import SwiftUI

struct WaveShape: Shape {
//    let radius : CGFloat = 50 // derived from the rectangle we're inside of
    let offset : CGFloat = 15
    let steps : Int = 20

    func path(in rect: CGRect) -> Path {
        let center = CGPoint(x: rect.midX, y: rect.midY)
        let radius = min(rect.size.height, rect.size.width) / 2
        let anglesubdiv = CGFloat(0.25) * CGFloat(360/steps) * CGFloat.pi / 180.0

        var path = Path()
        path.move(to: CGPoint(x: rect.maxX, y: rect.midY)) // 3 o'clock

        for i in (0..<steps) {
            let angle = CGFloat(i) * CGFloat(360/steps) * CGFloat.pi / 180.0

            let p1 = CGPoint(
                x: center.x + (radius+offset) * cos(angle+anglesubdiv),
                y: center.y + (radius+offset) * sin(angle+anglesubdiv)
            )
            let p2 = CGPoint(
                x: center.x + (radius) * cos(angle+anglesubdiv*2.0),
                y: center.y + (radius) * sin(angle+anglesubdiv*2.0)
            )
            let p3 = CGPoint(
                x: center.x + (radius-offset) * cos(angle+anglesubdiv*3.0),
                y: center.y + (radius-offset) * sin(angle+anglesubdiv*3.0)
            )
            let p4 = CGPoint(
                x: center.x + radius * cos(angle+anglesubdiv*4.0),
                y: center.y + radius * sin(angle+anglesubdiv*4.0)
            )
            // debug
//            path.addLine(to: p1)
//            path.addLine(to: p2)
//            path.addLine(to: p3)
//            path.addLine(to: p4)

            path.addQuadCurve(to: p2, control: p1)
            path.addQuadCurve(to: p4, control: p3)

        }

        path.closeSubpath()

        return path
    }
}

struct ContentView: View {
    var body: some View {
        VStack {
            WaveShape()
                .stroke(.black, lineWidth: 2)
        }
        .border(.red)

        .padding()
    }
}

#Preview {
    ContentView()
        .frame(width: 300, height: 300)
        .padding()
}