union: implement optional interfaces (Move, DirMove, Copy etc) - fixes #2619

Implement optional interfaces
- Purge
- PutStream
- Copy
- Move
- DirMove
- DirCacheFlush
- ChangeNotify
- About

Make Hashes() return the intersection of all the hashes supported by the remotes

backend/union/union.go

@@ -42,6 +42,8 @@ type Fs struct {
 	opt      Options      // options for this Fs
 	root     string       // the path we are working on
 	remotes  []fs.Fs      // slice of remotes
+	wr       fs.Fs        // writable remote
+	hashSet  hash.Set     // intersection of hash types
 }
 
 // Name of the remote (as passed into NewFs)
@@ -66,18 +68,119 @@ func (f *Fs) Features() *fs.Features {
 
 // Rmdir removes the root directory of the Fs object
 func (f *Fs) Rmdir(dir string) error {
-	return f.remotes[len(f.remotes)-1].Rmdir(dir)
+	return f.wr.Rmdir(dir)
 }
 
 // Hashes returns hash.HashNone to indicate remote hashing is unavailable
 func (f *Fs) Hashes() hash.Set {
-	// This could probably be set if all remotes share the same hashing algorithm
+	return f.hashSet
-	return hash.Set(hash.None)
 }
 
 // Mkdir makes the root directory of the Fs object
 func (f *Fs) Mkdir(dir string) error {
-	return f.remotes[len(f.remotes)-1].Mkdir(dir)
+	return f.wr.Mkdir(dir)
+}
+
+// Purge all files in the root and the root directory
+//
+// Implement this if you have a way of deleting all the files
+// quicker than just running Remove() on the result of List()
+//
+// Return an error if it doesn't exist
+func (f *Fs) Purge() error {
+	return f.wr.Features().Purge()
+}
+
+// Copy src to this remote using server side copy operations.
+//
+// This is stored with the remote path given
+//
+// It returns the destination Object and a possible error
+//
+// Will only be called if src.Fs().Name() == f.Name()
+//
+// If it isn't possible then return fs.ErrorCantCopy
+func (f *Fs) Copy(src fs.Object, remote string) (fs.Object, error) {
+	if src.Fs() != f.wr {
+		fs.Debugf(src, "Can't copy - not same remote type")
+		return nil, fs.ErrorCantCopy
+	}
+	return f.wr.Features().Copy(src, remote)
+}
+
+// Move src to this remote using server side move operations.
+//
+// This is stored with the remote path given
+//
+// It returns the destination Object and a possible error
+//
+// Will only be called if src.Fs().Name() == f.Name()
+//
+// If it isn't possible then return fs.ErrorCantMove
+func (f *Fs) Move(src fs.Object, remote string) (fs.Object, error) {
+	if src.Fs() != f.wr {
+		fs.Debugf(src, "Can't move - not same remote type")
+		return nil, fs.ErrorCantMove
+	}
+	return f.wr.Features().Move(src, remote)
+}
+
+// DirMove moves src, srcRemote to this remote at dstRemote
+// using server side move operations.
+//
+// Will only be called if src.Fs().Name() == f.Name()
+//
+// If it isn't possible then return fs.ErrorCantDirMove
+//
+// If destination exists then return fs.ErrorDirExists
+func (f *Fs) DirMove(src fs.Fs, srcRemote, dstRemote string) error {
+	srcFs, ok := src.(*Fs)
+	if !ok {
+		fs.Debugf(srcFs, "Can't move directory - not same remote type")
+		return fs.ErrorCantDirMove
+	}
+	return f.wr.Features().DirMove(srcFs.wr, srcRemote, dstRemote)
+}
+
+// ChangeNotify calls the passed function with a path
+// that has had changes. If the implementation
+// uses polling, it should adhere to the given interval.
+// At least one value will be written to the channel,
+// specifying the initial value and updated values might
+// follow. A 0 Duration should pause the polling.
+// The ChangeNotify implemantion must empty the channel
+// regulary. When the channel gets closed, the implemantion
+// should stop polling and release resources.
+func (f *Fs) ChangeNotify(fn func(string, fs.EntryType), ch <-chan time.Duration) {
+	for _, remote := range f.remotes {
+		if ChangeNotify := remote.Features().ChangeNotify; ChangeNotify != nil {
+			ChangeNotify(fn, ch)
+		}
+	}
+}
+
+// DirCacheFlush resets the directory cache - used in testing
+// as an optional interface
+func (f *Fs) DirCacheFlush() {
+	for _, remote := range f.remotes {
+		if DirCacheFlush := remote.Features().DirCacheFlush; DirCacheFlush != nil {
+			DirCacheFlush()
+		}
+	}
+}
+
+// PutStream uploads to the remote path with the modTime given of indeterminate size
+//
+// May create the object even if it returns an error - if so
+// will return the object and the error, otherwise will return
+// nil and the error
+func (f *Fs) PutStream(in io.Reader, src fs.ObjectInfo, options ...fs.OpenOption) (fs.Object, error) {
+	return f.wr.Features().PutStream(in, src, options...)
+}
+
+// About gets quota information from the Fs
+func (f *Fs) About() (*fs.Usage, error) {
+	return f.wr.Features().About()
 }
 
 // Put in to the remote path with the modTime given of the given size
@@ -86,7 +189,7 @@ func (f *Fs) Mkdir(dir string) error {
 // will return the object and the error, otherwise will return
 // nil and the error
 func (f *Fs) Put(in io.Reader, src fs.ObjectInfo, options ...fs.OpenOption) (fs.Object, error) {
-	return f.remotes[len(f.remotes)-1].Put(in, src, options...)
+	return f.wr.Put(in, src, options...)
 }
 
 // List the objects and directories in dir into entries.  The
@@ -204,6 +307,7 @@ func NewFs(name, root string, m configmap.Mapper) (fs.Fs, error) {
 		root:    root,
 		opt:     *opt,
 		remotes: remotes,
+		wr:      remotes[len(remotes)-1],
 	}
 	var features = (&fs.Features{
 		CaseInsensitive:         true,
@@ -212,16 +316,53 @@ func NewFs(name, root string, m configmap.Mapper) (fs.Fs, error) {
 		WriteMimeType:           true,
 		CanHaveEmptyDirectories: true,
 		BucketBased:             true,
+		SetTier:                 true,
+		GetTier:                 true,
 	}).Fill(f)
+	features = features.Mask(f.wr) // mask the features just on the writable fs
+
+	// FIXME maybe should be masking the bools here?
+
+	// Clear ChangeNotify and DirCacheFlush if all are nil
+	clearChangeNotify := true
+	clearDirCacheFlush := true
 	for _, remote := range f.remotes {
-		features = features.Mask(remote)
+		remoteFeatures := remote.Features()
+		if remoteFeatures.ChangeNotify != nil {
+			clearChangeNotify = false
 		}
+		if remoteFeatures.DirCacheFlush != nil {
+			clearDirCacheFlush = false
+		}
+	}
+	if clearChangeNotify {
+		features.ChangeNotify = nil
+	}
+	if clearDirCacheFlush {
+		features.DirCacheFlush = nil
+	}
+
 	f.features = features
 
+	// Get common intersection of hashes
+	hashSet := f.remotes[0].Hashes()
+	for _, remote := range f.remotes[1:] {
+		hashSet = hashSet.Overlap(remote.Hashes())
+	}
+	f.hashSet = hashSet
+
 	return f, nil
 }
 
 // Check the interfaces are satisfied
 var (
-	_ fs.Fs = &Fs{}
+	_ fs.Fs              = (*Fs)(nil)
+	_ fs.Purger          = (*Fs)(nil)
+	_ fs.PutStreamer     = (*Fs)(nil)
+	_ fs.Copier          = (*Fs)(nil)
+	_ fs.Mover           = (*Fs)(nil)
+	_ fs.DirMover        = (*Fs)(nil)
+	_ fs.DirCacheFlusher = (*Fs)(nil)
+	_ fs.ChangeNotifier  = (*Fs)(nil)
+	_ fs.Abouter         = (*Fs)(nil)
 )