Customize the Storage Provider

Overview

The IStorageProvider interface is designed to be implemented by platform-specific storage solutions, such as SQLite or FileSystem. This interface allows the Mobile SDK to interact with the storage layer without being tied to a specific implementation.

The SDK provides a default implementation InMemoryStorageClient. This is useful for testing or development purposes, but it is not suitable for production use. But we can create a custom storage provider to persist data.

Implementing a Custom Storage Provider with AsyncStorage

App.tsx

import {
  CloudWebSocketClient,
  createEcdsaDuoSession,
  type IStorageProvider,
  type StorageDomain,
} from '@silencelaboratories/silent-shard-sdk';
import AsyncStorage from '@react-native-async-storage/async-storage';

class AsyncStorageProvider implements IStorageProvider {
  async create(keyId: string, domain: StorageDomain, item: string): Promise<void> {
    const storageKey = this.getStorageKey(keyId, domain);

    // Check if item already exists
    const existing = await this.exists(keyId, domain);
    if (existing) {
      throw new Error(`Item already exists for key: ${storageKey}`);
    }

    await AsyncStorage.setItem(storageKey, item);
  }

  async read(keyId: string, domain: StorageDomain): Promise<string | null> {
    const storageKey = this.getStorageKey(keyId, domain);
    return AsyncStorage.getItem(storageKey);
  }

  async update(keyId: string, domain: StorageDomain, item: string): Promise<void> {
    const storageKey = this.getStorageKey(keyId, domain);

    // Verify existence before update
    const existing = await this.exists(keyId, domain);
    if (!existing) {
      throw new Error(`Item not found for update: ${storageKey}`);
    }

    await AsyncStorage.setItem(storageKey, item);
  }

  async delete(keyId: string, domain: StorageDomain): Promise<void> {
    const storageKey = this.getStorageKey(keyId, domain);
    await AsyncStorage.removeItem(storageKey);
  }

  async exists(keyId: string, domain: StorageDomain): Promise<boolean> {
    const storageKey = this.getStorageKey(keyId, domain);
    const value = await AsyncStorage.getItem(storageKey);
    return value !== null;
  }

  // Helper: Generate storage key from keyId and domain
  private getStorageKey(keyId: string, domain: StorageDomain): string {
    return `mpc-${domain}-${keyId}`;
  }
}

// Then you can use the CustomCloudClient in Session objects
const customStorageProvider = new AsyncStorageProvider();

const client = new CloudWebSocketClient('CLOUD_NODE_URL', true); // true for WSS, false for WS

export const initSession = async () => {
  return createEcdsaDuoSession({
    client: client,
    storage: customStorageProvider,
    cloudVerifyingKey: 'YOUR_CLOUD_VERIFICATION_KEY', // Replace with your actual key,
    messageSigner: {
      // This is a mock signer, replace with your actual implementation
      publicKeyB64: '',
      sign: async (message: string) => message,
      keyType: 'ED25519',
    },
  });
};