/* this exmaple is with DAI tokens */
​
// once biconomy is initalized in your dapp
let ethersProvider = new ethers.providers.Web3Provider(biconomy);
let signer = ethersProvider.getSigner();
​
let address = <wallet address>;
contract = new ethers.Contract(
              <CONTRACT_ADDRESS>,
              <CONTRACT_ABI>,
              signer.connectUnchecked()
            );
​
//all parameters are optional
//spender by default would be Biconomy's Fee Proxy contract
const daiPermitOptions = {
          expiry: Math.floor(Date.now() / 1000 + 3600),
          allowed: true
        };
        
const tokenAddress = <DAI_address>;
// any accepted ERC20 token can be used
// you can use PermitClient like below for popular tokens like DAI and USDC
​
//getting permit 
console.log("getting user's permit to spend tokens");
await permitClient.daiPermit(daiPermitOptions);
​
// Create your target method signature.. here we are calling addRating() method of our contract
let functionSignature = contractInterface.encodeFunctionData("setQuote", ["hello meta transactions"]);
let gasPrice = await ethersProvider.getGasPrice();
let gasLimit = await ethersProvider.estimateGas({
          to: config.contract.address,
          from: userAddress,
          data: data,
        });
console.log(gasLimit.toString());
        
const builtTx = await ercForwarderClient.buildTx({to:<CONTRACT_ADDRESS>,token:tokenAddress,txGas:Number(gasLimit),data:functionSignature});
const tx = builtTx.request;
//Show the fee to your users!!!
const fee = builtTx.cost;  
// number of ERC20 tokens user will pay on behalf of gas for this transaction
console.log(fee); 
​
// returns a json object with txHash (if transaction is successful), log, message, code and flag
const txResponse = await ercForwarderClient.sendTxEIP712Sign({req:tx});
const txHash = txResponse.txHash;
console.log(txHash);
​
//for personal signature type
//const txHash = await ercForwarderClient.sendTxPersonalSign(tx); 
​
//event emitter methods
ethersProvider.once(txHash, (result) => {
            // Emitted when the transaction has been mined
            console.log(result);
            //doStuff
          });                           

/* this exmaple is with DAI tokens */
// assuming permit is already obtained
// to see how to use permit client please refer to SDK front end example code or web3 example
​
// Import sigUtil for signing data - Optional
var sigUtil = require('eth-sig-util');
var ethers = require('ethers');
​
// ethersProvider is initialized with biconomy
let ethersProvider = new ethers.providers.Web3Provider(biconomy);
let signer = ethersProvider.getSigner();
​
// Initialize Contracts
let contract = new ethers.Contract(<CONTRACT_ADDRESS>,
              <CONTRACT_ABI>, signer.connectUnchecked());
​
let contractInterface = new ethers.utils.Interface(<CONTRACT_ABI>);
​
let address = <wallet public address>;
let privateKey = <private key>;
let wallet = new ethers.Wallet(privateKey);
​
// Create your target method signature.. here we are calling addRating() method of our contract
let functionSignature = contractInterface.encodeFunctionData("setQuote", ["hello meta transactions"]);
let gasPrice = await ethersProvider.getGasPrice();
let gasLimit = await ethersProvider.estimateGas({
          to: config.contract.address,
          from: userAddress,
          data: data,
        });
console.log(gasLimit.toString());
​
let rawTx, signedTx;
​
rawTx = {
      to: config.contract.address,
      data: functionSignature,
      from: address,
      value: "0x0",
      //gasLimit: web3.utils.toHex(gasLimit),
    };
​
signedTx = await wallet.signTransaction(rawTx);
​
// should get user message to sign for EIP712 or personal signature types
const forwardRequestData = await biconomy.getForwardRequestAndMessageToSign(
      signedTx
    );
console.log(forwardRequestData);
const signParams = forwardRequestData.eip712Format;
// returned data has personal signature format available as well
// data.personalSignatureFormat
​
// forward request that was created to prepare the data to sign
// you must pass the same request otherwise it would result in signature mistach 
const request = forwardRequestData.request;
​
const cost = forwardRequestData.cost;
console.log(cost);
//show the fees in number of ERC20 tokens to be spent
​
//https://github.com/ethers-io/ethers.js/issues/687
/** ethers automatically appends EIP712 domain type.
 *  only need to remove for EIP712 format
 * personal format is available as well by dataToSign.personalSignatureFormat 
 */
delete signParams.types.EIP712Domain; 
console.log(signParams);
const signature = await wallet._signTypedData(signParams.domain, signParams.types, signParams.message);        
​
​
// optionally one can sign using sigUtil
//sigUtil works perfectly fine
/*
const signature = sigUtil.signTypedMessage(new Buffer.from(privateKey, 'hex'), 
{data: dataToSign.eip712Format}, 'V4');
*/
​
let data = {
      signature: signature,
      forwardRequest: request,
      rawTransaction: signedTx,
      signatureType: biconomy.EIP712_SIGN,
    };
​
// send signed transaction with ethers
// promise resolves to transaction hash
let tx = await ethersProvider.send("eth_sendRawTransaction", [data]);
console.log("Transaction hash : ", tx);
​
//event emitter methods
    ethersProvider.once(tx, (transaction) => {
      // Emitted when the transaction has been mined
      console.log(transaction);
      //doStuff
    });
​
​