import { AnyAnalytics, CDNSettings } from "../../types";
import { createInstrumentationSignal } from "../../types/factories";
import { SignalGenerator } from "../signal-generators/types";

type EdgeFunctionSettings = { downloadURL: string; version?: number };

/**
 * Helper / facade that wraps the analytics, and abstracts away the details of the analytics instance.
 */
export class AnalyticsService {
  instance: AnyAnalytics;
  edgeFnSettings?: EdgeFunctionSettings;
  constructor(analyticsInstance: AnyAnalytics) {
    this.instance = analyticsInstance;
    this.edgeFnSettings = this.parseEdgeFnSettings(
      analyticsInstance.settings.cdnSettings,
    );
  }

  private parseEdgeFnSettings(
    cdnSettings: CDNSettings,
  ): EdgeFunctionSettings | undefined {
    const edgeFnSettings = cdnSettings.edgeFunction;
    if (edgeFnSettings && "downloadURL" in edgeFnSettings) {
      return edgeFnSettings;
    }
  }

  createSegmentInstrumentationEventGenerator(): SignalGenerator {
    let disable = false;
    const generator: SignalGenerator = {
      id: "segment-event-generator",
      register: async (signalEmitter) => {
        await this.instance.addSourceMiddleware(({ payload, next }) => {
          if (disable) {
            return;
          }
          const event = payload.obj;

          const isEventFromSignalEdgeFunction =
            event.context.__eventOrigin?.type === "Signal";

          if (!isEventFromSignalEdgeFunction) {
            signalEmitter.emit(createInstrumentationSignal(event));
          }

          return next(payload);
        });
        return () => {
          disable = true;
        };
      },
    };
    return generator;
  }
}