wp-calypso/client/landing/stepper/utils/performance-tracking.tsx

import { stop as stopDataCollection } from '@automattic/browser-data-collector';
import { useLayoutEffect, useMemo } from 'react';
import { useStore } from 'react-redux';
import {
	isPerformanceTrackingEnabled,
	startPerformanceTracking,
} from 'calypso/lib/performance-tracking/lib';
import {
	getCurrentUserCountryCode,
	getCurrentUserLocale,
} from 'calypso/state/current-user/selectors';
import { getSelectedSiteId } from 'calypso/state/ui/selectors';
import type { Collector, Report } from '@automattic/browser-data-collector';

// Manually start performance tracking.
// Used in the entry point to start data collection as close as possible to boot time.
export function startStepperPerformanceTracking( {
	fullPageLoad = false,
}: {
	fullPageLoad?: boolean;
} ) {
	startPerformanceTracking( 'stepper', { fullPageLoad } );
}

// This hook starts performance gathering for the Stepper everytime the flow or step change.
// The library we're using ignores follow-up `start` calls while there's an inflight tracking
// report, so this hook is always safe, even though the entry point starts its own report on
// first render.
export function useStartStepperPerformanceTracking( flow: string, step: string ) {
	useMemo( () => {
		startStepperPerformanceTracking( { fullPageLoad: false } );
		// We need to start tracking again everytime we change flow or step.
		// eslint-disable-next-line react-hooks/exhaustive-deps
	}, [ flow, step ] );
}

// Safe empty state for the current set of selectors.
const EMPTY_STATE = {
	ui: {},
};

function buildStepperCollector( state: object, flow: string, step: string ): Collector {
	const siteId = getSelectedSiteId( state );
	const userCountryCode = getCurrentUserCountryCode( state );
	const userLocale = getCurrentUserLocale( state );

	return ( report: Report ) => {
		// Data from Calypso state.
		report.data.set( 'siteId', siteId || '' );
		report.data.set( 'userCountryCode', userCountryCode );
		report.data.set( 'userLocale', userLocale );
		// Data from Stepper.
		report.data.set( 'flow', flow );
		report.data.set( 'step', step );

		return report;
	};
}

function stopPerformanceTracking(
	name: string,
	{ state = EMPTY_STATE, flow = '', step = '' } = {}
) {
	if ( isPerformanceTrackingEnabled() ) {
		stopDataCollection( name, {
			collectors: [ buildStepperCollector( state, flow, step ) ],
		} );
	}
}

function useStepperPerformanceTrackerStop( flow: string, step: string ) {
	const store = useStore();

	// Use `useLayoutEffect` + rAF to be as close as possible to the actual rendering.
	useLayoutEffect( () => {
		requestAnimationFrame( () => {
			stopPerformanceTracking( 'stepper', {
				/// @ts-expect-error State is not properly typed in the performance tracking lib.
				state: store.getState(),
				flow,
				step,
			} );
		} );
	}, [ store, flow, step ] );
}

// Stop performance data collection and report.
// This component is placed at the end of the render tree to indicate completion.
export function StepperPerformanceTrackerStop( { flow, step }: { flow: string; step: string } ) {
	useStepperPerformanceTrackerStop( flow, step );

	// Nothing to render, this component is all about side effects
	return null;
}