validation

var (
	Required = Rule{
		Name:    "required",
		Message: "is required",
		Validate: func(v interface{}) bool {
			if v == nil {
				return false
			}
			if s, ok := v.(string); ok {
				return strings.TrimSpace(s) != ""
			}
			return true
		},
	}

	Email = Rule{
		Name:    "email",
		Message: "must be a valid email address",
		Validate: func(v interface{}) bool {
			s, ok := v.(string)
			if !ok {
				return false
			}
			pattern := `^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$`
			matched, _ := regexp.MatchString(pattern, s)
			return matched
		},
	}
)