func (w *writecache) Put(b *blocks.Block) error {
	if _, ok := w.cache.Get(b.Key()); ok {
		return nil
	}
	w.cache.Add(b.Key(), struct{}{})
	return w.blockstore.Put(b)
}

// HasBlock announces the existance of a block to this bitswap service. The
// service will potentially notify its peers.
func (bs *Bitswap) HasBlock(blk blocks.Block) error {
	select {
	case <-bs.process.Closing():
		return errors.New("bitswap is closed")
	default:
	}

	err := bs.blockstore.Put(blk)
	if err != nil {
		log.Errorf("Error writing block to datastore: %s", err)
		return err
	}

	// NOTE: There exists the possiblity for a race condition here.  If a user
	// creates a node, then adds it to the dagservice while another goroutine
	// is waiting on a GetBlock for that object, they will receive a reference
	// to the same node. We should address this soon, but i'm not going to do
	// it now as it requires more thought and isnt causing immediate problems.
	bs.notifications.Publish(blk)

	bs.engine.AddBlock(blk)

	select {
	case bs.newBlocks <- blk.Cid():
		// send block off to be reprovided
	case <-bs.process.Closing():
		return bs.process.Close()
	}
	return nil
}

func assertBlocksEqual(t *testing.T, a, b *blocks.Block) {
	if !bytes.Equal(a.Data, b.Data) {
		t.Fatal("blocks aren't equal")
	}
	if a.Key() != b.Key() {
		t.Fatal("block keys aren't equal")
	}
}

func getOrFail(bitswap Instance, b *blocks.Block, t *testing.T, wg *sync.WaitGroup) {
	if _, err := bitswap.Blockstore().Get(b.Key()); err != nil {
		_, err := bitswap.Exchange.GetBlock(context.Background(), b.Key())
		if err != nil {
			t.Fatal(err)
		}
	}
	wg.Done()
}

func (bs *blockstore) Put(block blocks.Block) error {
	k := dshelp.CidToDsKey(block.Cid())

	// Has is cheaper than Put, so see if we already have it
	exists, err := bs.datastore.Has(k)
	if err == nil && exists {
		return nil // already stored.
	}
	return bs.datastore.Put(k, block.RawData())
}

func (w *writecache) Put(b blocks.Block) error {
	k := b.Key()
	if _, ok := w.cache.Get(k); ok {
		return nil
	}
	defer log.EventBegin(context.TODO(), "writecache.BlockAdded", &k).Done()

	w.cache.Add(b.Key(), struct{}{})
	return w.blockstore.Put(b)
}

func (s *BlockList) Push(b *blocks.Block) {
	if s.uniques == nil {
		s.uniques = make(map[key.Key]*list.Element)
	}
	_, ok := s.uniques[b.Key()]
	if !ok {
		e := s.list.PushBack(b)
		s.uniques[b.Key()] = e
	}
}

func (bs *blockstore) Put(block *blocks.Block) error {
	k := block.Key().DsKey()

	// Has is cheaper than Put, so see if we already have it
	exists, err := bs.datastore.Has(k)
	if err == nil && exists {
		return nil // already stored.
	}
	return bs.datastore.Put(k, block.Data)
}

func (b *bloomcache) Put(bl blocks.Block) error {
	if has, ok := b.hasCached(bl.Cid()); ok && has {
		return nil
	}

	err := b.blockstore.Put(bl)
	if err == nil {
		b.bloom.AddTS(bl.Cid().Bytes())
	}
	return err
}

func (b *arccache) Put(bl blocks.Block) error {
	if has, ok := b.hasCached(bl.Cid()); ok && has {
		return nil
	}

	err := b.blockstore.Put(bl)
	if err == nil {
		b.addCache(bl.Cid(), true)
	}
	return err
}

// AddBlock adds a particular block to the service, Putting it into the datastore.
// TODO pass a context into this if the remote.HasBlock is going to remain here.
func (s *BlockService) AddBlock(b *blocks.Block) (key.Key, error) {
	k := b.Key()
	err := s.Blockstore.Put(b)
	if err != nil {
		return k, err
	}
	if err := s.worker.HasBlock(b); err != nil {
		return "", errors.New("blockservice is closed")
	}
	return k, nil
}

func assertBlocksEqual(t *testing.T, a, b blocks.Block) {
	if !bytes.Equal(a.RawData(), b.RawData()) {
		t.Fatal("blocks aren't equal")
	}
	if a.Cid() != b.Cid() {
		t.Fatal("block keys aren't equal")
	}
}

func getCmd(nodes []int, block *blocks.Block) error {
	var wg sync.WaitGroup
	for _, node := range nodes {
		wg.Add(1)
		go func(i int) {
			ctx, cancel := context.WithTimeout(context.Background(), deadline)
			defer cancel()

			peers[i].Exchange.GetBlock(ctx, block.Key())
			fmt.Printf("Gotem from node %d.\n", i)
			peers[i].Exchange.Close()
			wg.Done()
		}(node)
	}

	wg.Wait()
	return nil
}

func (bs *Bitswap) updateReceiveCounters(b blocks.Block) error {
	bs.counterLk.Lock()
	defer bs.counterLk.Unlock()
	bs.blocksRecvd++
	has, err := bs.blockstore.Has(b.Cid())
	if err != nil {
		log.Infof("blockstore.Has error: %s", err)
		return err
	}
	if err == nil && has {
		bs.dupBlocksRecvd++
		bs.dupDataRecvd += uint64(len(b.RawData()))
	}

	if has {
		return ErrAlreadyHaveBlock
	}
	return nil
}

// Add adds a node to the dagService, storing the block in the BlockService
func (n *dagService) Add(nd *Node) (key.Key, error) {
	if n == nil { // FIXME remove this assertion. protect with constructor invariant
		return "", fmt.Errorf("dagService is nil")
	}

	d, err := nd.Encoded(false)
	if err != nil {
		return "", err
	}

	b := new(blocks.Block)
	b.Data = d
	b.Multihash, err = nd.Multihash()
	if err != nil {
		return "", err
	}

	return n.Blocks.AddBlock(b)
}

func decodeBlock(b blocks.Block) (node.Node, error) {
	c := b.Cid()

	switch c.Type() {
	case cid.Protobuf:
		decnd, err := DecodeProtobuf(b.RawData())
		if err != nil {
			if strings.Contains(err.Error(), "Unmarshal failed") {
				return nil, fmt.Errorf("The block referred to by '%s' was not a valid merkledag node", c)
			}
			return nil, fmt.Errorf("Failed to decode Protocol Buffers: %v", err)
		}

		decnd.cached = b.Cid()
		return decnd, nil
	case cid.Raw:
		return NewRawNode(b.RawData()), nil
	case cid.CBOR:
		return ipldcbor.Decode(b.RawData())
	default:
		return nil, fmt.Errorf("unrecognized object type: %s", c.Type())
	}
}

// AddBlock adds a particular block to the service, Putting it into the datastore.
// TODO pass a context into this if the remote.HasBlock is going to remain here.
func (s *blockService) AddBlock(o blocks.Block) (*cid.Cid, error) {
	c := o.Cid()
	if s.checkFirst {
		has, err := s.blockstore.Has(c)
		if err != nil {
			return nil, err
		}

		if has {
			return c, nil
		}
	}

	err := s.blockstore.Put(o)
	if err != nil {
		return nil, err
	}

	if err := s.exchange.HasBlock(o); err != nil {
		return nil, errors.New("blockservice is closed")
	}

	return c, nil
}

func (b *bloomcache) Put(bl blocks.Block) error {
	if has, ok := b.hasCached(bl.Key()); ok && has {
		return nil
	}

	err := b.blockstore.Put(bl)
	if err == nil {
		b.bloom.AddTS([]byte(bl.Key()))
		b.arc.Add(bl.Key(), true)
	}
	return err
}

func (m *impl) AddBlock(b blocks.Block) {
	m.blocks[b.Cid().KeyString()] = b
}

func (m *impl) AddBlock(b blocks.Block) {
	m.blocks[b.Key()] = b
}