Add support for server side bucket replication (#9882)

pkg/bucket/replication/and.go

@@ -0,0 +1,62 @@
+/*
+ * MinIO Cloud Storage, (C) 2020 MinIO, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package replication
+
+import (
+	"encoding/xml"
+)
+
+// And - a tag to combine a prefix and multiple tags for replication configuration rule.
+type And struct {
+	XMLName xml.Name `xml:"And" json:"And"`
+	Prefix  string   `xml:"Prefix,omitempty" json:"Prefix,omitempty"`
+	Tags    []Tag    `xml:"Tag,omitempty" json:"Tag,omitempty"`
+}
+
+var errDuplicateTagKey = Errorf("Duplicate Tag Keys are not allowed")
+
+// isEmpty returns true if Tags field is null
+func (a And) isEmpty() bool {
+	return len(a.Tags) == 0 && a.Prefix == ""
+}
+
+// Validate - validates the And field
+func (a And) Validate() error {
+	if a.ContainsDuplicateTag() {
+		return errDuplicateTagKey
+	}
+	for _, t := range a.Tags {
+		if err := t.Validate(); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+// ContainsDuplicateTag - returns true if duplicate keys are present in And
+func (a And) ContainsDuplicateTag() bool {
+	x := make(map[string]struct{}, len(a.Tags))
+
+	for _, t := range a.Tags {
+		if _, has := x[t.Key]; has {
+			return true
+		}
+		x[t.Key] = struct{}{}
+	}
+
+	return false
+}