frostfs-s3-gw/api/layer/multipart_upload.go

package layer

import (
	"bytes"
	"context"
	"crypto/md5"
	"encoding/base64"
	"encoding/hex"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"sort"
	"strconv"
	"strings"
	"time"

	"git.frostfs.info/TrueCloudLab/frostfs-s3-gw/api/auth"
	"git.frostfs.info/TrueCloudLab/frostfs-s3-gw/api/data"
	s3errors "git.frostfs.info/TrueCloudLab/frostfs-s3-gw/api/errors"
	"git.frostfs.info/TrueCloudLab/frostfs-s3-gw/api/layer/encryption"
	"git.frostfs.info/TrueCloudLab/frostfs-s3-gw/internal/logs"
	oid "git.frostfs.info/TrueCloudLab/frostfs-sdk-go/object/id"
	"git.frostfs.info/TrueCloudLab/frostfs-sdk-go/user"
	"github.com/minio/sio"
	"go.uber.org/zap"
)

const (
	UploadIDAttributeName         = "S3-Upload-Id"
	UploadPartNumberAttributeName = "S3-Upload-Part-Number"
	UploadCompletedParts          = "S3-Completed-Parts"

	// MultipartObjectSize contains the real object size if object is combined (payload contains list of parts).
	// This header is used to determine if object is combined.
	MultipartObjectSize = "S3-Multipart-Object-Size"

	metaPrefix = "meta-"
	aclPrefix  = "acl-"

	MaxSizeUploadsList  = 1000
	MaxSizePartsList    = 1000
	UploadMinPartNumber = 1
	UploadMaxPartNumber = 10000
	UploadMinSize       = 5 * 1024 * 1024      // 5MB
	UploadMaxSize       = 1024 * UploadMinSize // 5GB
)

type (
	UploadInfoParams struct {
		UploadID   string
		Bkt        *data.BucketInfo
		Key        string
		Encryption encryption.Params
	}

	CreateMultipartParams struct {
		Info          *UploadInfoParams
		Header        map[string]string
		Data          *UploadData
		CopiesNumbers []uint32
	}

	UploadData struct {
		TagSet     map[string]string
		ACLHeaders map[string]string
	}

	UploadPartParams struct {
		Info              *UploadInfoParams
		PartNumber        int
		Size              uint64
		Reader            io.Reader
		ContentMD5        string
		ContentSHA256Hash string
	}

	UploadCopyParams struct {
		Versioned     bool
		Info          *UploadInfoParams
		SrcObjInfo    *data.ObjectInfo
		SrcBktInfo    *data.BucketInfo
		SrcEncryption encryption.Params
		PartNumber    int
		Range         *RangeParams
	}

	CompleteMultipartParams struct {
		Info  *UploadInfoParams
		Parts []*CompletedPart
	}

	CompletedPart struct {
		ETag       string
		PartNumber int
	}

	EncryptedPart struct {
		Part
		EncryptedSize int64
	}

	Part struct {
		ETag         string
		LastModified string
		PartNumber   int
		Size         uint64
	}

	ListMultipartUploadsParams struct {
		Bkt            *data.BucketInfo
		Delimiter      string
		EncodingType   string
		KeyMarker      string
		MaxUploads     int
		Prefix         string
		UploadIDMarker string
	}

	ListPartsParams struct {
		Info             *UploadInfoParams
		MaxParts         int
		PartNumberMarker int
	}

	ListPartsInfo struct {
		Parts                []*Part
		Owner                user.ID
		NextPartNumberMarker int
		IsTruncated          bool
	}

	ListMultipartUploadsInfo struct {
		Prefixes           []string
		Uploads            []*UploadInfo
		IsTruncated        bool
		NextKeyMarker      string
		NextUploadIDMarker string
	}
	UploadInfo struct {
		IsDir    bool
		Key      string
		UploadID string
		Owner    user.ID
		Created  time.Time
	}
)

func (n *layer) CreateMultipartUpload(ctx context.Context, p *CreateMultipartParams) error {
	metaSize := len(p.Header)
	if p.Data != nil {
		metaSize += len(p.Data.ACLHeaders)
		metaSize += len(p.Data.TagSet)
	}

	info := &data.MultipartInfo{
		Key:           p.Info.Key,
		UploadID:      p.Info.UploadID,
		Owner:         n.gateOwner,
		Created:       TimeNow(ctx),
		Meta:          make(map[string]string, metaSize),
		CopiesNumbers: p.CopiesNumbers,
	}

	for key, val := range p.Header {
		info.Meta[metaPrefix+key] = val
	}

	if p.Data != nil {
		for key, val := range p.Data.ACLHeaders {
			info.Meta[aclPrefix+key] = val
		}

		for key, val := range p.Data.TagSet {
			info.Meta[tagPrefix+key] = val
		}
	}

	if p.Info.Encryption.Enabled() {
		if err := addEncryptionHeaders(info.Meta, p.Info.Encryption); err != nil {
			return fmt.Errorf("add encryption header: %w", err)
		}
	}

	return n.treeService.CreateMultipartUpload(ctx, p.Info.Bkt, info)
}

func (n *layer) UploadPart(ctx context.Context, p *UploadPartParams) (string, error) {
	multipartInfo, err := n.treeService.GetMultipartUpload(ctx, p.Info.Bkt, p.Info.Key, p.Info.UploadID)
	if err != nil {
		if errors.Is(err, ErrNodeNotFound) {
			return "", fmt.Errorf("%w: %s", s3errors.GetAPIError(s3errors.ErrNoSuchUpload), err.Error())
		}
		return "", err
	}

	if p.Size > UploadMaxSize {
		return "", fmt.Errorf("%w: %d/%d", s3errors.GetAPIError(s3errors.ErrEntityTooLarge), p.Size, UploadMaxSize)
	}

	objInfo, err := n.uploadPart(ctx, multipartInfo, p)
	if err != nil {
		return "", err
	}

	return objInfo.ETag(n.features.MD5Enabled()), nil
}

func (n *layer) uploadPart(ctx context.Context, multipartInfo *data.MultipartInfo, p *UploadPartParams) (*data.ObjectInfo, error) {
	encInfo := FormEncryptionInfo(multipartInfo.Meta)
	if err := p.Info.Encryption.MatchObjectEncryption(encInfo); err != nil {
		n.reqLogger(ctx).Warn(logs.MismatchedObjEncryptionInfo, zap.Error(err))
		return nil, s3errors.GetAPIError(s3errors.ErrInvalidEncryptionParameters)
	}

	bktInfo := p.Info.Bkt
	prm := PrmObjectCreate{
		Container:    bktInfo.CID,
		Attributes:   make([][2]string, 2),
		Payload:      p.Reader,
		CreationTime: TimeNow(ctx),
		CopiesNumber: multipartInfo.CopiesNumbers,
	}

	decSize := p.Size
	if p.Info.Encryption.Enabled() {
		r, encSize, err := encryptionReader(p.Reader, p.Size, p.Info.Encryption.Key())
		if err != nil {
			return nil, fmt.Errorf("failed to create ecnrypted reader: %w", err)
		}
		prm.Attributes = append(prm.Attributes, [2]string{AttributeDecryptedSize, strconv.FormatUint(p.Size, 10)})
		prm.Payload = r
		p.Size = encSize
	}

	prm.Attributes[0][0], prm.Attributes[0][1] = UploadIDAttributeName, p.Info.UploadID
	prm.Attributes[1][0], prm.Attributes[1][1] = UploadPartNumberAttributeName, strconv.Itoa(p.PartNumber)

	size, id, hash, md5Hash, err := n.objectPutAndHash(ctx, prm, bktInfo)
	if err != nil {
		return nil, err
	}
	if len(p.ContentMD5) > 0 {
		hashBytes, err := base64.StdEncoding.DecodeString(p.ContentMD5)
		if err != nil {
			return nil, s3errors.GetAPIError(s3errors.ErrInvalidDigest)
		}
		if hex.EncodeToString(hashBytes) != hex.EncodeToString(md5Hash) {
			prm := PrmObjectDelete{
				Object:    id,
				Container: bktInfo.CID,
			}
			n.prepareAuthParameters(ctx, &prm.PrmAuth, bktInfo.Owner)
			err = n.frostFS.DeleteObject(ctx, prm)
			if err != nil {
				n.reqLogger(ctx).Debug(logs.FailedToDeleteObject, zap.Stringer("cid", bktInfo.CID), zap.Stringer("oid", id))
			}
			return nil, s3errors.GetAPIError(s3errors.ErrInvalidDigest)
		}
	}
	if p.Info.Encryption.Enabled() {
		size = decSize
	}

	if !p.Info.Encryption.Enabled() && len(p.ContentSHA256Hash) > 0 && !auth.IsStandardContentSHA256(p.ContentSHA256Hash) {
		contentHashBytes, err := hex.DecodeString(p.ContentSHA256Hash)
		if err != nil {
			return nil, s3errors.GetAPIError(s3errors.ErrContentSHA256Mismatch)
		}
		if !bytes.Equal(contentHashBytes, hash) {
			err = n.objectDelete(ctx, bktInfo, id)
			if err != nil {
				n.reqLogger(ctx).Debug(logs.FailedToDeleteObject, zap.Stringer("cid", bktInfo.CID), zap.Stringer("oid", id))
			}
			return nil, s3errors.GetAPIError(s3errors.ErrContentSHA256Mismatch)
		}
	}

	n.reqLogger(ctx).Debug(logs.UploadPart,
		zap.String("multipart upload", p.Info.UploadID), zap.Int("part number", p.PartNumber),
		zap.Stringer("cid", bktInfo.CID), zap.Stringer("oid", id))

	partInfo := &data.PartInfo{
		Key:      p.Info.Key,
		UploadID: p.Info.UploadID,
		Number:   p.PartNumber,
		OID:      id,
		Size:     size,
		ETag:     hex.EncodeToString(hash),
		Created:  prm.CreationTime,
		MD5:      hex.EncodeToString(md5Hash),
	}

	oldPartID, err := n.treeService.AddPart(ctx, bktInfo, multipartInfo.ID, partInfo)
	oldPartIDNotFound := errors.Is(err, ErrNoNodeToRemove)
	if err != nil && !oldPartIDNotFound {
		return nil, err
	}
	if !oldPartIDNotFound {
		if err = n.objectDelete(ctx, bktInfo, oldPartID); err != nil {
			n.reqLogger(ctx).Error(logs.CouldntDeleteOldPartObject, zap.Error(err),
				zap.String("cid", bktInfo.CID.EncodeToString()),
				zap.String("oid", oldPartID.EncodeToString()))
		}
	}

	objInfo := &data.ObjectInfo{
		ID:  id,
		CID: bktInfo.CID,

		Owner:   bktInfo.Owner,
		Bucket:  bktInfo.Name,
		Size:    partInfo.Size,
		Created: partInfo.Created,
		HashSum: partInfo.ETag,
		MD5Sum:  partInfo.MD5,
	}

	return objInfo, nil
}

func (n *layer) UploadPartCopy(ctx context.Context, p *UploadCopyParams) (*data.ObjectInfo, error) {
	multipartInfo, err := n.treeService.GetMultipartUpload(ctx, p.Info.Bkt, p.Info.Key, p.Info.UploadID)
	if err != nil {
		if errors.Is(err, ErrNodeNotFound) {
			return nil, fmt.Errorf("%w: %s", s3errors.GetAPIError(s3errors.ErrNoSuchUpload), err.Error())
		}
		return nil, err
	}

	size := p.SrcObjInfo.Size
	srcObjectSize := p.SrcObjInfo.Size

	if objSize, err := GetObjectSize(p.SrcObjInfo); err == nil {
		srcObjectSize = objSize
		size = objSize
	}

	if p.Range != nil {
		size = p.Range.End - p.Range.Start + 1
		if p.Range.End > srcObjectSize {
			return nil, fmt.Errorf("%w: %d-%d/%d", s3errors.GetAPIError(s3errors.ErrInvalidCopyPartRangeSource), p.Range.Start, p.Range.End, srcObjectSize)
		}
	}
	if size > UploadMaxSize {
		return nil, fmt.Errorf("%w: %d/%d", s3errors.GetAPIError(s3errors.ErrEntityTooLarge), size, UploadMaxSize)
	}

	objPayload, err := n.GetObject(ctx, &GetObjectParams{
		ObjectInfo: p.SrcObjInfo,
		Versioned:  p.Versioned,
		Range:      p.Range,
		BucketInfo: p.SrcBktInfo,
		Encryption: p.SrcEncryption,
	})
	if err != nil {
		return nil, fmt.Errorf("get object to upload copy: %w", err)
	}

	params := &UploadPartParams{
		Info:       p.Info,
		PartNumber: p.PartNumber,
		Size:       size,
		Reader:     objPayload,
	}

	return n.uploadPart(ctx, multipartInfo, params)
}

func (n *layer) CompleteMultipartUpload(ctx context.Context, p *CompleteMultipartParams) (*UploadData, *data.ExtendedObjectInfo, error) {
	for i := 1; i < len(p.Parts); i++ {
		if p.Parts[i].PartNumber <= p.Parts[i-1].PartNumber {
			return nil, nil, s3errors.GetAPIError(s3errors.ErrInvalidPartOrder)
		}
	}

	multipartInfo, partsInfo, err := n.getUploadParts(ctx, p.Info)
	if err != nil {
		return nil, nil, err
	}
	encInfo := FormEncryptionInfo(multipartInfo.Meta)

	if len(partsInfo) < len(p.Parts) {
		return nil, nil, fmt.Errorf("%w: found %d parts, need %d", s3errors.GetAPIError(s3errors.ErrInvalidPart), len(partsInfo), len(p.Parts))
	}

	var multipartObjetSize uint64
	var encMultipartObjectSize uint64
	parts := make([]*data.PartInfo, 0, len(p.Parts))

	var completedPartsHeader strings.Builder
	md5Hash := md5.New()
	for i, part := range p.Parts {
		partInfo := partsInfo[part.PartNumber]
		if partInfo == nil || data.UnQuote(part.ETag) != partInfo.GetETag(n.features.MD5Enabled()) {
			return nil, nil, fmt.Errorf("%w: unknown part %d or etag mismatched", s3errors.GetAPIError(s3errors.ErrInvalidPart), part.PartNumber)
		}
		delete(partsInfo, part.PartNumber)

		// for the last part we have no minimum size limit
		if i != len(p.Parts)-1 && partInfo.Size < UploadMinSize {
			return nil, nil, fmt.Errorf("%w: %d/%d", s3errors.GetAPIError(s3errors.ErrEntityTooSmall), partInfo.Size, UploadMinSize)
		}
		parts = append(parts, partInfo)
		multipartObjetSize += partInfo.Size // even if encryption is enabled size is actual (decrypted)

		if encInfo.Enabled {
			encPartSize, err := sio.EncryptedSize(partInfo.Size)
			if err != nil {
				return nil, nil, fmt.Errorf("compute encrypted size: %w", err)
			}
			encMultipartObjectSize += encPartSize
		}

		partInfoStr := partInfo.ToHeaderString()
		if i != len(p.Parts)-1 {
			partInfoStr += ","
		}
		if _, err = completedPartsHeader.WriteString(partInfoStr); err != nil {
			return nil, nil, err
		}

		bytesHash, err := hex.DecodeString(partInfo.MD5)
		if err != nil {
			return nil, nil, fmt.Errorf("couldn't decode MD5 checksum of part: %w", err)
		}
		md5Hash.Write(bytesHash)
	}

	initMetadata := make(map[string]string, len(multipartInfo.Meta)+1)
	initMetadata[UploadCompletedParts] = completedPartsHeader.String()
	initMetadata[MultipartObjectSize] = strconv.FormatUint(multipartObjetSize, 10)

	uploadData := &UploadData{
		TagSet:     make(map[string]string),
		ACLHeaders: make(map[string]string),
	}
	for key, val := range multipartInfo.Meta {
		if strings.HasPrefix(key, metaPrefix) {
			initMetadata[strings.TrimPrefix(key, metaPrefix)] = val
		} else if strings.HasPrefix(key, tagPrefix) {
			uploadData.TagSet[strings.TrimPrefix(key, tagPrefix)] = val
		} else if strings.HasPrefix(key, aclPrefix) {
			uploadData.ACLHeaders[strings.TrimPrefix(key, aclPrefix)] = val
		}
	}

	if encInfo.Enabled {
		initMetadata[AttributeEncryptionAlgorithm] = encInfo.Algorithm
		initMetadata[AttributeHMACKey] = encInfo.HMACKey
		initMetadata[AttributeHMACSalt] = encInfo.HMACSalt
		initMetadata[AttributeDecryptedSize] = strconv.FormatUint(multipartObjetSize, 10)
		multipartObjetSize = encMultipartObjectSize
	}

	partsData, err := json.Marshal(parts)
	if err != nil {
		return nil, nil, fmt.Errorf("marshal parst for combined object: %w", err)
	}

	extObjInfo, err := n.PutObject(ctx, &PutObjectParams{
		BktInfo:         p.Info.Bkt,
		Object:          p.Info.Key,
		Reader:          bytes.NewReader(partsData),
		Header:          initMetadata,
		Size:            multipartObjetSize,
		Encryption:      p.Info.Encryption,
		CopiesNumbers:   multipartInfo.CopiesNumbers,
		CompleteMD5Hash: hex.EncodeToString(md5Hash.Sum(nil)) + "-" + strconv.Itoa(len(p.Parts)),
	})
	if err != nil {
		n.reqLogger(ctx).Error(logs.CouldNotPutCompletedObject,
			zap.String("uploadID", p.Info.UploadID),
			zap.String("uploadKey", p.Info.Key),
			zap.Error(err))

		return nil, nil, s3errors.GetAPIError(s3errors.ErrInternalError)
	}

	var addr oid.Address
	addr.SetContainer(p.Info.Bkt.CID)
	for _, partInfo := range partsInfo {
		if err = n.objectDelete(ctx, p.Info.Bkt, partInfo.OID); err != nil {
			n.reqLogger(ctx).Warn(logs.CouldNotDeleteUploadPart,
				zap.Stringer("cid", p.Info.Bkt.CID), zap.Stringer("oid", &partInfo.OID),
				zap.Error(err))
		}
		addr.SetObject(partInfo.OID)
		n.cache.DeleteObject(addr)
	}

	return uploadData, extObjInfo, n.treeService.DeleteMultipartUpload(ctx, p.Info.Bkt, multipartInfo)
}

func (n *layer) ListMultipartUploads(ctx context.Context, p *ListMultipartUploadsParams) (*ListMultipartUploadsInfo, error) {
	var result ListMultipartUploadsInfo
	if p.MaxUploads == 0 {
		return &result, nil
	}

	multipartInfos, err := n.treeService.GetMultipartUploadsByPrefix(ctx, p.Bkt, p.Prefix)
	if err != nil {
		return nil, err
	}

	uploads := make([]*UploadInfo, 0, len(multipartInfos))
	uniqDirs := make(map[string]struct{})

	for _, multipartInfo := range multipartInfos {
		info := uploadInfoFromMultipartInfo(multipartInfo, p.Prefix, p.Delimiter)
		if info != nil {
			if info.IsDir {
				if _, ok := uniqDirs[info.Key]; ok {
					continue
				}
				uniqDirs[info.Key] = struct{}{}
			}
			uploads = append(uploads, info)
		}
	}

	sort.Slice(uploads, func(i, j int) bool {
		if uploads[i].Key == uploads[j].Key {
			return uploads[i].UploadID < uploads[j].UploadID
		}
		return uploads[i].Key < uploads[j].Key
	})

	if p.KeyMarker != "" {
		if p.UploadIDMarker != "" {
			uploads = trimAfterUploadIDAndKey(p.KeyMarker, p.UploadIDMarker, uploads)
		} else {
			uploads = trimAfterUploadKey(p.KeyMarker, uploads)
		}
	}

	if len(uploads) > p.MaxUploads {
		result.IsTruncated = true
		uploads = uploads[:p.MaxUploads]
		result.NextUploadIDMarker = uploads[len(uploads)-1].UploadID
		result.NextKeyMarker = uploads[len(uploads)-1].Key
	}

	for _, ov := range uploads {
		if ov.IsDir {
			result.Prefixes = append(result.Prefixes, ov.Key)
		} else {
			result.Uploads = append(result.Uploads, ov)
		}
	}

	return &result, nil
}

func (n *layer) AbortMultipartUpload(ctx context.Context, p *UploadInfoParams) error {
	multipartInfo, parts, err := n.getUploadParts(ctx, p)
	if err != nil {
		return err
	}

	for _, info := range parts {
		if err = n.objectDelete(ctx, p.Bkt, info.OID); err != nil {
			n.reqLogger(ctx).Warn(logs.CouldntDeletePart, zap.String("cid", p.Bkt.CID.EncodeToString()),
				zap.String("oid", info.OID.EncodeToString()), zap.Int("part number", info.Number), zap.Error(err))
		}
	}

	return n.treeService.DeleteMultipartUpload(ctx, p.Bkt, multipartInfo)
}

func (n *layer) ListParts(ctx context.Context, p *ListPartsParams) (*ListPartsInfo, error) {
	var res ListPartsInfo
	multipartInfo, partsInfo, err := n.getUploadParts(ctx, p.Info)
	if err != nil {
		return nil, err
	}

	encInfo := FormEncryptionInfo(multipartInfo.Meta)
	if err = p.Info.Encryption.MatchObjectEncryption(encInfo); err != nil {
		n.reqLogger(ctx).Warn(logs.MismatchedObjEncryptionInfo, zap.Error(err))
		return nil, s3errors.GetAPIError(s3errors.ErrInvalidEncryptionParameters)
	}

	res.Owner = multipartInfo.Owner

	parts := make([]*Part, 0, len(partsInfo))

	for _, partInfo := range partsInfo {
		parts = append(parts, &Part{
			ETag:         data.Quote(partInfo.GetETag(n.features.MD5Enabled())),
			LastModified: partInfo.Created.UTC().Format(time.RFC3339),
			PartNumber:   partInfo.Number,
			Size:         partInfo.Size,
		})
	}

	sort.Slice(parts, func(i, j int) bool {
		return parts[i].PartNumber < parts[j].PartNumber
	})

	if len(parts) == 0 || p.PartNumberMarker >= parts[len(parts)-1].PartNumber {
		res.Parts = make([]*Part, 0)
		return &res, nil
	}
	if p.PartNumberMarker != 0 {
		for i, part := range parts {
			if part.PartNumber > p.PartNumberMarker {
				parts = parts[i:]
				break
			}
		}
	}

	if len(parts) > p.MaxParts {
		res.IsTruncated = true
		res.NextPartNumberMarker = parts[p.MaxParts-1].PartNumber
		parts = parts[:p.MaxParts]
	}

	res.Parts = parts

	return &res, nil
}

func (n *layer) getUploadParts(ctx context.Context, p *UploadInfoParams) (*data.MultipartInfo, map[int]*data.PartInfo, error) {
	multipartInfo, err := n.treeService.GetMultipartUpload(ctx, p.Bkt, p.Key, p.UploadID)
	if err != nil {
		if errors.Is(err, ErrNodeNotFound) {
			return nil, nil, fmt.Errorf("%w: %s", s3errors.GetAPIError(s3errors.ErrNoSuchUpload), err.Error())
		}
		return nil, nil, err
	}

	parts, err := n.treeService.GetParts(ctx, p.Bkt, multipartInfo.ID)
	if err != nil {
		return nil, nil, err
	}

	res := make(map[int]*data.PartInfo, len(parts))
	partsNumbers := make([]int, len(parts))
	oids := make([]string, len(parts))
	for i, part := range parts {
		res[part.Number] = part
		partsNumbers[i] = part.Number
		oids[i] = part.OID.EncodeToString()
	}

	n.reqLogger(ctx).Debug(logs.PartDetails,
		zap.Stringer("cid", p.Bkt.CID),
		zap.String("upload id", p.UploadID),
		zap.Ints("part numbers", partsNumbers),
		zap.Strings("oids", oids))

	return multipartInfo, res, nil
}

func trimAfterUploadIDAndKey(key, id string, uploads []*UploadInfo) []*UploadInfo {
	var res []*UploadInfo
	if len(uploads) != 0 && uploads[len(uploads)-1].Key < key {
		return res
	}

	for _, obj := range uploads {
		if obj.Key >= key && obj.UploadID > id {
			res = append(res, obj)
		}
	}

	return res
}

func trimAfterUploadKey(key string, objects []*UploadInfo) []*UploadInfo {
	var result []*UploadInfo
	if len(objects) != 0 && objects[len(objects)-1].Key <= key {
		return result
	}
	for i, obj := range objects {
		if obj.Key > key {
			result = objects[i:]
			break
		}
	}

	return result
}

func uploadInfoFromMultipartInfo(uploadInfo *data.MultipartInfo, prefix, delimiter string) *UploadInfo {
	var isDir bool
	key := uploadInfo.Key

	if !strings.HasPrefix(key, prefix) {
		return nil
	}

	if len(delimiter) > 0 {
		tail := strings.TrimPrefix(key, prefix)
		index := strings.Index(tail, delimiter)
		if index >= 0 {
			isDir = true
			key = prefix + tail[:index+1]
		}
	}

	return &UploadInfo{
		IsDir:    isDir,
		Key:      key,
		UploadID: uploadInfo.UploadID,
		Owner:    uploadInfo.Owner,
		Created:  uploadInfo.Created,
	}
}