godoxy/internal/serialization/validation.go

package serialization

import (
	"errors"
	"reflect"

	"github.com/go-playground/validator/v10"
)

var validate = validator.New()

var ErrValidationError = errors.New("validation error")

func Validator() *validator.Validate {
	return validate
}

func MustRegisterValidation(tag string, fn validator.Func) {
	err := validate.RegisterValidation(tag, fn)
	if err != nil {
		panic(err)
	}
}

type CustomValidator interface {
	Validate() error
}

var validatorType = reflect.TypeFor[CustomValidator]()

func ValidateWithCustomValidator(v reflect.Value) error {
	vt := v.Type()
	if v.Kind() == reflect.Pointer {
		elemType := vt.Elem()
		if vt.Implements(validatorType) {
			if v.IsNil() {
				return reflect.New(elemType).Interface().(CustomValidator).Validate()
			}
			return v.Interface().(CustomValidator).Validate()
		}
		if elemType.Implements(validatorType) {
			return v.Elem().Interface().(CustomValidator).Validate()
		}
	} else if vt.PkgPath() != "" { // not a builtin type
		// prioritize pointer method
		if v.CanAddr() {
			vAddr := v.Addr()
			if vAddr.Type().Implements(validatorType) {
				return vAddr.Interface().(CustomValidator).Validate()
			}
		}
		// fallback to value method
		if vt.Implements(validatorType) {
			return v.Interface().(CustomValidator).Validate()
		}
	}
	return nil
}