package rui

// ScrollEvent is the constant for "scroll-event" property tag.
//
// Used by `View`.
// Is fired when the content of the view is scrolled.
//
// General listener format:
// `func(view rui.View, frame rui.Frame)`.
//
// where:
// view - Interface of a view which generated this event,
// frame - New offset and size of the view's visible area.
//
// Allowed listener formats:
// `func(frame rui.Frame)`,
// `func(view rui.View)`,
// `func()`.
const ScrollEvent = "scroll-event"

func (view *viewData) onScroll(self View, x, y, width, height float64) {
	view.scroll.Left = x
	view.scroll.Top = y
	view.scroll.Width = width
	view.scroll.Height = height
	for _, listener := range GetScrollListeners(view) {
		listener(self, view.scroll)
	}
}

func (view *viewData) Scroll() Frame {
	return view.scroll
}

func (view *viewData) setScroll(x, y, width, height float64) {
	view.scroll.Left = x
	view.scroll.Top = y
	view.scroll.Width = width
	view.scroll.Height = height
}

// GetViewScroll returns ...
// If the second argument (subviewID) is not specified or it is "" then a value of the first argument (view) is returned
func GetViewScroll(view View, subviewID ...string) Frame {
	if len(subviewID) > 0 && subviewID[0] != "" {
		view = ViewByID(view, subviewID[0])
	}
	if view == nil {
		return Frame{}
	}
	return view.Scroll()
}

// GetScrollListeners returns the list of "scroll-event" listeners. If there are no listeners then the empty list is returned
// If the second argument (subviewID) is not specified or it is "" then the listeners list of the first argument (view) is returned
func GetScrollListeners(view View, subviewID ...string) []func(View, Frame) {
	return getEventListeners[View, Frame](view, subviewID, ResizeEvent)
}

// ScrollTo scrolls the view's content to the given position.
// If the second argument (subviewID) is "" then the first argument (view) is used
func ScrollViewTo(view View, subviewID string, x, y float64) {
	if subviewID != "" {
		view = ViewByID(view, subviewID)
	}
	if view != nil {
		view.Session().callFunc("scrollTo", view.htmlID(), x, y)
	}
}

// ScrollViewToEnd scrolls the view's content to the start of view.
// If the second argument (subviewID) is not specified or it is "" then the first argument (view) is used
func ScrollViewToStart(view View, subviewID ...string) {
	if len(subviewID) > 0 && subviewID[0] != "" {
		view = ViewByID(view, subviewID[0])
	}
	if view != nil {
		view.Session().callFunc("scrollToStart", view.htmlID())
	}
}

// ScrollViewToEnd scrolls the view's content to the end of view.
// If the second argument (subviewID) is not specified or it is "" then the first argument (view) is used
func ScrollViewToEnd(view View, subviewID ...string) {
	if len(subviewID) > 0 && subviewID[0] != "" {
		view = ViewByID(view, subviewID[0])
	}
	if view != nil {
		view.Session().callFunc("scrollToEnd", view.htmlID())
	}
}