archived-discord-bot/CompatApiClient/Compression/CompressionMessageHandler.cs

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

namespace CompatApiClient.Compression
{
    public class CompressionMessageHandler : DelegatingHandler
    {
        public ICollection<ICompressor> Compressors { get; }
        public static readonly string PostCompressionFlag = "X-Set-Content-Encoding";
        public static readonly string[] DefaultContentEncodings = { "gzip", "deflate" };
        public static readonly string DefaultAcceptEncodings = "gzip, deflate";

        private bool isServer;
        private bool isClient => !isServer;

        public CompressionMessageHandler(bool isServer = false)
        {
            this.isServer = isServer;
            Compressors = new ICompressor[]
            {
                new GZipCompressor(),
                new DeflateCompressor(),
            };
        }

        protected override async Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
        {
            if (isServer && request.Content?.Headers?.ContentEncoding != null)
            {
                var encoding = request.Content.Headers.ContentEncoding.FirstOrDefault();
                if (encoding != null)
                {
                    var compressor = Compressors.FirstOrDefault(c => c.EncodingType.Equals(encoding, StringComparison.InvariantCultureIgnoreCase));
                    if (compressor != null)
                        request.Content = new DecompressedContent(request.Content, compressor);
                }
            }
            if (isClient && (request.Method == HttpMethod.Post || request.Method == HttpMethod.Put) && request.Content != null && request.Headers != null && request.Headers.Contains(PostCompressionFlag))
            {
                var encoding = request.Headers.GetValues(PostCompressionFlag).FirstOrDefault();
                if (encoding != null)
                {
                    var compressor = Compressors.FirstOrDefault(c => c.EncodingType.Equals(encoding, StringComparison.InvariantCultureIgnoreCase));
                    if (compressor != null)
                        request.Content = new CompressedContent(request.Content, compressor);
                }
            }
            request.Headers?.Remove(PostCompressionFlag);
            var response = await base.SendAsync(request, cancellationToken).ConfigureAwait(false);
            if (isClient && response.Content?.Headers?.ContentEncoding != null)
            {
                var encoding = response.Content.Headers.ContentEncoding.FirstOrDefault();
                if (encoding != null)
                {
                    var compressor = Compressors.FirstOrDefault(c => c.EncodingType.Equals(encoding, StringComparison.InvariantCultureIgnoreCase));
                    if (compressor != null)
                        response.Content = new DecompressedContent(response.Content, compressor);
                }
            }
            if (isServer && response.Content != null && request.Headers?.AcceptEncoding != null)
            {
                var encoding = request.Headers.AcceptEncoding.FirstOrDefault();
                if (encoding == null)
                    return response;

                var compressor = Compressors.FirstOrDefault(c => c.EncodingType.Equals(encoding.Value, StringComparison.InvariantCultureIgnoreCase));
                if (compressor == null)
                    return response;

                response.Content = new CompressedContent(response.Content, compressor);
            }
            return response;
        }
    }
}