next.js/packages/next/src/build/webpack/plugins/telemetry-plugin/use-cache-tracker-utils.ts

export type UseCacheTrackerKey = `useCache/${string}`

export const createUseCacheTracker = () => new Map<UseCacheTrackerKey, number>()

/**
 * Example usage:
 *
 * const tracker1 = { 'useCache/file1': 1, 'useCache/file2': 2 };
 * const tracker2 = { 'useCache/file2': 3, 'useCache/file3': 4 };
 * const merged = mergeUseCacheTrackers(tracker1, tracker2);
 *
 * // Result: { 'useCache/file1': 1, 'useCache/file2': 5, 'useCache/file3': 4 }
 */
export const mergeUseCacheTrackers = (
  tracker1: Record<UseCacheTrackerKey, number> | undefined,
  tracker2: Record<UseCacheTrackerKey, number> | undefined
): Record<UseCacheTrackerKey, number> => {
  const mergedTracker: Record<UseCacheTrackerKey, number> = { ...tracker1 }

  if (tracker2) {
    for (const key in tracker2) {
      if (Object.prototype.hasOwnProperty.call(tracker2, key)) {
        const typedKey = key as UseCacheTrackerKey
        if (mergedTracker[typedKey] !== undefined) {
          mergedTracker[typedKey] += tracker2[typedKey]
        } else {
          mergedTracker[typedKey] = tracker2[typedKey]
        }
      }
    }
  }

  return mergedTracker
}