import type { TokenUsage, StreamingMetricsResult } from '../../types/streaming-adapter.types';
/**
 * Tracks streaming metrics including TTFT, duration, and token usage
 */
export declare class StreamingMetrics {
    private startTime;
    private firstTokenTime;
    private tokenUsage;
    constructor(startTime?: number);
    /**
     * Record when the first token/chunk arrives
     */
    recordFirstToken(): void;
    /**
     * Get Time to First Token in nanoseconds
     * @returns TTFT in nanoseconds, or null if first token hasn't arrived yet
     */
    getTTFT(): number | null;
    /**
     * Set token usage information
     * @param usage Token usage object
     */
    setTokenUsage(usage: TokenUsage): void;
    /**
     * Get current token usage
     * @returns Token usage object or null
     */
    getTokenUsage(): TokenUsage | null;
    /**
     * Get total duration in nanoseconds
     * @returns Duration in nanoseconds from start time to now
     */
    getDuration(): number;
    /**
     * Get all metrics
     * @returns Complete metrics result
     */
    getMetrics(): StreamingMetricsResult;
    /**
     * Reset metrics (useful for testing or reuse)
     */
    reset(startTime?: number): void;
}