/**
 * Lightweight stopwatch utility for profiling hot paths and measuring named checkpoints.
 *
 * The timer starts immediately on construction and can report durations in milliseconds or seconds.
 * It also keeps optional named checkpoints so callers can inspect elapsed time between milestones
 * without managing multiple timer instances.
 */
export declare class PerformanceTimer {
    private start;
    private readonly checkpoints;
    private accumulateContainer;
    constructor();
    getDuration(): number;
    getDurationSeconds(): number;
    /**
     * Resets the timer and returns the elapsed duration in milliseconds from the previous interval.
     *
     * @returns Duration measured before the reset.
     */
    reset(): number;
    resetSeconds(): number;
    /**
     * Resets the timer, stores the previous interval in the accumulation buffer, and returns the average
     * of the most recent samples in milliseconds.
     *
     * @param samples Maximum number of recent samples to average.
     * @returns Rolling average duration in milliseconds.
     */
    accumulate(samples: number): number;
    accumulateSeconds(samples: number): number;
    /**
     * Stores the current elapsed time under a checkpoint name.
     *
     * @param name Caller-defined checkpoint identifier.
     * @returns Elapsed time in milliseconds at the moment the checkpoint was recorded.
     */
    checkpoint(name: string): number;
    checkpointSeconds(name: string): number;
    getCheckpoint(name: string): number | undefined;
    getCheckpoints(): Map<string, number>;
    /**
     * Computes the time elapsed since a previously recorded checkpoint.
     *
     * @param name Checkpoint identifier to measure from.
     * @returns Milliseconds elapsed since the checkpoint, or `undefined` if it does not exist.
     */
    getTimeFromCheckpoint(name: string): number | undefined;
    getTimeFromCheckpointSeconds(name: string): number | undefined;
    /**
     * Measures the delta between two recorded checkpoints.
     *
     * @param checkpointFrom Start checkpoint name.
     * @param checkpointTo End checkpoint name.
     * @returns Difference in milliseconds, or `undefined` when either checkpoint is missing.
     */
    getCheckpointDifference(checkpointFrom: string, checkpointTo: string): number | undefined;
    getCheckpointDifferenceSeconds(checkpointFrom: string, checkpointTo: string): number | undefined;
}