Wave.swift

struct Wave: Shape {
    var amplitude: Double
    var frequency: Double

    func path(in rect: CGRect) -> Path {
        let sinCenterY = amplitude
        let path = CGMutablePath()
        path.move(to: CGPoint(x: 0, y: sinCenterY))
        let width = Double(rect.width)
        for x in stride(from: 0, through: width, by: 1) {
            let y = sinCenterY + amplitude * sin(frequency * x)
            path.addLine(to: CGPoint(x: x, y: y))
        }
        path.addLine(to: CGPoint(x: rect.maxX, y: rect.maxY))
        path.addLine(to: CGPoint(x: rect.minX, y: rect.maxY))
        path.addLine(to: CGPoint(x: Double(rect.minX), y: sinCenterY))
        return Path(path)
    }

    var animatableData: AnimatablePair<Double, Double> {
        get {
            return AnimatablePair(amplitude, frequency)
        }
        set {
            amplitude = newValue.first
            frequency = newValue.second
        }
    }
}