/**
 * Accumulates per-request metrics for Provider API calls.
 *
 * Created once per incoming request (in the start middleware), threaded through Context and RequestOptions,
 * incremented by Provider on each API call, and logged by the finish middleware.
 */
export class RequestMetrics {
  private _apiCallCount = 0;
  private _totalApiDurationNs = 0;
  private _totalThrottleDelayNs = 0;
  private _requestStartTime: bigint;

  private constructor() {
    this._requestStartTime = process.hrtime.bigint();
  }

  static startRequest(): RequestMetrics {
    return new RequestMetrics();
  }

  endRequest(): {
    durationNs: bigint;
    apiCallCount: number;
    totalApiDurationNs: number;
    totalThrottleDelayNs: number;
  } {
    return {
      durationNs: process.hrtime.bigint() - this._requestStartTime,
      apiCallCount: this._apiCallCount,
      totalApiDurationNs: this._totalApiDurationNs,
      totalThrottleDelayNs: this._totalThrottleDelayNs,
    };
  }

  /**
   * Record a completed API call.
   * Increments the call counter and accumulates the call's network duration and pre-flight
   * throttle delay (time spent waiting in the rate limiter before the request was dispatched).
   */
  recordExternalApiCall(duration: number, throttleDelay: number): void {
    this._apiCallCount++;
    this._totalApiDurationNs += duration;
    this._totalThrottleDelayNs += throttleDelay;
  }
}