package stone

import "image"

// Application represents an application.
type Application struct {
	DamageBuffer
	
	title string
	icons []image.Image
	backend Backend
	config Config
	callbackManager CallbackManager
}

// Run initializes the application, starts it, and then returns a channel that
// broadcasts events. If no suitable backend can be found, an error is returned.
func (application *Application) Run () (
	err     error,
) {
	// default values for certain parameters
	width, height := application.Size()
	if width  < 1 { width  = 80 }
	if height < 1 { height = 20 }
	application.DamageBuffer.SetSize(width, height)

	application.config.load()

	application.backend, err = instantiateBackend(application)
	if err != nil { return }
	
	application.backend.Run()
	return
}

// OnQuit registers an event handler to be called just before the application
// quits. This can happen when the user closes the application, or the backend
// experiences an unrecoverable error.
func (application *Application) OnQuit (
	onQuit func (),
) {
	application.callbackManager.onQuit = onQuit
}

// OnPress registers an event handler to be called when a key or mouse button
// is pressed.
func (application *Application) OnPress (
	onPress func (button Button, modifiers Modifiers),
) {
	application.callbackManager.onPress = onPress
}

// OnPress registers an event handler to be called when a key or mouse button
// is released.
func (application *Application) OnRelease (
	onRelease func (button Button),
) {
	application.callbackManager.onRelease = onRelease
}

// OnResize registers an event handler to be called when the application window
// is resized. After the event handler is called, any updates it makes will
// automatically be pushed to the screen.
func (application *Application) OnResize (
	onResize func (),
) {
	application.callbackManager.onResize = onResize
}

// OnMouseMove registers an event handler to be called when mouse motion is
// detected. The coordinates of the cell that the mouse now hovers over are
// given as input.
func (application *Application) OnMouseMove (
	onMouseMove func (x, y int),
) {
	application.callbackManager.onMouseMove = onMouseMove
}

// OnScroll registers an event handler to be called when the user uses the mouse
// scroll wheel. Horizontal and vertical amounts are given as input.
func (application *Application) OnScroll (
	onScroll func (x, y int),
) {
	application.callbackManager.onScroll = onScroll
}

// OnStart registers an event handler to be called once when the application
// starts, right before the first time updates are pushed to the screen.
// Anything done in here will be the first thing to appear on screen.
func (application *Application) OnStart (
	onStart func (),
) {
	application.callbackManager.onStart = onStart
}

// Draw "commits" changes made in the buffer to the display.
func (application *Application) Draw () {
	application.backend.Draw()
}

// SetTitle sets the application's title. If in a window, it will appear as the
// window's name.
func (application *Application) SetTitle (title string) (err error) {
	application.title = title
	if application.backend != nil {
		err = application.backend.SetTitle(title)
	}

	return 
}

// Title returns the application's title.
func (application *Application) Title () (title string) {
	title = application.title
	return
}

// SetIcon takes in a list of different sizes of an icon, and sets it as the
// application's icon.
func (application *Application) SetIcon (sizes []image.Image) (err error) {
	application.icons = sizes
	if application.backend != nil {
		err = application.backend.SetIcon(sizes)
	}

	return
}

// Icon returns all available sizes of the application's icon. If there is no
// icon, nil is returned.
func (application *Application) Icon () (sizes []image.Image) {
	sizes = application.icons
	return
}

// Config returns a pointer to the application's configuration.
func (application *Application) Config () (config *Config) {
	config = &application.config
	return
}