import UIKit

class CircleView: UIView {

    var viewLoaded:Bool = false

    var lineWidth:CGFloat = 10
    var animationDuration:Double = 5

    let circlePathLayer = CAShapeLayer()

    private func animate() -> Void {
        let animation = CABasicAnimation(keyPath: "strokeEnd")
        animation.fromValue = 0
        animation.toValue = 1
        animation.duration = self.animationDuration
        animation.autoreverses = false
        animation.repeatCount = 1.0
        self.circlePathLayer.add(animation, forKey: "line")
    }

    private func configure() {
        let frame = circlePathFrame()
        self.circlePathLayer.frame = frame
        self.circlePathLayer.lineWidth = self.lineWidth
        self.circlePathLayer.fillColor = UIColor.lightGray.cgColor
        self.circlePathLayer.strokeColor = UIColor.blue.cgColor
        //line shape (rounded corners)
        self.circlePathLayer.lineCap = kCALineCapRound
        self.circlePathLayer.path = UIBezierPath(ovalIn: frame).cgPath
        layer.addSublayer(circlePathLayer)
        backgroundColor = .green
    }

    private func circlePathFrame() -> CGRect {
        let circleRadius = self.radius()
        return CGRect(x:self.lineWidth/4, y: self.lineWidth/4, width: 2 * circleRadius , height: 2 * circleRadius)
    }

    private func radius() -> CGFloat {
        if self.frame.size.width > self.frame.size.height {
            return self.frame.size.height/2 - self.lineWidth/2
        }
        else {
            return self.frame.size.width/2 - self.lineWidth/2
        }
    }

    //MARK: - Layout subviews

    override public func layoutSubviews() {
        super.layoutSubviews()

        if let _ = self.superview,
            !self.viewLoaded {

            self.viewLoaded = true
            self.configure()
            self.animate()
        }
    }

    //MARK: - Reload circle

    func reloadCircle() -> Void {

        self.viewLoaded = false
        self.setNeedsLayout()
        self.layoutIfNeeded()
    }
}