }

            return stereoSamples;
        }
    }

}