apply PayloadSender fix from #1886 and add unit test

libraries/botframework-streaming/src/payloadTransport/payloadSender.ts

@@ -70,16 +70,26 @@ export class PayloadSender {
 
     private writePacket(packet: ISendPacket): void {
         try {
-            let sendHeaderBuffer: Buffer = Buffer.alloc(PayloadConstants.MaxHeaderLength);
-            HeaderSerializer.serialize(packet.header, sendHeaderBuffer);
-            this.sender.send(sendHeaderBuffer);
-
             if (packet.header.payloadLength > 0 && packet.payload) {
-                let count = packet.header.payloadLength;
-                while (count > 0) {
+
+                let leftOver = packet.header.payloadLength;
+
+                while (leftOver > 0) {                   
+                    let count = leftOver <= PayloadConstants.MaxPayloadLength ? leftOver : PayloadConstants.MaxPayloadLength;
                     let chunk = packet.payload.read(count);
+
+                    var header = packet.header;
+                    header.payloadLength = count;
+                    header.end = leftOver <= PayloadConstants.MaxPayloadLength;
+
+                    let sendHeaderBuffer: Buffer = Buffer.alloc(PayloadConstants.MaxHeaderLength);
+
+                    HeaderSerializer.serialize(header, sendHeaderBuffer);
+
+                    this.sender.send(sendHeaderBuffer);
+
                     this.sender.send(chunk);
-                    count -= chunk.length;
+                    leftOver-= chunk.length;
                 }
 
                 if (packet.sentCallback) {

libraries/botframework-streaming/tests/PayloadSender.test.js

@@ -5,6 +5,7 @@ const PayloadReceiver = require('../lib/PayloadTransport/payloadReceiver');
 const PayloadTypes = require('../lib/payloads/payloadTypes');
 const PayloadAssemblerManager = require('../lib/payloads/payloadAssemblerManager');
 const  chai  = require('chai');
+var sinon = require('sinon');
 var expect = chai.expect;
 
 class FauxSock{
@@ -38,7 +39,6 @@ class FauxSock{
 }
 describe('PayloadTransport', () => {
     describe('PayloadSender', () => {
-
         it('starts out disconnected.', () => {
             let ps = new PayloadSender.PayloadSender();
             expect(ps.isConnected).to.equal(false);
@@ -57,10 +57,50 @@ describe('PayloadTransport', () => {
 
             let stream = new SubscribableStream.SubscribableStream();
             stream.write('This is a test stream.');
-            let header = {payloadType: PayloadTypes.PayloadTypes.request, payloadLength: 22, id: '100', end: true};
-            let packet = {header: header, payload: stream, sendCallBack: undefined};
-
+            let header = {
+                payloadType: PayloadTypes.PayloadTypes.request,
+                payloadLength: stream.length,
+                id: '100',
+                end: true
+            };
+
+            const psSenderSpy = sinon.spy(ps.sender, 'send');
             expect(ps.sendPayload(header, stream, ()=>done()));
+            expect(psSenderSpy.calledTwice).to.be.true;
+        });
+
+        it('writes a large stream to its sender.', (done) => {
+            const ps = new PayloadSender.PayloadSender();
+            ps.connect(new FauxSock);
+            expect(ps.isConnected).to.equal(true);
+
+            const stream = new SubscribableStream.SubscribableStream();
+            let testString;
+            let count = 250;
+            while (count >= 0) {
+                testString += 'This is a LARGE test stream.';
+                count--;
+            }
+
+            stream.write(testString);
+            // Max PayloadLength is 4096
+            const header = {
+                payloadType: PayloadTypes.PayloadTypes.request,
+                payloadLength: stream.length,
+                id: '100',
+                end: true
+            };
+            const psSenderSpy = sinon.spy(ps.sender, 'send');
+
+            expect(ps.sendPayload(header, stream, () => {
+                // This try-catch is required as chai failures need to be caught and bubbled up via done(). 
+                try {
+                    expect(psSenderSpy.callCount).to.equal(4);
+                    done();
+                } catch (e) { 
+                    done(e);
+                }
+            }));
         });
 
         it('calls the packet sent callback.', (done) => {