wp-calypso/client/dashboard/app/queries/site-stats.ts

import { EngagementStatsDataPoint, fetchSiteEngagementStats } from '../../data/site-stats';

export const siteEngagementStatsQuery = ( siteId: number ) => ( {
	queryKey: [ 'site', siteId, 'engagement-stats' ],
	queryFn: () => fetchSiteEngagementStats( siteId ),
	select: ( { data: stats }: { data: Array< [ string, number, number, number, number ] > } ) => {
		// We need to normalize the returned data. We ask for 14 days of data (quantity:14)
		// and we get a response with an array of data like: `[ '2025-04-13', 1, 3, 0, 0 ]`.
		// Each number in the response is referring to the order of the field provided in `stat_fields`.
		// The returned array is sorted with ascending date order, so we need to use the last 7 entries
		// for our current data and the first 7 entries for the previous data.
		// Noting that we can't use `unit:'week'` because the API has a specific behavior for start/end of weeks.
		const calculateStats = ( data: Array< [ string, number, number, number, number ] > ) =>
			data.reduce(
				( accumulator: EngagementStatsDataPoint, [ , visitors, views, likes, comments ] ) => {
					accumulator.visitors += Number( visitors );
					accumulator.views += Number( views );
					accumulator.likes += Number( likes );
					accumulator.comments += Number( comments );
					return accumulator;
				},
				{ visitors: 0, views: 0, likes: 0, comments: 0 }
			);

		const dataLength = stats.length;
		const currentData = calculateStats( stats.slice( Math.max( 0, dataLength - 7 ) ) );
		const previousData = calculateStats( stats.slice( 0, Math.max( 0, dataLength - 7 ) ) );
		return { previousData, currentData };
	},
} );