Convert from Flow to Typescript (#816)

* convert to typescript
* add docs for custom node typing
* update webpack, gulpfile

src/ledger/parse/account-order.ts

@@ -0,0 +1,46 @@
+import BigNumber from 'bignumber.js'
+import parseAmount from './amount'
+import {parseTimestamp, adjustQualityForXRP} from './utils'
+import {removeUndefined} from '../../common'
+import {orderFlags} from './flags'
+
+// TODO: remove this function once rippled provides quality directly
+function computeQuality(takerGets, takerPays) {
+  const quotient = new BigNumber(takerPays.value).dividedBy(takerGets.value)
+  return quotient.toDigits(16, BigNumber.ROUND_HALF_UP).toString()
+}
+
+// rippled 'account_offers' returns a different format for orders than 'tx'
+// the flags are also different
+function parseAccountOrder(address: string, order: any): Object {
+  const direction = (order.flags & orderFlags.Sell) === 0 ? 'buy' : 'sell'
+  const takerGetsAmount = parseAmount(order.taker_gets)
+  const takerPaysAmount = parseAmount(order.taker_pays)
+  const quantity = (direction === 'buy') ? takerPaysAmount : takerGetsAmount
+  const totalPrice = (direction === 'buy') ? takerGetsAmount : takerPaysAmount
+
+  // note: immediateOrCancel and fillOrKill orders cannot enter the order book
+  // so we can omit those flags here
+  const specification = removeUndefined({
+    direction: direction,
+    quantity: quantity,
+    totalPrice: totalPrice,
+    passive: ((order.flags & orderFlags.Passive) !== 0) || undefined,
+    // rippled currently does not provide "expiration" in account_offers
+    expirationTime: parseTimestamp(order.expiration)
+  })
+
+  const makerExchangeRate = order.quality ?
+    adjustQualityForXRP(order.quality.toString(),
+      takerGetsAmount.currency, takerPaysAmount.currency) :
+    computeQuality(takerGetsAmount, takerPaysAmount)
+  const properties = {
+    maker: address,
+    sequence: order.seq,
+    makerExchangeRate: makerExchangeRate
+  }
+
+  return {specification, properties}
+}
+
+export default parseAccountOrder