v12.0.0 - initial commit

packages/server/lib/commission-math.js

@@ -0,0 +1,59 @@
+const BN = require('./bn')
+const configManager = require('./new-config-manager')
+const { utils: coinUtils } = require('@lamassu/coins')
+
+function truncateCrypto(cryptoAtoms, cryptoCode) {
+  const DECIMAL_PLACES = 6
+  if (cryptoAtoms.eq(0)) return cryptoAtoms
+
+  const scale = coinUtils.getCryptoCurrency(cryptoCode).unitScale
+  const scaleFactor = BN(10).pow(scale)
+
+  return new BN(cryptoAtoms)
+    .integerValue(BN.ROUND_DOWN)
+    .div(scaleFactor)
+    .decimalPlaces(DECIMAL_PLACES)
+    .times(scaleFactor)
+}
+
+function convertFiatToCryptoAtoms(fiatAmount, rate, cryptoCode) {
+  const unitScale = coinUtils.getCryptoCurrency(cryptoCode).unitScale
+  const unitScaleFactor = new BN(10).pow(unitScale)
+
+  const cryptoValue = new BN(fiatAmount).div(rate)
+  return cryptoValue.times(unitScaleFactor).integerValue(BN.ROUND_DOWN)
+}
+
+function fiatToCrypto(tx, rec, deviceId, config) {
+  const usableFiat = rec.fiat - rec.cashInFee
+
+  const commissions = configManager.getCommissions(
+    tx.cryptoCode,
+    deviceId,
+    config,
+  )
+  const tickerRate = new BN(tx.rawTickerPrice)
+  const discount = getDiscountRate(tx.discount, commissions[tx.direction])
+  const rate = tickerRate.times(discount).decimalPlaces(5)
+  const unitScale = coinUtils.getCryptoCurrency(tx.cryptoCode).unitScale
+  const unitScaleFactor = new BN(10).pow(unitScale)
+
+  return truncateCrypto(
+    new BN(usableFiat).div(rate.div(unitScaleFactor)),
+    tx.cryptoCode,
+  )
+}
+
+function getDiscountRate(discount, commission) {
+  const bnDiscount = discount ? new BN(discount) : new BN(0)
+  const bnCommission = new BN(commission)
+  const percentageDiscount = new BN(1).minus(bnDiscount.div(100))
+  const percentageCommission = bnCommission.div(100)
+  return new BN(1).plus(percentageDiscount.times(percentageCommission))
+}
+
+module.exports = {
+  fiatToCrypto,
+  getDiscountRate,
+  convertFiatToCryptoAtoms,
+}