/**
 * Copyright (c) Meta Platforms, Inc. and affiliates.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 *
 * @flow strict
 * @format
 */

import NativePerformanceObserver from './NativePerformanceObserver';
import {warnNoNativePerformanceObserver} from './PerformanceObserver';

type EventCountsForEachCallbackType =
  | (() => void)
  | ((value: number) => void)
  | ((value: number, key: string) => void)
  | ((value: number, key: string, map: Map<string, number>) => void);

let cachedEventCounts: ?Map<string, number>;

function getCachedEventCounts(): Map<string, number> {
  if (cachedEventCounts) {
    return cachedEventCounts;
  }
  if (!NativePerformanceObserver) {
    warnNoNativePerformanceObserver();
    return new Map();
  }

  cachedEventCounts = new Map<string, number>(
    NativePerformanceObserver.getEventCounts(),
  );
  // $FlowFixMe[incompatible-call]
  global.queueMicrotask(() => {
    // To be consistent with the calls to the API from the same task,
    // but also not to refetch the data from native too often,
    // schedule to invalidate the cache later,
    // after the current task is guaranteed to have finished.
    cachedEventCounts = null;
  });
  return cachedEventCounts ?? new Map();
}
/**
 * Implementation of the EventCounts Web Performance API
 * corresponding to the standard in
 * https://www.w3.org/TR/event-timing/#eventcounts
 */
export default class EventCounts {
  // flowlint unsafe-getters-setters:off
  get size(): number {
    return getCachedEventCounts().size;
  }

  entries(): Iterator<[string, number]> {
    return getCachedEventCounts().entries();
  }

  forEach(callback: EventCountsForEachCallbackType): void {
    return getCachedEventCounts().forEach(callback);
  }

  get(key: string): ?number {
    return getCachedEventCounts().get(key);
  }

  has(key: string): boolean {
    return getCachedEventCounts().has(key);
  }

  keys(): Iterator<string> {
    return getCachedEventCounts().keys();
  }

  values(): Iterator<number> {
    return getCachedEventCounts().values();
  }
}