final class WaveView: UIView {
    private let waveColor = UIColor(red: 187/255, green: 215/255, blue: 235/255, alpha: 1.0)
    private var phase: Double = 0.0

    private lazy var highSineWave: CAShapeLayer = {
        let waveShape = CAShapeLayer()
        waveShape.strokeColor = waveColor.cgColor
        waveShape.fillColor = UIColor.clear.cgColor
        waveShape.lineWidth = 2

        return waveShape
    }()

    private lazy var lowSineWave: CAShapeLayer = {
        let waveShape = CAShapeLayer()
        waveShape.strokeColor = waveColor.cgColor
        waveShape.fillColor = UIColor.clear.cgColor
        waveShape.lineWidth = 2

        return waveShape
    }()

    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

    override init(frame: CGRect) {
        super.init(frame: frame)
    }

    func startAnimate() {
        addWaves()
        animateWaves()
    }

    func addWaves() {
        layer.addSublayer(highSineWave)
        layer.addSublayer(lowSineWave)
    }

    func animateWaves() {
        DispatchQueue.main.async {
            UIView.animate(withDuration: 1.0, delay: 0.0, options: [.curveLinear], animations: {
                self.highSineWave.path = self.path(in: self.frame, frequency: 25, strength: 25)
                self.lowSineWave.path = self.path(in: self.frame, frequency: 15, strength: 10)

            }, completion: { (finished) in
                if self.phase >= 18.98 {
                    self.phase = 0.0
                }
                self.phase += 0.001

                self.animateWaves()
            })
        }

    }

    func path(in rect: CGRect, frequency: Double, strength: Double) -> CGPath {
        let path = UIBezierPath()

        // calculate some important values up front
        let width = Double(rect.width)
        let height = Double(rect.height)
        let midWidth = width / 2
        let midHeight = height / 2
        let oneOverMidWidth = 1 / midWidth

        // split our total width up based on the frequency
        let wavelength = width / frequency

        // start at the left center
        path.move(to: CGPoint(x: 0, y: midHeight))

        // now count across individual horizontal points one by one
        for x in stride(from: 0, through: width, by: 1) {
            // find our current position relative to the wavelength
            let relativeX = x / wavelength

            // find how far we are from the horizontal center
            let distanceFromMidWidth = x - midWidth

            // bring that into the range of -1 to 1
            let normalDistance = oneOverMidWidth * distanceFromMidWidth

            let parabola = -(normalDistance * normalDistance) + 1

            // calculate the sine of that position, adding our phase offset
            let sine = sin(relativeX + phase)

            // multiply that sine by our strength to determine final offset, then move it down to the middle of our view
            let y = parabola * strength * sine + midHeight

            // add a line to here
            path.addLine(to: CGPoint(x: x, y: y))
        }

        return path.cgPath
    }
}