func publish(ctx context.Context, n *core.IpfsNode, k crypto.PrivKey, ref path.Path, opts *publishOpts) (*IpnsEntry, error) {

	if opts.verifyExists {
		// verify the path exists
		_, err := core.Resolve(ctx, n, ref)
		if err != nil {
			return nil, err
		}
	}

	eol := time.Now().Add(opts.pubValidTime)
	err := n.Namesys.PublishWithEOL(ctx, k, ref, eol)
	if err != nil {
		return nil, err
	}

	hash, err := k.GetPublic().Hash()
	if err != nil {
		return nil, err
	}

	return &IpnsEntry{
		Name:  key.Key(hash).String(),
		Value: ref.String(),
	}, nil
}

func publish(ctx context.Context, n *core.IpfsNode, k crypto.PrivKey, ref path.Path, opts *publishOpts) (*IpnsEntry, error) {

	if opts.verifyExists {
		// verify the path exists
		_, err := core.Resolve(ctx, n.Namesys, n.Resolver, ref)
		if err != nil {
			return nil, err
		}
	}

	eol := time.Now().Add(opts.pubValidTime)
	err := n.Namesys.PublishWithEOL(ctx, k, ref, eol)
	if err != nil {
		return nil, err
	}

	pid, err := peer.IDFromPrivateKey(k)
	if err != nil {
		return nil, err
	}

	return &IpnsEntry{
		Name:  pid.Pretty(),
		Value: ref.String(),
	}, nil
}

func (ns *mpns) addToDHTCache(key ci.PrivKey, value path.Path, eol time.Time) {
	rr, ok := ns.resolvers["dht"].(*routingResolver)
	if !ok {
		// should never happen, purely for sanity
		log.Panicf("unexpected type %T as DHT resolver.", ns.resolvers["dht"])
	}
	if rr.cache == nil {
		// resolver has no caching
		return
	}

	var err error
	value, err = path.ParsePath(value.String())
	if err != nil {
		log.Error("could not parse path")
		return
	}

	name, err := peer.IDFromPrivateKey(key)
	if err != nil {
		log.Error("while adding to cache, could not get peerid from private key")
		return
	}

	if time.Now().Add(DefaultResolverCacheTTL).Before(eol) {
		eol = time.Now().Add(DefaultResolverCacheTTL)
	}
	rr.cache.Add(name.Pretty(), cacheEntry{
		val: value,
		eol: eol,
	})
}

func NewReader(path path.Path, dag mdag.DAGService, dagnode *mdag.Node, compression int) (*Reader, error) {

	reader := &Reader{
		signalChan: make(chan struct{}),
		dag:        dag,
	}

	var err error
	if compression != gzip.NoCompression {
		reader.gzipWriter, err = gzip.NewWriterLevel(&reader.buf, compression)
		if err != nil {
			return nil, err
		}
		reader.writer = tar.NewWriter(reader.gzipWriter)
	} else {
		reader.writer = tar.NewWriter(&reader.buf)
	}

	// writeToBuf will write the data to the buffer, and will signal when there
	// is new data to read
	_, filename := gopath.Split(path.String())
	go reader.writeToBuf(dagnode, filename, 0)

	return reader, nil
}

// resolveOnce implements resolver.
// TXT records for a given domain name should contain a b58
// encoded multihash.
func (r *DNSResolver) resolveOnce(ctx context.Context, name string) (path.Path, error) {
	segments := strings.SplitN(name, "/", 2)
	domain := segments[0]

	if !isd.IsDomain(domain) {
		return "", errors.New("not a valid domain name")
	}
	log.Infof("DNSResolver resolving %s", domain)

	rootChan := make(chan lookupRes, 1)
	go workDomain(r, domain, rootChan)

	subChan := make(chan lookupRes, 1)
	go workDomain(r, "_dnslink."+domain, subChan)

	var subRes lookupRes
	select {
	case subRes = <-subChan:
	case <-ctx.Done():
		return "", ctx.Err()
	}

	var p path.Path
	if subRes.error == nil {
		p = subRes.path
	} else {
		var rootRes lookupRes
		select {
		case rootRes = <-rootChan:
		case <-ctx.Done():
			return "", ctx.Err()
		}
		if rootRes.error == nil {
			p = rootRes.path
		} else {
			return "", ErrResolveFailed
		}
	}
	if len(segments) > 1 {
		return path.FromSegments("", strings.TrimRight(p.String(), "/"), segments[1])
	} else {
		return p, nil
	}
}

// ResolveToKey resolves a path to a key.
//
// It first checks if the path is already in the form of just a key (<key> or
// /ipfs/<key>) and returns immediately if so. Otherwise, it falls back onto
// Resolve to perform resolution of the dagnode being referenced.
func ResolveToKey(ctx context.Context, n *IpfsNode, p path.Path) (key.Key, error) {

	// If the path is simply a key, parse and return it. Parsed paths are already
	// normalized (read: prepended with /ipfs/ if needed), so segment[1] should
	// always be the key.
	if p.IsJustAKey() {
		return key.B58KeyDecode(p.Segments()[1]), nil
	}

	// Fall back onto regular dagnode resolution. Retrieve the second-to-last
	// segment of the path and resolve its link to the last segment.
	head, tail, err := p.PopLastSegment()
	if err != nil {
		return key.Key(""), err
	}
	dagnode, err := Resolve(ctx, n, head)
	if err != nil {
		return key.Key(""), err
	}

	// Extract and return the key of the link to the target dag node.
	link, err := dagnode.GetNodeLink(tail)
	if err != nil {
		return key.Key(""), err
	}

	return key.Key(link.Hash), nil
}

// ResolveToKey resolves a path to a key.
//
// It first checks if the path is already in the form of just a key (<key> or
// /ipfs/<key>) and returns immediately if so. Otherwise, it falls back onto
// Resolve to perform resolution of the dagnode being referenced.
func ResolveToCid(ctx context.Context, n *IpfsNode, p path.Path) (*cid.Cid, error) {

	// If the path is simply a key, parse and return it. Parsed paths are already
	// normalized (read: prepended with /ipfs/ if needed), so segment[1] should
	// always be the key.
	if p.IsJustAKey() {
		return cid.Decode(p.Segments()[1])
	}

	// Fall back onto regular dagnode resolution. Retrieve the second-to-last
	// segment of the path and resolve its link to the last segment.
	head, tail, err := p.PopLastSegment()
	if err != nil {
		return nil, err
	}
	dagnode, err := Resolve(ctx, n.Namesys, n.Resolver, head)
	if err != nil {
		return nil, err
	}

	// Extract and return the key of the link to the target dag node.
	link, _, err := dagnode.ResolveLink([]string{tail})
	if err != nil {
		return nil, err
	}

	return link.Cid, nil
}

func publish(ctx context.Context, n *core.IpfsNode, k crypto.PrivKey, ref path.Path) (*IpnsEntry, error) {
	// First, verify the path exists
	_, err := core.Resolve(ctx, n, ref)
	if err != nil {
		return nil, err
	}

	err = n.Namesys.Publish(ctx, k, ref)
	if err != nil {
		return nil, err
	}

	hash, err := k.GetPublic().Hash()
	if err != nil {
		return nil, err
	}

	return &IpnsEntry{
		Name:  key.Key(hash).String(),
		Value: ref.String(),
	}, nil
}

// Resolve resolves the given path by parsing out protocol-specific
// entries (e.g. /ipns/<node-key>) and then going through the /ipfs/
// entries and returning the final merkledag node.  Effectively
// enables /ipns/, /dns/, etc. in commands.
func Resolve(ctx context.Context, n *IpfsNode, p path.Path) (*merkledag.Node, error) {
	if strings.HasPrefix(p.String(), "/ipns/") {
		// resolve ipns paths

		// TODO(cryptix): we sould be able to query the local cache for the path
		if n.Namesys == nil {
			return nil, ErrNoNamesys
		}

		seg := p.Segments()

		if len(seg) < 2 || seg[1] == "" { // just "/<protocol/>" without further segments
			return nil, path.ErrNoComponents
		}

		extensions := seg[2:]
		resolvable, err := path.FromSegments("/", seg[0], seg[1])
		if err != nil {
			return nil, err
		}

		respath, err := n.Namesys.Resolve(ctx, resolvable.String())
		if err != nil {
			return nil, err
		}

		segments := append(respath.Segments(), extensions...)
		p, err = path.FromSegments("/", segments...)
		if err != nil {
			return nil, err
		}
	}

	// ok, we have an ipfs path now (or what we'll treat as one)
	return n.Resolver.ResolvePath(ctx, p)
}