Complete Workflow Example

End-to-end example: Fund → Transfer → Rollover → Withdraw.

Setup

import { Account as TongoAccount } from "@fatsolutions/tongo-sdk";
import { Account, RpcProvider } from "starknet";

const provider = new RpcProvider({
    nodeUrl: "https://starknet-sepolia.g.alchemy.com/starknet/version/rpc/v0_8/YOUR_API_KEY",
    specVersion: "0.8.1",
});

const signer = new Account({
    provider,
    address: "YOUR_ADDRESS",
    signer: "YOUR_PRIVATE_KEY"
});

// Tongo contract address on Sepolia
// This contract wraps STRK with a 1:1 rate (1 STRK = 1 Tongo STRK)
const tongoAddress = "0x00b4cca30f0f641e01140c1c388f55641f1c3fe5515484e622b6cb91d8cee585";

// Create two Tongo accounts
const account1 = new TongoAccount(82130983n, tongoAddress, provider);
const account2 = new TongoAccount(12930923n, tongoAddress, provider);

Important Prerequisites:

• Your Starknet account (YOUR_ADDRESS) must have:
  • Testnet ETH for gas fees
  • STRK tokens (this contract wraps STRK on Sepolia)
  • Get both from: https://starknet-faucet.vercel.app/
• The funding operation will approve the Tongo contract to spend your STRK tokens

1. Fund Account 1

console.log("=== Funding Account 1 ===");

// Fund with 100 Tongo units (Tongo uses 32-bit balances)
const fundOp = await account1.fund({ amount: 100n });
await fundOp.populateApprove();

const fundTx = await signer.execute([
    fundOp.approve!,
    fundOp.toCalldata()
]);

console.log("Fund TX:", fundTx.transaction_hash);
await provider.waitForTransaction(fundTx.transaction_hash);

const state1 = await account1.state();
console.log("Account 1 balance:", state1.balance); // 100n

2. Transfer to Account 2

console.log("=== Transferring to Account 2 ===");

// Transfer 25 Tongo units to account 2
const transferOp = await account1.transfer({
    to: account2.publicKey,
    amount: 25n
});

const transferTx = await signer.execute(transferOp.toCalldata());
console.log("Transfer TX:", transferTx.transaction_hash);
await provider.waitForTransaction(transferTx.transaction_hash);

// Check sender
const state1After = await account1.state();
console.log("Account 1 balance:", state1After.balance); // 75n

// Check recipient
const state2 = await account2.state();
console.log("Account 2 pending:", state2.pending); // 25n

3. Rollover Account 2

console.log("=== Rolling Over Account 2 ===");

const rolloverOp = await account2.rollover();
const rolloverTx = await signer.execute(rolloverOp.toCalldata());

console.log("Rollover TX:", rolloverTx.transaction_hash);
await provider.waitForTransaction(rolloverTx.transaction_hash);

const state2After = await account2.state();
console.log("Account 2 balance:", state2After.balance); // 25n
console.log("Account 2 pending:", state2After.pending); // 0n

4. Withdraw from Account 2

console.log("=== Withdrawing from Account 2 ===");

// Withdraw 10 Tongo units back to ERC20
const withdrawOp = await account2.withdraw({
    to: signer.address,
    amount: 10n
});

const withdrawTx = await signer.execute(withdrawOp.toCalldata());
console.log("Withdraw TX:", withdrawTx.transaction_hash);
await provider.waitForTransaction(withdrawTx.transaction_hash);

const state2Final = await account2.state();
console.log("Account 2 final balance:", state2Final.balance); // 15n

Key Concepts

• Tongo Units: Amounts are in Tongo units (32-bit integers, max: 4,294,967,295)
• 1:1 Rate: This contract wraps STRK with a 1:1 conversion rate
• 32-bit Limit: Cannot use full STRK decimal amounts (10^18), use smaller integers
• Fund Operation: Requires both approval and fund call (use array with both)
• Other Operations: Single call each (transfer, rollover, withdraw)

Complete Script

async function completeWorkflow() {
    // 1. Fund with 100 Tongo units
    const fundOp = await account1.fund({ amount: 100n });
    await fundOp.populateApprove();
    const fundTx = await signer.execute([fundOp.approve!, fundOp.toCalldata()]);
    await provider.waitForTransaction(fundTx.transaction_hash);

    // 2. Transfer 25 Tongo units
    const transferOp = await account1.transfer({
        to: account2.publicKey,
        amount: 25n
    });
    const transferTx = await signer.execute(transferOp.toCalldata());
    await provider.waitForTransaction(transferTx.transaction_hash);

    // 3. Rollover
    const rolloverOp = await account2.rollover();
    const rolloverTx = await signer.execute(rolloverOp.toCalldata());
    await provider.waitForTransaction(rolloverTx.transaction_hash);

    // 4. Withdraw 10 Tongo units
    const withdrawOp = await account2.withdraw({
        to: signer.address,
        amount: 10n
    });
    const withdrawTx = await signer.execute(withdrawOp.toCalldata());
    await provider.waitForTransaction(withdrawTx.transaction_hash);

    console.log("Complete workflow finished!");
}