using System;
using System.IO;

namespace Ryuclaw.Audio.Shared
{
    public class WaveStreamer : IDisposable
    {
        private readonly FileStream _fileStream;
        private readonly BinaryReader _reader;

        private long _dataPosition;  // This will store the position where audio data begins in the file.
        private int _dataLength;    // This will store the length of the audio data.

        private WaveHeader _header;

        public WaveStreamer(string filePath)
        {
            _header = new WaveHeader();
            _fileStream = new FileStream(filePath, FileMode.Open);
            _reader = new BinaryReader(_fileStream);
            LoadHeader();
        }

        private void LoadHeader()
        {
            // RIFF header
            string chunkID = new string(_reader.ReadChars(4));
            if (chunkID != "RIFF") throw new Exception("Not a valid WAV file.");

            var ChunkSize = _reader.ReadInt32(); // Chunk size
            string format = new string(_reader.ReadChars(4));
            if (format != "WAVE") throw new Exception("Not a valid WAV file.");

            // fmt sub-chunk
            string subchunk1ID = new string(_reader.ReadChars(4));
            if (subchunk1ID != "fmt ") throw new Exception("Expected fmt chunk.");

            int subChunk1Size = _reader.ReadInt32();
            short audioFormat = _reader.ReadInt16();
            var NumChannels = _reader.ReadInt16();
            var SampleRate = _reader.ReadInt32();
            var ByteRate = _reader.ReadInt32(); // Byte rate
            var BlockAlign = _reader.ReadInt16(); // Block align
            var BitsPerSample = _reader.ReadInt16();
            _header = new WaveHeader(SampleRate, ChunkSize, ByteRate, BitsPerSample, NumChannels, BlockAlign);
            if (audioFormat != 1 || subChunk1Size != 16)
            {
                throw new Exception("Only PCM format WAV files are supported.");
            }

            // data sub-chunk
            string subchunk2ID = new string(_reader.ReadChars(4));
            if (subchunk2ID != "data") throw new Exception("Expected data chunk.");

            _dataLength = _reader.ReadInt32();
            _dataPosition = _fileStream.Position;  // Store the position where audio data begins.
        }

        public byte[] ReadData(int byteCount)
        {
            _fileStream.Seek(_dataPosition, SeekOrigin.Begin);
            byte[] buffer = _reader.ReadBytes(byteCount);  // Read a chunk of audio data.
            _dataPosition = _fileStream.Position;  // Update the position to start from next time.
            return buffer;
        }

        public bool HasDataLeft()
        {
            return _fileStream.Position < _dataPosition + _dataLength;
        }

        public void Dispose()
        {
            _reader.Dispose();
            _fileStream.Dispose();
        }
    }
}