namespace SA.WebApi.Middlewares
{
    public class RequestMiddleware
    {
        private static NLog.Logger logger = NLog.LogManager.GetCurrentClassLogger();
        private readonly RequestDelegate _next;

        public RequestMiddleware(RequestDelegate next)
        {
            _next = next;
        }

        public async Task Invoke(HttpContext httpContext)
        {
            //LogHelper.Info($"Request body: {await ReadBodyAsync(httpContext.Request)}");
            logger.Trace($"Request body: {await ReadBodyAsync(httpContext.Request)}");
            await _next.Invoke(httpContext);
        }

        private async Task<string> ReadBodyAsync(HttpRequest request)
        {
            if (request.ContentLength > 0)
            {
                await EnableRewindAsync(request).ConfigureAwait(false);
                var encoding = GetRequestEncoding(request);
                return await this.ReadStreamAsync(request.Body, encoding).ConfigureAwait(false);
            }
            return null;
        }

        private Encoding GetRequestEncoding(HttpRequest request)
        {
            var requestContentType = request.ContentType;
            var requestMediaType = requestContentType == null ? default(MediaType) : new MediaType(requestContentType);
            var requestEncoding = requestMediaType.Encoding;
            if (requestEncoding == null)
            {
                requestEncoding = Encoding.UTF8;
            }
            return requestEncoding;
        }

        private async Task EnableRewindAsync(HttpRequest request)
        {
            if (!request.Body.CanSeek)
            {
                request.EnableBuffering();

                await request.Body.DrainAsync(CancellationToken.None);
                request.Body.Seek(0L, SeekOrigin.Begin);
            }
        }

        private async Task<string> ReadStreamAsync(Stream stream, Encoding encoding)
        {
            using (StreamReader sr = new StreamReader(stream, encoding, true, 1024, true))//这里注意Body部分不能随StreamReader一起释放
            {
                var str = await sr.ReadToEndAsync();
                stream.Seek(0, SeekOrigin.Begin);//内容读取完成后需要将当前位置初始化，否则后面的InputFormatter会无法读取
                return str;
            }
        }
    }
}