/**
 * Core Web Vitals per page view, measured with the browser's own
 * PerformanceObserver. A page view is one visible stretch of one route: it
 * ends when the route changes through `pushState`/`popstate` or the page is
 * hidden, and a page that becomes visible again starts a new one. TTFB and
 * LCP belong to the document load only; INP and CLS are measured within each
 * page view. A metric the browser cannot measure is left out, never zero, and
 * a page view the manifest has no route for carries no route. No report
 * carries the page's path, which can hold slugs and emails; `pageview` has it.
 */
export type WebVitalsNavigationType = "load" | "client" | "resume";
export interface PageViewVitals {
    route?: string;
    navigationType: WebVitalsNavigationType;
    ttfbMs?: number;
    lcpMs?: number;
    inpMs?: number;
    cls?: number;
}
export interface WebVitalsLocation {
    route: string | null;
    pathname: string;
}
interface LayoutShiftLike {
    startTime: number;
    value: number;
    hadRecentInput: boolean;
}
interface InteractionLike {
    interactionId?: number;
    duration: number;
}
export interface WebVitalsTrackerOptions {
    /** Read when a page view ends: whether layout shifts are being observed. */
    measuresLayoutShift: () => boolean;
    report: (vitals: PageViewVitals) => void;
    interactionCount?: () => number | undefined;
}
/**
 * The page-view state machine, separate from the observers that feed it so
 * the metric rules can be exercised without a browser.
 */
export declare function createWebVitalsTracker(options: WebVitalsTrackerOptions): {
    startLoad(location: WebVitalsLocation, ttfbMs: number | undefined): void;
    /**
     * `replace` keeps the page view and moves it to the new route, since
     * redirects and URL canonicalization replace the entry the person landed
     * on. Any other change of path is a new page view.
     */
    navigate(location: WebVitalsLocation, kind: "push" | "replace"): void;
    hidden(): void;
    /** Drops the current page view without reporting it. */
    discard(): void;
    visible(location: WebVitalsLocation): void;
    largestContentfulPaint(startTimeMs: number): void;
    finalizeLargestContentfulPaint(): void;
    layoutShift(entry: LayoutShiftLike): void;
    interaction(entry: InteractionLike): void;
};
export type WebVitalsTracker = ReturnType<typeof createWebVitalsTracker>;
export interface WebVitalsController {
    navigate(kind: "push" | "replace"): void;
}
/**
 * Starts measuring the current document. Returns null where the browser has
 * no PerformanceObserver, so no page view is reported as measured.
 */
export declare function installWebVitals(locate: () => WebVitalsLocation, report: (vitals: PageViewVitals) => void): WebVitalsController | null;
export {};