3 files changed, 47 insertions, 0 deletions
diff --git a/utils/math/math.go b/utils/math/math.go
new file mode 100644
index 0000000..01035b9
--- /dev/null
+++ b/utils/math/math.go
@@ -0,0 +1,8 @@
+package math
+
+func GCD(a, b int) int {
+	for b != 0 {
+		a, b = b, a%b
+	}
+	return a
+}
diff --git a/utils/validators/tags.go b/utils/validators/tags.go
new file mode 100644
index 0000000..8fe8ab9
--- /dev/null
+++ b/utils/validators/tags.go
@@ -0,0 +1,8 @@
+package validators
+
+import "regexp"
+
+func IsValidTagName(tag string) bool {
+	match, _ := regexp.MatchString(`^[a-zA-Z0-9_]+$`, tag)
+	return match
+}
diff --git a/utils/validators/users.go b/utils/validators/users.go
new file mode 100644
index 0000000..70ec34d
--- /dev/null
+++ b/utils/validators/users.go
@@ -0,0 +1,31 @@
+package validators
+
+import (
+	"regexp"
+	"slices"
+	"strings"
+)
+
+func IsValidUsername(username string) bool {
+	match, _ := regexp.MatchString(`^[a-zA-Z0-9_-]+$`, username)
+	return match
+}
+
+func IsReservedUsername(username string) bool {
+	reserved := []string{
+		"admin", "administrator", "mod", "moderator", "janitor",
+		"api", "www", "mail", "email", "support", "help",
+		"about", "contact", "privacy", "terms", "tos",
+		"null", "undefined", "system", "bot", "guest",
+		"login", "register", "signup", "signin", "logout",
+		"profile", "settings", "shifoo", "deleted",
+	}
+
+	lowerUsername := strings.ToLower(username)
+	return slices.Contains(reserved, lowerUsername)
+}
+
+func IsValidEmail(email string) bool {
+	match, _ := regexp.MatchString(`^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$`, email)
+	return match
+}