BakaMusicPlayer/Bmp.Core.Common/Net/SeekableHttpStream.cs

using System.Net.Http.Headers;

namespace Bmp.Core.Common.Net
{
    public class SeekableHttpStream : Stream
    {
        private readonly string _url;

        private long _length;
        private long _position = 0;

        private HttpClient? _httpClient;
        private HttpResponseMessage? _httpResponseMessage;
        private HttpContent? _httpContent;
        private Stream? _underlyingHttpStream;

        public SeekableHttpStream(string url)
        {
            _url = url;
            Init();
        }

        private void Init()
        {
            DeInit();

            _httpClient = new HttpClient();

            var req = new HttpRequestMessage(HttpMethod.Get, _url);

            if (_position != 0)
            {
                req.Headers.Range ??= new();
                req.Headers.Range!.Ranges.Add(new RangeItemHeaderValue(_position, null));
            }

            _httpResponseMessage = _httpClient.Send(req, HttpCompletionOption.ResponseHeadersRead);

            _httpResponseMessage!.EnsureSuccessStatusCode();
            _httpContent = _httpResponseMessage.Content;
            if (_httpContent.Headers.ContentLength.HasValue) _length = _position + _httpContent.Headers.ContentLength.Value;

            _underlyingHttpStream = _httpContent.ReadAsStream();
        }

        private void DeInit()
        {
            _underlyingHttpStream?.Close();
            _httpContent?.Dispose();
            _httpClient?.Dispose();
        }

        public override void Close()
        {
            base.Close();
            DeInit();
        }

        public override int Read(byte[] buffer, int offset, int count)
        {
            var read = _underlyingHttpStream!.Read(buffer, offset, count);
            _position += read;
            return read;
        }

        public override long Seek(long offset, SeekOrigin origin)
        {
            switch (origin)
            {
                case SeekOrigin.Begin:
                    _position = offset;
                    Init();
                    break;

                case SeekOrigin.Current:
                    _position += offset;
                    Init();
                    break;

                case SeekOrigin.End:
                    _position = _length + offset;
                    Init();
                    break;
                default: throw new ArgumentOutOfRangeException(nameof(offset));
            }

            return _position;
        }

        //-----------------------------------------------

        public override void Flush()
        {
            throw new NotSupportedException();
        }

        public override void SetLength(long value)
        {
            throw new NotSupportedException();
        }

        public override void Write(byte[] buffer, int offset, int count)
        {
            throw new NotSupportedException();
        }

        public override bool CanRead => true;
        public override bool CanSeek => true;
        public override bool CanWrite => false;
        public override long Length => _length;

        public override long Position { get => _position; set => Seek(value, SeekOrigin.Begin); }
    }
}