package stone

import "image"
import "errors"

type Backend interface {
	Run      ()
	SetTitle (title string) (err error)
	SetIcon  (icons []image.Image) (err error)
	Draw     ()
}

type BackendFactory func (
	application *Application,
	callbackManager *CallbackManager,
) (
	backend Backend,
	err error,
)

var factories []BackendFactory

func RegisterBackend (factory BackendFactory) {
	factories = append(factories, factory)
}

func instantiateBackend (application *Application) (backend Backend, err error) {
	// find a suitable backend
	for _, factory := range factories {
		backend, err = factory(application, &application.callbackManager)
		if err == nil && backend != nil { return }
	}

	// if none were found, but there was no error produced, produce an
	// error
	if err == nil {
		err = errors.New("no available backends")
	}

	return
}