Add comprehensive test suite

internal/handlers/validation.go

@@ -0,0 +1,45 @@
+package handlers
+
+import (
+	"regexp"
+	"strings"
+
+	"github.com/gin-gonic/gin/binding"
+	"github.com/go-playground/validator/v10"
+)
+
+func init() {
+	// Register custom validators
+	if v, ok := binding.Validator.Engine().(*validator.Validate); ok {
+		v.RegisterValidation("alphanumdash", alphanumdashValidator)
+	}
+}
+
+// alphanumdashValidator validates that a string contains only alphanumeric characters and hyphens
+var alphanumdashValidator validator.Func = func(fl validator.FieldLevel) bool {
+	value := fl.Field().String()
+	// Allow alphanumeric and hyphens only
+	match := regexp.MustCompile(`^[a-zA-Z0-9-]+$`).MatchString(value)
+	return match
+}
+
+// IsValidSubdomainFormat checks if a subdomain string is valid (exported for use in validation)
+func IsValidSubdomainFormat(subdomain string) bool {
+	// Must be at least 3 characters
+	if len(subdomain) < 3 {
+		return false
+	}
+
+	// Must not exceed 63 characters
+	if len(subdomain) > 63 {
+		return false
+	}
+
+	// Must not start or end with hyphen
+	if strings.HasPrefix(subdomain, "-") || strings.HasSuffix(subdomain, "-") {
+		return false
+	}
+
+	// Must contain only alphanumeric and hyphens
+	return regexp.MustCompile(`^[a-zA-Z0-9-]+$`).MatchString(subdomain)
+}