function CountXRPDifference(affected_nodes, address) {
  // Helper to find an account in an AffectedNodes array and see how much
  // its balance changed, if at all. Fortunately, each account appears at most
  // once in the AffectedNodes array, so we can return as soon as we find it.

  for (let i=0; i<affected_nodes.length; i++) {
    if ((affected_nodes[i].hasOwnProperty("ModifiedNode"))) {
      // modifies an existing ledger entry
      let ledger_entry = affected_nodes[i].ModifiedNode
      if (ledger_entry.LedgerEntryType === "AccountRoot" &&
          ledger_entry.FinalFields.Account === address) {
        if (!ledger_entry.PreviousFields.hasOwnProperty("Balance")) {
          console.log("XRP balance did not change.")
        }
        // Balance is in PreviousFields, so it changed. Time for
        // high-precision math!
        const old_balance = new Big(ledger_entry.PreviousFields.Balance)
        const new_balance = new Big(ledger_entry.FinalFields.Balance)
        const diff_in_drops = new_balance.minus(old_balance)
        const xrp_amount = diff_in_drops.div(10e6)
        if (xrp_amount.gte(0)) {
          console.log("Received "+xrp_amount.toString()+" XRP.")
          return
        } else {
          console.log("Spent "+xrp_amount.abs().toString()+" XRP.")
          return
        }
      }
    } else if ((affected_nodes[i].hasOwnProperty("CreatedNode"))) {
      // created a ledger entry. maybe the account just got funded?
      let ledger_entry = affected_nodes[i].CreatedNode
      if (ledger_entry.LedgerEntryType === "AccountRoot" &&
          ledger_entry.NewFields.Account === address) {
        const balance_drops = new Big(ledger_entry.NewFields.Balance)
        const xrp_amount = balance_drops.div(10e6)
        console.log("Received "+xrp_amount.toString()+" XRP (account funded).")
        return
      }
    } // accounts cannot be deleted at this time, so we ignore DeletedNode
  }

  console.log("Did not find address in affected nodes.")
  return
}

function CountXRPReceived(tx, address) {
  if (tx.meta.TransactionResult !== "tesSUCCESS") {
    console.log("Transaction failed.")
    return
  }
  if (tx.transaction.TransactionType === "Payment") {
    if (tx.transaction.Destination !== address) {
      console.log("Not the destination of this payment.")
      return
    }
    if (typeof tx.meta.delivered_amount === "string") {
      const amount_in_drops = new Big(tx.meta.delivered_amount)
      const xrp_amount = amount_in_drops.div(10e6)
      console.log("Received " + xrp_amount.toString() + " XRP.")
      return
    } else {
      console.log("Received non-XRP currency.")
      return
    }
  } elif (["PaymentChannelClaim", "PaymentChannelFund", "OfferCreate",
          "CheckCash", "EscrowFinish"].includes(tx.transaction.TransactionType) {
    CountXRPDifference(tx.meta.AffectedNodes, address)
  } else {
    console.log("Not a currency-delivering transaction type (" +
                tx.transaction.TransactionType + ").")
  }
}