export interface BundleMetrics {
    /** Total JS load time (ms) */
    jsLoadTime?: number;
    /** Total CSS load time (ms) */
    cssLoadTime?: number;
    /** Number of JS resources */
    jsCount?: number;
    /** Number of CSS resources */
    cssCount?: number;
    /** Total transfer size (bytes) */
    totalTransferSize?: number;
}
export interface UseBundleMetricsOptions {
    /** Enable tracking (default: true) */
    enabled?: boolean;
    /** Refresh interval in ms (default: 5000) */
    refreshInterval?: number;
    /** Callback when metrics update */
    onUpdate?: (metrics: BundleMetrics) => void;
}
/**
 * Hook to track bundle/resource loading metrics
 *
 * @example
 * ```tsx
 * const { metrics, refresh } = useBundleMetrics();
 * console.log('JS Load Time:', metrics.jsLoadTime);
 * ```
 */
export declare const useBundleMetrics: (options?: UseBundleMetricsOptions) => {
    metrics: BundleMetrics;
    refresh: () => void;
};
/**
 * Format bytes to human readable string
 */
export declare const formatBytes: (bytes?: number) => string;
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