autofill.js

  // Once the page load, check if we have a connected web3 wallet and if we
  // allow ETH deposits and if so fetch the ETH deposit address
  // and create a transaction with web3.
  useEffect(() => {
    if (
      !(exchangeRates && exchangeRates.isDone) ||
      !Web3.givenProvider ||
      !window.ethereum ||
      invoice.acceptedCurrencies.indexOf('ETH') === -1
      ) return

    (async () => {
      const web3WalletAddress = iframeApiClient.GetInvoiceDepositAddress(
        invoice.apiKey,
        invoice.id,
        'ETH',
      )
      web3WalletAddressReq.bind(web3WalletAddress)

      const web3 = new Web3(Web3.givenProvider)

      let accounts, errAccounts
      // Proper web3 wallets (like MetaMask) should provide a global ethereum
      // object with an enable() method. It should trigger a web3 prompt that asks
      // the user to allow the webpage to read web3 wallet addresses. The method
      // returns a Promise that’s either resolved with user accounts after
      // user approval, or rejected with an Error after user rejection.
      if (window.ethereum.enable) {
        [accounts, errAccounts] = await maybe(window.ethereum.enable())
      }

      // If some wallet is not fully complying with the enable() method it will
      // most probably return nothing. In that case we should fallback to
      // web3's get accounts.
      if (!accounts && !errAccounts) {
        [accounts, errAccounts] = await maybe(web3.eth.getAccounts())
      }

      if (errAccounts) {
        console.log('Could not get web3 accounts: ', errAccounts)
        return
      }

      const gasEth = web3.utils.fromWei(await web3.eth.getGasPrice(), 'ether')
      const invoiceInEth = exchangeRates!.convert(invoice, 'ETH')
      const invoiceWithGas = invoiceInEth.add(new MoneyAmount({
        amount: gasEth,
        currency: 'ETH',
      }))
      const invoiceInWei = web3.utils.toWei(toWeiCompatibleString(invoiceInEth.amount), 'ether')

      // find an account with enough ETH balance and send a web3 tx from it
      for (const account of accounts) {
        const [balanceWei, errBalance] = await maybe(web3.eth.getBalance(account))

        if (errBalance) {
          console.log('Could not get balance of ' + account + ': ', errBalance)
          continue
        }

        const balanceEth = web3.utils.fromWei(balanceWei, 'ether')
        console.log(`Balance of ${account}: ${balanceEth}`)

        const isWeb3WalletBalanceEnough = new MoneyAmount({
          amount: balanceEth,
          currency: 'ETH',
        }).gte(invoiceWithGas)

        if (isWeb3WalletBalanceEnough) {
          web3WalletAddress.then(res => {
            // The web3Wallet in the store will start a polling for the eth
            // address and will show instructions for the user.
            dispatch(invoiceActions.setWeb3Wallet({
              address: res.address,
              wallet: web3.currentProvider.isMetaMask ? 'MetaMask' : 'Web3',
            }))

            web3.eth
              .sendTransaction({
                from: account,
                to: res.address,
                value: invoiceInWei,
              })
              .on('error', (error) => {
                dispatch(invoiceActions.setWeb3Wallet(null))
              })
          }).catch(e => {})

          // break from the for loop so we don't accidentaly send another tx
          break
        }
      }
    })().catch(e => {})
  }, [exchangeRates!.isDone])