private async Task HandleOperation()

in src/Service/Controllers/RestController.cs [192:311]
97 lines of code
11 McCabe index (conditional complexity)

        private async Task<IActionResult> HandleOperation(
            string route,
            EntityActionOperation operationType)
        {
            if (route.Equals(REDIRECTED_ROUTE))
            {
                return NotFound();
            }

            Stopwatch stopwatch = Stopwatch.StartNew();
            // This activity tracks the entire REST request.
            using Activity? activity = TelemetryTracesHelper.DABActivitySource.StartActivity($"{HttpContext.Request.Method} {(route.Split('/').Length > 1 ? route.Split('/')[1] : string.Empty)}");

            try
            {
                TelemetryMetricsHelper.IncrementActiveRequests(ApiType.REST);

                if (activity is not null)
                {
                    activity.TrackRestControllerActivityStarted(
                        Enum.Parse<HttpMethod>(HttpContext.Request.Method, ignoreCase: true),
                        HttpContext.Request.Headers["User-Agent"].ToString(),
                        operationType.ToString(),
                        route,
                        HttpContext.Request.QueryString.ToString(),
                        HttpContext.Request.Headers["X-MS-API-ROLE"].FirstOrDefault() ?? HttpContext.User.FindFirst("role")?.Value,
                        ApiType.REST);
                }

                // Validate the PathBase matches the configured REST path.
                string routeAfterPathBase = _restService.GetRouteAfterPathBase(route);

                // Explicitly handle OpenAPI description document retrieval requests.
                if (string.Equals(routeAfterPathBase, OpenApiDocumentor.OPENAPI_ROUTE, StringComparison.OrdinalIgnoreCase))
                {
                    if (_openApiDocumentor.TryGetDocument(out string? document))
                    {
                        return Content(document, MediaTypeNames.Application.Json);
                    }

                    return NotFound();
                }

                (string entityName, string primaryKeyRoute) = _restService.GetEntityNameAndPrimaryKeyRouteFromRoute(routeAfterPathBase);

                // This activity tracks the query execution. This will create a new activity nested under the REST request activity.
                using Activity? queryActivity = TelemetryTracesHelper.DABActivitySource.StartActivity($"QUERY {entityName}");
                IActionResult? result = await _restService.ExecuteAsync(entityName, operationType, primaryKeyRoute);

                RuntimeConfig runtimeConfig = _runtimeConfigProvider.GetConfig();
                string dataSourceName = runtimeConfig.GetDataSourceNameFromEntityName(entityName);
                DatabaseType databaseType = runtimeConfig.GetDataSourceFromDataSourceName(dataSourceName).DatabaseType;

                if (queryActivity is not null)
                {
                    queryActivity.TrackQueryActivityStarted(
                        databaseType,
                        dataSourceName);
                }

                if (result is null)
                {
                    throw new DataApiBuilderException(
                        message: $"Not Found",
                        statusCode: HttpStatusCode.NotFound,
                        subStatusCode: DataApiBuilderException.SubStatusCodes.EntityNotFound);
                }

                int statusCode = (result as ObjectResult)?.StatusCode ?? (result as StatusCodeResult)?.StatusCode ?? (result as JsonResult)?.StatusCode ?? 200;
                if (activity is not null && activity.IsAllDataRequested)
                {
                    HttpStatusCode httpStatusCode = Enum.Parse<HttpStatusCode>(statusCode.ToString(), ignoreCase: true);
                    activity.TrackRestControllerActivityFinished(httpStatusCode);
                }

                return result;
            }
            catch (DataApiBuilderException ex)
            {
                _logger.LogError(
                    exception: ex,
                    message: "{correlationId} Error handling REST request.",
                    HttpContextExtensions.GetLoggerCorrelationId(HttpContext));

                Response.StatusCode = (int)ex.StatusCode;
                activity?.TrackRestControllerActivityFinishedWithException(ex, ex.StatusCode);

                HttpMethod method = Enum.Parse<HttpMethod>(HttpContext.Request.Method, ignoreCase: true);
                TelemetryMetricsHelper.TrackError(method, ex.StatusCode, route, ApiType.REST, ex);
                return ErrorResponse(ex.SubStatusCode.ToString(), ex.Message, ex.StatusCode);
            }
            catch (Exception ex)
            {
                _logger.LogError(
                    exception: ex,
                    message: "{correlationId} Internal server error occured during REST request processing.",
                    HttpContextExtensions.GetLoggerCorrelationId(HttpContext));

                Response.StatusCode = (int)HttpStatusCode.InternalServerError;

                HttpMethod method = Enum.Parse<HttpMethod>(HttpContext.Request.Method, ignoreCase: true);
                activity?.TrackRestControllerActivityFinishedWithException(ex, HttpStatusCode.InternalServerError);

                TelemetryMetricsHelper.TrackError(method, HttpStatusCode.InternalServerError, route, ApiType.REST, ex);
                return ErrorResponse(
                    DataApiBuilderException.SubStatusCodes.UnexpectedError.ToString(),
                    SERVER_ERROR,
                    HttpStatusCode.InternalServerError);
            }
            finally
            {
                stopwatch.Stop();
                HttpMethod method = Enum.Parse<HttpMethod>(HttpContext.Request.Method, ignoreCase: true);
                HttpStatusCode httpStatusCode = Enum.Parse<HttpStatusCode>(Response.StatusCode.ToString(), ignoreCase: true);
                TelemetryMetricsHelper.TrackRequest(method, httpStatusCode, route, ApiType.REST);
                TelemetryMetricsHelper.TrackRequestDuration(method, httpStatusCode, route, ApiType.REST, stopwatch.Elapsed);

                TelemetryMetricsHelper.DecrementActiveRequests(ApiType.REST);
            }
        }