From db3aedd5218e68d06705f1aef53484f6c7376c19 Mon Sep 17 00:00:00 2001
From: Nikita Tokarchuk <tokarchuk+bitbucket@nevisq.com>
Date: Thu, 7 Feb 2019 23:35:36 +0100
Subject: [PATCH] Protection structure

---
 mongox/base/getprotection.go | 33 +++++++++++++++++++++++++++++++++
 mongox/base/protection.go    | 11 +++++++++++
 2 files changed, 44 insertions(+)
 create mode 100644 mongox/base/getprotection.go
 create mode 100644 mongox/base/protection.go

diff --git a/mongox/base/getprotection.go b/mongox/base/getprotection.go
new file mode 100644
index 0000000..28b4cc1
--- /dev/null
+++ b/mongox/base/getprotection.go
@@ -0,0 +1,33 @@
+package base
+
+import (
+	"reflect"
+)
+
+// GetProtection function finds protection field in the source document otherwise returns nil
+func GetProtection(source interface{}) *Protection {
+
+	v := reflect.ValueOf(source)
+	if v.Kind() != reflect.Ptr || v.IsNil() {
+		return nil
+	}
+
+	el := v.Elem()
+	numField := el.NumField()
+
+	for i := 0; i < numField; i++ {
+		field := el.Field(i)
+
+		switch field.Interface().(type) {
+		case *Protection:
+			return field.Interface().(*Protection)
+		case Protection:
+			ptr := field.Addr()
+			return ptr.Interface().(*Protection)
+		default:
+			continue
+		}
+	}
+
+	return nil
+}
diff --git a/mongox/base/protection.go b/mongox/base/protection.go
new file mode 100644
index 0000000..01c0176
--- /dev/null
+++ b/mongox/base/protection.go
@@ -0,0 +1,11 @@
+package base
+
+import (
+	"github.com/mongodb/mongo-go-driver/bson/primitive"
+)
+
+// Protection field stores unique document id and version
+type Protection struct {
+	X primitive.ObjectID `bson:"_x" json:"_x" index:",hashed"`
+	V int64              `bson:"_v" json:"_v"`
+}