func TestGetBlocksSequential(t *testing.T) {
	var servs = Mocks(t, 4)
	for _, s := range servs {
		defer s.Close()
	}
	bg := blocksutil.NewBlockGenerator()
	blks := bg.Blocks(50)

	var keys []key.Key
	for _, blk := range blks {
		keys = append(keys, blk.Key())
		servs[0].AddBlock(blk)
	}

	t.Log("one instance at a time, get blocks concurrently")

	for i := 1; i < len(servs); i++ {
		ctx, _ := context.WithTimeout(context.TODO(), time.Second*50)
		out := servs[i].GetBlocks(ctx, keys)
		gotten := make(map[key.Key]*blocks.Block)
		for blk := range out {
			if _, ok := gotten[blk.Key()]; ok {
				t.Fatal("Got duplicate block!")
			}
			gotten[blk.Key()] = blk
		}
		if len(gotten) != len(blks) {
			t.Fatalf("Didnt get enough blocks back: %d/%d", len(gotten), len(blks))
		}
	}
}

func TestDoesNotDeadLockIfContextCancelledBeforePublish(t *testing.T) {

	g := blocksutil.NewBlockGenerator()
	ctx, cancel := context.WithCancel(context.Background())
	n := New()
	defer n.Shutdown()

	t.Log("generate a large number of blocks. exceed default buffer")
	bs := g.Blocks(1000)
	ks := func() []key.Key {
		var keys []key.Key
		for _, b := range bs {
			keys = append(keys, b.Key())
		}
		return keys
	}()

	_ = n.Subscribe(ctx, ks...) // ignore received channel

	t.Log("cancel context before any blocks published")
	cancel()
	for _, b := range bs {
		n.Publish(b)
	}

	t.Log("publishing the large number of blocks to the ignored channel must not deadlock")
}

func TestBasicBitswap(t *testing.T) {
	net := tn.VirtualNetwork(mockrouting.NewServer(), delay.Fixed(kNetworkDelay))
	sg := NewTestSessionGenerator(net)
	defer sg.Close()
	bg := blocksutil.NewBlockGenerator()

	t.Log("Test a one node trying to get one block from another")

	instances := sg.Instances(2)
	blocks := bg.Blocks(1)
	err := instances[0].Exchange.HasBlock(blocks[0])
	if err != nil {
		t.Fatal(err)
	}

	ctx, cancel := context.WithTimeout(context.Background(), time.Second*5)
	defer cancel()
	blk, err := instances[1].Exchange.GetBlock(ctx, blocks[0].Key())
	if err != nil {
		t.Fatal(err)
	}

	t.Log(blk)
	for _, inst := range instances {
		err := inst.Exchange.Close()
		if err != nil {
			t.Fatal(err)
		}
	}
}

func TestGetBlocks(t *testing.T) {
	store := bstore()
	ex := Exchange(store)
	g := blocksutil.NewBlockGenerator()

	expected := g.Blocks(2)

	for _, b := range expected {
		if err := ex.HasBlock(context.Background(), b); err != nil {
			t.Fail()
		}
	}

	request := func() []key.Key {
		var ks []key.Key

		for _, b := range expected {
			ks = append(ks, b.Key())
		}
		return ks
	}()

	received, err := ex.GetBlocks(context.Background(), request)
	if err != nil {
		t.Fatal(err)
	}

	var count int
	for _ = range received {
		count++
	}
	if len(expected) != count {
		t.Fail()
	}
}

func exampleKeys() []*cid.Cid {
	res := make([]*cid.Cid, 1<<8)
	gen := bu.NewBlockGenerator()
	for i := uint64(0); i < 1<<8; i++ {
		res[i] = gen.Next().Cid()
	}
	return res
}

func TestDoubleGet(t *testing.T) {
	net := tn.VirtualNetwork(mockrouting.NewServer(), delay.Fixed(kNetworkDelay))
	sg := NewTestSessionGenerator(net)
	defer sg.Close()
	bg := blocksutil.NewBlockGenerator()

	t.Log("Test a one node trying to get one block from another")

	instances := sg.Instances(2)
	blocks := bg.Blocks(1)

	ctx1, cancel1 := context.WithCancel(context.Background())
	blkch1, err := instances[1].Exchange.GetBlocks(ctx1, []*cid.Cid{blocks[0].Cid()})
	if err != nil {
		t.Fatal(err)
	}

	ctx2, cancel2 := context.WithCancel(context.Background())
	defer cancel2()

	blkch2, err := instances[1].Exchange.GetBlocks(ctx2, []*cid.Cid{blocks[0].Cid()})
	if err != nil {
		t.Fatal(err)
	}

	// ensure both requests make it into the wantlist at the same time
	time.Sleep(time.Millisecond * 100)
	cancel1()

	_, ok := <-blkch1
	if ok {
		t.Fatal("expected channel to be closed")
	}

	err = instances[0].Exchange.HasBlock(blocks[0])
	if err != nil {
		t.Fatal(err)
	}

	select {
	case blk, ok := <-blkch2:
		if !ok {
			t.Fatal("expected to get the block here")
		}
		t.Log(blk)
	case <-time.After(time.Second * 5):
		t.Fatal("timed out waiting on block")
	}

	for _, inst := range instances {
		err := inst.Exchange.Close()
		if err != nil {
			t.Fatal(err)
		}
	}
}

func TestClose(t *testing.T) {
	vnet := tn.VirtualNetwork(mockrouting.NewServer(), delay.Fixed(kNetworkDelay))
	sesgen := NewTestSessionGenerator(vnet)
	defer sesgen.Close()
	bgen := blocksutil.NewBlockGenerator()

	block := bgen.Next()
	bitswap := sesgen.Next()

	bitswap.Exchange.Close()
	bitswap.Exchange.GetBlock(context.Background(), block.Key())
}

func TestClose(t *testing.T) {
	vnet := getVirtualNetwork()
	sesgen := NewTestSessionGenerator(vnet)
	defer sesgen.Close()
	bgen := blocksutil.NewBlockGenerator()

	block := bgen.Next()
	bitswap := sesgen.Next()

	bitswap.Exchange.Close()
	bitswap.Exchange.GetBlock(context.Background(), block.Cid())
}

// TODO simplify this test. get to the _essence_!
func TestSendToWantingPeer(t *testing.T) {
	if testing.Short() {
		t.SkipNow()
	}

	net := tn.VirtualNetwork(mockrouting.NewServer(), delay.Fixed(kNetworkDelay))
	sg := NewTestSessionGenerator(net)
	defer sg.Close()
	bg := blocksutil.NewBlockGenerator()

	prev := rebroadcastDelay.Set(time.Second / 2)
	defer func() { rebroadcastDelay.Set(prev) }()

	peers := sg.Instances(2)
	peerA := peers[0]
	peerB := peers[1]

	t.Logf("Session %v\n", peerA.Peer)
	t.Logf("Session %v\n", peerB.Peer)

	timeout := time.Second
	waitTime := time.Second * 5

	alpha := bg.Next()
	// peerA requests and waits for block alpha
	ctx, cancel := context.WithTimeout(context.Background(), waitTime)
	defer cancel()
	alphaPromise, err := peerA.Exchange.GetBlocks(ctx, []key.Key{alpha.Key()})
	if err != nil {
		t.Fatal(err)
	}

	// peerB announces to the network that he has block alpha
	ctx, cancel = context.WithTimeout(context.Background(), timeout)
	defer cancel()
	err = peerB.Exchange.HasBlock(ctx, alpha)
	if err != nil {
		t.Fatal(err)
	}

	// At some point, peerA should get alpha (or timeout)
	blkrecvd, ok := <-alphaPromise
	if !ok {
		t.Fatal("context timed out and broke promise channel!")
	}

	if blkrecvd.Key() != alpha.Key() {
		t.Fatal("Wrong block!")
	}

}

func PerformDistributionTest(t *testing.T, numInstances, numBlocks int) {
	ctx := context.Background()
	if testing.Short() {
		t.SkipNow()
	}
	net := tn.VirtualNetwork(mockrouting.NewServer(), delay.Fixed(kNetworkDelay))
	sg := NewTestSessionGenerator(net)
	defer sg.Close()
	bg := blocksutil.NewBlockGenerator()

	instances := sg.Instances(numInstances)
	blocks := bg.Blocks(numBlocks)

	t.Log("Give the blocks to the first instance")

	var blkeys []key.Key
	first := instances[0]
	for _, b := range blocks {
		blkeys = append(blkeys, b.Key())
		first.Exchange.HasBlock(ctx, b)
	}

	t.Log("Distribute!")

	wg := sync.WaitGroup{}
	for _, inst := range instances[1:] {
		wg.Add(1)
		go func(inst Instance) {
			defer wg.Done()
			outch, err := inst.Exchange.GetBlocks(ctx, blkeys)
			if err != nil {
				t.Fatal(err)
			}
			for _ = range outch {
			}
		}(inst)
	}
	wg.Wait()

	t.Log("Verify!")

	for _, inst := range instances {
		for _, b := range blocks {
			if _, err := inst.Blockstore().Get(b.Key()); err != nil {
				t.Fatal(err)
			}
		}
	}
}

func TestWriteThroughWorks(t *testing.T) {
	bstore := &PutCountingBlockstore{
		blockstore.NewBlockstore(dssync.MutexWrap(ds.NewMapDatastore())),
		0,
	}
	bstore2 := blockstore.NewBlockstore(dssync.MutexWrap(ds.NewMapDatastore()))
	exch := offline.Exchange(bstore2)
	bserv := NewWriteThrough(bstore, exch)
	bgen := butil.NewBlockGenerator()

	block := bgen.Next()

	t.Logf("PutCounter: %d", bstore.PutCounter)
	bserv.AddBlock(block)
	if bstore.PutCounter != 1 {
		t.Fatalf("expected just one Put call, have: %d", bstore.PutCounter)
	}

	bserv.AddBlock(block)
	if bstore.PutCounter != 2 {
		t.Fatal("Put should have called again, should be 2 is: %d", bstore.PutCounter)
	}
}

func PerformDistributionTest(t *testing.T, numInstances, numBlocks int) {
	ctx := context.Background()
	if testing.Short() {
		t.SkipNow()
	}
	net := tn.VirtualNetwork(mockrouting.NewServer(), delay.Fixed(kNetworkDelay))
	sg := NewTestSessionGenerator(net)
	defer sg.Close()
	bg := blocksutil.NewBlockGenerator()

	instances := sg.Instances(numInstances)
	blocks := bg.Blocks(numBlocks)

	t.Log("Give the blocks to the first instance")

	nump := len(instances) - 1
	// assert we're properly connected
	for _, inst := range instances {
		peers := inst.Exchange.wm.ConnectedPeers()
		for i := 0; i < 10 && len(peers) != nump; i++ {
			time.Sleep(time.Millisecond * 50)
			peers = inst.Exchange.wm.ConnectedPeers()
		}
		if len(peers) != nump {
			t.Fatal("not enough peers connected to instance")
		}
	}

	var blkeys []key.Key
	first := instances[0]
	for _, b := range blocks {
		blkeys = append(blkeys, b.Key())
		first.Exchange.HasBlock(b)
	}

	t.Log("Distribute!")

	wg := sync.WaitGroup{}
	errs := make(chan error)

	for _, inst := range instances[1:] {
		wg.Add(1)
		go func(inst Instance) {
			defer wg.Done()
			outch, err := inst.Exchange.GetBlocks(ctx, blkeys)
			if err != nil {
				errs <- err
			}
			for _ = range outch {
			}
		}(inst)
	}

	go func() {
		wg.Wait()
		close(errs)
	}()

	for err := range errs {
		if err != nil {
			t.Fatal(err)
		}
	}

	t.Log("Verify!")

	for _, inst := range instances {
		for _, b := range blocks {
			if _, err := inst.Blockstore().Get(b.Key()); err != nil {
				t.Fatal(err)
			}
		}
	}
}

func TestWantlistCleanup(t *testing.T) {
	net := tn.VirtualNetwork(mockrouting.NewServer(), delay.Fixed(kNetworkDelay))
	sg := NewTestSessionGenerator(net)
	defer sg.Close()
	bg := blocksutil.NewBlockGenerator()

	instances := sg.Instances(1)[0]
	bswap := instances.Exchange
	blocks := bg.Blocks(20)

	var keys []*cid.Cid
	for _, b := range blocks {
		keys = append(keys, b.Cid())
	}

	ctx, cancel := context.WithTimeout(context.Background(), time.Millisecond*50)
	defer cancel()
	_, err := bswap.GetBlock(ctx, keys[0])
	if err != context.DeadlineExceeded {
		t.Fatal("shouldnt have fetched any blocks")
	}

	time.Sleep(time.Millisecond * 50)

	if len(bswap.GetWantlist()) > 0 {
		t.Fatal("should not have anyting in wantlist")
	}

	ctx, cancel = context.WithTimeout(context.Background(), time.Millisecond*50)
	defer cancel()
	_, err = bswap.GetBlocks(ctx, keys[:10])
	if err != nil {
		t.Fatal(err)
	}

	<-ctx.Done()
	time.Sleep(time.Millisecond * 50)

	if len(bswap.GetWantlist()) > 0 {
		t.Fatal("should not have anyting in wantlist")
	}

	_, err = bswap.GetBlocks(context.Background(), keys[:1])
	if err != nil {
		t.Fatal(err)
	}

	ctx, cancel = context.WithCancel(context.Background())
	_, err = bswap.GetBlocks(ctx, keys[10:])
	if err != nil {
		t.Fatal(err)
	}

	time.Sleep(time.Millisecond * 50)
	if len(bswap.GetWantlist()) != 11 {
		t.Fatal("should have 11 keys in wantlist")
	}

	cancel()
	time.Sleep(time.Millisecond * 50)
	if !(len(bswap.GetWantlist()) == 1 && bswap.GetWantlist()[0] == keys[0]) {
		t.Fatal("should only have keys[0] in wantlist")
	}
}