Source for part 1 of large sticky toggles CodeSlicing episode

StickyTogglePhase1.swift

//
//  StickyTogglePhase1.swift
//
//  Permission is hereby granted, free of charge, to any person obtaining a copy
//  of this software and associated documentation files (the "Software"), to deal
//  in the Software without restriction, including without limitation the rights
//  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
//  of the Software, and to permit persons to whom the Software is furnished to do so,
//  subject to the following conditions:
//
//  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
//  INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
//  PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
//  COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
//  AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
//  WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
//
//  Created by Adam Fordyce on 14/12/2020.
//  Copyright © 2020 Adam Fordyce. All rights reserved.
//

import SwiftUI
import PureSwiftUI

private let toggleLayoutConfig = LayoutGuideConfig.grid(columns: 10, rows: 10)

private struct StickyToggle: View {
    var body: some View {
        let debug = false
        StretchableSquare(stretchFactor: 0, isTop: true, debug: debug)
            .toggleStyle(color: .green, debug: debug)
            .frame(360)
            .shadowIfNot(debug, radius: 10)
            .layoutGuide(toggleLayoutConfig)
            .showLayoutGuides(debug)
    }
}

private extension Shape {
    @ViewBuilder func toggleStyle(color: Color, debug: Bool = false) -> some View {
        if debug {
            stroke(Color.black, style: .init(lineWidth: 2, lineCap: .round, lineJoin: .round))
        } else {
            fill(color)
        }
    }
}

private struct StretchableSquare: Shape {
    
    var isTop: Bool
    var debug: Bool
    var animatableData: CGFloat
    
    init(stretchFactor: CGFloat, isTop: Bool, debug: Bool = false) {
        animatableData = stretchFactor
        self.isTop = isTop
        self.debug = debug
    }
    
    func path(in rect: CGRect) -> Path {
        var path = Path()
        
        let g = toggleLayoutConfig.layout(in: rect)
            .scaled(-1, factor: isTop ? 0 : 1)

        let p1 = g.topLeading
        let p2 = g.topTrailing
        let cpToP3 = g[10, 1].to(g[6, 1], animatableData)
        
        let p3 = g.bottomTrailing.to(g[6, 10], animatableData)
        let p4 = g.bottomLeading.to(g[4, 10], animatableData)
        let cpToP1 = g[0, 1].to(g[4, 1], animatableData)
        
        path.move(p1)
        path.line(p2)
        
        path.quadCurve(p3, cp: cpToP3, showControlPoints: debug)
        
        path.line(p4)
        
        path.quadCurve(p1, cp: cpToP1, showControlPoints: debug)
        
        return path
    }
}

struct StickyTogglePhase1_Previews: PreviewProvider {
    struct StickyTogglePhase1_Harness: View {

        var body: some View {
            StickyToggle()
        }
    }

    static var previews: some View {
        StickyTogglePhase1_Harness()
            .previewDevice(.iPhone_8_Plus)
    }
}