package tomo

import "sync"
import "image"
import "errors"
import "git.tebibyte.media/tomo/tomo/canvas"

var backendLock sync.Mutex
var backend Backend

// Run initializes a backend, runs the specified callback function, and runs the
// event loop in that order. This function blocks until Stop is called, or the
// backend experiences a fatal error.
func Run (callback func ()) error {
	loadPlugins()

	if backend != nil {
		return errors.New("there is already a backend running")
	}

	back, err := Initialize()
	if err != nil { return err }
	
	backendLock.Lock()
	backend = back
	backendLock.Unlock()

	callback()
	return backend.Run()
}

func assertBackend () {
	if backend == nil { panic("nil backend") }
}

// Stop stops the backend, unblocking run. Run may be called again after calling
// Stop.
func Stop () {
	assertBackend()
	backend.Stop()
	
	backendLock.Lock()
	backend = nil
	backendLock.Unlock()
}

// Do performs a callback function in the event loop thread as soon as possible.
func Do (callback func ()) {
	backendLock.Lock()
	if backend != nil { backend.Do(callback) }
	backendLock.Unlock()
}

// NewWindow creates and returns a window within the specified bounds on screen.
func NewWindow (bounds image.Rectangle) (MainWindow, error) {
	assertBackend()
	return backend.NewWindow(bounds)
}

// NewPlainWindow is like NewWindow, but it creates an undecorated window that
// does not appear in window lists. It is intended for creating things like
// docks, panels, etc.
func NewPlainWindow (bounds image.Rectangle) (MainWindow, error) {
	assertBackend()
	return backend.NewPlainWindow(bounds)
}

// NewBox creates and returns a basic Box.
func NewBox () Box {
	assertBackend()
	return backend.NewBox()
}

// NewTextBox creates and returns a Box that can display text.
func NewTextBox () TextBox {
	assertBackend()
	return backend.NewTextBox()
}

// NewCanvasBox creates and returns a Box that can display custom graphics.
func NewCanvasBox () CanvasBox {
	assertBackend()
	return backend.NewCanvasBox()
}

// NewContainerBox creates and returns a Box that can contain other boxes.
func NewContainerBox () ContainerBox {
	assertBackend()
	return backend.NewContainerBox()
}

// NewTexture creates a new texture from an image. When no longer in use, it
// must be freed using Close().
func NewTexture (source image.Image) canvas.TextureCloser {
	assertBackend()
	return backend.NewTexture(source)
}