import SpriteKit

class DemoScene: SKScene {
    override func didMoveToView(view: SKView) {
        super.didMoveToView(view)

        self.scaleMode = .ResizeFill
        self.name = "DemoScene"

        // Add label to put it left bottom corner
        let leftBottomLabel = SKLabelNode()
        leftBottomLabel.text = "Left Bottom"
        leftBottomLabel.name = "leftBottomLabel"    // a C language identifier
        leftBottomLabel.autoLayoutEnabled = true    // enable autolayout for this node
        addChild(leftBottomLabel)

        // Add color sprite with non-default anchor point to put in the center
        let centerSprite = SKSpriteNode(color: SKColor.greenColor(), size: CGSizeZero)
        centerSprite.name = "centerSprite"
        centerSprite.anchorPoint = CGPoint(x: 1, y: 1)  // non-default anchor point
        centerSprite.autoLayoutEnabled = true
        addChild(centerSprite)

        // Get dictionary of all nodes in this scene
        let nodesDic = self.nodesDic()  // self. is required to avoid compile error

        // Configure Auto Layout constraints

        // Pin label to left bottom corner, use label's intrinsic size
        let width = Float(leftBottomLabel.frame.width)
        var format = "H:|[leftBottomLabel(\(width))]"
        var constraints = NSLayoutConstraint.constraintsWithVisualFormat(format, options: .DirectionLeadingToTrailing, metrics: nil, views: nodesDic)
        addConstraints(constraints) // add constraints

        let height = Float(leftBottomLabel.frame.height)
        format = "V:|[leftBottomLabel(\(height))]"
        constraints = NSLayoutConstraint.constraintsWithVisualFormat(format, options: .DirectionLeadingToTrailing, metrics: nil, views: nodesDic)
        addConstraints(constraints) // add constraints

        // Put color sprite in the center
        // Make it's size related to parent (aka "superview")

        // Constraint center (x, y) to parent's (x, y)
        // it's save to do it here because parent is skene filling whole SKView
        var constraint = NSLayoutConstraint(item: centerSprite, attribute: .CenterX, relatedBy: .Equal, toItem: self, attribute: .CenterX, multiplier: 1, constant: 0)
        addConstraint(constraint)
        constraint = NSLayoutConstraint(item: centerSprite, attribute: .CenterY, relatedBy: .Equal, toItem: self, attribute: .CenterY, multiplier: 1, constant: 0)
        addConstraint(constraint)

        // Make the the centerSprite's width to be 20% of the parent's width
        constraint = NSLayoutConstraint(item: centerSprite, attribute: .Width, relatedBy: .Equal, toItem: self, attribute: .Width, multiplier: 0.2, constant: 0)
        addConstraint(constraint)

        // Make the centerSprite's height to be equal to centerSprite's width
        constraint = NSLayoutConstraint(item: centerSprite, attribute: .Height, relatedBy: .Equal, toItem: centerSprite, attribute: .Height, multiplier: 1, constant: 0)
        centerSprite.addConstraint(constraint)  // centerSprite's constraint on itself
    }

    override func didChangeSize(oldSize: CGSize) {
        dispatch_async(dispatch_get_main_queue()) {
            layoutNodes()
        }
    }
}

let button = SKSpriteNode(color: SKColor.greenColor(), size: CGSizeZero)
button.autoLayoutEnabled = true
addChild(button)

layout(button.layoutProxyView()) { button in
    // button in closure is not the same as 'let button' declared before
    button.left == button.superview!.left   // same as "H:|[button]"
    button.bottom == button.superview!.bottom   // same as "V:|[button]"
    button.height == button.superview!.height * 0.1
    button.width == button.height
}