using NAudio.Wave;
using System;
using System.Collections.Generic;

namespace SongVocalSectionAnalyser.AudioAnalysis
{
    public class SongDataWaveProvider : IWaveProvider
    {
        private readonly IReadOnlyList<short> _samples;

        private readonly int _endSample;

        public event Action<int> Playing;

        public SongDataWaveProvider(SongData data, TimeSpan? begin = null, TimeSpan? end = null)
        {
            WaveFormat = new WaveFormat(data.SampleRate, 16, 1);
            _samples = data.Samples;

            var maxTime = (float)_samples.Count / data.SampleRate;
            if (begin.HasValue)
            {
                if (begin.Value.TotalSeconds > maxTime) throw new ArgumentOutOfRangeException(nameof(begin));
                _currentSample = (int)(begin.Value.TotalSeconds * data.SampleRate);
            }
            else
            {
                _currentSample = 0;
            }

            _endSample = end.HasValue && end.Value.TotalSeconds < maxTime
                ? (int)Math.Ceiling(end.Value.TotalSeconds * data.SampleRate)
                : _samples.Count;
        }

        private int _currentSample;
        private bool _hiByte;

        public int Read(byte[] buffer, int offset, int count)
        {
            if (_currentSample == _endSample)
            {
                OnPlaying();
                return 0;
            }

            OnPlaying();

            var read = 0;
            for (var i = 0; i < count; i++)
            {
                if (_currentSample == _endSample) break;


                buffer[i] = _hiByte
                    ? (byte)(_samples[_currentSample] >> 8)
                    : (byte)(_samples[_currentSample]);

                if (_hiByte)
                {
                    OnPlaying();
                    ++_currentSample;
                }
                _hiByte = !_hiByte;

                ++read;
            }

            return read;
        }

        public WaveFormat WaveFormat { get; }

        protected virtual void OnPlaying()
        {
            Playing?.Invoke(_currentSample);
        }
    }
}