​
Execute Batch Swap

Slippage is an important concept in trading that can have a significant impact on your trading outcomes. It refers to the difference between the expected price of a trade and the actual price at which the trade is executed. Slippage can occur in various market conditions and for several reasons, and it’s crucial for traders to be aware of its potential effects.Fibrous uses slippage settings to prevent you from losing money; there is no need to increase your slippage when you spot an arbitrage opportunity.Fibrous is still in alpha version. Please make sure you have adjusted your slippage properly.
Generate transaction data for calling the Fibrous Router contract to execute multiple swaps in a single transaction.

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Basic Setup

First, let’s set up the router and get the token information: 
import { Router as FibrousRouter } from "fibrous-router-sdk";
import { parseUnits } from "ethers";

const fibrous = new FibrousRouter();
const chainId = fibrous.supportedChains.find(chain => chain.chain_name == "starknet")?.chain_id;
if (!chainId) {
    throw new Error("Chain not supported");
}
// Get the supported tokens for the Starknet chain
const tokens = await fibrous.supportedTokens(chainId);

const ethToken = tokens.get("eth");
const strkToken = tokens.get("strk");
const usdcToken = tokens.get("usdc");
const usdtToken = tokens.get("usdt");

if (!ethToken || !strkToken || !usdcToken || !usdtToken) {
    throw new Error("Required tokens not found");
}

const tokenInAddress_1 = ethToken.address;
const tokenInAddress_2 = strkToken.address;
const tokenInAddress_3 = usdcToken.address;

const tokenOutAddress = usdtToken.address;

const tokenInDecimals_1 = ethToken.decimals;
const tokenInDecimals_2 = strkToken.decimals;
const tokenInDecimals_3 = usdcToken.decimals;

const inputAmounts = [
    BigInt(parseUnits("0.001", tokenInDecimals_1)), // 0.001 ETH
    BigInt(parseUnits("10", tokenInDecimals_2)), // 10 STRK
    BigInt(parseUnits("5", tokenInDecimals_3)), // 5 USDC
];

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Usage on Backend

For backend implementations on Starknet: 
import { Router as FibrousRouter } from "fibrous-router-sdk";
import { Call } from "starknet";
import { parseUnits } from "ethers";
import { account } from "./account";

const fibrous = new FibrousRouter();
const chainId = fibrous.supportedChains.find(chain => chain.chain_name == "starknet")?.chain_id;
if (!chainId) {
    throw new Error("Chain not supported");
}
// Get the supported tokens for the Starknet chain
const tokens = await fibrous.supportedTokens(chainId);

const ethToken = tokens.get("eth");
const strkToken = tokens.get("strk");
const usdcToken = tokens.get("usdc");
const usdtToken = tokens.get("usdt");

if (!ethToken || !strkToken || !usdcToken || !usdtToken) {
    throw new Error("Required tokens not found");
}

const tokenInAddress_1 = ethToken.address;
const tokenInAddress_2 = strkToken.address;
const tokenInAddress_3 = usdcToken.address;

const tokenOutAddress = usdtToken.address;

const tokenInDecimals_1 = ethToken.decimals;
const tokenInDecimals_2 = strkToken.decimals;
const tokenInDecimals_3 = usdcToken.decimals;

const inputAmounts = [
    BigInt(parseUnits("0.001", tokenInDecimals_1)), // 0.001 ETH
    BigInt(parseUnits("10", tokenInDecimals_2)), // 10 STRK
    BigInt(parseUnits("5", tokenInDecimals_3)), // 5 USDC
];
const public_key = process.env.STARKNET_PUBLIC_KEY;
const privateKey = process.env.STARKNET_PRIVATE_KEY;
const RPC_URL = process.env.STARKNET_RPC_URL;
const destination = process.env.STARKNET_PUBLIC_KEY; // The address to receive the tokens after the swap is completed (required)
if (!privateKey || !public_key || !RPC_URL || !destination) {
    throw new Error("Missing environment variables");
}
// Call the buildTransaction method in order to build the transaction
// slippage: The maximum acceptable slippage of the buyAmount amount.
const slippage = 1; // 1%
const tokenInAddresses = [
    tokenInAddress_1,
    tokenInAddress_2,
    tokenInAddress_3,
];
const tokenOutAddresses = [tokenOutAddress];
const swapCalls = await fibrous.buildBatchTransaction(
    inputAmounts,
    tokenInAddresses,
    tokenOutAddresses,
    slippage,
    destination,
    "starknet", // chainName will be deprecated in the next version, use chainId instead
    {reverse: false, direct: false, excludeProtocols: []},
    chainId,
);

// https://www.starknetjs.com/docs/guides/connect_account
// If this account is based on a Cairo v2 contract (for example OpenZeppelin account 0.7.0 or later), do not forget to add the parameter "1" after the privateKey parameter

const account0 = account(privateKey, public_key, "1", RPC_URL);
const approveCalls: Call[] = [];
for (let i = 0; i < inputAmounts.length; i++) {
    const approveCall: Call = await fibrous.buildApproveStarknet(
        inputAmounts[i],
        tokenInAddresses[i],
    );
    approveCalls.push(approveCall);
}
// Type guard: Starknet chains return Call[]
if (
    Array.isArray(swapCalls) &&
    swapCalls.every(
        (call) => "contractAddress" in call && "entrypoint" in call,
    )
) {
    const resp = await account0.execute([...approveCalls, ...swapCalls]);
    console.log(`https://voyager.online/tx/${resp.transaction_hash}`);
} else {
    console.error("Invalid swap call data for Starknet batch transaction");
}
The swap call returns a transaction object with the following structure: 
{
  contractAddress:ROUTER_ADDRESS,
  entrypoint: "swap",
  calldata: calldata,
}

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Important Notes

  1. All swaps in a batch must succeed for the transaction to be successful
  2. Make sure to have sufficient balance for all tokens being swapped
  3. Approve all tokens before executing the batch swap
  4. Consider gas costs for multiple swaps in a single transaction
  5. Monitor the transaction status for all swaps in the batch
  6. Handle errors appropriately for each swap in the batch