import { getActiveClient } from '~/client/api/activeClient';

/**
 * ```js
 * import { backupCache } from '@amityco/ts-sdk'
 * const success = await backupCache()
 * ```
 *
 * Writes the {@link Amity.Cache} to a persistent storage.
 *
 * The strategy for persistent storage will depend on the runtime,
 * which is supported by @react-native-async-storage/async-storage.
 *
 * The current userId will be appended to the given storageKey to avoid
 * collision between multiple client instances over time.
 *
 * @param storageKey the name of the persistent storage
 * @param persistIf a custom function to define the persistence policy. Default
 * will check the value of {@link Amity.CacheEntry["offline"]}, which can be
 * defined globally when customizing {@link Amity.Cache["persistIf"]}
 * @returns a success boolean if the cache was dumped to persistent storage
 *
 * @category Cache API
 */
export const backupCache = async (
  storageKey = 'amitySdk',
  persistIf = (entry: Amity.CacheEntry) => entry.offline,
): Promise<boolean> => {
  const { log, cache, userId } = getActiveClient();

  if (!cache) return false;
  log('cache/api/backupCache', { storageKey });

  // prepare a subset of the cache where only
  // objects to backup are there
  const offlineEntries = Object.fromEntries(
    Object.entries(cache.data).filter(([_, entry]) => persistIf(entry)),
  );

  // nothing to backup, abort
  if (!Object.keys(offlineEntries).length) return false;

  if (localStorage) {
    await localStorage.setItem(`${storageKey}#${userId}`, JSON.stringify(offlineEntries));
  }

  return true;
};