// 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)

	if !isd.IsDomain(segments[0]) {
		return "", errors.New("not a valid domain name")
	}

	log.Infof("DNSResolver resolving %s", segments[0])
	txt, err := r.lookupTXT(segments[0])
	if err != nil {
		return "", err
	}

	for _, t := range txt {
		p, err := parseEntry(t)
		if err == nil {
			if len(segments) > 1 {
				return path.FromSegments("", strings.TrimRight(p.String(), "/"), segments[1])
			}
			return p, nil
		}
	}

	return "", ErrResolveFailed
}

func TestRecurivePathResolution(t *testing.T) {
	ctx := context.Background()
	dstore := sync.MutexWrap(datastore.NewMapDatastore())
	bstore := blockstore.NewBlockstore(dstore)
	bserv, err := blockservice.New(bstore, offline.Exchange(bstore))
	if err != nil {
		t.Fatal(err)
	}

	dagService := merkledag.NewDAGService(bserv)

	a, _ := randNode()
	b, _ := randNode()
	c, cKey := randNode()

	err = b.AddNodeLink("grandchild", c)
	if err != nil {
		t.Fatal(err)
	}

	err = a.AddNodeLink("child", b)
	if err != nil {
		t.Fatal(err)
	}

	err = dagService.AddRecursive(a)
	if err != nil {
		t.Fatal(err)
	}

	aKey, err := a.Key()
	if err != nil {
		t.Fatal(err)
	}

	segments := []string{aKey.String(), "child", "grandchild"}
	p, err := path.FromSegments("/ipfs/", segments...)
	if err != nil {
		t.Fatal(err)
	}

	resolver := &path.Resolver{DAG: dagService}
	node, err := resolver.ResolvePath(ctx, p)
	if err != nil {
		t.Fatal(err)
	}

	key, err := node.Key()
	if err != nil {
		t.Fatal(err)
	}
	if key.String() != cKey.String() {
		t.Fatal(fmt.Errorf(
			"recursive path resolution failed for %s: %s != %s",
			p.String(), key.String(), cKey.String()))
	}
}

func TestRecurivePathResolution(t *testing.T) {
	ctx := context.Background()
	dagService := dagmock.Mock()

	a, _ := randNode()
	b, _ := randNode()
	c, cKey := randNode()

	err := b.AddNodeLink("grandchild", c)
	if err != nil {
		t.Fatal(err)
	}

	err = a.AddNodeLink("child", b)
	if err != nil {
		t.Fatal(err)
	}

	for _, n := range []*merkledag.Node{a, b, c} {
		_, err = dagService.Add(n)
		if err != nil {
			t.Fatal(err)
		}
	}

	aKey, err := a.Key()
	if err != nil {
		t.Fatal(err)
	}

	segments := []string{aKey.String(), "child", "grandchild"}
	p, err := path.FromSegments("/ipfs/", segments...)
	if err != nil {
		t.Fatal(err)
	}

	resolver := &path.Resolver{DAG: dagService}
	node, err := resolver.ResolvePath(ctx, p)
	if err != nil {
		t.Fatal(err)
	}

	key, err := node.Key()
	if err != nil {
		t.Fatal(err)
	}
	if key.String() != cKey.String() {
		t.Fatal(fmt.Errorf(
			"recursive path resolution failed for %s: %s != %s",
			p.String(), key.String(), cKey.String()))
	}
}

// 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)
}

// 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
	}
}

// resolveOnce implements resolver.
func (ns *mpns) resolveOnce(ctx context.Context, name string) (path.Path, error) {
	if !strings.HasPrefix(name, "/ipns/") {
		name = "/ipns/" + name
	}
	segments := strings.SplitN(name, "/", 4)
	if len(segments) < 3 || segments[0] != "" {
		log.Warningf("Invalid name syntax for %s", name)
		return "", ErrResolveFailed
	}

	for protocol, resolver := range ns.resolvers {
		log.Debugf("Attempting to resolve %s with %s", segments[2], protocol)
		p, err := resolver.resolveOnce(ctx, segments[2])
		if err == nil {
			if len(segments) > 3 {
				return path.FromSegments("", strings.TrimRight(p.String(), "/"), segments[3])
			} else {
				return p, err
			}
		}
	}
	log.Warningf("No resolver found for %s", name)
	return "", ErrResolveFailed
}