Convert from Flow to Typescript (#816)

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

src/broadcast.ts

@@ -0,0 +1,73 @@
+
+import * as _ from 'lodash'
+import {RippleAPI} from './api'
+
+class RippleAPIBroadcast extends RippleAPI {
+
+  // TODO: Should this default to 0, or null/undefined?
+  ledgerVersion: number = 0
+  private _apis: RippleAPI[]
+
+  constructor(servers, options) {
+    super(options)
+
+    const apis: RippleAPI[] = servers.map(server => new RippleAPI(
+      _.assign({}, options, {server})
+    ))
+
+    // exposed for testing
+    this._apis = apis
+
+    this.getMethodNames().forEach(name => {
+      this[name] = function() { // eslint-disable-line no-loop-func
+        return Promise.race(apis.map(api => api[name](...arguments)))
+      }
+    })
+
+    // connection methods must be overridden to apply to all api instances
+    this.connect = async function() {
+      await Promise.all(apis.map(api => api.connect()))
+    }
+    this.disconnect = async function() {
+      await Promise.all(apis.map(api => api.disconnect()))
+    }
+    this.isConnected = function() {
+      return apis.map(api => api.isConnected()).every(Boolean)
+    }
+
+    // synchronous methods are all passed directly to the first api instance
+    const defaultAPI = apis[0]
+    const syncMethods = ['sign', 'generateAddress', 'computeLedgerHash']
+    syncMethods.forEach(name => {
+      this[name] = defaultAPI[name].bind(defaultAPI)
+    })
+
+    apis.forEach(api => {
+      api.on('ledger', this.onLedgerEvent.bind(this))
+      api.on('error', (errorCode, errorMessage, data) =>
+        this.emit('error', errorCode, errorMessage, data))
+    })
+  }
+
+  onLedgerEvent(ledger) {
+    if (ledger.ledgerVersion > this.ledgerVersion) {
+      this.ledgerVersion = ledger.ledgerVersion
+      this.emit('ledger', ledger)
+    }
+  }
+
+  getMethodNames() {
+    const methodNames: string[] = []
+    const rippleAPI = this._apis[0]
+    for (const name of Object.getOwnPropertyNames(rippleAPI)) {
+      if (typeof rippleAPI[name] === 'function') {
+        methodNames.push(name)
+      }
+    }
+    return methodNames
+  }
+}
+
+export {
+  RippleAPIBroadcast
+}