protected override void PopulateAttributes()

in src/Google.Cloud.Functions.Framework/GcfEvents/GcfConverters.cs [517:547]
29 lines of code
11 McCabe index (conditional complexity)

            protected override void PopulateAttributes(Request request, CloudEvent evt)
            {
                // We need the event name and the app ID in order to create subject and source like this:
                // Subject://firebaseanalytics.googleapis.com/projects/{project}/apps/{app}
                // Source: events/{eventName}
                // The eventName is available in the resource, which is of the form projects/{project-id}/events/{event-name}
                // The app name is available via the data, via userDim -> appInfo -> appId
                // If either of these isn't where we expect, we throw a ConversionException
                string resource = request.Context.Resource.Name!;
                string service = request.Context.Resource.Service!;
                var data = request.Data;

                string[] splitResource = resource.Split('/');
                string? eventName = splitResource.Length == 4 && splitResource[0] == "projects" && splitResource[2] == "events" ? splitResource[3] : null;
                string? appId = data.TryGetValue("userDim", out var userDim) && userDim is JsonElement userDimElement &&
                    userDimElement.TryGetProperty("appInfo", out var appInfoElement) &&
                    appInfoElement.TryGetProperty("appId", out var appIdElement) &&
                    appIdElement.ValueKind == JsonValueKind.String
                    ? appIdElement.GetString() : null;

                if (eventName is object && appId is object)
                {
                    string projectId = splitResource[1]; // Definitely valid, given that we got the event name.
                    evt.Source = new Uri($"//{service}/projects/{projectId}/apps/{appId}", UriKind.RelativeOrAbsolute);
                    evt.Subject = $"events/{eventName}";
                }
                else
                {
                    throw new ConversionException("Firebase Analytics event does not contain expected data");
                }
            }