csharp/src/KubernetesClient/WatcherDelegatingHandler.cs

using System;
using System.Collections.Generic;
using System.IO;
using System.Net;
using System.Net.Http;
using System.Threading;
using System.Threading.Tasks;

namespace k8s
{
    /// <summary>
    /// This HttpDelegatingHandler is to rewrite the response and return first line to autorest client
    /// then use WatchExt to create a watch object which interact with the replaced http response to get watch works.
    /// </summary>
    internal class WatcherDelegatingHandler : DelegatingHandler
    {
        protected override async Task<HttpResponseMessage> SendAsync(
            HttpRequestMessage request,
            CancellationToken cancellationToken)
        {
            request.Version = HttpVersion.Version20;
            var originResponse = await base.SendAsync(request, cancellationToken).ConfigureAwait(false);

            // all watches are GETs, so we can ignore others
            if (originResponse.IsSuccessStatusCode && request.Method == HttpMethod.Get)
            {
                var query = request.RequestUri.Query;
                var index = query.IndexOf("watch=true", StringComparison.InvariantCulture);
                if (index > 0 && (query[index - 1] == '&' || query[index - 1] == '?'))
                {
                    originResponse.Content = new LineSeparatedHttpContent(originResponse.Content, cancellationToken);
                }
            }

            return originResponse;
        }

        internal class CancelableStream : Stream
        {
            private readonly Stream _innerStream;
            private readonly CancellationToken _cancellationToken;

            public CancelableStream(Stream innerStream, CancellationToken cancellationToken)
            {
                _innerStream = innerStream;
                _cancellationToken = cancellationToken;
            }

            public override void Flush() =>
                _innerStream.FlushAsync(_cancellationToken).GetAwaiter().GetResult();

            public override async Task FlushAsync(CancellationToken cancellationToken)
            {
                using (var cancellationTokenSource = CreateCancellationTokenSource(cancellationToken))
                {
                    await _innerStream.FlushAsync(cancellationTokenSource.Token).ConfigureAwait(false);
                }
            }

            public override int Read(byte[] buffer, int offset, int count) =>
                _innerStream.ReadAsync(buffer, offset, count, _cancellationToken).GetAwaiter().GetResult();

            public override async Task<int> ReadAsync(byte[] buffer, int offset, int count,
                CancellationToken cancellationToken)
            {
                using (var cancellationTokenSource = CreateCancellationTokenSource(cancellationToken))
                {
                    return await _innerStream.ReadAsync(buffer, offset, count, cancellationTokenSource.Token)
                        .ConfigureAwait(false);
                }
            }

            public override long Seek(long offset, SeekOrigin origin) => _innerStream.Seek(offset, origin);

            public override void SetLength(long value) => _innerStream.SetLength(value);

            public override void Write(byte[] buffer, int offset, int count) =>
                _innerStream.WriteAsync(buffer, offset, count, _cancellationToken).GetAwaiter().GetResult();

            public override async Task WriteAsync(byte[] buffer, int offset, int count,
                CancellationToken cancellationToken)
            {
                using (var cancellationTokenSource = CreateCancellationTokenSource(cancellationToken))
                {
                    await _innerStream.WriteAsync(buffer, offset, count, cancellationTokenSource.Token)
                        .ConfigureAwait(false);
                }
            }

            public override bool CanRead => _innerStream.CanRead;

            public override bool CanSeek => _innerStream.CanSeek;

            public override bool CanWrite => _innerStream.CanWrite;

            public override long Length => _innerStream.Length;

            public override long Position
            {
                get => _innerStream.Position;
                set => _innerStream.Position = value;
            }

            protected override void Dispose(bool disposing)
            {
                if (disposing)
                {
                    _innerStream.Dispose();
                }

                base.Dispose(disposing);
            }

            private LinkedCancellationTokenSource CreateCancellationTokenSource(CancellationToken userCancellationToken)
            {
                return new LinkedCancellationTokenSource(_cancellationToken, userCancellationToken);
            }

            private readonly struct LinkedCancellationTokenSource : IDisposable
            {
                private readonly CancellationTokenSource _cancellationTokenSource;

                public LinkedCancellationTokenSource(CancellationToken token1, CancellationToken token2)
                {
                    if (token1.CanBeCanceled && token2.CanBeCanceled)
                    {
                        _cancellationTokenSource = CancellationTokenSource.CreateLinkedTokenSource(token1, token2);
                        Token = _cancellationTokenSource.Token;
                    }
                    else
                    {
                        _cancellationTokenSource = null;
                        Token = token1.CanBeCanceled ? token1 : token2;
                    }
                }

                public CancellationToken Token { get; }

                public void Dispose()
                {
                    _cancellationTokenSource?.Dispose();
                }
            }
        }

        public class LineSeparatedHttpContent : HttpContent
        {
            private readonly HttpContent _originContent;
            private readonly CancellationToken _cancellationToken;
            private Stream _originStream;

            public LineSeparatedHttpContent(HttpContent originContent, CancellationToken cancellationToken)
            {
                _originContent = originContent;
                _cancellationToken = cancellationToken;
            }

            public TextReader StreamReader { get; private set; }

            protected override async Task SerializeToStreamAsync(Stream stream, TransportContext context)
            {
                _originStream = await _originContent.ReadAsStreamAsync().ConfigureAwait(false);

                var reader = new PeekableStreamReader(new CancelableStream(_originStream, _cancellationToken));
                StreamReader = reader;

                var firstLine = await reader.PeekLineAsync().ConfigureAwait(false);

                var writer = new StreamWriter(stream);

                await writer.WriteAsync(firstLine).ConfigureAwait(false);
                await writer.FlushAsync().ConfigureAwait(false);
            }

            protected override bool TryComputeLength(out long length)
            {
                length = 0;
                return false;
            }
        }

        internal class PeekableStreamReader : TextReader
        {
            private readonly Queue<string> _buffer;
            private readonly StreamReader _inner;

            public PeekableStreamReader(Stream stream)
            {
                _buffer = new Queue<string>();
                _inner = new StreamReader(stream);
            }

            public override string ReadLine() => throw new NotImplementedException();

            public override Task<string> ReadLineAsync()
            {
                if (_buffer.Count > 0)
                {
                    return Task.FromResult(_buffer.Dequeue());
                }

                return _inner.ReadLineAsync();
            }

            public async Task<string> PeekLineAsync()
            {
                var line = await ReadLineAsync().ConfigureAwait(false);
                _buffer.Enqueue(line);
                return line;
            }

            public override int Read() => throw new NotImplementedException();

            public override int Read(char[] buffer, int index, int count) => throw new NotImplementedException();

            public override Task<int> ReadAsync(char[] buffer, int index, int count) =>
                throw new NotImplementedException();

            public override int ReadBlock(char[] buffer, int index, int count) => throw new NotImplementedException();

            public override Task<int> ReadBlockAsync(char[] buffer, int index, int count) =>
                throw new NotImplementedException();

            public override string ReadToEnd() => throw new NotImplementedException();

            public override Task<string> ReadToEndAsync() => throw new NotImplementedException();

            protected override void Dispose(bool disposing)
            {
                if (disposing)
                {
                    _inner.Dispose();
                }

                base.Dispose(disposing);
            }
        }
    }
}