wikimedia/mediawiki-extensions-Wikibase

import Tracker from '@/tracking/Tracker';

interface VisibilityApi extends Pick<Document, 'hidden'> {
    readonly msHidden?: boolean;
    readonly webkitHidden?: boolean;
}

export default class MwInitTracker {
    private readonly tracker: Tracker;
    private readonly performance: Performance;
    private readonly visibilityApi: VisibilityApi;

    public constructor( tracker: Tracker, performance: Performance, visibilityApi: VisibilityApi ) {
        this.tracker = tracker;
        this.performance = performance;
        this.visibilityApi = visibilityApi;
    }

    /**
     * @returns method to finish the tracking
     */
    public startClickDelayTracker(): () => void {
        const clickStarted = this.performance.now();

        return (): void => {
            const clickDelay = this.performance.now() - clickStarted;
            this.tracker.recordTiming( 'clickDelay', clickDelay );
        };
    }

    public recordTimeToLinkListenersAttached(): void {
        if ( this.isTabInBackground() ) {
            // We only care of the performance of foreground tabs
            return;
        }
        const now = this.performance.now();
        if ( !this.performance.getEntriesByName || this.performance.getEntriesByName( 'mwStartup' ).length === 0 ) {
            // not browser or not mediawiki environment
            return;
        }
        const mwStartupMark = this.performance.getEntriesByName( 'mwStartup' )[ 0 ];
        this.tracker.recordTiming(
            'timeToLinkListenersAttached',
            now - mwStartupMark.startTime,
        );
    }

    private isTabInBackground(): boolean|undefined {
        return this.visibilityApi.hidden || this.visibilityApi.msHidden || this.visibilityApi.webkitHidden;
    }
}