// Package sync is the implementation of sync/copy/move
package sync

import (
	"fmt"
	"sort"
	"sync"

	"github.com/ncw/rclone/fs"
	"github.com/ncw/rclone/fs/accounting"
	"github.com/ncw/rclone/fs/filter"
	"github.com/ncw/rclone/fs/fserrors"
	"github.com/ncw/rclone/fs/hash"
	"github.com/ncw/rclone/fs/march"
	"github.com/ncw/rclone/fs/operations"
	"github.com/pkg/errors"
	"golang.org/x/net/context"
)

type syncCopyMove struct {
	// parameters
	fdst               fs.Fs
	fsrc               fs.Fs
	deleteMode         fs.DeleteMode // how we are doing deletions
	DoMove             bool
	deleteEmptySrcDirs bool
	dir                string
	// internal state
	ctx            context.Context        // internal context for controlling go-routines
	cancel         func()                 // cancel the context
	deletersWg     sync.WaitGroup         // for delete before go routine
	deleteFilesCh  chan fs.Object         // channel to receive deletes if delete before
	trackRenames   bool                   // set if we should do server side renames
	dstFilesMu     sync.Mutex             // protect dstFiles
	dstFiles       map[string]fs.Object   // dst files, always filled
	srcFiles       map[string]fs.Object   // src files, only used if deleteBefore
	srcFilesChan   chan fs.Object         // passes src objects
	srcFilesResult chan error             // error result of src listing
	dstFilesResult chan error             // error result of dst listing
	dstEmptyDirsMu sync.Mutex             // protect dstEmptyDirs
	dstEmptyDirs   []fs.DirEntry          // potentially empty directories
	srcEmptyDirsMu sync.Mutex             // protect srcEmptyDirs
	srcEmptyDirs   []fs.DirEntry          // potentially empty directories
	checkerWg      sync.WaitGroup         // wait for checkers
	toBeChecked    fs.ObjectPairChan      // checkers channel
	transfersWg    sync.WaitGroup         // wait for transfers
	toBeUploaded   fs.ObjectPairChan      // copiers channel
	errorMu        sync.Mutex             // Mutex covering the errors variables
	err            error                  // normal error from copy process
	noRetryErr     error                  // error with NoRetry set
	fatalErr       error                  // fatal error
	commonHash     hash.Type              // common hash type between src and dst
	renameMapMu    sync.Mutex             // mutex to protect the below
	renameMap      map[string][]fs.Object // dst files by hash - only used by trackRenames
	renamerWg      sync.WaitGroup         // wait for renamers
	toBeRenamed    fs.ObjectPairChan      // renamers channel
	trackRenamesWg sync.WaitGroup         // wg for background track renames
	trackRenamesCh chan fs.Object         // objects are pumped in here
	renameCheck    []fs.Object            // accumulate files to check for rename here
	backupDir      fs.Fs                  // place to store overwrites/deletes
	suffix         string                 // suffix to add to files placed in backupDir
}

func newSyncCopyMove(fdst, fsrc fs.Fs, deleteMode fs.DeleteMode, DoMove bool, deleteEmptySrcDirs bool) (*syncCopyMove, error) {
	s := &syncCopyMove{
		fdst:               fdst,
		fsrc:               fsrc,
		deleteMode:         deleteMode,
		DoMove:             DoMove,
		deleteEmptySrcDirs: deleteEmptySrcDirs,
		dir:                "",
		srcFilesChan:       make(chan fs.Object, fs.Config.Checkers+fs.Config.Transfers),
		srcFilesResult:     make(chan error, 1),
		dstFilesResult:     make(chan error, 1),
		toBeChecked:        make(fs.ObjectPairChan, fs.Config.Transfers),
		toBeUploaded:       make(fs.ObjectPairChan, fs.Config.Transfers),
		deleteFilesCh:      make(chan fs.Object, fs.Config.Checkers),
		trackRenames:       fs.Config.TrackRenames,
		commonHash:         fsrc.Hashes().Overlap(fdst.Hashes()).GetOne(),
		toBeRenamed:        make(fs.ObjectPairChan, fs.Config.Transfers),
		trackRenamesCh:     make(chan fs.Object, fs.Config.Checkers),
	}
	s.ctx, s.cancel = context.WithCancel(context.Background())
	if s.trackRenames {
		// Don't track renames for remotes without server-side move support.
		if !operations.CanServerSideMove(fdst) {
			fs.Errorf(fdst, "Ignoring --track-renames as the destination does not support server-side move or copy")
			s.trackRenames = false
		}
		if s.commonHash == hash.HashNone {
			fs.Errorf(fdst, "Ignoring --track-renames as the source and destination do not have a common hash")
			s.trackRenames = false
		}
	}
	if s.trackRenames {
		// track renames needs delete after
		if s.deleteMode != fs.DeleteModeOff {
			s.deleteMode = fs.DeleteModeAfter
		}
	}
	// Make Fs for --backup-dir if required
	if fs.Config.BackupDir != "" {
		var err error
		s.backupDir, err = fs.NewFs(fs.Config.BackupDir)
		if err != nil {
			return nil, fserrors.FatalError(errors.Errorf("Failed to make fs for --backup-dir %q: %v", fs.Config.BackupDir, err))
		}
		if !operations.CanServerSideMove(s.backupDir) {
			return nil, fserrors.FatalError(errors.New("can't use --backup-dir on a remote which doesn't support server side move or copy"))
		}
		if !operations.SameConfig(fdst, s.backupDir) {
			return nil, fserrors.FatalError(errors.New("parameter to --backup-dir has to be on the same remote as destination"))
		}
		if operations.Overlapping(fdst, s.backupDir) {
			return nil, fserrors.FatalError(errors.New("destination and parameter to --backup-dir mustn't overlap"))
		}
		if operations.Overlapping(fsrc, s.backupDir) {
			return nil, fserrors.FatalError(errors.New("source and parameter to --backup-dir mustn't overlap"))
		}
		s.suffix = fs.Config.Suffix
	}
	return s, nil
}

// Check to see if the context has been cancelled
func (s *syncCopyMove) aborting() bool {
	select {
	case <-s.ctx.Done():
		return true
	default:
	}
	return false
}

// This reads the map and pumps it into the channel passed in, closing
// the channel at the end
func (s *syncCopyMove) pumpMapToChan(files map[string]fs.Object, out chan<- fs.Object) {
outer:
	for _, o := range files {
		if s.aborting() {
			break outer
		}
		select {
		case out <- o:
		case <-s.ctx.Done():
			break outer
		}
	}
	close(out)
	s.srcFilesResult <- nil
}

// This checks the types of errors returned while copying files
func (s *syncCopyMove) processError(err error) {
	if err == nil {
		return
	}
	s.errorMu.Lock()
	defer s.errorMu.Unlock()
	switch {
	case fserrors.IsFatalError(err):
		if !s.aborting() {
			s.cancel()
		}
		s.fatalErr = err
	case fserrors.IsNoRetryError(err):
		s.noRetryErr = err
	default:
		s.err = err
	}
}

// Returns the current error (if any) in the order of prececedence
//   fatalErr
//   normal error
//   noRetryErr
func (s *syncCopyMove) currentError() error {
	s.errorMu.Lock()
	defer s.errorMu.Unlock()
	if s.fatalErr != nil {
		return s.fatalErr
	}
	if s.err != nil {
		return s.err
	}
	return s.noRetryErr
}

// pairChecker reads Objects~s on in send to out if they need transferring.
//
// FIXME potentially doing lots of hashes at once
func (s *syncCopyMove) pairChecker(in fs.ObjectPairChan, out fs.ObjectPairChan, wg *sync.WaitGroup) {
	defer wg.Done()
	for {
		if s.aborting() {
			return
		}
		select {
		case pair, ok := <-in:
			if !ok {
				return
			}
			src := pair.Src
			accounting.Stats.Checking(src.Remote())
			// Check to see if can store this
			if src.Storable() {
				if operations.NeedTransfer(pair.Dst, pair.Src) {
					// If files are treated as immutable, fail if destination exists and does not match
					if fs.Config.Immutable && pair.Dst != nil {
						fs.Errorf(pair.Dst, "Source and destination exist but do not match: immutable file modified")
						s.processError(fs.ErrorImmutableModified)
					} else {
						// If destination already exists, then we must move it into --backup-dir if required
						if pair.Dst != nil && s.backupDir != nil {
							remoteWithSuffix := pair.Dst.Remote() + s.suffix
							overwritten, _ := s.backupDir.NewObject(remoteWithSuffix)
							_, err := operations.Move(s.backupDir, overwritten, remoteWithSuffix, pair.Dst)
							if err != nil {
								s.processError(err)
							} else {
								// If successful zero out the dst as it is no longer there and copy the file
								pair.Dst = nil
								out <- pair
							}
						} else {
							out <- pair
						}
					}
				} else {
					// If moving need to delete the files we don't need to copy
					if s.DoMove {
						// Delete src if no error on copy
						s.processError(operations.DeleteFile(src))
					}
				}
			}
			accounting.Stats.DoneChecking(src.Remote())
		case <-s.ctx.Done():
			return
		}
	}
}

// pairRenamer reads Objects~s on in and attempts to rename them,
// otherwise it sends them out if they need transferring.
func (s *syncCopyMove) pairRenamer(in fs.ObjectPairChan, out fs.ObjectPairChan, wg *sync.WaitGroup) {
	defer wg.Done()
	for {
		if s.aborting() {
			return
		}
		select {
		case pair, ok := <-in:
			if !ok {
				return
			}
			src := pair.Src
			if !s.tryRename(src) {
				// pass on if not renamed
				out <- pair
			}
		case <-s.ctx.Done():
			return
		}
	}
}

// pairCopyOrMove reads Objects on in and moves or copies them.
func (s *syncCopyMove) pairCopyOrMove(in fs.ObjectPairChan, fdst fs.Fs, wg *sync.WaitGroup) {
	defer wg.Done()
	var err error
	for {
		if s.aborting() {
			return
		}
		select {
		case pair, ok := <-in:
			if !ok {
				return
			}
			src := pair.Src
			accounting.Stats.Transferring(src.Remote())
			if s.DoMove {
				_, err = operations.Move(fdst, pair.Dst, src.Remote(), src)
			} else {
				_, err = operations.Copy(fdst, pair.Dst, src.Remote(), src)
			}
			s.processError(err)
			accounting.Stats.DoneTransferring(src.Remote(), err == nil)
		case <-s.ctx.Done():
			return
		}
	}
}

// This starts the background checkers.
func (s *syncCopyMove) startCheckers() {
	s.checkerWg.Add(fs.Config.Checkers)
	for i := 0; i < fs.Config.Checkers; i++ {
		go s.pairChecker(s.toBeChecked, s.toBeUploaded, &s.checkerWg)
	}
}

// This stops the background checkers
func (s *syncCopyMove) stopCheckers() {
	close(s.toBeChecked)
	fs.Infof(s.fdst, "Waiting for checks to finish")
	s.checkerWg.Wait()
}

// This starts the background transfers
func (s *syncCopyMove) startTransfers() {
	s.transfersWg.Add(fs.Config.Transfers)
	for i := 0; i < fs.Config.Transfers; i++ {
		go s.pairCopyOrMove(s.toBeUploaded, s.fdst, &s.transfersWg)
	}
}

// This stops the background transfers
func (s *syncCopyMove) stopTransfers() {
	close(s.toBeUploaded)
	fs.Infof(s.fdst, "Waiting for transfers to finish")
	s.transfersWg.Wait()
}

// This starts the background renamers.
func (s *syncCopyMove) startRenamers() {
	if !s.trackRenames {
		return
	}
	s.renamerWg.Add(fs.Config.Checkers)
	for i := 0; i < fs.Config.Checkers; i++ {
		go s.pairRenamer(s.toBeRenamed, s.toBeUploaded, &s.renamerWg)
	}
}

// This stops the background renamers
func (s *syncCopyMove) stopRenamers() {
	if !s.trackRenames {
		return
	}
	close(s.toBeRenamed)
	fs.Infof(s.fdst, "Waiting for renames to finish")
	s.renamerWg.Wait()
}

// This starts the collection of possible renames
func (s *syncCopyMove) startTrackRenames() {
	if !s.trackRenames {
		return
	}
	s.trackRenamesWg.Add(1)
	go func() {
		defer s.trackRenamesWg.Done()
		for o := range s.trackRenamesCh {
			s.renameCheck = append(s.renameCheck, o)
		}
	}()
}

// This stops the background rename collection
func (s *syncCopyMove) stopTrackRenames() {
	if !s.trackRenames {
		return
	}
	close(s.trackRenamesCh)
	s.trackRenamesWg.Wait()
}

// This starts the background deletion of files for --delete-during
func (s *syncCopyMove) startDeleters() {
	if s.deleteMode != fs.DeleteModeDuring && s.deleteMode != fs.DeleteModeOnly {
		return
	}
	s.deletersWg.Add(1)
	go func() {
		defer s.deletersWg.Done()
		err := operations.DeleteFilesWithBackupDir(s.deleteFilesCh, s.backupDir)
		s.processError(err)
	}()
}

// This stops the background deleters
func (s *syncCopyMove) stopDeleters() {
	if s.deleteMode != fs.DeleteModeDuring && s.deleteMode != fs.DeleteModeOnly {
		return
	}
	close(s.deleteFilesCh)
	s.deletersWg.Wait()
}

// This deletes the files in the dstFiles map.  If checkSrcMap is set
// then it checks to see if they exist first in srcFiles the source
// file map, otherwise it unconditionally deletes them.  If
// checkSrcMap is clear then it assumes that the any source files that
// have been found have been removed from dstFiles already.
func (s *syncCopyMove) deleteFiles(checkSrcMap bool) error {
	if accounting.Stats.Errored() {
		fs.Errorf(s.fdst, "%v", fs.ErrorNotDeleting)
		return fs.ErrorNotDeleting
	}

	// Delete the spare files
	toDelete := make(fs.ObjectsChan, fs.Config.Transfers)
	go func() {
		for remote, o := range s.dstFiles {
			if checkSrcMap {
				_, exists := s.srcFiles[remote]
				if exists {
					continue
				}
			}
			if s.aborting() {
				break
			}
			toDelete <- o
		}
		close(toDelete)
	}()
	return operations.DeleteFilesWithBackupDir(toDelete, s.backupDir)
}

// This deletes the empty directories in the slice passed in.  It
// ignores any errors deleting directories
func deleteEmptyDirectories(f fs.Fs, entries fs.DirEntries) error {
	if len(entries) == 0 {
		return nil
	}
	if accounting.Stats.Errored() {
		fs.Errorf(f, "%v", fs.ErrorNotDeletingDirs)
		return fs.ErrorNotDeletingDirs
	}

	// Now delete the empty directories starting from the longest path
	sort.Sort(entries)
	var errorCount int
	var okCount int
	for i := len(entries) - 1; i >= 0; i-- {
		entry := entries[i]
		dir, ok := entry.(fs.Directory)
		if ok {
			// TryRmdir only deletes empty directories
			err := operations.TryRmdir(f, dir.Remote())
			if err != nil {
				fs.Debugf(fs.LogDirName(f, dir.Remote()), "Failed to Rmdir: %v", err)
				errorCount++
			} else {
				okCount++
			}
		} else {
			fs.Errorf(f, "Not a directory: %v", entry)
		}
	}
	if errorCount > 0 {
		fs.Debugf(f, "failed to delete %d directories", errorCount)
	}
	if okCount > 0 {
		fs.Debugf(f, "deleted %d directories", okCount)
	}
	return nil
}

// renameHash makes a string with the size and the hash for rename detection
//
// it may return an empty string in which case no hash could be made
func (s *syncCopyMove) renameHash(obj fs.Object) (hash string) {
	var err error
	hash, err = obj.Hash(s.commonHash)
	if err != nil {
		fs.Debugf(obj, "Hash failed: %v", err)
		return ""
	}
	if hash == "" {
		return ""
	}
	return fmt.Sprintf("%d,%s", obj.Size(), hash)
}

// pushRenameMap adds the object with hash to the rename map
func (s *syncCopyMove) pushRenameMap(hash string, obj fs.Object) {
	s.renameMapMu.Lock()
	s.renameMap[hash] = append(s.renameMap[hash], obj)
	s.renameMapMu.Unlock()
}

// popRenameMap finds the object with hash and pop the first match from
// renameMap or returns nil if not found.
func (s *syncCopyMove) popRenameMap(hash string) (dst fs.Object) {
	s.renameMapMu.Lock()
	dsts, ok := s.renameMap[hash]
	if ok && len(dsts) > 0 {
		dst, dsts = dsts[0], dsts[1:]
		if len(dsts) > 0 {
			s.renameMap[hash] = dsts
		} else {
			delete(s.renameMap, hash)
		}
	}
	s.renameMapMu.Unlock()
	return dst
}

// makeRenameMap builds a map of the destination files by hash that
// match sizes in the slice of objects in s.renameCheck
func (s *syncCopyMove) makeRenameMap() {
	fs.Infof(s.fdst, "Making map for --track-renames")

	// first make a map of possible sizes we need to check
	possibleSizes := map[int64]struct{}{}
	for _, obj := range s.renameCheck {
		possibleSizes[obj.Size()] = struct{}{}
	}

	// pump all the dstFiles into in
	in := make(chan fs.Object, fs.Config.Checkers)
	go s.pumpMapToChan(s.dstFiles, in)

	// now make a map of size,hash for all dstFiles
	s.renameMap = make(map[string][]fs.Object)
	var wg sync.WaitGroup
	wg.Add(fs.Config.Transfers)
	for i := 0; i < fs.Config.Transfers; i++ {
		go func() {
			defer wg.Done()
			for obj := range in {
				// only create hash for dst fs.Object if its size could match
				if _, found := possibleSizes[obj.Size()]; found {
					accounting.Stats.Checking(obj.Remote())
					hash := s.renameHash(obj)
					if hash != "" {
						s.pushRenameMap(hash, obj)
					}
					accounting.Stats.DoneChecking(obj.Remote())
				}
			}
		}()
	}
	wg.Wait()
	fs.Infof(s.fdst, "Finished making map for --track-renames")
}

// tryRename renames a src object when doing track renames if
// possible, it returns true if the object was renamed.
func (s *syncCopyMove) tryRename(src fs.Object) bool {
	accounting.Stats.Checking(src.Remote())
	defer accounting.Stats.DoneChecking(src.Remote())

	// Calculate the hash of the src object
	hash := s.renameHash(src)
	if hash == "" {
		return false
	}

	// Get a match on fdst
	dst := s.popRenameMap(hash)
	if dst == nil {
		return false
	}

	// Find dst object we are about to overwrite if it exists
	dstOverwritten, _ := s.fdst.NewObject(src.Remote())

	// Rename dst to have name src.Remote()
	_, err := operations.Move(s.fdst, dstOverwritten, src.Remote(), dst)
	if err != nil {
		fs.Debugf(src, "Failed to rename to %q: %v", dst.Remote(), err)
		return false
	}

	// remove file from dstFiles if present
	s.dstFilesMu.Lock()
	delete(s.dstFiles, dst.Remote())
	s.dstFilesMu.Unlock()

	fs.Infof(src, "Renamed from %q", dst.Remote())
	return true
}

// Syncs fsrc into fdst
//
// If Delete is true then it deletes any files in fdst that aren't in fsrc
//
// If DoMove is true then files will be moved instead of copied
//
// dir is the start directory, "" for root
func (s *syncCopyMove) run() error {
	if operations.Same(s.fdst, s.fsrc) {
		fs.Errorf(s.fdst, "Nothing to do as source and destination are the same")
		return nil
	}

	// Start background checking and transferring pipeline
	s.startCheckers()
	s.startRenamers()
	s.startTransfers()
	s.startDeleters()
	s.dstFiles = make(map[string]fs.Object)

	s.startTrackRenames()

	// set up a march over fdst and fsrc
	m := march.New(s.ctx, s.fdst, s.fsrc, s.dir, s)
	m.Run()

	s.stopTrackRenames()
	if s.trackRenames {
		// Build the map of the remaining dstFiles by hash
		s.makeRenameMap()
		// Attempt renames for all the files which don't have a matching dst
		for _, src := range s.renameCheck {
			s.toBeRenamed <- fs.ObjectPair{Src: src, Dst: nil}
		}
	}

	// Stop background checking and transferring pipeline
	s.stopCheckers()
	s.stopRenamers()
	s.stopTransfers()
	s.stopDeleters()

	// Delete files after
	if s.deleteMode == fs.DeleteModeAfter {
		if s.currentError() != nil {
			fs.Errorf(s.fdst, "%v", fs.ErrorNotDeleting)
		} else {
			s.processError(s.deleteFiles(false))
		}
	}

	// Prune empty directories
	if s.deleteMode != fs.DeleteModeOff {
		if s.currentError() != nil {
			fs.Errorf(s.fdst, "%v", fs.ErrorNotDeletingDirs)
		} else {
			s.processError(deleteEmptyDirectories(s.fdst, s.dstEmptyDirs))
		}
	}

	// Delete empty fsrc subdirectories
	// if DoMove and --delete-empty-src-dirs flag is set
	if s.DoMove && s.deleteEmptySrcDirs {
		//delete empty subdirectories that were part of the move
		s.processError(deleteEmptyDirectories(s.fsrc, s.srcEmptyDirs))
	}
	return s.currentError()
}

// DstOnly have an object which is in the destination only
func (s *syncCopyMove) DstOnly(dst fs.DirEntry) (recurse bool) {
	if s.deleteMode == fs.DeleteModeOff {
		return false
	}
	switch x := dst.(type) {
	case fs.Object:
		switch s.deleteMode {
		case fs.DeleteModeAfter:
			// record object as needs deleting
			s.dstFilesMu.Lock()
			s.dstFiles[x.Remote()] = x
			s.dstFilesMu.Unlock()
		case fs.DeleteModeDuring, fs.DeleteModeOnly:
			s.deleteFilesCh <- x
		default:
			panic(fmt.Sprintf("unexpected delete mode %d", s.deleteMode))
		}
	case fs.Directory:
		// Do the same thing to the entire contents of the directory
		// Record directory as it is potentially empty and needs deleting
		if s.fdst.Features().CanHaveEmptyDirectories {
			s.dstEmptyDirsMu.Lock()
			s.dstEmptyDirs = append(s.dstEmptyDirs, dst)
			s.dstEmptyDirsMu.Unlock()
		}
		return true
	default:
		panic("Bad object in DirEntries")

	}
	return false
}

// SrcOnly have an object which is in the source only
func (s *syncCopyMove) SrcOnly(src fs.DirEntry) (recurse bool) {
	if s.deleteMode == fs.DeleteModeOnly {
		return false
	}
	switch x := src.(type) {
	case fs.Object:
		if s.trackRenames {
			// Save object to check for a rename later
			s.trackRenamesCh <- x
		} else {
			// No need to check since doesn't exist
			s.toBeUploaded <- fs.ObjectPair{Src: x, Dst: nil}
		}
	case fs.Directory:
		// Do the same thing to the entire contents of the directory
		// Record the directory for deletion
		s.srcEmptyDirsMu.Lock()
		s.srcEmptyDirs = append(s.srcEmptyDirs, src)
		s.srcEmptyDirsMu.Unlock()
		return true
	default:
		panic("Bad object in DirEntries")
	}
	return false
}

// Match is called when src and dst are present, so sync src to dst
func (s *syncCopyMove) Match(dst, src fs.DirEntry) (recurse bool) {
	switch srcX := src.(type) {
	case fs.Object:
		if s.deleteMode == fs.DeleteModeOnly {
			return false
		}
		dstX, ok := dst.(fs.Object)
		if ok {
			s.toBeChecked <- fs.ObjectPair{Src: srcX, Dst: dstX}
		} else {
			// FIXME src is file, dst is directory
			err := errors.New("can't overwrite directory with file")
			fs.Errorf(dst, "%v", err)
			s.processError(err)
		}
	case fs.Directory:
		// Do the same thing to the entire contents of the directory
		_, ok := dst.(fs.Directory)
		if ok {
			// Record the src directory for deletion
			s.srcEmptyDirsMu.Lock()
			s.srcEmptyDirs = append(s.srcEmptyDirs, src)
			s.srcEmptyDirsMu.Unlock()
			return true
		}
		// FIXME src is dir, dst is file
		err := errors.New("can't overwrite file with directory")
		fs.Errorf(dst, "%v", err)
		s.processError(err)
	default:
		panic("Bad object in DirEntries")
	}
	return false
}

// Syncs fsrc into fdst
//
// If Delete is true then it deletes any files in fdst that aren't in fsrc
//
// If DoMove is true then files will be moved instead of copied
//
// dir is the start directory, "" for root
func runSyncCopyMove(fdst, fsrc fs.Fs, deleteMode fs.DeleteMode, DoMove bool, deleteEmptySrcDirs bool) error {
	if deleteMode != fs.DeleteModeOff && DoMove {
		return fserrors.FatalError(errors.New("can't delete and move at the same time"))
	}
	// Run an extra pass to delete only
	if deleteMode == fs.DeleteModeBefore {
		if fs.Config.TrackRenames {
			return fserrors.FatalError(errors.New("can't use --delete-before with --track-renames"))
		}
		// only delete stuff during in this pass
		do, err := newSyncCopyMove(fdst, fsrc, fs.DeleteModeOnly, false, deleteEmptySrcDirs)
		if err != nil {
			return err
		}
		err = do.run()
		if err != nil {
			return err
		}
		// Next pass does a copy only
		deleteMode = fs.DeleteModeOff
	}
	do, err := newSyncCopyMove(fdst, fsrc, deleteMode, DoMove, deleteEmptySrcDirs)
	if err != nil {
		return err
	}
	return do.run()
}

// Sync fsrc into fdst
func Sync(fdst, fsrc fs.Fs) error {
	return runSyncCopyMove(fdst, fsrc, fs.Config.DeleteMode, false, false)
}

// CopyDir copies fsrc into fdst
func CopyDir(fdst, fsrc fs.Fs) error {
	return runSyncCopyMove(fdst, fsrc, fs.DeleteModeOff, false, false)
}

// moveDir moves fsrc into fdst
func moveDir(fdst, fsrc fs.Fs, deleteEmptySrcDirs bool) error {
	return runSyncCopyMove(fdst, fsrc, fs.DeleteModeOff, true, deleteEmptySrcDirs)
}

// MoveDir moves fsrc into fdst
func MoveDir(fdst, fsrc fs.Fs, deleteEmptySrcDirs bool) error {
	if operations.Same(fdst, fsrc) {
		fs.Errorf(fdst, "Nothing to do as source and destination are the same")
		return nil
	}

	// First attempt to use DirMover if exists, same Fs and no filters are active
	if fdstDirMove := fdst.Features().DirMove; fdstDirMove != nil && operations.SameConfig(fsrc, fdst) && filter.Active.InActive() {
		if fs.Config.DryRun {
			fs.Logf(fdst, "Not doing server side directory move as --dry-run")
			return nil
		}
		fs.Debugf(fdst, "Using server side directory move")
		err := fdstDirMove(fsrc, "", "")
		switch err {
		case fs.ErrorCantDirMove, fs.ErrorDirExists:
			fs.Infof(fdst, "Server side directory move failed - fallback to file moves: %v", err)
		case nil:
			fs.Infof(fdst, "Server side directory move succeeded")
			return nil
		default:
			fs.CountError(err)
			fs.Errorf(fdst, "Server side directory move failed: %v", err)
			return err
		}
	}

	// The two remotes mustn't overlap if we didn't do server side move
	if operations.Overlapping(fdst, fsrc) {
		err := fs.ErrorCantMoveOverlapping
		fs.Errorf(fdst, "%v", err)
		return err
	}

	// Otherwise move the files one by one
	return moveDir(fdst, fsrc, deleteEmptySrcDirs)
}