package stone

import "time"
import "errors"

type Backend interface {
	Run           (callback func (application *Application)) ()
	Await         (timeout time.Duration) (keepRunning bool)
	Poll          ()                      (keepRunning bool)
	SetTitle      (title string)
	JustPressed   (button Button) (pressed  bool)
	JustReleased  (button Button) (released bool)
	Pressed       (button Button) (pressed  bool)
	Repeated      (button Button) (repeated bool)
	Typed         () (text    string)
	Resized       () (resized bool)
	MousePosition () (x, y int)
}

type BackendFactory func (application *Application) (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)
		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
}