Driver Development

/**
 * Defines a custom storage driver
 * @param driver - Driver implementation object
 * @param callback - Optional success callback
 * @param errorCallback - Optional error callback
 * @returns Promise resolving when driver is defined
 */
function defineDriver(
  driver: LocalForageDriver,
  callback?: () => void,
  errorCallback?: (error: any) => void
): Promise<void>;

import localforage from 'localforage';

// Define a simple in-memory storage driver
const memoryDriver = {
  _driver: 'memoryStorageDriver',
  _initStorage: function(options) {
    const dbInfo = {};
    dbInfo.db = {};
    this._dbInfo = dbInfo;
  },
  _support: true,
  
  async getItem(key) {
    return this._dbInfo.db[key] || null;
  },
  
  async setItem(key, value) {
    this._dbInfo.db[key] = value;
    return value;
  },
  
  async removeItem(key) {
    delete this._dbInfo.db[key];
  },
  
  async clear() {
    this._dbInfo.db = {};
  },
  
  async length() {
    return Object.keys(this._dbInfo.db).length;
  },
  
  async key(n) {
    const keys = Object.keys(this._dbInfo.db);
    return keys[n] || null;
  },
  
  async keys() {
    return Object.keys(this._dbInfo.db);
  },
  
  async iterate(iteratee) {
    const keys = Object.keys(this._dbInfo.db);
    for (let i = 0; i < keys.length; i++) {
      const key = keys[i];
      const value = this._dbInfo.db[key];
      const result = iteratee(value, key, i);
      if (result !== undefined) {
        return result;
      }
    }
  }
};

// Register the custom driver
await localforage.defineDriver(memoryDriver);

// Use the custom driver
await localforage.setDriver('memoryStorageDriver');

// Define a driver with async support detection
const customAsyncDriver = {
  _driver: 'customAsyncStorageDriver',
  _support: async function() {
    // Check if the storage backend is available
    return typeof customStorageAPI !== 'undefined';
  },
  // ... implement other required methods
};

await localforage.defineDriver(customAsyncDriver);

/**
 * Gets the name of the current storage driver
 * @returns The current driver name
 */
function driver(): string;

import localforage from 'localforage';

// Check which driver is currently being used
const currentDriver = localforage.driver();
console.log('Current driver:', currentDriver);
// Output might be: 'asyncStorage' (IndexedDB), 'webSQLStorage', or 'localStorageWrapper'

// Conditional logic based on current driver
const driverName = localforage.driver();
if (driverName === localforage.INDEXEDDB) {
  console.log('Using IndexedDB - optimal for large data');
} else if (driverName === localforage.LOCALSTORAGE) {
  console.log('Using localStorage - limited storage capacity');
}

// Store driver information for debugging
const debugInfo = {
  driver: localforage.driver(),
  timestamp: new Date().toISOString(),
  config: localforage.config()
};

/**
 * Gets the implementation of a specific driver
 * @param driver - Name of the driver to retrieve
 * @returns Promise resolving to the driver implementation
 */
function getDriver(driver: string): Promise<LocalForageDriver>;

import localforage from 'localforage';

// Get IndexedDB driver implementation
const idbDriver = await localforage.getDriver(localforage.INDEXEDDB);
console.log('IndexedDB driver:', idbDriver);

// Inspect driver capabilities
const currentDriverName = localforage.driver();
const driverImpl = await localforage.getDriver(currentDriverName);
console.log('Current driver methods:', Object.keys(driverImpl));

// Check if driver supports optional methods
const driver = await localforage.getDriver(localforage.INDEXEDDB);
if (typeof driver.dropInstance === 'function') {
  console.log('Driver supports dropInstance method');
}

// Get custom driver implementation
await localforage.defineDriver(myCustomDriver);
const customDriver = await localforage.getDriver('myCustomDriverName');

/**
 * Checks if a driver is supported in the current environment
 * @param driverName - Name of the driver to check
 * @returns Boolean indicating if the driver is supported
 */
function supports(driverName: string): boolean;

import localforage from 'localforage';

// Check support for specific drivers
const supportsIndexedDB = localforage.supports(localforage.INDEXEDDB);
const supportsWebSQL = localforage.supports(localforage.WEBSQL);
const supportsLocalStorage = localforage.supports(localforage.LOCALSTORAGE);

console.log('Driver support:');
console.log('- IndexedDB:', supportsIndexedDB);
console.log('- WebSQL:', supportsWebSQL);  
console.log('- localStorage:', supportsLocalStorage);

// Build optimal driver list based on support
const supportedDrivers = [];
if (localforage.supports(localforage.INDEXEDDB)) {
  supportedDrivers.push(localforage.INDEXEDDB);
}
if (localforage.supports(localforage.WEBSQL)) {
  supportedDrivers.push(localforage.WEBSQL);
}
if (localforage.supports(localforage.LOCALSTORAGE)) {
  supportedDrivers.push(localforage.LOCALSTORAGE);
}

await localforage.setDriver(supportedDrivers);

// Check custom driver support
const supportsCustom = localforage.supports('myCustomDriver');
if (!supportsCustom) {
  console.warn('Custom driver not supported, falling back to defaults');
}

/**
 * Waits for localForage to be ready
 * @param callback - Optional callback function
 * @returns Promise resolving when localForage is ready
 */
function ready(callback?: (error: any) => void): Promise<void>;

import localforage from 'localforage';

// Wait for localForage to be ready before operations
await localforage.ready();
console.log('localForage is ready');

// Now safe to perform storage operations
await localforage.setItem('key', 'value');

// Using callbacks
localforage.ready((error) => {
  if (error) {
    console.error('localForage failed to initialize:', error);
  } else {
    console.log('localForage is ready');
    // Perform initial storage operations
  }
});

// Combine with driver setup
localforage.config({
  driver: localforage.INDEXEDDB,
  name: 'MyApp'
});

await localforage.ready();
console.log('Configured with driver:', localforage.driver());

/**
 * Gets the current serializer instance
 * @param callback - Optional callback function
 * @returns Promise resolving to the serializer object
 */
function getSerializer(callback?: (serializer: LocalForageSerializer) => void): Promise<LocalForageSerializer>;

import localforage from 'localforage';

// Get the current serializer
const serializer = await localforage.getSerializer();
console.log('Serializer methods:', Object.keys(serializer));

// Use serializer directly for custom operations
const serializer = await localforage.getSerializer();
const data = { key: 'value', array: [1, 2, 3] };

serializer.serialize(data, (serializedData, error) => {
  if (error) {
    console.error('Serialization error:', error);
  } else {
    console.log('Serialized data:', serializedData);
    
    // Deserialize back
    const originalData = serializer.deserialize(serializedData);
    console.log('Deserialized data:', originalData);
  }
});

interface LocalForageDriver {
  /**
   * Unique identifier for the driver
   */
  _driver: string;
  
  /**
   * Initialize storage with given options
   */
  _initStorage(options: LocalForageOptions): void;
  
  /**
   * Support check - boolean or async function
   */
  _support?: boolean | (() => Promise<boolean>);
  
  // Required storage methods
  getItem<T>(key: string, callback?: (err: any, value: T | null) => void): Promise<T | null>;
  setItem<T>(key: string, value: T, callback?: (err: any, value: T) => void): Promise<T>;
  removeItem(key: string, callback?: (err: any) => void): Promise<void>;
  clear(callback?: (err: any) => void): Promise<void>;
  length(callback?: (err: any, numberOfKeys: number) => void): Promise<number>;
  key(keyIndex: number, callback?: (err: any, key: string) => void): Promise<string>;
  keys(callback?: (err: any, keys: string[]) => void): Promise<string[]>;
  iterate<T, U>(
    iteratee: (value: T, key: string, iterationNumber: number) => U,
    callback?: (err: any, result: U) => void
  ): Promise<U>;
  
  // Optional methods
  dropInstance?(dbInstanceOptions?: LocalForageDbInstanceOptions, callback?: (err: any) => void): Promise<void>;
}

interface LocalForageSerializer {
  /**
   * Serialize a value for storage
   */
  serialize<T>(value: T | ArrayBuffer | Blob, callback: (value: string, error: any) => void): void;
  
  /**
   * Deserialize a stored value
   */
  deserialize<T>(value: string): T | ArrayBuffer | Blob;
  
  /**
   * Convert string to ArrayBuffer
   */
  stringToBuffer(serializedString: string): ArrayBuffer;
  
  /**
   * Convert ArrayBuffer to string
   */
  bufferToString(buffer: ArrayBuffer): string;
}

// Template for creating a custom driver
const customDriverTemplate = {
  // Required: Unique driver identifier
  _driver: 'customStorageDriver',
  
  // Required: Initialization function
  _initStorage: function(options) {
    // Initialize storage backend
    // Store configuration in this._dbInfo
    const dbInfo = {
      db: null, // Your storage backend connection
      name: options.name,
      storeName: options.storeName
    };
    this._dbInfo = dbInfo;
    
    // Perform any async initialization if needed
    return new Promise((resolve, reject) => {
      // Initialize your storage backend
      // resolve() when ready, reject(error) on failure
      resolve();
    });
  },
  
  // Optional: Support detection
  _support: function() {
    // Return boolean or Promise<boolean>
    return typeof YourStorageAPI !== 'undefined';
  },
  
  // Required: Implement all storage methods
  async getItem(key, callback) {
    try {
      const value = await this._dbInfo.db.get(key);
      if (callback) callback(null, value);
      return value;
    } catch (error) {
      if (callback) callback(error);
      throw error;
    }
  },
  
  async setItem(key, value, callback) {
    try {
      await this._dbInfo.db.set(key, value);
      if (callback) callback(null, value);
      return value;
    } catch (error) {
      if (callback) callback(error);
      throw error;
    }
  }
  
  // ... implement other required methods
};

// Register and use a custom driver
async function setupCustomStorage() {
  // Define the driver
  await localforage.defineDriver(customDriverTemplate);
  
  // Check if it's supported
  if (localforage.supports('customStorageDriver')) {
    // Set as primary driver
    await localforage.setDriver('customStorageDriver');
    console.log('Custom driver is active');
  } else {
    console.warn('Custom driver not supported, using fallback');
    await localforage.setDriver([
      localforage.INDEXEDDB,
      localforage.LOCALSTORAGE
    ]);
  }
  
  // Wait for initialization
  await localforage.ready();
  
  // Now ready to use
  await localforage.setItem('test', 'Custom driver works!');
}

setupCustomStorage();

// Driver identifiers available as constants
localforage.INDEXEDDB    // 'asyncStorage'
localforage.WEBSQL       // 'webSQLStorage'
localforage.LOCALSTORAGE // 'localStorageWrapper'

// Usage in driver selection
await localforage.setDriver([
  localforage.INDEXEDDB,    // Primary choice
  localforage.WEBSQL,       // Secondary fallback
  localforage.LOCALSTORAGE  // Final fallback
]);