import { BaseStore } from './base-store.js';
import { StoreInMemory } from './store-inmemory.js';

/**
 * Storage Adapter that takes another Storage Adapter (e.g. IndexedDB) and "syncs" its contents to system memory for faster read access.
 *
 * All read operations will use system memory - all write operations will use the provided adapter.
 */
export class StoreInMemorySynced extends BaseStore {
  constructor(
    private inMemoryCache: StoreInMemory,
    private store: BaseStore,
  ) {
    super();

    // Hook into all write operations so that we can sync the In-Memory cache.
    this.store.on('set', async (payload) => {
      await this.inMemoryCache.set(payload.key, payload.value);
      this.emit('set', { key: payload.key, value: payload.value });
    });

    this.store.on('delete', async (payload) => {
      await this.inMemoryCache.delete(payload.key);
      this.emit('delete', { key: payload.key });
    });

    this.store.on('clear', async () => {
      await this.inMemoryCache.clear();
      this.emit('clear', undefined);
    });
  }

  static async create(store: BaseStore) {
    // Instantiate in-memory cache and IndexedDB.
    const inMemoryCache = new StoreInMemory();

    // Create instance of this store.
    const memorySyncedStore = new this(inMemoryCache, store);

    // Sync the data from IndexedDB into the In-Memory cache.
    const indexedDBEntries = await store.all();
    for (let [key, value] of Object.entries(indexedDBEntries)) {
      inMemoryCache.set(key, value);
    }

    // Return our instance of this store.
    return memorySyncedStore;
  }

  async all<T>() {
    return await this.inMemoryCache.all<T>();
  }

  async keys() {
    return await this.inMemoryCache.keys();
  }

  async get<T>(key: string) {
    // TODO: Consider whether you want to structuredClone this to prevent mutation.
    return await this.inMemoryCache.get<T>(key);
  }

  async set<T>(key: string, value: T) {
    await this.store.set(key, value);
  }

  async delete(key: string) {
    await this.store.delete(key);
  }

  async clear() {
    await this.store.clear();
  }

  async has(key: string) {
    return await this.inMemoryCache.has(key);
  }

  async close() {
    await this.store.close();
  }
}