1 files changed, 15 insertions, 0 deletions
diff --git a/models/topic.go b/models/topic.go
index 3b1737f8af..247aac5fff 100644
--- a/models/topic.go
+++ b/models/topic.go
@@ -6,6 +6,7 @@ package models
 
 import (
 	"fmt"
+	"regexp"
 	"strings"
 
 	"code.gitea.io/gitea/modules/util"
@@ -20,6 +21,8 @@ func init() {
 	)
 }
 
+var topicPattern = regexp.MustCompile(`^[a-z0-9][a-z0-9-]*$`)
+
 // Topic represents a topic of repositories
 type Topic struct {
 	ID          int64
@@ -51,6 +54,11 @@ func (err ErrTopicNotExist) Error() string {
 	return fmt.Sprintf("topic is not exist [name: %s]", err.Name)
 }
 
+// ValidateTopic checks topics by length and match pattern rules
+func ValidateTopic(topic string) bool {
+	return len(topic) <= 35 && topicPattern.MatchString(topic)
+}
+
 // GetTopicByName retrieves topic by name
 func GetTopicByName(name string) (*Topic, error) {
 	var topic Topic
@@ -182,6 +190,13 @@ func SaveTopics(repoID int64, topicNames ...string) error {
 		}
 	}
 
+	topicNames = topicNames[:0]
+	if err := sess.Table("topic").Cols("name").
+		Join("INNER", "repo_topic", "topic.id = repo_topic.topic_id").
+		Where("repo_topic.repo_id = ?", repoID).Find(&topicNames); err != nil {
+		return err
+	}
+
 	if _, err := sess.ID(repoID).Cols("topics").Update(&Repository{
 		Topics: topicNames,
 	}); err != nil {