Convert from Flow to Typescript (#816)

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

src/ledger/balances.ts

@@ -0,0 +1,62 @@
+import * as utils from './utils'
+import {validate} from '../common'
+import {Connection} from '../common'
+import {TrustlinesOptions, Trustline} from './trustlines-types'
+
+
+type Balance = {
+  value: string,
+  currency: string,
+  counterparty?: string
+}
+
+type GetBalances = Array<Balance>
+
+function getTrustlineBalanceAmount(trustline: Trustline) {
+  return {
+    currency: trustline.specification.currency,
+    counterparty: trustline.specification.counterparty,
+    value: trustline.state.balance
+  }
+}
+
+function formatBalances(options, balances) {
+  const result = balances.trustlines.map(getTrustlineBalanceAmount)
+  if (!(options.counterparty ||
+       (options.currency && options.currency !== 'XRP')
+  )) {
+    const xrpBalance = {
+      currency: 'XRP',
+      value: balances.xrp
+    }
+    result.unshift(xrpBalance)
+  }
+  if (options.limit && result.length > options.limit) {
+    const toRemove = result.length - options.limit
+    result.splice(-toRemove, toRemove)
+  }
+  return result
+}
+
+function getLedgerVersionHelper(connection: Connection, optionValue?: number
+): Promise<number> {
+  if (optionValue !== undefined && optionValue !== null) {
+    return Promise.resolve(optionValue)
+  }
+  return connection.getLedgerVersion()
+}
+
+function getBalances(address: string, options: TrustlinesOptions = {}
+): Promise<GetBalances> {
+  validate.getTrustlines({address, options})
+
+  return Promise.all([
+    getLedgerVersionHelper(this.connection, options.ledgerVersion).then(
+      ledgerVersion =>
+        utils.getXRPBalance(this.connection, address, ledgerVersion)),
+    this.getTrustlines(address, options)
+  ]).then(results =>
+    formatBalances(options, {xrp: results[0], trustlines: results[1]}))
+}
+
+export default getBalances