dropbox: add support for viewing shared files and folders

backend/dropbox/dropbox.go

@@ -142,6 +142,31 @@ memory.  It can be set smaller if you are tight on memory.`, maxChunkSize),
 			Help:     "Impersonate this user when using a business account.",
 			Default:  "",
 			Advanced: true,
+		}, {
+			Name: "shared_files",
+			Help: `Instructs rclone to work on individual shared files.
+
+In this mode rclone's features are extremely limited - only list (ls, lsl, etc.) 
+operations and read operations (e.g. downloading) are supported in this mode.
+All other operations will be disabled.`,
+			Default:  false,
+			Advanced: true,
+		}, {
+			Name: "shared_folders",
+			Help: `Instructs rclone to work on shared folders.
+			
+When this flag is used with no path only the List operation is supported and 
+all available shared folders will be listed. If you specify a path the first part 
+will be interpreted as the name of shared folder. Rclone will then try to mount this 
+shared to the root namespace. On success shared folder rclone proceeds normally. 
+The shared folder is now pretty much a normal folder and all normal operations 
+are supported. 
+
+Note that we don't unmount the shared folder afterwards so the 
+--dropbox-shared-folders can be omitted after the first use of a particular 
+shared folder.`,
+			Default:  false,
+			Advanced: true,
 		}, {
 			Name:     config.ConfigEncoding,
 			Help:     config.ConfigEncodingHelp,
@@ -161,9 +186,11 @@ memory.  It can be set smaller if you are tight on memory.`, maxChunkSize),
 
 // Options defines the configuration for this backend
 type Options struct {
-	ChunkSize   fs.SizeSuffix        `config:"chunk_size"`
-	Impersonate string               `config:"impersonate"`
-	Enc         encoder.MultiEncoder `config:"encoding"`
+	ChunkSize     fs.SizeSuffix        `config:"chunk_size"`
+	Impersonate   string               `config:"impersonate"`
+	SharedFiles   bool                 `config:"shared_files"`
+	SharedFolders bool                 `config:"shared_folders"`
+	Enc           encoder.MultiEncoder `config:"encoding"`
 }
 
 // Fs represents a remote dropbox server
@@ -186,7 +213,9 @@ type Fs struct {
 //
 // Dropbox Objects always have full metadata
 type Object struct {
-	fs      *Fs       // what this object is part of
+	fs      *Fs // what this object is part of
+	id      string
+	url     string
 	remote  string    // The remote path
 	bytes   int64     // size of the object
 	modTime time.Time // time it was last modified
@@ -332,8 +361,60 @@ func NewFs(name, root string, m configmap.Mapper) (fs.Fs, error) {
 		CaseInsensitive:         true,
 		ReadMimeType:            true,
 		CanHaveEmptyDirectories: true,
-	}).Fill(f)
-	f.setRoot(root)
+	})
+
+	// do not fill features yet
+	if f.opt.SharedFiles {
+		f.setRoot(root)
+		if f.root == "" {
+			return f, nil
+		}
+		_, err := f.findSharedFile(f.root)
+		f.root = ""
+		if err == nil {
+			return f, fs.ErrorIsFile
+		}
+		return f, nil
+	}
+
+	if f.opt.SharedFolders {
+		f.setRoot(root)
+		if f.root == "" {
+			return f, nil // our root it empty so we probably want to list shared folders
+		}
+
+		dir := path.Dir(f.root)
+		if dir == "." {
+			dir = f.root
+		}
+
+		// root is not empty so we have find the right shared folder if it exists
+		id, err := f.findSharedFolder(dir)
+		if err != nil {
+			// if we didn't find the specified shared folder we have to bail out here
+			return nil, err
+		}
+		// we found the specified shared folder so let's mount it
+		// this will add it to the users normal root namespace and allows us
+		// to actually perform operations on it using the normal api endpoints.
+		err = f.mountSharedFolder(id)
+		if err != nil {
+			switch e := err.(type) {
+			case sharing.MountFolderAPIError:
+				if e.EndpointError == nil || (e.EndpointError != nil && e.EndpointError.Tag != sharing.MountFolderErrorAlreadyMounted) {
+					return nil, err
+				}
+			default:
+				return nil, err
+			}
+			// if the moint failed we have to abort here
+		}
+		// if the mount succeeded it's now a normal folder in the users root namespace
+		// we disable shared folder mode and proceed normally
+		f.opt.SharedFolders = false
+	}
+
+	f.features.Fill(f)
 
 	// If root starts with / then use the actual root
 	if strings.HasPrefix(root, "/") {
@@ -355,6 +436,7 @@ func NewFs(name, root string, m configmap.Mapper) (fs.Fs, error) {
 		}
 		fs.Debugf(f, "Using root namespace %q", f.ns)
 	}
+	f.setRoot(root)
 
 	// See if the root is actually an object
 	_, err = f.getFileMetadata(f.slashRoot)
@@ -465,9 +547,158 @@ func (f *Fs) newObjectWithInfo(remote string, info *files.FileMetadata) (fs.Obje
 // NewObject finds the Object at remote.  If it can't be found
 // it returns the error fs.ErrorObjectNotFound.
 func (f *Fs) NewObject(ctx context.Context, remote string) (fs.Object, error) {
+	if f.opt.SharedFiles {
+		return f.findSharedFile(remote)
+	}
 	return f.newObjectWithInfo(remote, nil)
 }
 
+// listSharedFoldersApi lists all available shared folders mounted and not mounted
+// we'll need the id later so we have to return them in original format
+func (f *Fs) listSharedFoldersAPI() (result []*sharing.SharedFolderMetadata, err error) {
+	started := false
+	var res *sharing.ListFoldersResult
+	for {
+		if !started {
+			arg := sharing.ListFoldersArgs{
+				Limit: 100,
+			}
+			err := f.pacer.Call(func() (bool, error) {
+				res, err = f.sharing.ListFolders(&arg)
+				return shouldRetry(err)
+			})
+			if err != nil {
+				return nil, err
+			}
+			started = true
+		} else {
+			arg := sharing.ListFoldersContinueArg{
+				Cursor: res.Cursor,
+			}
+			err := f.pacer.Call(func() (bool, error) {
+				res, err = f.sharing.ListFoldersContinue(&arg)
+				return shouldRetry(err)
+			})
+			if err != nil {
+				return nil, errors.Wrap(err, "list continue")
+			}
+		}
+		result = append(result, res.Entries...)
+		if res.Cursor == "" {
+			break
+		}
+	}
+
+	return result, nil
+}
+
+// listSharedFolders lists shared folders as normal dir entries
+func (f *Fs) listSharedFolders() (entries fs.DirEntries, err error) {
+	result, err := f.listSharedFoldersAPI()
+	if err != nil {
+		return nil, err
+	}
+	for _, entry := range result {
+		entryPath := entry.Name
+		leaf := f.opt.Enc.ToStandardName(entryPath)
+		d := fs.NewDir(leaf, time.Now())
+		entries = append(entries, d)
+	}
+	return entries, nil
+}
+
+// findSharedFolder find the id for a given shared folder name
+// somewhat annoyingly there is no endpoint to query a shared folder by it's name
+// so our only option is to iterate over all shared folders
+func (f *Fs) findSharedFolder(name string) (id string, err error) {
+	entries, err := f.listSharedFoldersAPI()
+	if err != nil {
+		return "", err
+	}
+	for _, entry := range entries {
+		if entry.Name == name {
+			return entry.SharedFolderId, nil
+		}
+	}
+	return "", fs.ErrorDirNotFound
+}
+
+// mountSharedFolders mount a shared folder to the root namespace
+func (f *Fs) mountSharedFolder(id string) error {
+	arg := sharing.MountFolderArg{
+		SharedFolderId: id,
+	}
+	err := f.pacer.Call(func() (bool, error) {
+		_, err := f.sharing.MountFolder(&arg)
+		return shouldRetry(err)
+	})
+	return err
+}
+
+// listSharedFolders lists shared the user as access to (note this means individual
+// files not files contained in shared folders)
+func (f *Fs) listReceivedFiles() (entries fs.DirEntries, err error) {
+	started := false
+	var res *sharing.ListFilesResult
+	for {
+		if !started {
+			arg := sharing.ListFilesArg{
+				Limit: 100,
+			}
+			err := f.pacer.Call(func() (bool, error) {
+				res, err = f.sharing.ListReceivedFiles(&arg)
+				return shouldRetry(err)
+			})
+			if err != nil {
+				return nil, err
+			}
+			started = true
+		} else {
+			arg := sharing.ListFilesContinueArg{
+				Cursor: res.Cursor,
+			}
+			err := f.pacer.Call(func() (bool, error) {
+				res, err = f.sharing.ListReceivedFilesContinue(&arg)
+				return shouldRetry(err)
+			})
+			if err != nil {
+				return nil, errors.Wrap(err, "list continue")
+			}
+		}
+		for _, entry := range res.Entries {
+			fmt.Printf("%+v\n", entry)
+			entryPath := entry.Name
+			o := &Object{
+				fs:      f,
+				url:     entry.PreviewUrl,
+				remote:  entryPath,
+				modTime: entry.TimeInvited,
+			}
+			if err != nil {
+				return nil, err
+			}
+			entries = append(entries, o)
+		}
+		if res.Cursor == "" {
+			break
+		}
+	}
+	return entries, nil
+}
+
+func (f *Fs) findSharedFile(name string) (o *Object, err error) {
+	files, err := f.listReceivedFiles()
+	if err != nil {
+		return nil, err
+	}
+	for _, entry := range files {
+		if entry.(*Object).remote == name {
+			return entry.(*Object), nil
+		}
+	}
+	return nil, fs.ErrorObjectNotFound
+}
+
 // List the objects and directories in dir into entries.  The
 // entries can be returned in any order but should be for a
 // complete directory.
@@ -478,6 +709,13 @@ func (f *Fs) NewObject(ctx context.Context, remote string) (fs.Object, error) {
 // This should return ErrDirNotFound if the directory isn't
 // found.
 func (f *Fs) List(ctx context.Context, dir string) (entries fs.DirEntries, err error) {
+	if f.opt.SharedFiles {
+		return f.listReceivedFiles()
+	}
+	if f.opt.SharedFolders {
+		return f.listSharedFolders()
+	}
+
 	root := f.slashRoot
 	if dir != "" {
 		root += "/" + dir
@@ -564,6 +802,9 @@ func (f *Fs) List(ctx context.Context, dir string) (entries fs.DirEntries, err e
 //
 // The new object may have been created if an error is returned
 func (f *Fs) Put(ctx context.Context, in io.Reader, src fs.ObjectInfo, options ...fs.OpenOption) (fs.Object, error) {
+	if f.opt.SharedFiles || f.opt.SharedFolders {
+		return nil, fserrors.NoRetryError(errors.New("not support in shared files mode"))
+	}
 	// Temporary Object under construction
 	o := &Object{
 		fs:     f,
@@ -579,6 +820,9 @@ func (f *Fs) PutStream(ctx context.Context, in io.Reader, src fs.ObjectInfo, opt
 
 // Mkdir creates the container if it doesn't exist
 func (f *Fs) Mkdir(ctx context.Context, dir string) error {
+	if f.opt.SharedFiles || f.opt.SharedFolders {
+		return fserrors.NoRetryError(errors.New("not support in shared files mode"))
+	}
 	root := path.Join(f.slashRoot, dir)
 
 	// can't create or run metadata on root
@@ -656,6 +900,9 @@ func (f *Fs) purgeCheck(ctx context.Context, dir string, check bool) (err error)
 //
 // Returns an error if it isn't empty
 func (f *Fs) Rmdir(ctx context.Context, dir string) error {
+	if f.opt.SharedFiles || f.opt.SharedFolders {
+		return fserrors.NoRetryError(errors.New("not support in shared files mode"))
+	}
 	return f.purgeCheck(ctx, dir, true)
 }
 
@@ -929,6 +1176,9 @@ func (o *Object) Remote() string {
 
 // Hash returns the dropbox special hash
 func (o *Object) Hash(ctx context.Context, t hash.Type) (string, error) {
+	if o.fs.opt.SharedFiles || o.fs.opt.SharedFolders {
+		return "", fserrors.NoRetryError(errors.New("not support in shared files mode"))
+	}
 	if t != DbHashType {
 		return "", hash.ErrUnsupported
 	}
@@ -948,6 +1198,7 @@ func (o *Object) Size() int64 {
 //
 // This isn't a complete set of metadata and has an inacurate date
 func (o *Object) setMetadataFromEntry(info *files.FileMetadata) error {
+	o.id = info.Id
 	o.bytes = int64(info.Size)
 	o.modTime = info.ClientModified
 	o.hash = info.ContentHash
@@ -1016,10 +1267,27 @@ func (o *Object) Storable() bool {
 
 // Open an object for read
 func (o *Object) Open(ctx context.Context, options ...fs.OpenOption) (in io.ReadCloser, err error) {
+	if o.fs.opt.SharedFiles {
+		if len(options) != 0 {
+			return nil, errors.New("OpenOptions not supported for shared files")
+		}
+		arg := sharing.GetSharedLinkMetadataArg{
+			Url: o.url,
+		}
+		err = o.fs.pacer.Call(func() (bool, error) {
+			_, in, err = o.fs.sharing.GetSharedLinkFile(&arg)
+			return shouldRetry(err)
+		})
+		if err != nil {
+			return nil, err
+		}
+		return
+	}
+
 	fs.FixRangeOption(options, o.bytes)
 	headers := fs.OpenOptionHeaders(options)
 	arg := files.DownloadArg{
-		Path:         o.fs.opt.Enc.FromStandardPath(o.remotePath()),
+		Path:         o.id,
 		ExtraHeaders: headers,
 	}
 	err = o.fs.pacer.Call(func() (bool, error) {
@@ -1153,6 +1421,9 @@ func (o *Object) uploadChunked(in0 io.Reader, commitInfo *files.CommitInfo, size
 //
 // The new object may have been created if an error is returned
 func (o *Object) Update(ctx context.Context, in io.Reader, src fs.ObjectInfo, options ...fs.OpenOption) error {
+	if o.fs.opt.SharedFiles || o.fs.opt.SharedFolders {
+		return fserrors.NoRetryError(errors.New("not support in shared files mode"))
+	}
 	remote := o.remotePath()
 	if ignoredFiles.MatchString(remote) {
 		return fserrors.NoRetryError(errors.Errorf("file name %q is disallowed - not uploading", path.Base(remote)))
@@ -1181,6 +1452,9 @@ func (o *Object) Update(ctx context.Context, in io.Reader, src fs.ObjectInfo, op
 
 // Remove an object
 func (o *Object) Remove(ctx context.Context) (err error) {
+	if o.fs.opt.SharedFiles || o.fs.opt.SharedFolders {
+		return fserrors.NoRetryError(errors.New("not support in shared files mode"))
+	}
 	err = o.fs.pacer.Call(func() (bool, error) {
 		_, err = o.fs.srv.DeleteV2(&files.DeleteArg{
 			Path: o.fs.opt.Enc.FromStandardPath(o.remotePath()),