/*---------------------------------------------------------------------------------------------
 *  Copyright (c) Microsoft Corporation. All rights reserved.
 *  Licensed under the MIT License. See License.txt in the project root for license information.
 *--------------------------------------------------------------------------------------------*/

import { globals } from './platform';

const hasPerformanceNow =
  globals.performance && typeof globals.performance.now === 'function';

export class StopWatch {
  private _highResolution: boolean;
  private _startTime: number;
  private _stopTime: number;

  public static create(highResolution = true): StopWatch {
    return new StopWatch(highResolution);
  }

  constructor(highResolution: boolean) {
    this._highResolution = hasPerformanceNow && highResolution;
    this._startTime = this._now();
    this._stopTime = -1;
  }

  public stop(): void {
    this._stopTime = this._now();
  }

  public elapsed(): number {
    if (this._stopTime !== -1) {
      return this._stopTime - this._startTime;
    }
    return this._now() - this._startTime;
  }

  private _now(): number {
    return this._highResolution ? globals.performance.now() : Date.now();
  }
}