package validate

var (
	ErrRequired = NewError("is required")
)

// Required validates that a value is not the zero value for its type: an
// empty string, 0, a nil pointer, and so on.
//
// It is defined for comparable types only. For slices and maps, use
// MinSize(1); for "non-whitespace", combine with a trimming step.
func Required[T comparable]() func(T) error {
	var zero T

	return func(value T) error {
		if value == zero {
			return ErrRequired
		}
		return nil
	}
}