using NAudio.Flac;
using NAudio.Wave;
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;

namespace SongVocalIsolateAutomation.AudioProcessing
{
    internal class WaveLoader
    {
        public static WaveData LoadFlac(string path, bool trimZeroPrefix = true)
        {
            using (var waveStream = new FlacReader(path))
            {
                var waveFormat = waveStream.WaveFormat;

                var allSamples = ReadAllSamples(waveStream, waveFormat);

                allSamples = trimZeroPrefix
                    ? allSamples.SkipWhile(p => p == 0).ToArray()
                    : allSamples;

                return new WaveData(allSamples, waveFormat.Channels, waveFormat.SampleRate);
            }
        }

        private static float[] ReadAllSamples(WaveStream waveStream, WaveFormat waveFormat)
        {
            if (WaveFormatEncoding.Pcm != waveFormat.Encoding)
                throw new NotSupportedException("PCM only support");
            if (16 != waveFormat.BitsPerSample && 24 != waveFormat.BitsPerSample)
                throw new NotSupportedException("16 or 24 bit per sample only support");

            float[] allSamples;
            {
                waveStream.Seek(0, SeekOrigin.Begin);

                var sampleData = new List<float>((int)((waveStream.TotalTime.TotalSeconds + 1) * waveFormat.SampleRate));

                if (16 == waveFormat.BitsPerSample)
                {
                    var buffer = new byte[waveFormat.BlockAlign];
                    while (true)
                    {
                        var read = waveStream.Read(buffer, 0, buffer.Length);
                        if (buffer.Length != read) break;

                        for (var i = 0; i < waveFormat.BlockAlign; i++)
                        {
                            //little-endian
                            var value = (short)(buffer[i] | (buffer[++i] << 8));

                            sampleData.Add(value / 32768f);
                        }
                    }
                }

                if (24 == waveFormat.BitsPerSample)
                {
                    var buffer = new byte[waveFormat.BlockAlign];
                    while (true)
                    {
                        var read = waveStream.Read(buffer, 0, buffer.Length);
                        if (buffer.Length != read) break;

                        for (var i = 0; i < waveFormat.BlockAlign; i++)
                        {
                            //little-endian
                            var value = (int)(buffer[i] | (buffer[++i] << 8) | (buffer[++i] << 24));

                            sampleData.Add(value / 2147483648f);
                        }
                    }
                }

                allSamples = sampleData.ToArray();
            }
            return allSamples;
        }
    }
}