TimeProvider.ts

/*
 * Unless explicitly stated otherwise all files in this repository are licensed under the Apache License Version 2.0.
 * This product includes software developed at Datadog (https://www.datadoghq.com/).
 * Copyright 2016-Present Datadog, Inc.
 */

/**
 * A Timestamp structure holding the
 */
export type Timestamp = {
  // Result of Date API. Unix timestamp in ms.
  unix: number;
  // Result of performance.now API. Timestamp in ms (with microsecond precision)
  // since JS context start.
  react_native: number | null;
};

/**
 * Simple class providing timestamps in milliseconds.
 * If available, it will use the `performance.now()` method, and will fallback on `Date.now()` otherwise.
 */
export class TimeProvider {
  private canUsePerformanceNow =
    // eslint-disable-next-line @typescript-eslint/ban-ts-comment
    // @ts-ignore
    global.performance && typeof performance.now === 'function';

  /** Keeps an average offset between the unix time and the provided timestamp. */
  private baseOffset: number;

  constructor() {
    const timestamp = this.getTimestamp();
    if (timestamp.react_native == null) {
      this.baseOffset = 0;
    } else {
      this.baseOffset = timestamp.unix - timestamp.react_native;
    }
  }

  getTimestamp(): Timestamp {
    return {
      unix: Date.now(),
      react_native: this.performanceNow(),
    };
  }

  now(): number {
    const timestamp = this.getTimestamp();
    if (timestamp.react_native == null) {
      return timestamp.unix;
    } else {
      return this.baseOffset + timestamp.react_native;
    }
  }

  getDebugInfo(): object {
    return {
      ['baseOffset']: this.baseOffset,
      ['Date.now()']: Date.now(),
      ['performance.now()']: this.performanceNow(),
      ['now()']: this.now(),
    };
  }

  private performanceNow(): number | null {
    if (this.canUsePerformanceNow) {
      // eslint-disable-next-line @typescript-eslint/ban-ts-comment
      // @ts-ignore
      return performance.now();
    }
    return null;
  }
}

export const TimeProviderInstance = new TimeProvider();