// adds a '-' to the beginning of each path element so we can use 'data' as a
// special link in the structure without having to worry about
func escapePath(pth string) string {
	elems := path.SplitList(strings.Trim(pth, "/"))
	for i, e := range elems {
		elems[i] = "-" + e
	}
	return path.Join(elems)
}

// Mkdir creates a directory at 'path' under the directory 'd', creating
// intermediary directories as needed if 'mkparents' is set to true
func Mkdir(r *Root, pth string, mkparents bool, flush bool) error {
	if pth == "" {
		return fmt.Errorf("no path given to Mkdir")
	}
	parts := path.SplitList(pth)
	if parts[0] == "" {
		parts = parts[1:]
	}

	// allow 'mkdir /a/b/c/' to create c
	if parts[len(parts)-1] == "" {
		parts = parts[:len(parts)-1]
	}

	if len(parts) == 0 {
		// this will only happen on 'mkdir /'
		if mkparents {
			return nil
		}
		return fmt.Errorf("cannot create directory '/': Already exists")
	}

	cur := r.GetValue().(*Directory)
	for i, d := range parts[:len(parts)-1] {
		fsn, err := cur.Child(d)
		if err == os.ErrNotExist && mkparents {
			mkd, err := cur.Mkdir(d)
			if err != nil {
				return err
			}
			fsn = mkd
		} else if err != nil {
			return err
		}

		next, ok := fsn.(*Directory)
		if !ok {
			return fmt.Errorf("%s was not a directory", path.Join(parts[:i]))
		}
		cur = next
	}

	final, err := cur.Mkdir(parts[len(parts)-1])
	if err != nil {
		if !mkparents || err != os.ErrExist || final == nil {
			return err
		}
	}

	if flush {
		err := final.Flush()
		if err != nil {
			return err
		}
	}

	return nil
}

func escapeDhtKey(s string) (key.Key, error) {
	parts := path.SplitList(s)
	switch len(parts) {
	case 1:
		return key.B58KeyDecode(s), nil
	case 3:
		k := key.B58KeyDecode(parts[2])
		return key.Key(path.Join(append(parts[:2], k.String()))), nil
	default:
		return "", errors.New("invalid key")
	}
}

func escapeDhtKey(s string) (string, error) {
	parts := path.SplitList(s)
	switch len(parts) {
	case 1:
		return string(b58.Decode(s)), nil
	case 3:
		k := b58.Decode(parts[2])
		return path.Join(append(parts[:2], string(k))), nil
	default:
		return "", errors.New("invalid key")
	}
}

// Resolve returns the subcommands at the given path
func (c *Command) Resolve(pth []string) ([]*Command, error) {
	cmds := make([]*Command, len(pth)+1)
	cmds[0] = c

	cmd := c
	for i, name := range pth {
		cmd = cmd.Subcommand(name)

		if cmd == nil {
			pathS := path.Join(pth[:i])
			return nil, fmt.Errorf("Undefined command: '%s'", pathS)
		}

		cmds[i+1] = cmd
	}

	return cmds, nil
}

// Lookup performs a lookup under this node.
func (s *Root) Lookup(ctx context.Context, name string) (fs.Node, error) {
	switch name {
	case "mach_kernel", ".hidden", "._.":
		// Just quiet some log noise on OS X.
		return nil, fuse.ENOENT
	}

	if lnk, ok := s.LocalLinks[name]; ok {
		return lnk, nil
	}

	nd, ok := s.LocalDirs[name]
	if ok {
		switch nd := nd.(type) {
		case *Directory:
			return nd, nil
		case *FileNode:
			return nd, nil
		default:
			return nil, fuse.EIO
		}
	}

	// other links go through ipns resolution and are symlinked into the ipfs mountpoint
	resolved, err := s.Ipfs.Namesys.Resolve(s.Ipfs.Context(), name)
	if err != nil {
		log.Warningf("ipns: namesys resolve error: %s", err)
		return nil, fuse.ENOENT
	}

	segments := resolved.Segments()
	if segments[0] == "ipfs" {
		p := path.Join(resolved.Segments()[1:])
		return &Link{s.IpfsRoot + "/" + p}, nil
	}

	log.Error("Invalid path.Path: ", resolved)
	return nil, errors.New("invalid path from ipns record")
}

// DirLookup will look up a file or directory at the given path
// under the directory 'd'
func DirLookup(d *Directory, pth string) (FSNode, error) {
	pth = strings.Trim(pth, "/")
	parts := path.SplitList(pth)
	if len(parts) == 1 && parts[0] == "" {
		return d, nil
	}

	var cur FSNode
	cur = d
	for i, p := range parts {
		chdir, ok := cur.(*Directory)
		if !ok {
			return nil, fmt.Errorf("cannot access %s: Not a directory", path.Join(parts[:i+1]))
		}

		child, err := chdir.Child(p)
		if err != nil {
			return nil, err
		}

		cur = child
	}
	return cur, nil
}

func (i *gatewayHandler) deleteHandler(w http.ResponseWriter, r *http.Request) {
	urlPath := r.URL.Path
	ctx, cancel := context.WithCancel(i.node.Context())
	defer cancel()

	ipfsNode, err := core.Resolve(ctx, i.node, path.Path(urlPath))
	if err != nil {
		// FIXME HTTP error code
		webError(w, "Could not resolve name", err, http.StatusInternalServerError)
		return
	}

	k, err := ipfsNode.Key()
	if err != nil {
		webError(w, "Could not get key from resolved node", err, http.StatusInternalServerError)
		return
	}

	h, components, err := path.SplitAbsPath(path.FromKey(k))
	if err != nil {
		webError(w, "Could not split path", err, http.StatusInternalServerError)
		return
	}

	tctx, cancel := context.WithTimeout(ctx, time.Minute)
	defer cancel()
	rootnd, err := i.node.Resolver.DAG.Get(tctx, key.Key(h))
	if err != nil {
		webError(w, "Could not resolve root object", err, http.StatusBadRequest)
		return
	}

	pathNodes, err := i.node.Resolver.ResolveLinks(tctx, rootnd, components[:len(components)-1])
	if err != nil {
		webError(w, "Could not resolve parent object", err, http.StatusBadRequest)
		return
	}

	// TODO(cyrptix): assumes len(pathNodes) > 1 - not found is an error above?
	err = pathNodes[len(pathNodes)-1].RemoveNodeLink(components[len(components)-1])
	if err != nil {
		webError(w, "Could not delete link", err, http.StatusBadRequest)
		return
	}

	newnode := pathNodes[len(pathNodes)-1]
	for i := len(pathNodes) - 2; i >= 0; i-- {
		newnode, err = pathNodes[i].UpdateNodeLink(components[i], newnode)
		if err != nil {
			webError(w, "Could not update node links", err, http.StatusInternalServerError)
			return
		}
	}

	if err := i.node.DAG.AddRecursive(newnode); err != nil {
		webError(w, "Could not add recursively new node", err, http.StatusInternalServerError)
		return
	}

	// Redirect to new path
	key, err := newnode.Key()
	if err != nil {
		webError(w, "Could not get key of new node", err, http.StatusInternalServerError)
		return
	}

	i.addUserHeaders(w) // ok, _now_ write user's headers.
	w.Header().Set("IPFS-Hash", key.String())
	http.Redirect(w, r, gopath.Join(ipfsPathPrefix+key.String(), path.Join(components[:len(components)-1])), http.StatusCreated)
}

func (i *gatewayHandler) putHandler(w http.ResponseWriter, r *http.Request) {
	// TODO(cryptix): move me to ServeHTTP and pass into all handlers
	ctx, cancel := context.WithCancel(i.node.Context())
	defer cancel()

	rootPath, err := path.ParsePath(r.URL.Path)
	if err != nil {
		webError(w, "putHandler: ipfs path not valid", err, http.StatusBadRequest)
		return
	}

	rsegs := rootPath.Segments()
	if rsegs[0] == ipnsPathPrefix {
		webError(w, "putHandler: updating named entries not supported", errors.New("WritableGateway: ipns put not supported"), http.StatusBadRequest)
		return
	}

	var newnode *dag.Node
	if rsegs[len(rsegs)-1] == "QmUNLLsPACCz1vLxQVkXqqLX5R1X345qqfHbsf67hvA3Nn" {
		newnode = uio.NewEmptyDirectory()
	} else {
		putNode, err := i.newDagFromReader(r.Body)
		if err != nil {
			webError(w, "putHandler: Could not create DAG from request", err, http.StatusInternalServerError)
			return
		}
		newnode = putNode
	}

	var newPath string
	if len(rsegs) > 1 {
		newPath = path.Join(rsegs[2:])
	}

	var newkey key.Key
	rnode, err := core.Resolve(ctx, i.node, rootPath)
	switch ev := err.(type) {
	case path.ErrNoLink:
		// ev.Node < node where resolve failed
		// ev.Name < new link
		// but we need to patch from the root
		rnode, err := i.node.DAG.Get(ctx, key.B58KeyDecode(rsegs[1]))
		if err != nil {
			webError(w, "putHandler: Could not create DAG from request", err, http.StatusInternalServerError)
			return
		}

		e := dagutils.NewDagEditor(rnode, i.node.DAG)
		err = e.InsertNodeAtPath(ctx, newPath, newnode, uio.NewEmptyDirectory)
		if err != nil {
			webError(w, "putHandler: InsertNodeAtPath failed", err, http.StatusInternalServerError)
			return
		}

		nnode, err := e.Finalize(i.node.DAG)
		if err != nil {
			webError(w, "putHandler: could not get node", err, http.StatusInternalServerError)
			return
		}

		newkey, err = nnode.Key()
		if err != nil {
			webError(w, "putHandler: could not get key of edited node", err, http.StatusInternalServerError)
			return
		}

	case nil:
		// object set-data case
		rnode.Data = newnode.Data

		newkey, err = i.node.DAG.Add(rnode)
		if err != nil {
			nnk, _ := newnode.Key()
			rk, _ := rnode.Key()
			webError(w, fmt.Sprintf("putHandler: Could not add newnode(%q) to root(%q)", nnk.B58String(), rk.B58String()), err, http.StatusInternalServerError)
			return
		}
	default:
		log.Warningf("putHandler: unhandled resolve error %T", ev)
		webError(w, "could not resolve root DAG", ev, http.StatusInternalServerError)
		return
	}

	i.addUserHeaders(w) // ok, _now_ write user's headers.
	w.Header().Set("IPFS-Hash", newkey.String())
	http.Redirect(w, r, gopath.Join(ipfsPathPrefix, newkey.String(), newPath), http.StatusCreated)
}

//.........这里部分代码省略.........
		w.Header().Set("Cache-Control", "public, max-age=29030400")

		// set modtime to a really long time ago, since files are immutable and should stay cached
		modtime = time.Unix(1, 0)
	}

	if err == nil {
		defer dr.Close()
		name := gopath.Base(urlPath)
		http.ServeContent(w, r, name, modtime, dr)
		return
	}

	// storage for directory listing
	var dirListing []directoryItem
	// loop through files
	foundIndex := false
	for _, link := range nd.Links {
		if link.Name == "index.html" {
			log.Debugf("found index.html link for %s", urlPath)
			foundIndex = true

			if urlPath[len(urlPath)-1] != '/' {
				// See comment above where originalUrlPath is declared.
				http.Redirect(w, r, originalUrlPath+"/", 302)
				log.Debugf("redirect to %s", originalUrlPath+"/")
				return
			}

			// return index page instead.
			nd, err := core.Resolve(ctx, i.node, path.Path(urlPath+"/index.html"))
			if err != nil {
				internalWebError(w, err)
				return
			}
			dr, err := uio.NewDagReader(ctx, nd, i.node.DAG)
			if err != nil {
				internalWebError(w, err)
				return
			}
			defer dr.Close()

			// write to request
			http.ServeContent(w, r, "index.html", modtime, dr)
			break
		}

		// See comment above where originalUrlPath is declared.
		di := directoryItem{humanize.Bytes(link.Size), link.Name, gopath.Join(originalUrlPath, link.Name)}
		dirListing = append(dirListing, di)
	}

	if !foundIndex {
		if r.Method != "HEAD" {
			// construct the correct back link
			// https://github.com/ipfs/go-ipfs/issues/1365
			var backLink string = prefix + urlPath

			// don't go further up than /ipfs/$hash/
			pathSplit := path.SplitList(backLink)
			switch {
			// keep backlink
			case len(pathSplit) == 3: // url: /ipfs/$hash

			// keep backlink
			case len(pathSplit) == 4 && pathSplit[3] == "": // url: /ipfs/$hash/

			// add the correct link depending on wether the path ends with a slash
			default:
				if strings.HasSuffix(backLink, "/") {
					backLink += "./.."
				} else {
					backLink += "/.."
				}
			}

			// strip /ipfs/$hash from backlink if IPNSHostnameOption touched the path.
			if ipnsHostname {
				backLink = prefix + "/"
				if len(pathSplit) > 5 {
					// also strip the trailing segment, because it's a backlink
					backLinkParts := pathSplit[3 : len(pathSplit)-2]
					backLink += path.Join(backLinkParts) + "/"
				}
			}

			// See comment above where originalUrlPath is declared.
			tplData := listingTemplateData{
				Listing:  dirListing,
				Path:     originalUrlPath,
				BackLink: backLink,
			}
			err := listingTemplate.Execute(w, tplData)
			if err != nil {
				internalWebError(w, err)
				return
			}
		}
	}
}

func (i *gatewayHandler) deleteHandler(w http.ResponseWriter, r *http.Request) {
	urlPath := r.URL.Path
	ctx, cancel := context.WithCancel(i.node.Context())
	defer cancel()

	p, err := path.ParsePath(urlPath)
	if err != nil {
		webError(w, "failed to parse path", err, http.StatusBadRequest)
		return
	}

	c, components, err := path.SplitAbsPath(p)
	if err != nil {
		webError(w, "Could not split path", err, http.StatusInternalServerError)
		return
	}

	tctx, cancel := context.WithTimeout(ctx, time.Minute)
	defer cancel()
	rootnd, err := i.node.Resolver.DAG.Get(tctx, c)
	if err != nil {
		webError(w, "Could not resolve root object", err, http.StatusBadRequest)
		return
	}

	pathNodes, err := i.node.Resolver.ResolveLinks(tctx, rootnd, components[:len(components)-1])
	if err != nil {
		webError(w, "Could not resolve parent object", err, http.StatusBadRequest)
		return
	}

	pbnd, ok := pathNodes[len(pathNodes)-1].(*dag.ProtoNode)
	if !ok {
		webError(w, "Cannot read non protobuf nodes through gateway", dag.ErrNotProtobuf, http.StatusBadRequest)
		return
	}

	// TODO(cyrptix): assumes len(pathNodes) > 1 - not found is an error above?
	err = pbnd.RemoveNodeLink(components[len(components)-1])
	if err != nil {
		webError(w, "Could not delete link", err, http.StatusBadRequest)
		return
	}

	var newnode *dag.ProtoNode = pbnd
	for j := len(pathNodes) - 2; j >= 0; j-- {
		if _, err := i.node.DAG.Add(newnode); err != nil {
			webError(w, "Could not add node", err, http.StatusInternalServerError)
			return
		}

		pathpb, ok := pathNodes[j].(*dag.ProtoNode)
		if !ok {
			webError(w, "Cannot read non protobuf nodes through gateway", dag.ErrNotProtobuf, http.StatusBadRequest)
			return
		}

		newnode, err = pathpb.UpdateNodeLink(components[j], newnode)
		if err != nil {
			webError(w, "Could not update node links", err, http.StatusInternalServerError)
			return
		}
	}

	if _, err := i.node.DAG.Add(newnode); err != nil {
		webError(w, "Could not add root node", err, http.StatusInternalServerError)
		return
	}

	// Redirect to new path
	ncid := newnode.Cid()

	i.addUserHeaders(w) // ok, _now_ write user's headers.
	w.Header().Set("IPFS-Hash", ncid.String())
	http.Redirect(w, r, gopath.Join(ipfsPathPrefix+ncid.String(), path.Join(components[:len(components)-1])), http.StatusCreated)
}

//.........这里部分代码省略.........
	if !dir {
		name := gopath.Base(urlPath)
		http.ServeContent(w, r, name, modtime, dr)
		return
	}

	links, err := i.api.Ls(ctx, urlPath)
	if err != nil {
		internalWebError(w, err)
		return
	}

	// storage for directory listing
	var dirListing []directoryItem
	// loop through files
	foundIndex := false
	for _, link := range links {
		if link.Name == "index.html" {
			log.Debugf("found index.html link for %s", urlPath)
			foundIndex = true

			if urlPath[len(urlPath)-1] != '/' {
				// See comment above where originalUrlPath is declared.
				http.Redirect(w, r, originalUrlPath+"/", 302)
				log.Debugf("redirect to %s", originalUrlPath+"/")
				return
			}

			p, err := path.ParsePath(urlPath + "/index.html")
			if err != nil {
				internalWebError(w, err)
				return
			}

			// return index page instead.
			dr, err := i.api.Cat(ctx, p.String())
			if err != nil {
				internalWebError(w, err)
				return
			}
			defer dr.Close()

			// write to request
			http.ServeContent(w, r, "index.html", modtime, dr)
			break
		}

		// See comment above where originalUrlPath is declared.
		di := directoryItem{humanize.Bytes(link.Size), link.Name, gopath.Join(originalUrlPath, link.Name)}
		dirListing = append(dirListing, di)
	}

	if !foundIndex {
		if r.Method != "HEAD" {
			// construct the correct back link
			// https://github.com/ipfs/go-ipfs/issues/1365
			var backLink string = prefix + urlPath

			// don't go further up than /ipfs/$hash/
			pathSplit := path.SplitList(backLink)
			switch {
			// keep backlink
			case len(pathSplit) == 3: // url: /ipfs/$hash

			// keep backlink
			case len(pathSplit) == 4 && pathSplit[3] == "": // url: /ipfs/$hash/

			// add the correct link depending on wether the path ends with a slash
			default:
				if strings.HasSuffix(backLink, "/") {
					backLink += "./.."
				} else {
					backLink += "/.."
				}
			}

			// strip /ipfs/$hash from backlink if IPNSHostnameOption touched the path.
			if ipnsHostname {
				backLink = prefix + "/"
				if len(pathSplit) > 5 {
					// also strip the trailing segment, because it's a backlink
					backLinkParts := pathSplit[3 : len(pathSplit)-2]
					backLink += path.Join(backLinkParts) + "/"
				}
			}

			// See comment above where originalUrlPath is declared.
			tplData := listingTemplateData{
				Listing:  dirListing,
				Path:     originalUrlPath,
				BackLink: backLink,
			}
			err := listingTemplate.Execute(w, tplData)
			if err != nil {
				internalWebError(w, err)
				return
			}
		}
	}
}