package catalog

import "errors"

var (
	ErrSystemImmutable = errors.New("system records cannot be modified or deleted")
	ErrNotFound        = errors.New("not found")
)

// clientError is a validation/business message safe to return to API clients.
type clientError struct {
	msg string
}

func (e *clientError) Error() string { return e.msg }

// ClientMsg marks a message as safe to expose in HTTP 4xx responses.
func ClientMsg(msg string) error {
	return &clientError{msg: msg}
}

// ClientError reports whether err is a known client-facing catalog error.
func ClientError(err error) (msg string, ok bool) {
	if err == nil {
		return "", false
	}
	var ce *clientError
	if errors.As(err, &ce) {
		return ce.msg, true
	}
	switch {
	case errors.Is(err, ErrNotFound):
		return "not found", true
	case errors.Is(err, ErrSystemImmutable):
		return err.Error(), true
	default:
		return "", false
	}
}