extension CAShapeLayer {
    func drawCircleAtLocation(location: CGPoint, withRadius radius: CGFloat, andColor color: UIColor, filled: Bool) {
        fillColor = filled ? color.cgColor : UIColor.white.cgColor
        strokeColor = color.cgColor
        let origin = CGPoint(x: location.x - radius, y: location.y - radius)
        path = UIBezierPath(ovalIn: CGRect(origin: origin, size: CGSize(width: radius * 2, height: radius * 2))).cgPath
    }
}

private var handle: UInt8 = 0;

extension UIBarButtonItem {
    private var badgeLayer: CAShapeLayer? {
        if let badge: AnyObject = objc_getAssociatedObject(self, &handle) as AnyObject? {
            return badge as? CAShapeLayer
        } else {
            return nil
        }
    }

    func addBadge(number: Int, withOffset offset: CGPoint = CGPoint.zero, andColor color: UIColor = UIColor.red, andFilled filled: Bool = true) {
        guard let view = self.value(forKey: "view") as? UIView else { return }

        badgeLayer?.removeFromSuperlayer()

        var badgeWidth = 8
        var numberOffset = 4

        if number > 9 {
            badgeWidth = 12
            numberOffset = 6
        }

        // Initialize Badge
        let badge = CAShapeLayer()
        let radius = CGFloat(7)
        let location = CGPoint(x: view.frame.width - (radius + offset.x), y: (radius + offset.y))
        badge.drawCircleAtLocation(location: location, withRadius: radius, andColor: color, filled: filled)
        view.layer.addSublayer(badge)

        // Initialiaze Badge's label
        let label = CATextLayer()
        label.string = "\(number)"
        label.alignmentMode = CATextLayerAlignmentMode.center
        label.fontSize = 11
        label.frame = CGRect(origin: CGPoint(x: location.x - CGFloat(numberOffset), y: offset.y), size: CGSize(width: badgeWidth, height: 16))
        label.foregroundColor = filled ? UIColor.white.cgColor : color.cgColor
        label.backgroundColor = UIColor.clear.cgColor
        label.contentsScale = UIScreen.main.scale
        badge.addSublayer(label)

        // Save Badge as UIBarButtonItem property
        objc_setAssociatedObject(self, &handle, badge, .OBJC_ASSOCIATION_RETAIN_NONATOMIC)
    }

    func updateBadge(number: Int) {
        if let text = badgeLayer?.sublayers?.filter({ $0 is CATextLayer }).first as? CATextLayer {
            text.string = "\(number)"
        }
    }

    func removeBadge() {
        badgeLayer?.removeFromSuperlayer()
    }
}