package x

import "image"
import "git.tebibyte.media/tomo/tomo"
import "git.tebibyte.media/tomo/tomo/event"
import "git.tebibyte.media/tomo/tomo/canvas"

type containerBox struct {
	*box

	hOverflow, vOverflow bool
	contentBounds image.Rectangle
	scroll        image.Point
	
	gap      image.Point
	children []anyBox
	layout   tomo.Layout

	on struct {
		contentBoundsChange event.FuncBroadcaster
	}
}

func (backend *Backend) NewContainerBox() tomo.ContainerBox {
	box := &containerBox {
		box: backend.NewBox().(*box),
	}
	box.drawer = box
	box.outer  = box
	return box
}

func (this *containerBox) Box () tomo.Box {
	return this
}

func (this *containerBox) SetOverflow (horizontal, vertical bool) {
	if this.hOverflow == horizontal && this.vOverflow == vertical { return }
	this.hOverflow = horizontal
	this.vOverflow = vertical
	this.invalidateLayout()
}

func (this *containerBox) ContentBounds () image.Rectangle {
	return this.contentBounds
}

func (this *containerBox) ScrollTo (point image.Point) {
	// TODO: constrain scroll
	this.scroll = point
	this.invalidateLayout()
}

func (this *containerBox) OnContentBoundsChange (callback func()) event.Cookie {
	return this.on.contentBoundsChange.Connect(callback)
}

func (this *containerBox) SetGap (gap image.Point) {
	if this.gap == gap { return }
	this.gap = gap
	this.invalidateLayout()
}

func (this *containerBox) Add (child tomo.Object) {
	box := assertAnyBox(child.Box())
	if indexOf(this.children, box) > -1 { return }
	
	box.setParent(this)
	this.children = append(this.children, box)
	this.invalidateLayout()
}

func (this *containerBox) Delete (child tomo.Object) {
	box := assertAnyBox(child.Box())
	index := indexOf(this.children, box)
	if index < 0 { return }
	
	box.setParent(nil)
	this.children = remove(this.children, index)
	this.invalidateLayout()
}

func (this *containerBox) Insert (child, before tomo.Object) {
	box := assertAnyBox(child.Box())
	if indexOf(this.children, box) > -1 { return }

	beforeBox := assertAnyBox(before.Box())
	index     := indexOf(this.children, beforeBox)
	if index < 0 { return }
	
	box.setParent(this)
	this.children = insert(this.children, index, box)
	this.invalidateLayout()
}

func (this *containerBox) Clear () {
	for _, box := range this.children {
		box.setParent(nil)
	}
	this.children = nil
	this.invalidateLayout()
}

func (this *containerBox) Length () int {
	return len(this.children)
}

func (this *containerBox) At (index int) tomo.Object {
	if index < 0 || index >= len(this.children) {
		return nil
	}
	return this.children[index]
}

func (this *containerBox) SetLayout (layout tomo.Layout) {
	this.layout = layout
	this.invalidateLayout()
}

func (this *containerBox) Draw (can canvas.Canvas) {
	this.drawBorders(can)
	pen := can.Pen()
	pen.Fill(this.color)

	// TODO: do this in doLayout and save the result
	rocks := make([]image.Rectangle, len(this.children))
	for index, box := range this.children {
		rocks[index] = box.Bounds()
	}
	// TODO: use shatter algorithm here to optimize amount of pixels drawn
	// and not draw over child boxes
	for _, tile := range canvas.Shatter(this.bounds, rocks...) {
		pen.Rectangle(tile)
	}
}

func (this *containerBox) window () *window {
	if this.parent == nil { return nil }
	return this.parent.window()
}

func (this *containerBox) canvas () canvas.Canvas {
	return this.box.canvas
}

func (this *containerBox) layoutHints () tomo.LayoutHints {
	innerBounds := this.InnerBounds().Sub(this.scroll)
	return tomo.LayoutHints {
		Bounds:    innerBounds,
		OverflowX: this.hOverflow,
		OverflowY: this.vOverflow,
		Gap:       this.gap,
	}
}

func (this *containerBox) doLayout () {
	this.box.doLayout()
	// TODO: possibly store all children as tomo.Box-es and don't allocate a
	// slice here
	previousContentBounds := this.contentBounds
	boxes := make([]tomo.Box, len(this.children))
	for index, box := range this.children {
		boxes[index] = box
	}
	if this.layout != nil {
		// TODO maybe we should pass more information into Arrange such
		// as overflow information and scroll
		this.layout.Arrange(this.layoutHints(), boxes)
	}
	if previousContentBounds != this.contentBounds {
		this.on.contentBoundsChange.Broadcast()
	}
}

func (this *containerBox) recursiveRedo () {
	this.doLayout()
	this.doDraw()
	for _, child := range this.children {
		child.recursiveRedo()
	}
}