package layouts

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

// Cut is a layout that can be divided into smaller and smaller sections.
type Cut struct {
	branches [2]*Cut
	expand   [2]bool
	vertical bool
}

// Vertical divides the layout in equal halves vertically.
func (this *Cut) Vertical () (top, bottom *Cut) {
	this.fill()
	this.even()
	this.vertical = true
	return this.Branches()
}

// Top divides the layout vertically, expanding the top half and contracting the
// bottom half.
func (this *Cut) Top () (top, bottom *Cut) {
	this.fill()
	this.first()
	this.vertical = true
	return this.Branches()
}

// Bottom divides the layout vertically, expanding the bottom half and
// contracting the top half.
func (this *Cut) Bottom () (top, bottom *Cut) {
	this.fill()
	this.second()
	this.vertical = true
	return this.Branches()
}

// Horizontal divides the layout in equal halves horizontally.
func (this *Cut) Horizontal () (top, bottom *Cut) {
	this.fill()
	this.even()
	return this.Branches()
}

// Left divides the layout horizontally, expanding the left half and contracting
// the right half.
func (this *Cut) Left () (top, bottom *Cut) {
	this.fill()
	this.first()
	return this.Branches()
}

// Right divides the layout horizontally, expanding the right half and
// contracting the left half.
func (this *Cut) Right () (top, bottom *Cut) {
	this.fill()
	this.second()
	return this.Branches()
}

// Branches returns the two halves of this layout.
func (this *Cut) Branches () (first, second *Cut) {
	return this.branches[0], this.branches[1]
}

func (this *Cut) real () bool {
	return this != nil && this.branches[0] != nil && this.branches[1] != nil
}

func (this *Cut) fill () {
	this.branches[0] = &Cut { }
	this.branches[1] = &Cut { }
}

func (this *Cut) first () {
	this.expand[0] = true
	this.expand[1] = false
}

func (this *Cut) second () {
	this.expand[0] = false
	this.expand[1] = true
}

func (this *Cut) even () {
	this.expand[0] = true
	this.expand[1] = true
}

func (this *Cut) MinimumSize (hints tomo.LayoutHints, boxes []tomo.Box) image.Point {
	size, _ := this.minimumSize(hints, boxes)
	return size
}

func (this *Cut) Arrange (hints tomo.LayoutHints, boxes []tomo.Box) {
	this.arrange(hints, boxes)
}

func (this *Cut) minimumSize (hints tomo.LayoutHints, boxes []tomo.Box) (image.Point, []tomo.Box) {
	size := image.Point { }

	for index, branch := range this.branches {
		if len(boxes) == 0 { break }

		var point image.Point
		if branch.real() {
			point, boxes = branch.minimumSize(hints, boxes)
		} else {
			point = boxes[0].MinimumSize()
			boxes = boxes[1:]
		}

		if this.vertical {
			if point.X > size.X { size.X  = point.X     }
			if index   > 0      { size.Y += hints.Gap.Y }
			size.Y += point.Y
		} else {
			if point.Y > size.Y { size.Y  = point.Y     }
			if index   > 0      { size.X += hints.Gap.X }
			size.X += point.X
		}
	}

	return size, boxes
}

func (this *Cut) arrange (hints tomo.LayoutHints, boxes []tomo.Box) []tomo.Box {
	// collect minimum sizes and physical endpoints
	var minimums [2]image.Point
	var leaves   [2]tomo.Box
	var nBranches int
	remaining := boxes
	for index, branch := range this.branches {
		if branch.real() {
			minimums[index], remaining = branch.minimumSize(hints, remaining)
		} else {
			if len(remaining) == 0 { break }
			leaves[index]   = remaining[0]
			minimums[index] = remaining[0].MinimumSize()
			remaining       = remaining[1:]
		}
		nBranches ++
	}

	// determine the amount of space to divide among expanding branches
	gaps := nBranches - 1
	var freeSpace float64; if this.vertical {
		freeSpace = float64(hints.Bounds.Dy() - hints.Gap.Y * gaps)
	} else {
		freeSpace = float64(hints.Bounds.Dx() - hints.Gap.X * gaps)
	}
	var nExpanding float64
	for index, minimum := range minimums {
		if this.expand[index] {
			nExpanding ++
		} else if this.vertical {
			freeSpace -= float64(minimum.Y)
		} else {
			freeSpace -= float64(minimum.X)
		}
	}
	expandingSize := freeSpace / nExpanding

	// calculate the size and position of branches
	var bounds [2]image.Rectangle
	x := float64(hints.Bounds.Min.X)
	y := float64(hints.Bounds.Min.Y)
	for index, minimum := range minimums {
		// get size along significant axis
		var size float64; if this.expand[index] {
			size = expandingSize
		} else if this.vertical {
			size = float64(minimum.Y)
		} else {
			size = float64(minimum.X)
		}

		// figure out bounds from size
		if this.vertical {
			bounds[index].Max = image.Pt (
				int(hints.Bounds.Dx()),
				int(size))
		} else {
			bounds[index].Max = image.Pt (
				int(size),
				int(hints.Bounds.Dy()))
		}
		bounds[index] = bounds[index].Add(image.Pt(int(x), int(y)))

		// move along
		if this.vertical {
			y += float64(hints.Gap.Y) + size
		} else {
			x += float64(hints.Gap.X) + size
		}
	}

	// apply the size and position
	for index, bound := range bounds {
		if leaves[index] != nil {
			leaves[index].SetBounds(bound)
			boxes = boxes[1:]
		} else if this.branches[index] != nil {
			newHints := hints
			newHints.Bounds = bound
			boxes = this.branches[index].arrange(newHints, boxes)
		}
	}
	
	return boxes
}