wallet_balance_manager.js

const walletBalanceChanged = balance => {
  const GAS_PRICE = 1e10;
  const TX_GAS = 40e3;
  const TX_PRICE = GAS_PRICE * TX_GAS;

  let txsNum = balance / TX_PRICE;

  const txsLvls = [2, 10, 20];

  if (txsNum <= 2) {
    return { action: 'contractWithdraw', amount: txsLvls[1] * TX_PRICE - balance };
  }
  if (20 < txsNum) {
    return { action: 'contractDeposit', amount: balance - txsLvls[1] * TX_PRICE };
  }
  return { action: null };
};