public async Task PerformRequestAsync()

in RESTProxy/Models/Endpoint.cs [258:342]
59 lines of code
7 McCabe index (conditional complexity)

        public async Task<HttpResponseMessage> PerformRequestAsync(
            string pathAndQuery,
            HttpMethod method,
            IPrincipal onBehalfOf,
            string body = null,
            string correlationId = null,
            string clientRequestId = null,
            string clientName = null)
        {
            // This is the real API endpoint that we'll be contacting.  We'll just append
            // pathAndQuery directly to this to get the final REST Uri that we need to use.
            string finalUri = string.Format(
                "{0}{1}",
                this.BaseUri,
                pathAndQuery);

            WebRequest request = HttpWebRequest.Create(finalUri);
            request.Method = method.ToString();
            request.ContentLength = 0;  // will be updated if there is a body.

            try
            {
                HttpResponseMessage errorMessage;

                // No reason to progress any further if they don't have the right permissions
                // to access the API that they're trying to use.
                if (!this.TryHasPermission(onBehalfOf, method, out errorMessage))
                {
                    return errorMessage;
                }

                // Every API request needs to authenticate itself by providing an AccessToken
                // in the authorization header.
                string accessToken = await this.GetAccessTokenAsync();
                request.Headers[HttpRequestHeader.Authorization] = string.Format("bearer {0}", accessToken);

                if (!string.IsNullOrWhiteSpace(clientName))
                {
                    request.Headers[ProxyManager.ClientNameHeader] = clientName;
                }

                // Add any additional headers that the client may have specified in their request
                if (!string.IsNullOrWhiteSpace(correlationId))
                {
                    request.Headers[ProxyManager.MSCorrelationIdHeader] = correlationId;
                }

                if (!string.IsNullOrWhiteSpace(clientRequestId))
                {
                    request.Headers[ProxyManager.MSClientRequestIdHeader] = clientRequestId;
                }

                // Write the body to the request stream if one was provided.
                // Not every REST API will require a body.  For instance, the GET requests have
                // no body, and the (current) POST API's also have no body.
                if (!string.IsNullOrWhiteSpace(body))
                {
                    byte[] bytes = System.Text.Encoding.UTF8.GetBytes(body);
                    request.ContentLength = bytes.Length;
                    request.ContentType = $"{ProxyManager.JsonMediaType}; charset=UTF-8";

                    using (Stream requestStream = await request.GetRequestStreamAsync())
                    {
                        requestStream.Write(bytes, 0, bytes.Length);
                    }
                }

                // Get the response.
                using (WebResponse response = await request.GetResponseAsync())
                {
                    // Even though we got a simple WebResponse, in our scenario we would prefer
                    // an HttpWebResponse since it exposes a StatusCode property.
                    HttpWebResponse httpResponse = response as HttpWebResponse;
                    return this.GetResponseMessage(httpResponse);
                }
            }
            catch (WebException ex)
            {
                // Even though WebException stores the response as a simple WebResponse, in our scenario
                // it should actually be an HttpWebResponse.  We'd prefer that one, since HttpWebResponse
                // exposes a StatusCode property.
                HttpWebResponse httpResponse = ex.Response as HttpWebResponse;
                return this.GetResponseMessage(httpResponse);
            }
        }