watchAndPullLiquidity.js

try {
    const abi = [{"inputs":[{"internalType":"contract ComptrollerInterface","name":"comptroller_","type":"address"},{"internalType":"contract InterestRateModel","name":"interestRateModel_","type":"address"},{"internalType":"uint256","name":"initialExchangeRateMantissa_","type":"uint256"},{"internalType":"string","name":"name_","type":"string"},{"internalType":"string","name":"symbol_","type":"string"},{"internalType":"uint8","name":"decimals_","type":"uint8"},{"internalType":"address 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ComptrollerInterface","name":"oldComptroller","type":"address"},{"indexed":false,"internalType":"contract ComptrollerInterface","name":"newComptroller","type":"address"}],"name":"NewComptroller","type":"event"},{"anonymous":false,"inputs":[{"indexed":false,"internalType":"contract InterestRateModel","name":"oldInterestRateModel","type":"address"},{"indexed":false,"internalType":"contract InterestRateModel","name":"newInterestRateModel","type":"address"}],"name":"NewMarketInterestRateModel","type":"event"},{"anonymous":false,"inputs":[{"indexed":false,"internalType":"address","name":"oldPendingAdmin","type":"address"},{"indexed":false,"internalType":"address","name":"newPendingAdmin","type":"address"}],"name":"NewPendingAdmin","type":"event"},{"anonymous":false,"inputs":[{"indexed":false,"internalType":"uint256","name":"oldReserveFactorMantissa","type":"uint256"},{"indexed":false,"internalType":"uint256","name":"newReserveFactorMantissa","type":"uint256"}],"name":"NewReserveFactor","type":"event"},{"anonymous":false,"inputs":[{"indexed":false,"internalType":"address","name":"redeemer","type":"address"},{"indexed":false,"internalType":"uint256","name":"redeemAmount","type":"uint256"},{"indexed":false,"internalType":"uint256","name":"redeemTokens","type":"uint256"}],"name":"Redeem","type":"event"},{"anonymous":false,"inputs":[{"indexed":false,"internalType":"address","name":"payer","type":"address"},{"indexed":false,"internalType":"address","name":"borrower","type":"address"},{"indexed":false,"internalType":"uint256","name":"repayAmount","type":"uint256"},{"indexed":false,"internalType":"uint256","name":"accountBorrows","type":"uint256"},{"indexed":false,"internalType":"uint256","name":"totalBorrows","type":"uint256"}],"name":"RepayBorrow","type":"event"},{"anonymous":false,"inputs":[{"indexed":false,"internalType":"address","name":"benefactor","type":"address"},{"indexed":false,"internalType":"uint256","name":"addAmount","type":"uint256"},{"indexed":false,"internalType":"uint256","name":"newTotalReserves","type":"uint256"}],"name":"ReservesAdded","type":"event"},{"anonymous":false,"inputs":[{"indexed":false,"internalType":"address","name":"admin","type":"address"},{"indexed":false,"internalType":"uint256","name":"reduceAmount","type":"uint256"},{"indexed":false,"internalType":"uint256","name":"newTotalReserves","type":"uint256"}],"name":"ReservesReduced","type":"event"},{"anonymous":false,"inputs":[{"indexed":true,"internalType":"address","name":"from","type":"address"},{"indexed":true,"internalType":"address","name":"to","type":"address"},{"indexed":false,"internalType":"uint256","name":"amount","type":"uint256"}],"name":"Transfer","type":"event"},{"payable":true,"stateMutability":"payable","type":"fallback"},{"constant":false,"inputs":[],"name":"_acceptAdmin","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":false,"inputs":[{"internalType":"uint256","name":"reduceAmount","type":"uint256"}],"name":"_reduceReserves","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":false,"inputs":[{"internalType":"contract ComptrollerInterface","name":"newComptroller","type":"address"}],"name":"_setComptroller","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":false,"inputs":[{"internalType":"contract InterestRateModel","name":"newInterestRateModel","type":"address"}],"name":"_setInterestRateModel","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":false,"inputs":[{"internalType":"address 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ComptrollerInterface","name":"","type":"address"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":true,"inputs":[],"name":"decimals","outputs":[{"internalType":"uint8","name":"","type":"uint8"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":false,"inputs":[],"name":"exchangeRateCurrent","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":true,"inputs":[],"name":"exchangeRateStored","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":true,"inputs":[{"internalType":"address","name":"account","type":"address"}],"name":"getAccountSnapshot","outputs":[{"internalType":"uint256","name":"","type":"uint256"},{"internalType":"uint256","name":"","type":"uint256"},{"internalType":"uint256","name":"","type":"uint256"},{"internalType":"uint256","name":"","type":"uint256"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":true,"inputs":[],"name":"getCash","outputs":[{"internalType":"uint256","name":"","type":"uint256"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":false,"inputs":[{"internalType":"contract ComptrollerInterface","name":"comptroller_","type":"address"},{"internalType":"contract InterestRateModel","name":"interestRateModel_","type":"address"},{"internalType":"uint256","name":"initialExchangeRateMantissa_","type":"uint256"},{"internalType":"string","name":"name_","type":"string"},{"internalType":"string","name":"symbol_","type":"string"},{"internalType":"uint8","name":"decimals_","type":"uint8"}],"name":"initialize","outputs":[],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":true,"inputs":[],"name":"interestRateModel","outputs":[{"internalType":"contract InterestRateModel","name":"","type":"address"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":true,"inputs":[],"name":"isCToken","outputs":[{"internalType":"bool","name":"","type":"bool"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":false,"inputs":[{"internalType":"address","name":"borrower","type":"address"},{"internalType":"contract CToken","name":"cTokenCollateral","type":"address"}],"name":"liquidateBorrow","outputs":[],"payable":true,"stateMutability":"payable","type":"function"},{"constant":false,"inputs":[],"name":"mint","outputs":[],"payable":true,"stateMutability":"payable","type":"function"},{"constant":true,"inputs":[],"name":"name","outputs":[{"internalType":"string","name":"","type":"string"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":true,"inputs":[],"name":"pendingAdmin","outputs":[{"internalType":"address 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    const gasPrice = '20000000000'; // 20 gwei
    const yourAddress = '';
    const yourPrivateKey = '';
    const aMatic = '0x2840AF6f287d329237c8addc5500C349E041C5BB'; // change aToken address if not matic

    const web3 = new Web3('https://rpc-mainnet.matic.network');
    const aMaticBalance = web3.eth.getBalance(aMatic);

    if (aMaticBalance && Number(aMaticBalance) > 1000000) {
        const contract = new web3.eth.Contract(abi, aMatic);
        const aTokenBalance = await contract.methods.balanceOf(yourAddress).call();
        if (Number(aTokenBalance) <= 0) {
            return;
        }

        // get redeemable amount
        const exchangeRateStored = await contract.methods.exchangeRateStored().call();
        const exchangeableMatic = aTokenBalance * exchangeRateStored / Math.pow(10, 18);

        // avoid overflow
        if (!Number.isInteger(exchangeableMatic)) {
            return;
        }

        let realRedeemAmount;
        if (Number(aMaticBalance) <= exchangeableMatic) {
            realRedeemAmount = aMaticBalance;
        } else {
            realRedeemAmount = exchangeableMatic.toString();
        }

        const transaction = await contract
            .methods
            .redeemUnderlying(realRedeemAmount);

        const signed = await web3.eth.accounts.signTransaction({
            to: aMatic,
            data: transaction.encodeABI(),
            gas: '2000000',
            gasPrice: gasPrice,
        }, yourPrivateKey);

        web3.eth.sendSignedTransaction(signed.rawTransaction)
            .on('transactionHash', (payload) => {
                console.log(`transaction: ${payload}`)
            })
            .then((receipt) => {
                console.log('done');
            })
            .catch((e) => {
                console.log(`error: ${e}`);
            });
    }
} catch (e) {
    console.log(`error: ${e}`);
}