func TestSendMessageAsyncButWaitForResponse(t *testing.T) {
	net := VirtualNetwork(mockrouting.NewServer(), delay.Fixed(0))
	responderPeer := testutil.RandIdentityOrFatal(t)
	waiter := net.Adapter(testutil.RandIdentityOrFatal(t))
	responder := net.Adapter(responderPeer)

	var wg sync.WaitGroup

	wg.Add(1)

	expectedStr := "received async"

	responder.SetDelegate(lambda(func(
		ctx context.Context,
		fromWaiter peer.ID,
		msgFromWaiter bsmsg.BitSwapMessage) {

		msgToWaiter := bsmsg.New(true)
		msgToWaiter.AddBlock(blocks.NewBlock([]byte(expectedStr)))
		waiter.SendMessage(ctx, fromWaiter, msgToWaiter)
	}))

	waiter.SetDelegate(lambda(func(
		ctx context.Context,
		fromResponder peer.ID,
		msgFromResponder bsmsg.BitSwapMessage) {

		// TODO assert that this came from the correct peer and that the message contents are as expected
		ok := false
		for _, b := range msgFromResponder.Blocks() {
			if string(b.Data) == expectedStr {
				wg.Done()
				ok = true
			}
		}

		if !ok {
			t.Fatal("Message not received from the responder")
		}
	}))

	messageSentAsync := bsmsg.New(true)
	messageSentAsync.AddBlock(blocks.NewBlock([]byte("data")))
	errSending := waiter.SendMessage(
		context.Background(), responderPeer.ID(), messageSentAsync)
	if errSending != nil {
		t.Fatal(errSending)
	}

	wg.Wait() // until waiter delegate function is executed
}

func (mq *msgQueue) addMessage(entries []*bsmsg.Entry) {
	mq.outlk.Lock()
	defer func() {
		mq.outlk.Unlock()
		select {
		case mq.work <- struct{}{}:
		default:
		}
	}()

	// if we have no message held allocate a new one
	if mq.out == nil {
		mq.out = bsmsg.New(false)
	}

	// TODO: add a msg.Combine(...) method
	// otherwise, combine the one we are holding with the
	// one passed in
	for _, e := range entries {
		if e.Cancel {
			mq.out.Cancel(e.Cid)
		} else {
			mq.out.AddEntry(e.Cid, e.Priority)
		}
	}
}

func TestConsistentAccounting(t *testing.T) {
	ctx, cancel := context.WithCancel(context.Background())
	defer cancel()
	sender := newEngine(ctx, "Ernie")
	receiver := newEngine(ctx, "Bert")

	// Send messages from Ernie to Bert
	for i := 0; i < 1000; i++ {

		m := message.New(false)
		content := []string{"this", "is", "message", "i"}
		m.AddBlock(blocks.NewBlock([]byte(strings.Join(content, " "))))

		sender.Engine.MessageSent(receiver.Peer, m)
		receiver.Engine.MessageReceived(sender.Peer, m)
	}

	// Ensure sender records the change
	if sender.Engine.numBytesSentTo(receiver.Peer) == 0 {
		t.Fatal("Sent bytes were not recorded")
	}

	// Ensure sender and receiver have the same values
	if sender.Engine.numBytesSentTo(receiver.Peer) != receiver.Engine.numBytesReceivedFrom(sender.Peer) {
		t.Fatal("Inconsistent book-keeping. Strategies don't agree")
	}

	// Ensure sender didn't record receving anything. And that the receiver
	// didn't record sending anything
	if receiver.Engine.numBytesSentTo(sender.Peer) != 0 || sender.Engine.numBytesReceivedFrom(receiver.Peer) != 0 {
		t.Fatal("Bert didn't send bytes to Ernie")
	}
}

func partnerCancels(e *Engine, keys []string, partner peer.ID) {
	cancels := message.New(false)
	for _, k := range keys {
		block := blocks.NewBlock([]byte(k))
		cancels.Cancel(block.Cid())
	}
	e.MessageReceived(partner, cancels)
}

func partnerWants(e *Engine, keys []string, partner peer.ID) {
	add := message.New(false)
	for i, letter := range keys {
		block := blocks.NewBlock([]byte(letter))
		add.AddEntry(block.Cid(), math.MaxInt32-i)
	}
	e.MessageReceived(partner, add)
}

// TODO: use goprocess here once i trust it
func (pm *WantManager) Run() {
	tock := time.NewTicker(rebroadcastDelay.Get())
	defer tock.Stop()
	for {
		select {
		case entries := <-pm.incoming:

			// add changes to our wantlist
			var filtered []*bsmsg.Entry
			for _, e := range entries {
				if e.Cancel {
					if pm.wl.Remove(e.Cid) {
						filtered = append(filtered, e)
					}
				} else {
					if pm.wl.AddEntry(e.Entry) {
						filtered = append(filtered, e)
					}
				}
			}

			// broadcast those wantlist changes
			for _, p := range pm.peers {
				p.addMessage(filtered)
			}

		case <-tock.C:
			// resend entire wantlist every so often (REALLY SHOULDNT BE NECESSARY)
			var es []*bsmsg.Entry
			for _, e := range pm.wl.Entries() {
				es = append(es, &bsmsg.Entry{Entry: e})
			}

			for _, p := range pm.peers {
				p.outlk.Lock()
				p.out = bsmsg.New(true)
				p.outlk.Unlock()

				p.addMessage(es)
			}
		case p := <-pm.connect:
			pm.startPeerHandler(p)
		case p := <-pm.disconnect:
			pm.stopPeerHandler(p)
		case req := <-pm.peerReqs:
			var peers []peer.ID
			for p := range pm.peers {
				peers = append(peers, p)
			}
			req <- peers
		case <-pm.ctx.Done():
			return
		}
	}
}

func (pm *WantManager) SendBlock(ctx context.Context, env *engine.Envelope) {
	// Blocks need to be sent synchronously to maintain proper backpressure
	// throughout the network stack
	defer env.Sent()

	msg := bsmsg.New(false)
	msg.AddBlock(env.Block)
	log.Infof("Sending block %s to %s", env.Block, env.Peer)
	err := pm.network.SendMessage(ctx, env.Peer, msg)
	if err != nil {
		log.Infof("sendblock error: %s", err)
	}
}

// TODO: use goprocess here once i trust it
func (pm *WantManager) Run() {
	tock := time.NewTicker(rebroadcastDelay.Get())
	defer tock.Stop()
	for {
		select {
		case entries := <-pm.incoming:

			// add changes to our wantlist
			for _, e := range entries {
				if e.Cancel {
					pm.wl.Remove(e.Key)
				} else {
					pm.wl.Add(e.Key, e.Priority)
				}
			}

			// broadcast those wantlist changes
			for _, p := range pm.peers {
				p.addMessage(entries)
			}

		case <-tock.C:
			// resend entire wantlist every so often (REALLY SHOULDNT BE NECESSARY)
			var es []*bsmsg.Entry
			for _, e := range pm.wl.Entries() {
				es = append(es, &bsmsg.Entry{Entry: e})
			}
			for _, p := range pm.peers {
				p.outlk.Lock()
				p.out = bsmsg.New(true)
				p.outlk.Unlock()

				p.addMessage(es)
			}
		case p := <-pm.connect:
			pm.startPeerHandler(p)
		case p := <-pm.disconnect:
			pm.stopPeerHandler(p)
		case <-pm.ctx.Done():
			return
		}
	}
}

func (pm *WantManager) startPeerHandler(p peer.ID) *msgQueue {
	mq, ok := pm.peers[p]
	if ok {
		mq.refcnt++
		return nil
	}

	mq = pm.newMsgQueue(p)

	// new peer, we will want to give them our full wantlist
	fullwantlist := bsmsg.New(true)
	for _, e := range pm.wl.Entries() {
		fullwantlist.AddEntry(e.Cid, e.Priority)
	}
	mq.out = fullwantlist
	mq.work <- struct{}{}

	pm.peers[p] = mq
	go mq.runQueue(pm.ctx)
	return mq
}

func TestPeerIsAddedToPeersWhenMessageReceivedOrSent(t *testing.T) {

	ctx, cancel := context.WithCancel(context.Background())
	defer cancel()
	sanfrancisco := newEngine(ctx, "sf")
	seattle := newEngine(ctx, "sea")

	m := message.New(true)

	sanfrancisco.Engine.MessageSent(seattle.Peer, m)
	seattle.Engine.MessageReceived(sanfrancisco.Peer, m)

	if seattle.Peer == sanfrancisco.Peer {
		t.Fatal("Sanity Check: Peers have same Key!")
	}

	if !peerIsPartner(seattle.Peer, sanfrancisco.Engine) {
		t.Fatal("Peer wasn't added as a Partner")
	}

	if !peerIsPartner(sanfrancisco.Peer, seattle.Engine) {
		t.Fatal("Peer wasn't added as a Partner")
	}
}