/**
 * A class to measure performance of code execution.
 *
 * This utility records elapsed time during execution and provides a detailed
 * breakdown of elapsed time between checkpoints.
 *
 * Usage example:
 *   const timer = new PerformanceTimer();
 *   timer.checkpoint('Start Processing');
 *   // ... code for processing
 *   timer.checkpoint('After Task 1');
 *   // ... additional processing code
 *   timer.stop();
 *   console.log(timer.generateReport());
 *
 * Methods:
 *   - checkpoint(label: string): Record a timestamped checkpoint.
 *   - stop(): Stop the timer and compute the total elapsed time.
 *   - generateReport(): Return a performance report with total time and phases.
 *   - formatPerformanceReport(): Return a formatted string of the performance report.
 *   - getElapsedSeconds(): Get the current elapsed time in seconds.
 */
export declare class PerformanceTimer {
    private startTime;
    private checkpoints;
    private totalTime;
    constructor();
    /**
     * Gets the current elapsed time in seconds.
     *
     * @returns The elapsed time in seconds with 3 decimal places of precision.
     */
    getElapsedSeconds(): number;
    /**
     * Records a checkpoint with the given label.
     *
     * @param label - A descriptive label for the checkpoint.
     */
    checkpoint(label: string): void;
    /**
     * Stops the timer and sets the total elapsed time.
     */
    stop(): void;
    /**
     * Generates a performance report containing the total elapsed time and
     * breakdown of phases between checkpoints.
     *
     * @returns A performance report object.
     * @throws Error if the timer is not stopped before generating the report.
     */
    analyseReportData(): PerformanceReport;
    /**
     * Returns a formatted string of the performance report.
     *
     * @returns A string detailing the total execution time and phase breakdown.
     */
    generateReport(): string;
}
/**
 * Interface representing a single phase of performance measurement.
 */
export interface PerformancePhase {
    label: string;
    duration: number;
}
/**
 * Interface representing the full performance report.
 */
export interface PerformanceReport {
    totalTime: number;
    phases: PerformancePhase[];
}