Single Transaction Bridging

This example is for Single Transaction Bridging txs, which use the /v2/build-tx endpoint.

In the example below, a POST request is being made to the /v2/build-tx endpoint using route data retrieved from /v2/quote endpoint. Before any bridging transaction is initiated, check that the Socket contracts have allowance of users' tokens, as specified in the Approvals section. In case the contracts don't have approval, an approval transaction needs to be made using the data returned from /v2/approval/build-tx endpoint.

note

An API Key is needed for this step. Fill in this form for access.

Javascript example

const ethers = require("ethers");

const API_KEY = "72a5b4b0-e727-48be-8aa1-5da9d62fe635"; // SOCKET PUBLIC API KEY

// Makes a GET request to Bungee APIs for quote
async function getQuote(
  fromChainId,
  fromTokenAddress,
  toChainId,
  toTokenAddress,
  fromAmount,
  userAddress,
  uniqueRoutesPerBridge,
  sort,
  singleTxOnly
) {
  const response = await fetch(
    `https://api.socket.tech/v2/quote?fromChainId=${fromChainId}&fromTokenAddress=${fromTokenAddress}&toChainId=${toChainId}&toTokenAddress=${toTokenAddress}&fromAmount=${fromAmount}&userAddress=${userAddress}&uniqueRoutesPerBridge=${uniqueRoutesPerBridge}&sort=${sort}&singleTxOnly=${singleTxOnly}`,
    {
      method: "GET",
      headers: {
        "API-KEY": API_KEY,
        Accept: "application/json",
        "Content-Type": "application/json",
      },
    }
  );

  const json = await response.json();
  return json;
}

// Makes a POST request to Bungee APIs for swap/bridge transaction data
async function getRouteTransactionData(route) {
  const response = await fetch("https://api.socket.tech/v2/build-tx", {
    method: "POST",
    headers: {
      "API-KEY": API_KEY,
      Accept: "application/json",
      "Content-Type": "application/json",
    },
    body: JSON.stringify({ route: route }),
  });

  const json = await response.json();
  return json;
}

// GET request to check token allowance given to allowanceTarget by owner
async function checkAllowance(chainId, owner, allowanceTarget, tokenAddress) {
  const response = await fetch(
    `https://api.socket.tech/v2/approval/check-allowance?chainID=${chainId}&owner=${owner}&allowanceTarget=${allowanceTarget}&tokenAddress=${tokenAddress}`,
    {
      method: "GET",
      headers: {
        "API-KEY": API_KEY,
        Accept: "application/json",
        "Content-Type": "application/json",
      },
    }
  );

  const json = await response.json();
  return json;
}

// Fetches transaction data for token approval
async function getApprovalTransactionData(
  chainId,
  owner,
  allowanceTarget,
  tokenAddress,
  amount
) {
  const response = await fetch(
    `https://api.socket.tech/v2/approval/build-tx?chainID=${chainId}&owner=${owner}&allowanceTarget=${allowanceTarget}&tokenAddress=${tokenAddress}&amount=${amount}`,
    {
      method: "GET",
      headers: {
        "API-KEY": API_KEY,
        Accept: "application/json",
        "Content-Type": "application/json",
      },
    }
  );

  const json = await response.json();
  return json;
}

// Fetches status of the bridging transaction
async function getBridgeStatus(transactionHash, fromChainId, toChainId) {
  const response = await fetch(
    `https://api.socket.tech/v2/bridge-status?transactionHash=${transactionHash}&fromChainId=${fromChainId}&toChainId=${toChainId}`,
    {
      method: "GET",
      headers: {
        "API-KEY": API_KEY,
        Accept: "application/json",
        "Content-Type": "application/json",
      },
    }
  );

  const json = await response.json();
  return json;
}

// Main function
async function main() {
  // Uses web3 wallet in browser as provider
  const provider = new ethers.providers.Web3Provider(window.ethereum, "any");

  // Prompt user for account connections
  await provider.send("eth_requestAccounts", []);

  // Stores signer
  const signer = provider.getSigner();

  // Bridging Params fetched from users
  const fromChainId = 137;
  const toChainId = 56;
  const fromAssetAddress = "0x2791bca1f2de4661ed88a30c99a7a9449aa84174";
  const toAssetAddress = "0x55d398326f99059fF775485246999027B3197955";
  const amount = 100000000; // 100 USDC, USDC is 6 decimals
  const userAddress = "0x3e8cB4bd04d81498aB4b94a392c334F5328b237b";
  const uniqueRoutesPerBridge = true; // Returns the best route for a given DEX / bridge combination
  const sort = "output"; // "output" | "gas" | "time"
  const singleTxOnly = true;

  // Quote for bridging 100 USDC on Polygon to USDT on BSC
  // For single transaction bridging, mark singleTxOnly flag as true in query params
  const quote = await getQuote(
    fromChainId,
    fromAssetAddress,
    toChainId,
    toAssetAddress,
    amount,
    userAddress,
    uniqueRoutesPerBridge,
    sort,
    singleTxOnly
  );

  // Choosing first route from the returned route results
  const route = quote.result.routes[0];

  // Fetching transaction data for swap/bridge tx
  const apiReturnData = await getRouteTransactionData(route);

  // Used to check for ERC-20 approvals
  const approvalData = apiReturnData.result.approvalData;
  const { allowanceTarget, minimumApprovalAmount } = approvalData;

  // approvalData from apiReturnData is null for native tokens
  // Values are returned for ERC20 tokens but token allowance needs to be checked
  if (approvalData !== null) {
    // Fetches token allowance given to Bungee contracts
    const allowanceCheckStatus = await checkAllowance(
      fromChainId,
      userAddress,
      allowanceTarget,
      fromAssetAddress
    );
    const allowanceValue = allowanceCheckStatus.result?.value;

    // If Bungee contracts don't have sufficient allowance
    if (minimumApprovalAmount > allowanceValue) {
      // Approval tx data fetched
      const approvalTransactionData = await getApprovalTransactionData(
        fromChainId,
        userAddress,
        allowanceTarget,
        fromAssetAddress,
        amount
      );

      const gasPrice = await signer.getGasPrice();

      const gasEstimate = await provider.estimateGas({
        from: signer.address,
        to: approvalTransactionData.result?.to,
        value: "0x00",
        data: approvalTransactionData.result?.data,
        gasPrice: gasPrice,
      });

      const tx = await signer.sendTransaction({
        from: approvalTransactionData.result?.from,
        to: approvalTransactionData.result?.to,
        value: "0x00",
        data: approvalTransactionData.result?.data,
        gasPrice: gasPrice,
        gasLimit: gasEstimate,
      });

      // Initiates approval transaction on user's frontend which user has to sign
      const receipt = await tx.wait();

      console.log("Approval Transaction Hash :", receipt.transactionHash);
    }
  }

  const gasPrice = await signer.getGasPrice();

  const gasEstimate = await provider.estimateGas({
    from: signer.address,
    to: apiReturnData.result.txTarget,
    value: apiReturnData.result.value,
    data: apiReturnData.result.txData,
    gasPrice: gasPrice,
  });

  const tx = await signer.sendTransaction({
    from: signer.address,
    to: apiReturnData.result.txTarget,
    data: apiReturnData.result.txData,
    value: apiReturnData.result.value,
    gasPrice: gasPrice,
    gasLimit: gasEstimate,
  });

  // Initiates swap/bridge transaction on user's frontend which user has to sign
  const receipt = await tx.wait();

  const txHash = receipt.transactionHash;

  console.log("Bridging Transaction : ", receipt.transactionHash);

  // Checks status of transaction every 20 secs
  const txStatus = setInterval(async () => {
    const status = await getBridgeStatus(txHash, fromChainId, toChainId);

    console.log(
      `SOURCE TX : ${status.result.sourceTxStatus}\nDEST TX : ${status.result.destinationTxStatus}`
    );

    if (status.result.destinationTxStatus == "COMPLETED") {
      console.log("DEST TX HASH :", status.result.destinationTransactionHash);
      clearInterval(txStatus);
    }
  }, 20000);
}

main();