using System.IO;
using System.IO.Compression;
using System.Linq;
using System.Net;
using System.Net.Http;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using System.Web.Http;

namespace DeviceRepair.Api.Models
{
    public class CompressedContentResult<T> : IHttpActionResult
    {
        private readonly T _value;
        private readonly HttpRequestMessage _request;
        private readonly ApiController _controller;

        public CompressedContentResult(T value, HttpRequestMessage request, ApiController controller)
        {
            _value = value;
            _request = request;
            _controller = controller;
        }

        public Task<HttpResponseMessage> ExecuteAsync(CancellationToken cancellationToken)
        {
            var response = _controller.Request.CreateResponse(HttpStatusCode.OK, _value, _controller.Configuration.Formatters.JsonFormatter);

            // 检查客户端是否接受 GZIP 压缩  
            var acceptsEncoding = _request.Headers.AcceptEncoding;
            var gzipSupported = acceptsEncoding.Any(x => x.Value.Contains("gzip"));

            if (gzipSupported)
            {
                var originalContent = response.Content.ReadAsStringAsync().Result; // 注意：这里同步读取可能会导致问题，但在示例中为了简化  
                byte[] compressedContent = CompressString(originalContent);

                var compressedStream = new MemoryStream(compressedContent);
                var compressedContentResult = new StreamContent(compressedStream);
                compressedContentResult.Headers.ContentType = response.Content.Headers.ContentType;
                compressedContentResult.Headers.ContentEncoding.Add("gzip");

                response.Content = compressedContentResult;
            }

            return Task.FromResult(response);
        }

        private byte[] CompressString(string str)
        {
            byte[] buffer = Encoding.UTF8.GetBytes(str);
            var memoryStream = new MemoryStream();
            using (var gZipStream = new GZipStream(memoryStream, CompressionMode.Compress, true))
            {
                gZipStream.Write(buffer, 0, buffer.Length);
            }

            memoryStream.Position = 0;
            return memoryStream.ToArray();
        }
    }
}