Set Fee currency (#8)

Fees are by default paid with the fiat money. This means that you bought
crypto for the specified amount (e.g. 25 USD) and the fees are charged
separately. When you want to spend 100 USD over 4 weeks, meaning 1 order
per week, the last order won't be placed since there is not enough fiat
money left.
In my case I wanted to spend 100 EUR a month, meaning 25 € once per
week. When testing it the first time I was charged 25,065 EUR. By
setting the fee to XBT instead of EUR, I can run the script 4 times a
month.

README.md

@@ -36,6 +36,7 @@ KRAKEN_API_SECRET="privateKeyFromTheKrakenSettings"
 KRAKEN_ORDER_TYPE="market" # "limit" (default) or "market"
 KRAKEN_API_FIAT="USD" # the governmental shitcoin you are selling
 KRAKEN_BUY_AMOUNT=21 # fiat amount you trade for the future of money
+KRAKEN_FEE_CURRENCY="XBT" # pay fee in this currency, e.g. buying XBT for USD and paying fee in XBT
 
 # used for withdrawal
 KRAKEN_MAX_REL_FEE=0.5 # maximum fee in % that you are willing to pay

commands/stack.js

@@ -1,5 +1,5 @@
 module.exports = async (kraken, validate, { getEnv, getEnvOpt }) => {
-  const [fiat, amount] = getEnv('KRAKEN_API_FIAT', 'KRAKEN_BUY_AMOUNT')
+  const [fiat, amount, feeCurrency] = getEnv('KRAKEN_API_FIAT', 'KRAKEN_BUY_AMOUNT', 'KRAKEN_FEE_CURRENCY')
   const ordertype = getEnvOpt('KRAKEN_ORDER_TYPE', 'limit', ['limit', 'market'])
   // if living in Germany, one needs to add an additional parameter to explicitly agree to the trade
   // if the parameter is not set one will get the following error: EOrder:Trading agreement required
@@ -10,6 +10,16 @@ module.exports = async (kraken, validate, { getEnv, getEnvOpt }) => {
   const crypto = 'XBT'
   const pair = `${crypto}${fiat}`
 
+  // for explanation of oflags see https://www.kraken.com/features/api#add-standard-order
+  var fee = ""
+  if (feeCurrency == crypto) {
+    fee = "fcib"
+  } else if (feeCurrency == fiat) {
+    fee = "fciq"
+  } else {
+    fee = ""
+  }
+
   // Fetch and display information
   const { result: balance } = await kraken.api('Balance')
   const { result: ticker } = await kraken.api('Ticker', { pair })
@@ -32,6 +42,7 @@ module.exports = async (kraken, validate, { getEnv, getEnvOpt }) => {
   const details = { pair, type: 'buy', ordertype, price, volume }
   if (validate) details.validate = true
   if (trading_agreement) details.trading_agreement = trading_agreement
+  if (fee) details.oflags = fee
 
   const { result: { descr: { order }, txid } } = await kraken.api('AddOrder', details)