Create and use Generalized Accounts

Introduction

The whole script is located in the repository and this page explains in detail how to:

• initialize an instance of the SDK with a random account,
• top up generated account using faucet on testnet,
• make it a generalized account,
• transfer AE using generalized account.

1. Create SDK instance and generate an account

import {
  AeSdk, Node, MemoryAccount, AccountGeneralized, CompilerHttp, MIN_GAS_PRICE,
} from '@aeternity/aepp-sdk';

const aeSdk = new AeSdk({
  nodes: [{ name: 'testnet', instance: new Node('https://testnet.aeternity.io') }],
  accounts: [MemoryAccount.generate()],
  onCompiler: new CompilerHttp('https://v7.compiler.aepps.com'),
});
const { address } = aeSdk;

2. Top up generated account using faucet on testnet

const { status } = await fetch(`https://faucet.aepps.com/account/${address}`, { method: 'POST' });
console.assert(status === 200, 'Invalid faucet response code', status);

3. Create a Generalized Account

console.log('Account info before making generalized', await aeSdk.getAccount(address));
const sourceCode = `contract BlindAuth =
  stateful entrypoint authorize(shouldAuthorize: bool, _: int) : bool =
    switch(Auth.tx_hash)
      None    => abort("Not in Auth context")
      Some(_) => shouldAuthorize
`;

Authorize entrypoint doesn't implement any specific logic, it just returns the argument. It means that anybody can make a transaction on behalf of this account. You can implement an arbitrary validation logic in authorize entrypoint based on the contract state, transaction to approve, and call arguments. Also, you can involve custom signing algorithms.

const { gaContractId } = await aeSdk.createGeneralizedAccount('authorize', [], { sourceCode });
console.log('Attached contract address', gaContractId);

You can pass bytecode and aci options instead of sourceCode to don't depend on compiler.

console.log(await aeSdk.getAccount(address));

Note that account kind changed from basic to generalized, added contractId, authFun fields.

4. Switch SDK instance to AccountGeneralized

After making the account generalized, the node would stop accepting transactions signed using the private key of that account. So, we need to replace the instance of MemoryAccount with AccountGeneralized.

aeSdk.removeAccount(address);
aeSdk.addAccount(new AccountGeneralized(address), { select: true });

5. Transfer AE

Calling the spend function will create, sign and broadcast a SpendTx to the network using AccountGeneralized. It requires authData option.

console.log('balance before', await aeSdk.getBalance(address));
const authData = { sourceCode, args: [true, 42] };
const recipient = 'ak_21A27UVVt3hDkBE5J7rhhqnH5YNb4Y1dqo4PnSybrH85pnWo7E';
await aeSdk.spend(1e18, recipient, { authData });
console.log('balance after', await aeSdk.getBalance(address));

Note arguments of authorize entrypoint have to be unique, otherwise the transaction would be rejected by the node with "Invalid tx" message. Therefore, in this example a transaction with the same authorize arguments can't be submitted more than once. As a workaround "authorize" entrypoint accepts a number that acts as a nonce.

You may need to put a signed hash of a transaction to authData, for this purpose you need to pass a callback in authData. Use buildAuthTxHash method to get a hash equal to Auth.tx_hash in an authorize entrypoint.

await aeSdk.spend(2e18, recipient, {
  async authData(transaction) {
    const fee = 10n ** 14n;
    const gasPrice = MIN_GAS_PRICE;
    const authTxHash = await aeSdk.buildAuthTxHash(transaction, { fee, gasPrice });
    console.log('Auth.tx_hash', authTxHash.toString('hex'));
    authData.args[1] += 1;
    Object.assign(authData, { fee, gasPrice });
    return authData;
  },
});
console.log('balance after 2nd spend', await aeSdk.getBalance(address));