@unilogin/sdk/src/core/services/validations/AmountValidator.ts

SDK is a JS library, that communicates with relayer. SDK allows managing contract, by creating basic contract-calling messages.

import {utils} from 'ethers';
import {TransferDetails, SEND_TRANSACTION_GAS_LIMIT, isStringANumberRegex} from '@unilogin/commons';
import {Validator, TransferErrors} from './Validator';

const {formatEther} = utils;

export class AmountValidator implements Validator<TransferDetails> {
  constructor(private readonly balance: string) {
  }

  async validate(transferDetails: TransferDetails, errors: TransferErrors) {
    const {amount, transferToken} = transferDetails;
    if (!amount) {
      errors['amount'].push('Empty amount');
      return;
    }
    if (!amount.match(isStringANumberRegex)) {
      errors['amount'].push(`Amount ${amount} is not a valid number`);
      return;
    }
    const {gasPrice, gasToken} = transferDetails.gasParameters;
    const amountAsBigNumber = utils.parseEther(amount);
    const balanceAsBigNumber = utils.parseEther(this.balance);
    const gasCostInWei = utils.bigNumberify(SEND_TRANSACTION_GAS_LIMIT.toString()).mul(gasPrice);
    const amountWithFee = amountAsBigNumber.add(gasCostInWei);
    if (amountAsBigNumber.gt(balanceAsBigNumber)) {
      errors['amount'].push(`Insufficient funds. Sending ${formatEther(amountAsBigNumber)} eth, got only ${formatEther(balanceAsBigNumber)} eth`);
    } else if (gasToken === transferToken && amountWithFee.gt(balanceAsBigNumber)) {
      errors['amount'].push(`Insufficient funds. Sending ${formatEther(amountAsBigNumber)} eth + ${formatEther(gasCostInWei)} eth fee, got only ${formatEther(balanceAsBigNumber)} eth`);
    }
  }
}