static computeTimeOrigin()

in src/sdk/lh-trace-processor.ts [883:926]
40 lines of code
13 McCabe index (conditional complexity)

  static computeTimeOrigin(traceEventSubsets, method) {
    const lastNavigationStart = () => {
      // Our time origin will be the last frame navigation in the trace
      const frameEvents = traceEventSubsets.frameEvents;
      return frameEvents.filter(this._isNavigationStartOfInterest).pop();
    };

    const lighthouseMarker = () => {
      const frameEvents = traceEventSubsets.keyEvents;
      return frameEvents.find(
        evt =>
          evt.name === 'clock_sync' &&
          evt.args.sync_id === TraceProcessor.TIMESPAN_MARKER_ID
      );
    };

    switch (method) {
      case 'firstResourceSendRequest': {
        // Our time origin will be the timestamp of the first request that's sent in the frame.
        const fetchStart = traceEventSubsets.keyEvents.find(event => {
          if (event.name !== 'ResourceSendRequest') return false;
          const data = event.args.data || {};
          return data.frame === traceEventSubsets.mainFrameIds.frameId;
        });
        if (!fetchStart) throw this.createNoResourceSendRequestError();
        return fetchStart;
      }
      case 'lastNavigationStart': {
        const navigationStart = lastNavigationStart();
        if (!navigationStart) throw this.createNoNavstartError();
        return navigationStart;
      }
      case 'lighthouseMarker': {
        const marker = lighthouseMarker();
        if (!marker) throw this.createNoLighthouseMarkerError();
        return marker;
      }
      case 'auto': {
        const marker = lighthouseMarker() || lastNavigationStart();
        if (!marker) throw this.createNoNavstartError();
        return marker;
      }
    }
  }