Move username regex check in a helper function

service/api/helpers/get-limits.go

@@ -6,7 +6,7 @@ import (
 )
 
 const (
-	DEFAULT_LIMIT  = 15 // don't know if should be moved to config
+	DEFAULT_LIMIT  = 15
 	DEFAULT_OFFSET = 0
 )
 

service/api/helpers/regex-helpers.go

@@ -0,0 +1,33 @@
+package helpers
+
+import (
+	"net/http"
+	"regexp"
+
+	"github.com/sirupsen/logrus"
+)
+
+func MatchRegexOrBadRequest(str string, regex string, error_description string, w http.ResponseWriter, l logrus.FieldLogger) bool {
+
+	stat, err := regexp.Match(regex, []byte(str))
+
+	if err != nil {
+		SendInternalError(err, "Error while matching username regex", w, l)
+		return false
+	}
+
+	if !stat {
+		// string didn't match the regex, so it's invalid, let's send a bad request error
+		SendBadRequest(w, error_description, l)
+		return false
+	}
+	// string matched the regex, so it's valid
+	return true
+}
+
+func MatchUsernameOrBadRequest(username string, w http.ResponseWriter, l logrus.FieldLogger) bool {
+	return MatchRegexOrBadRequest(username,
+		`^[a-zA-Z0-9_]{3,16}$`, "Username must be between 3 and 16 characters long and can only contain letters, numbers and underscores",
+		w,
+		l)
+}