// Generic operations on filesystems and objects

package fs

import (
	"fmt"
	"io"
	"mime"
	"path"
	"strings"
	"sync"
	"sync/atomic"
	"time"

	"golang.org/x/text/unicode/norm"
)

// CalculateModifyWindow works out modify window for Fses passed in -
// sets Config.ModifyWindow
//
// This is the largest modify window of all the fses in use, and the
// user configured value
func CalculateModifyWindow(fs ...Fs) {
	for _, f := range fs {
		if f != nil {
			precision := f.Precision()
			if precision > Config.ModifyWindow {
				Config.ModifyWindow = precision
			}
			if precision == ModTimeNotSupported {
				Debug(f, "Modify window not supported")
				return
			}
		}
	}
	Debug(fs[0], "Modify window is %s", Config.ModifyWindow)
}

// HashEquals checks to see if src == dst, but ignores empty strings
// and returns true if either is empty.
func HashEquals(src, dst string) bool {
	if src == "" || dst == "" {
		return true
	}
	return src == dst
}

// CheckHashes checks the two files to see if they have common
// known hash types and compares them
//
// Returns
//
// equal - which is equality of the hashes
//
// hash - the HashType. This is HashNone if either of the hashes were
// unset or a compatible hash couldn't be found.
//
// err - may return an error which will already have been logged
//
// If an error is returned it will return equal as false
func CheckHashes(src, dst Object) (equal bool, hash HashType, err error) {
	common := src.Fs().Hashes().Overlap(dst.Fs().Hashes())
	// Debug(nil, "Shared hashes: %v", common)
	if common.Count() == 0 {
		return true, HashNone, nil
	}
	hash = common.GetOne()
	srcHash, err := src.Hash(hash)
	if err != nil {
		Stats.Error()
		ErrorLog(src, "Failed to calculate src hash: %s", err)
		return false, hash, err
	}
	if srcHash == "" {
		return true, HashNone, nil
	}
	dstHash, err := dst.Hash(hash)
	if err != nil {
		Stats.Error()
		ErrorLog(dst, "Failed to calculate dst hash: %s", err)
		return false, hash, err
	}
	if dstHash == "" {
		return true, HashNone, nil
	}
	return srcHash == dstHash, hash, nil
}

// Equal checks to see if the src and dst objects are equal by looking at
// size, mtime and hash
//
// If the src and dst size are different then it is considered to be
// not equal.  If --size-only is in effect then this is the only check
// that is done.
//
// If the size is the same and the mtime is the same then it is
// considered to be equal.  This check is skipped if using --checksum.
//
// If the size is the same and mtime is different, unreadable or
// --checksum is set and the hash is the same then the file is
// considered to be equal.  In this case the mtime on the dst is
// updated if --checksum is not set.
//
// Otherwise the file is considered to be not equal including if there
// were errors reading info.
func Equal(src, dst Object) bool {
	if src.Size() != dst.Size() {
		Debug(src, "Sizes differ")
		return false
	}
	if Config.SizeOnly {
		Debug(src, "Sizes identical")
		return true
	}

	var srcModTime time.Time
	if !Config.CheckSum {
		if Config.ModifyWindow == ModTimeNotSupported {
			Debug(src, "Sizes identical")
			return true
		}
		// Size the same so check the mtime
		srcModTime = src.ModTime()
		dstModTime := dst.ModTime()
		dt := dstModTime.Sub(srcModTime)
		ModifyWindow := Config.ModifyWindow
		if dt >= ModifyWindow || dt <= -ModifyWindow {
			Debug(src, "Modification times differ by %s: %v, %v", dt, srcModTime, dstModTime)
		} else {
			Debug(src, "Size and modification time the same (differ by %s, within tolerance %s)", dt, ModifyWindow)
			return true
		}
	}

	// mtime is unreadable or different but size is the same so
	// check the hash
	same, hash, _ := CheckHashes(src, dst)
	if !same {
		Debug(src, "Hash differ")
		return false
	}

	if !Config.CheckSum {
		// Size and hash the same but mtime different so update the
		// mtime of the dst object here
		dst.SetModTime(srcModTime)
	}

	if hash == HashNone {
		Debug(src, "Size of src and dst objects identical")
	} else {
		Debug(src, "Size and %v of src and dst objects identical", hash)
	}
	return true
}

// MimeType returns a guess at the mime type from the extension
func MimeType(o Object) string {
	mimeType := mime.TypeByExtension(path.Ext(o.Remote()))
	if mimeType == "" {
		mimeType = "application/octet-stream"
	}
	return mimeType
}

// Used to remove a failed copy
//
// Returns whether the file was succesfully removed or not
func removeFailedCopy(dst Object) bool {
	if dst == nil {
		return false
	}
	Debug(dst, "Removing failed copy")
	removeErr := dst.Remove()
	if removeErr != nil {
		Debug(dst, "Failed to remove failed copy: %s", removeErr)
		return false
	}
	return true
}

// Copy src object to dst or f if nil
//
// If dst is nil then the object must not exist already.  If you do
// call Copy() with dst nil on a pre-existing file then some filing
// systems (eg Drive) may duplicate the file.
func Copy(f Fs, dst, src Object) {
	const maxTries = 10
	tries := 0
	doUpdate := dst != nil
	var err, inErr error
tryAgain:
	// Try server side copy first - if has optional interface and
	// is same underlying remote
	actionTaken := "Copied (server side copy)"
	if fCopy, ok := f.(Copier); ok && src.Fs().Name() == f.Name() {
		var newDst Object
		newDst, err = fCopy.Copy(src, src.Remote())
		if err == nil {
			dst = newDst
		}
	} else {
		err = ErrorCantCopy
	}
	// If can't server side copy, do it manually
	if err == ErrorCantCopy {
		var in0 io.ReadCloser
		in0, err = src.Open()
		if err != nil {
			Stats.Error()
			ErrorLog(src, "Failed to open: %s", err)
			return
		}

		// On big files add a buffer
		if src.Size() > 10<<20 {
			in0, _ = newAsyncReader(in0, 4, 4<<20)
		}

		in := NewAccount(in0, src) // account the transfer

		if doUpdate {
			actionTaken = "Copied (updated existing)"
			err = dst.Update(in, src.ModTime(), src.Size())
		} else {
			actionTaken = "Copied (new)"
			dst, err = f.Put(in, src.Remote(), src.ModTime(), src.Size())
		}
		inErr = in.Close()
	}
	// Retry if err returned a retry error
	if r, ok := err.(Retry); ok && r.Retry() && tries < maxTries {
		tries++
		Log(src, "Received error: %v - retrying %d/%d", err, tries, maxTries)
		if removeFailedCopy(dst) {
			// If we removed dst, then nil it out and note we are not updating
			dst = nil
			doUpdate = false
		}
		goto tryAgain
	}
	if err == nil {
		err = inErr
	}
	if err != nil {
		Stats.Error()
		ErrorLog(src, "Failed to copy: %s", err)
		removeFailedCopy(dst)
		return
	}

	// Verify sizes are the same after transfer
	if src.Size() != dst.Size() {
		Stats.Error()
		err = fmt.Errorf("Corrupted on transfer: sizes differ %d vs %d", src.Size(), dst.Size())
		ErrorLog(dst, "%s", err)
		removeFailedCopy(dst)
		return
	}

	// Verify hashes are the same after transfer - ignoring blank hashes
	// TODO(klauspost): This could be extended, so we always create a hash type matching
	// the destination, and calculate it while sending.
	common := src.Fs().Hashes().Overlap(dst.Fs().Hashes())
	// Debug(src, "common hashes: %v", common)
	if !Config.SizeOnly && common.Count() > 0 {
		// Get common hash type
		hashType := common.GetOne()

		srcSum, err := src.Hash(hashType)
		if err != nil {
			Stats.Error()
			ErrorLog(src, "Failed to read src hash: %s", err)
		} else if srcSum != "" {
			dstSum, err := dst.Hash(hashType)
			if err != nil {
				Stats.Error()
				ErrorLog(dst, "Failed to read hash: %s", err)
			} else if !HashEquals(srcSum, dstSum) {
				Stats.Error()
				err = fmt.Errorf("Corrupted on transfer: %v hash differ %q vs %q", hashType, srcSum, dstSum)
				ErrorLog(dst, "%s", err)
				removeFailedCopy(dst)
				return
			}
		}
	}

	Debug(src, actionTaken)
}

// Check to see if src needs to be copied to dst and if so puts it in out
func checkOne(pair ObjectPair, out ObjectPairChan) {
	src, dst := pair.src, pair.dst
	if dst == nil {
		Debug(src, "Couldn't find file - need to transfer")
		out <- pair
		return
	}
	// Check to see if can store this
	if !src.Storable() {
		return
	}
	// If we should ignore existing files, don't transfer
	if Config.IgnoreExisting {
		Debug(src, "Destination exists, skipping")
		return
	}
	// Check to see if changed or not
	if Equal(src, dst) {
		Debug(src, "Unchanged skipping")
		return
	}
	out <- pair
}

// PairChecker reads Objects~s on in send to out if they need transferring.
//
// FIXME potentially doing lots of hashes at once
func PairChecker(in ObjectPairChan, out ObjectPairChan, wg *sync.WaitGroup) {
	defer wg.Done()
	for pair := range in {
		src := pair.src
		Stats.Checking(src)
		checkOne(pair, out)
		Stats.DoneChecking(src)
	}
}

// PairCopier reads Objects on in and copies them.
func PairCopier(in ObjectPairChan, fdst Fs, wg *sync.WaitGroup) {
	defer wg.Done()
	for pair := range in {
		src := pair.src
		Stats.Transferring(src)
		if Config.DryRun {
			Log(src, "Not copying as --dry-run")
		} else {
			Copy(fdst, pair.dst, src)
		}
		Stats.DoneTransferring(src)
	}
}

// PairMover reads Objects on in and moves them if possible, or copies
// them if not
func PairMover(in ObjectPairChan, fdst Fs, wg *sync.WaitGroup) {
	defer wg.Done()
	// See if we have Move available
	fdstMover, haveMover := fdst.(Mover)
	for pair := range in {
		src := pair.src
		dst := pair.dst
		Stats.Transferring(src)
		if Config.DryRun {
			Log(src, "Not moving as --dry-run")
		} else if haveMover {
			// Delete destination if it exists
			if pair.dst != nil {
				err := dst.Remove()
				if err != nil {
					Stats.Error()
					ErrorLog(dst, "Couldn't delete: %v", err)
				}
			}
			_, err := fdstMover.Move(src, src.Remote())
			if err != nil {
				Stats.Error()
				ErrorLog(dst, "Couldn't move: %v", err)
			} else {
				Debug(src, "Moved")
			}
		} else {
			Copy(fdst, pair.dst, src)
		}
		Stats.DoneTransferring(src)
	}
}

// DeleteFiles removes all the files passed in the channel
func DeleteFiles(toBeDeleted ObjectsChan) {
	var wg sync.WaitGroup
	wg.Add(Config.Transfers)
	for i := 0; i < Config.Transfers; i++ {
		go func() {
			defer wg.Done()
			for dst := range toBeDeleted {
				if Config.DryRun {
					Log(dst, "Not deleting as --dry-run")
				} else {
					Stats.Checking(dst)
					err := dst.Remove()
					Stats.DoneChecking(dst)
					if err != nil {
						Stats.Error()
						ErrorLog(dst, "Couldn't delete: %s", err)
					} else {
						Debug(dst, "Deleted")
					}
				}
			}
		}()
	}
	Log(nil, "Waiting for deletions to finish")
	wg.Wait()
}

// Read a map of Object.Remote to Object for the given Fs.
// If includeAll is specified all files will be added,
// otherwise only files passing the filter will be added.
func readFilesMap(fs Fs, includeAll bool) map[string]Object {
	files := make(map[string]Object)
	normalised := make(map[string]struct{})
	for o := range fs.List() {
		remote := o.Remote()
		normalisedRemote := strings.ToLower(norm.NFC.String(remote))
		if _, ok := files[remote]; !ok {
			// Make sure we don't delete excluded files if not required
			if includeAll || Config.Filter.IncludeObject(o) {
				files[remote] = o
				if _, ok := normalised[normalisedRemote]; ok {
					Log(o, "Warning: File found with same name but different case on %v", o.Fs())
				}
			} else {
				Debug(o, "Excluded from sync (and deletion)")
			}
		} else {
			Log(o, "Duplicate file detected")
		}
		normalised[normalisedRemote] = struct{}{}
	}
	return files
}

// Same returns true if fdst and fsrc point to the same underlying Fs
func Same(fdst, fsrc Fs) bool {
	return fdst.Name() == fsrc.Name() && fdst.Root() == fsrc.Root()
}

// 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
func syncCopyMove(fdst, fsrc Fs, Delete bool, DoMove bool) error {
	if Same(fdst, fsrc) {
		ErrorLog(fdst, "Nothing to do as source and destination are the same")
		return nil
	}

	err := fdst.Mkdir()
	if err != nil {
		Stats.Error()
		return err
	}

	Log(fdst, "Building file list")

	// Read the files of both source and destination
	var listWg sync.WaitGroup
	listWg.Add(2)

	var dstFiles map[string]Object
	var srcFiles map[string]Object
	var srcObjects = make(ObjectsChan, Config.Transfers)

	// Read dst files including excluded files if DeleteExcluded is set
	go func() {
		dstFiles = readFilesMap(fdst, Config.Filter.DeleteExcluded)
		listWg.Done()
	}()

	// Read src file not including excluded files
	go func() {
		srcFiles = readFilesMap(fsrc, false)
		listWg.Done()
		for _, v := range srcFiles {
			srcObjects <- v
		}
		close(srcObjects)
	}()

	startDeletion := make(chan struct{}, 0)

	// Delete files if asked
	var delWg sync.WaitGroup
	delWg.Add(1)
	go func() {
		if !Delete {
			return
		}
		defer func() {
			Debug(fdst, "Deletion finished")
			delWg.Done()
		}()

		_ = <-startDeletion
		Debug(fdst, "Starting deletion")

		if Stats.Errored() {
			ErrorLog(fdst, "Not deleting files as there were IO errors")
			return
		}

		// Delete the spare files
		toDelete := make(ObjectsChan, Config.Transfers)

		go func() {
			for key, fs := range dstFiles {
				_, exists := srcFiles[key]
				if !exists {
					toDelete <- fs
				}
			}
			close(toDelete)
		}()
		DeleteFiles(toDelete)
	}()

	// Wait for all files to be read
	listWg.Wait()

	// Start deleting, unless we must delete after transfer
	if Delete && !Config.DeleteAfter {
		close(startDeletion)
	}

	// If deletes must finish before starting transfers, we must wait now.
	if Delete && Config.DeleteBefore {
		Log(fdst, "Waiting for deletes to finish (before)")
		delWg.Wait()
	}

	// Read source files checking them off against dest files
	toBeChecked := make(ObjectPairChan, Config.Transfers)
	toBeUploaded := make(ObjectPairChan, Config.Transfers)

	var checkerWg sync.WaitGroup
	checkerWg.Add(Config.Checkers)
	for i := 0; i < Config.Checkers; i++ {
		go PairChecker(toBeChecked, toBeUploaded, &checkerWg)
	}

	var copierWg sync.WaitGroup
	copierWg.Add(Config.Transfers)
	for i := 0; i < Config.Transfers; i++ {
		if DoMove {
			go PairMover(toBeUploaded, fdst, &copierWg)
		} else {
			go PairCopier(toBeUploaded, fdst, &copierWg)
		}
	}

	go func() {
		for src := range srcObjects {
			remote := src.Remote()
			if dst, dstFound := dstFiles[remote]; dstFound {
				toBeChecked <- ObjectPair{src, dst}
			} else {
				// No need to check since doesn't exist
				toBeUploaded <- ObjectPair{src, nil}
			}
		}
		close(toBeChecked)
	}()

	Log(fdst, "Waiting for checks to finish")
	checkerWg.Wait()
	close(toBeUploaded)
	Log(fdst, "Waiting for transfers to finish")
	copierWg.Wait()

	// If deleting after, start deletion now
	if Delete && Config.DeleteAfter {
		close(startDeletion)
	}
	// Unless we have already waited, wait for deletion to finish.
	if Delete && !Config.DeleteBefore {
		Log(fdst, "Waiting for deletes to finish (during+after)")
		delWg.Wait()
	}

	return nil
}

// Sync fsrc into fdst
func Sync(fdst, fsrc Fs) error {
	return syncCopyMove(fdst, fsrc, true, false)
}

// CopyDir copies fsrc into fdst
func CopyDir(fdst, fsrc Fs) error {
	return syncCopyMove(fdst, fsrc, false, false)
}

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

	// First attempt to use DirMover
	if fdstDirMover, ok := fdst.(DirMover); ok && fsrc.Name() == fdst.Name() {
		err := fdstDirMover.DirMove(fsrc)
		Debug(fdst, "Using server side directory move")
		switch err {
		case ErrorCantDirMove, ErrorDirExists:
			Debug(fdst, "Server side directory move failed - fallback to copy/delete: %v", err)
		case nil:
			Debug(fdst, "Server side directory move succeeded")
			return nil
		default:
			Stats.Error()
			ErrorLog(fdst, "Server side directory move failed: %v", err)
			return err
		}
	}

	// Now move the files
	err := syncCopyMove(fdst, fsrc, false, true)
	if err != nil || Stats.Errored() {
		ErrorLog(fdst, "Not deleting files as there were IO errors")
		return err
	}
	return Purge(fsrc)
}

// Check the files in fsrc and fdst according to Size and hash
func Check(fdst, fsrc Fs) error {
	differences := int32(0)
	var (
		wg                 sync.WaitGroup
		dstFiles, srcFiles map[string]Object
	)

	wg.Add(2)
	go func() {
		defer wg.Done()
		// Read the destination files
		Log(fdst, "Building file list")
		dstFiles = readFilesMap(fdst, false)
		Debug(fdst, "Done building file list")
	}()

	go func() {
		defer wg.Done()
		// Read the source files
		Log(fsrc, "Building file list")
		srcFiles = readFilesMap(fsrc, false)
		Debug(fdst, "Done building file list")
	}()

	wg.Wait()

	// FIXME could do this as it goes along and make it use less
	// memory.

	// Move all the common files into commonFiles and delete then
	// from srcFiles and dstFiles
	commonFiles := make(map[string][]Object)
	for remote, src := range srcFiles {
		if dst, ok := dstFiles[remote]; ok {
			commonFiles[remote] = []Object{dst, src}
			delete(srcFiles, remote)
			delete(dstFiles, remote)
		}
	}

	Log(fdst, "%d files not in %v", len(dstFiles), fsrc)
	for _, dst := range dstFiles {
		Stats.Error()
		ErrorLog(dst, "File not in %v", fsrc)
		atomic.AddInt32(&differences, 1)
	}

	Log(fsrc, "%d files not in %s", len(srcFiles), fdst)
	for _, src := range srcFiles {
		Stats.Error()
		ErrorLog(src, "File not in %v", fdst)
		atomic.AddInt32(&differences, 1)
	}

	checks := make(chan []Object, Config.Transfers)
	go func() {
		for _, check := range commonFiles {
			checks <- check
		}
		close(checks)
	}()

	var checkerWg sync.WaitGroup
	checkerWg.Add(Config.Checkers)
	for i := 0; i < Config.Checkers; i++ {
		go func() {
			defer checkerWg.Done()
			for check := range checks {
				dst, src := check[0], check[1]
				Stats.Checking(src)
				if src.Size() != dst.Size() {
					Stats.DoneChecking(src)
					Stats.Error()
					ErrorLog(src, "Sizes differ")
					atomic.AddInt32(&differences, 1)
					continue
				}
				same, _, err := CheckHashes(src, dst)
				Stats.DoneChecking(src)
				if err != nil {
					continue
				}
				if !same {
					Stats.Error()
					atomic.AddInt32(&differences, 1)
					ErrorLog(src, "Md5sums differ")
				}
				Debug(src, "OK")
			}
		}()
	}

	Log(fdst, "Waiting for checks to finish")
	checkerWg.Wait()
	Log(fdst, "%d differences found", Stats.GetErrors())
	if differences > 0 {
		return fmt.Errorf("%d differences found", differences)
	}
	return nil
}

// ListFn lists the Fs to the supplied function
//
// Lists in parallel which may get them out of order
func ListFn(f Fs, fn func(Object)) error {
	in := f.List()
	var wg sync.WaitGroup
	wg.Add(Config.Checkers)
	for i := 0; i < Config.Checkers; i++ {
		go func() {
			defer wg.Done()
			for o := range in {
				if Config.Filter.IncludeObject(o) {
					fn(o)
				}
			}
		}()
	}
	wg.Wait()
	return nil
}

// mutex for synchronized output
var outMutex sync.Mutex

// Synchronized fmt.Fprintf
//
// Ignores errors from Fprintf
func syncFprintf(w io.Writer, format string, a ...interface{}) {
	outMutex.Lock()
	defer outMutex.Unlock()
	_, _ = fmt.Fprintf(w, format, a...)
}

// List the Fs to the supplied writer
//
// Shows size and path - obeys includes and excludes
//
// Lists in parallel which may get them out of order
func List(f Fs, w io.Writer) error {
	return ListFn(f, func(o Object) {
		syncFprintf(w, "%9d %s\n", o.Size(), o.Remote())
	})
}

// ListLong lists the Fs to the supplied writer
//
// Shows size, mod time and path - obeys includes and excludes
//
// Lists in parallel which may get them out of order
func ListLong(f Fs, w io.Writer) error {
	return ListFn(f, func(o Object) {
		Stats.Checking(o)
		modTime := o.ModTime()
		Stats.DoneChecking(o)
		syncFprintf(w, "%9d %s %s\n", o.Size(), modTime.Local().Format("2006-01-02 15:04:05.000000000"), o.Remote())
	})
}

// Md5sum list the Fs to the supplied writer
//
// Produces the same output as the md5sum command - obeys includes and
// excludes
//
// Lists in parallel which may get them out of order
func Md5sum(f Fs, w io.Writer) error {
	return hashLister(HashMD5, f, w)
}

// Sha1sum list the Fs to the supplied writer
//
// Obeys includes and excludes
//
// Lists in parallel which may get them out of order
func Sha1sum(f Fs, w io.Writer) error {
	return hashLister(HashSHA1, f, w)
}

func hashLister(ht HashType, f Fs, w io.Writer) error {
	return ListFn(f, func(o Object) {
		Stats.Checking(o)
		sum, err := o.Hash(ht)
		Stats.DoneChecking(o)
		if err == ErrHashUnsupported {
			sum = "UNSUPPORTED"
		} else if err != nil {
			Debug(o, "Failed to read %v: %v", ht, err)
			sum = "ERROR"
		}
		syncFprintf(w, "%*s  %s\n", HashWidth[ht], sum, o.Remote())
	})
}

// Count counts the objects and their sizes in the Fs
//
// Obeys includes and excludes
func Count(f Fs) (objects int64, size int64, err error) {
	err = ListFn(f, func(o Object) {
		atomic.AddInt64(&objects, 1)
		atomic.AddInt64(&size, o.Size())
	})
	return
}

// ListDir lists the directories/buckets/containers in the Fs to the supplied writer
func ListDir(f Fs, w io.Writer) error {
	for dir := range f.ListDir() {
		syncFprintf(w, "%12d %13s %9d %s\n", dir.Bytes, dir.When.Format("2006-01-02 15:04:05"), dir.Count, dir.Name)
	}
	return nil
}

// Mkdir makes a destination directory or container
func Mkdir(f Fs) error {
	err := f.Mkdir()
	if err != nil {
		Stats.Error()
		return err
	}
	return nil
}

// Rmdir removes a container but not if not empty
func Rmdir(f Fs) error {
	if Config.DryRun {
		Log(f, "Not deleting as dry run is set")
	} else {
		err := f.Rmdir()
		if err != nil {
			Stats.Error()
			return err
		}
	}
	return nil
}

// Purge removes a container and all of its contents
//
// FIXME doesn't delete local directories
func Purge(f Fs) error {
	doFallbackPurge := true
	var err error
	if purger, ok := f.(Purger); ok {
		doFallbackPurge = false
		if Config.DryRun {
			Log(f, "Not purging as --dry-run set")
		} else {
			err = purger.Purge()
			if err == ErrorCantPurge {
				doFallbackPurge = true
			}
		}
	}
	if doFallbackPurge {
		// DeleteFiles and Rmdir observe --dry-run
		DeleteFiles(f.List())
		err = Rmdir(f)
	}
	if err != nil {
		Stats.Error()
		return err
	}
	return nil
}

// Delete removes all the contents of a container.  Unlike Purge, it
// obeys includes and excludes.
func Delete(f Fs) error {
	wg := new(sync.WaitGroup)
	delete := make(ObjectsChan, Config.Transfers)
	wg.Add(1)
	go func() {
		defer wg.Done()
		DeleteFiles(delete)
	}()
	err := ListFn(f, func(o Object) {
		delete <- o
	})
	close(delete)
	return err
}