import SwiftUI

struct Arrow: Shape {

    var headHeight = 0.5
    var shaftWidth = 0.5

    var animatableData: AnimatablePair<Double, Double> {
        get { AnimatablePair (headHeight, shaftWidth) }
        set {
            headHeight = newValue.first
            shaftWidth = newValue.second }
    }
    func path(in rect: CGRect) -> Path {

        let height = rect.height * headHeight
        let thickness = rect.width * shaftWidth / 2

        return Path { path in
            path.move(to: CGPoint(x: rect.midX, y: 0))
            path.addLine(to: CGPoint(x: rect.maxX, y: height))
            path.addLine(to: CGPoint(x: rect.midX + thickness, y: height))
            path.addLine(to: CGPoint(x: rect.midX + thickness, y: rect.maxY))
            path.addLine(to: CGPoint(x: rect.midX - thickness, y: rect.maxY))
            path.addLine(to: CGPoint(x: rect.midX - thickness, y: height))
            path.addLine(to: CGPoint(x: 0, y: height))
            path.closeSubpath()
        }
    }
}

struct ContentView: View {
    @State private var headHeight = 0.5
    @State private var shaftWidth = 0.25

    var body: some View {

     Arrow(headHeight: headHeight, shaftWidth: shaftWidth)
            .fill(.blue)
            .onTapGesture {
                withAnimation {
                    headHeight = Double.random(in: 0.2...0.8)
                    shaftWidth = Double.random(in: 0.2...0.8)
            }
        }
    }
}

struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView()
    }
}