package objects

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

// ScrollSide determines which Scrollbars are active in a ScrollContainer.
type ScrollSide int; const (
	ScrollVertical ScrollSide = 1 << iota
	ScrollHorizontal
	ScrollBoth = ScrollVertical | ScrollHorizontal
)

// Horizontal returns true if the side includes a horizontal bar.
func (sides ScrollSide) Horizontal () bool {
	return sides & ScrollHorizontal > 0
}

// Vertical returns true if the side includes a vertical bar.
func (sides ScrollSide) Vertical () bool {
	return sides & ScrollVertical > 0
}

// String returns one of:
//   - both
//   - horizontal
//   - vertical
//   - none
func (sides ScrollSide) String () string {
	switch {
	case sides.Horizontal() && sides.Vertical(): return "both"
	case sides.Horizontal():                     return "horizontal"
	case sides.Vertical():                       return "vertical"
	default:                                     return "none"
	}
}

// ScrollContainer couples a ContentBox with one or two Scrollbars.
type ScrollContainer struct {
	tomo.ContainerBox
	layout *scrollContainerLayout

	horizontalCookie event.Cookie
	verticalCookie   event.Cookie
}

// NewScrollContainer creates a new scroll container.
func NewScrollContainer (sides ScrollSide) *ScrollContainer {
	this := &ScrollContainer {
		ContainerBox: tomo.NewContainerBox(),
		layout:       &scrollContainerLayout { },
	}
	if sides.Vertical() {
		this.layout.vertical = NewVerticalScrollbar()
		this.Add(this.layout.vertical)
	}
	if sides.Horizontal() {
		this.layout.horizontal = NewHorizontalScrollbar()
		this.Add(this.layout.horizontal)
	}
	this.CaptureScroll(true)
	this.OnScroll(this.handleScroll)
	theme.Apply(this, theme.R("objects", "ScrollContainer", sides.String()))
	this.SetLayout(this.layout)
	return this
}

// SetRoot sets the root child of the ScrollContainer. There can only be one at
// a time, and setting it will remove and unlink the current child if there is
// one.
func (this *ScrollContainer) SetRoot (root tomo.ContentBox) {
	if this.layout.root != nil {
		// delete root and close cookies
		this.Delete(this.layout.root)
		if this.horizontalCookie != nil {
			this.horizontalCookie.Close()
			this.horizontalCookie = nil
		}
		if this.verticalCookie != nil {
			this.verticalCookie.Close()
			this.verticalCookie = nil
		}
	}
	this.layout.root = root
	if root != nil {
		// insert root at the beginning (for keynav)
		switch {
		case this.layout.vertical != nil:
			this.Insert(root, this.layout.vertical)
		case this.layout.horizontal != nil:
			this.Insert(root, this.layout.horizontal)
		default:
			this.Add(root)
		}
		
		// link root and remember cookies
		if this.layout.horizontal != nil {
			this.horizontalCookie = this.layout.horizontal.Link(root)
		}
		if this.layout.vertical != nil {
			this.verticalCookie =  this.layout.vertical.Link(root)
		}
	}
}

// SetValue sets the horizontal and vertical scrollbar values where 0 is all the
// way to the left/top, and 1 is all the way to the right/bottom.
func (this *ScrollContainer) SetValue (x, y float64) {
	if this.layout.horizontal != nil {
		this.layout.horizontal.SetValue(x)
	}
	if this.layout.vertical != nil {
		this.layout.vertical.SetValue(y)
	}
}

// Value returns the horizontal and vertical scrollbar values where 0 is all the
// way to the left/top, and 1 is all the way to the right/bottom.
func (this *ScrollContainer) Value () (x, y float64) {
	if this.layout.horizontal != nil {
		x = this.layout.horizontal.Value()
	}
	if this.layout.vertical != nil {
		y = this.layout.vertical.Value()
	}
	return x, y
}

func (this *ScrollContainer) handleScroll (x, y float64) {
	if this.layout.root == nil { return }
	this.layout.root.ScrollTo (
		this.layout.root.ContentBounds().Min.
		Sub(image.Pt(int(x), int(y))))
}

type scrollContainerLayout struct {
	root       tomo.ContentBox
	horizontal *Scrollbar
	vertical   *Scrollbar
}

func (this *scrollContainerLayout) MinimumSize (hints tomo.LayoutHints, boxes []tomo.Box) image.Point {
	var minimum image.Point; if this.root != nil {
		minimum = this.root.MinimumSize()
	}
	if this.horizontal != nil {
		minimum.Y += this.horizontal.MinimumSize().Y
	}
	if this.vertical != nil {
		minimum.X += this.vertical.MinimumSize().X
		minimum.Y = max(minimum.Y, this.vertical.MinimumSize().Y)
	}
	if this.horizontal != nil {
		minimum.X = max(minimum.X, this.horizontal.MinimumSize().X)
	}
	return minimum
}

func (this *scrollContainerLayout) Arrange (hints tomo.LayoutHints, boxes []tomo.Box) {
	rootBounds := hints.Bounds
	if this.horizontal != nil {
		rootBounds.Max.Y -= this.horizontal.MinimumSize().Y
	}
	if this.vertical != nil {
		rootBounds.Max.X -= this.vertical.MinimumSize().X
	}
	if this.root != nil {
		this.root.SetBounds(rootBounds)
	}
	if this.horizontal != nil {
		this.horizontal.SetBounds(image.Rect (
			hints.Bounds.Min.X,
			rootBounds.Max.Y,
			rootBounds.Max.X,
			hints.Bounds.Max.Y))
	}
	if this.vertical != nil {
		this.vertical.SetBounds(image.Rect (
			rootBounds.Max.X,
			hints.Bounds.Min.Y,
			hints.Bounds.Max.X,
			rootBounds.Max.Y))
	}
}

func max (x, y int) int {
	if x > y { return x }
	return y
}