Add listBucketObjectsVersions implementation (#8093)

This API implementation simply behaves like listObjects()
but returns back single version for each object, this
implementation should be considered dummy it is only
meant for some applications which rely on this.

cmd/api-response.go

@@ -44,6 +44,45 @@ type LocationResponse struct {
 	Location string   `xml:",chardata"`
 }
 
+// ListVersionsResponse - format for list bucket versions response.
+type ListVersionsResponse struct {
+	XMLName xml.Name `xml:"http://s3.amazonaws.com/doc/2006-03-01/ ListVersionsResult" json:"-"`
+
+	Name      string
+	Prefix    string
+	KeyMarker string
+
+	// When response is truncated (the IsTruncated element value in the response
+	// is true), you can use the key name in this field as marker in the subsequent
+	// request to get next set of objects. Server lists objects in alphabetical
+	// order Note: This element is returned only if you have delimiter request parameter
+	// specified. If response does not include the NextMaker and it is truncated,
+	// you can use the value of the last Key in the response as the marker in the
+	// subsequent request to get the next set of object keys.
+	NextKeyMarker string `xml:"NextKeyMarker,omitempty"`
+
+	// When the number of responses exceeds the value of MaxKeys,
+	// NextVersionIdMarker specifies the first object version not
+	// returned that satisfies the search criteria. Use this value
+	// for the version-id-marker request parameter in a subsequent request.
+	NextVersionIDMarker string `xml:"NextVersionIdMarker"`
+
+	// Marks the last version of the Key returned in a truncated response.
+	VersionIDMarker string `xml:"VersionIdMarker"`
+
+	MaxKeys   int
+	Delimiter string
+	// A flag that indicates whether or not ListObjects returned all of the results
+	// that satisfied the search criteria.
+	IsTruncated bool
+
+	CommonPrefixes []CommonPrefix
+	Versions       []ObjectVersion
+
+	// Encoding type used to encode object keys in the response.
+	EncodingType string `xml:"EncodingType,omitempty"`
+}
+
 // ListObjectsResponse - format for list objects response.
 type ListObjectsResponse struct {
 	XMLName xml.Name `xml:"http://s3.amazonaws.com/doc/2006-03-01/ ListBucketResult" json:"-"`
@@ -191,6 +230,14 @@ type Bucket struct {
 	CreationDate string // time string of format "2006-01-02T15:04:05.000Z"
 }
 
+// ObjectVersion container for object version metadata
+type ObjectVersion struct {
+	XMLName xml.Name `xml:"http://s3.amazonaws.com/doc/2006-03-01/ Version" json:"-"`
+	Object
+	VersionID string `xml:"VersionId"`
+	IsLatest  bool
+}
+
 // Object container for object metadata
 type Object struct {
 	Key          string
@@ -328,6 +375,52 @@ func generateListBucketsResponse(buckets []BucketInfo) ListBucketsResponse {
 	return data
 }
 
+// generates an ListBucketVersions response for the said bucket with other enumerated options.
+func generateListVersionsResponse(bucket, prefix, marker, delimiter, encodingType string, maxKeys int, resp ListObjectsInfo) ListVersionsResponse {
+	var versions []ObjectVersion
+	var prefixes []CommonPrefix
+	var owner = Owner{}
+	var data = ListVersionsResponse{}
+
+	owner.ID = globalMinioDefaultOwnerID
+	for _, object := range resp.Objects {
+		var content = ObjectVersion{}
+		if object.Name == "" {
+			continue
+		}
+		content.Key = s3EncodeName(object.Name, encodingType)
+		content.LastModified = object.ModTime.UTC().Format(timeFormatAMZLong)
+		if object.ETag != "" {
+			content.ETag = "\"" + object.ETag + "\""
+		}
+		content.Size = object.Size
+		content.StorageClass = object.StorageClass
+		content.Owner = owner
+		content.VersionID = "null"
+		content.IsLatest = true
+		versions = append(versions, content)
+	}
+	data.Name = bucket
+	data.Versions = versions
+
+	data.EncodingType = encodingType
+	data.Prefix = s3EncodeName(prefix, encodingType)
+	data.KeyMarker = s3EncodeName(marker, encodingType)
+	data.Delimiter = s3EncodeName(delimiter, encodingType)
+	data.MaxKeys = maxKeys
+
+	data.NextKeyMarker = s3EncodeName(resp.NextMarker, encodingType)
+	data.IsTruncated = resp.IsTruncated
+
+	for _, prefix := range resp.Prefixes {
+		var prefixItem = CommonPrefix{}
+		prefixItem.Prefix = s3EncodeName(prefix, encodingType)
+		prefixes = append(prefixes, prefixItem)
+	}
+	data.CommonPrefixes = prefixes
+	return data
+}
+
 // generates an ListObjectsV1 response for the said bucket with other enumerated options.
 func generateListObjectsV1Response(bucket, prefix, marker, delimiter, encodingType string, maxKeys int, resp ListObjectsInfo) ListObjectsResponse {
 	var contents []Object