cinny/src/client/secretStorageKeys.ts

import type { CryptoCallbacks } from 'matrix-js-sdk/lib/crypto-api';

const secretStorageKeys = new Map<string, Uint8Array<ArrayBuffer>>();

export function storePrivateKey(keyId: string, privateKey: Uint8Array) {
  if (privateKey instanceof Uint8Array === false) {
    throw new Error('Unable to store, privateKey is invalid.');
  }
  // Our own copy, on a plain ArrayBuffer (what the SDK's callback type wants).
  secretStorageKeys.set(keyId, new Uint8Array(privateKey));
}

export function clearSecretStorageKeys() {
  secretStorageKeys.clear();
}

export const cryptoCallbacks: CryptoCallbacks = {
  async getSecretStorageKey({ keys }) {
    const keyId = Object.keys(keys).find((id) => secretStorageKeys.get(id) instanceof Uint8Array);
    const privateKey = keyId ? secretStorageKeys.get(keyId) : undefined;
    // The SDK expects null (not undefined) when no key is cached.
    return keyId && privateKey ? [keyId, privateKey] : null;
  },
  cacheSecretStorageKey(keyId, keyInfo, privateKey) {
    secretStorageKeys.set(keyId, privateKey);
  },
};