PageSlide.swift

//
//  PageSlide.swift
//  personal-best
//
//  Created by Shaun Donnelly on 20/06/2020.
//  Copyright © 2020 Shaun Donnelly. All rights reserved.
//

import SwiftUI

struct PageSlideControl: View {

  struct PageSlideButtonStyle: ViewModifier {
    func body(content: Content) -> some View {
      return content
        .padding()
        .foregroundColor(.white)
        .background(Color.blue)
    }
  }

  @Binding var selectedPageIndex: Int
  let titleOne: String
  let titleTwo: String

  var body: some View {
    HStack(spacing: 0) {
      Button(action: {
        withAnimation {
          self.selectedPageIndex = 0
        }
      }) {
        Text(titleOne).bold()
      }.modifier(PageSlideButtonStyle())
      Button(action: {
        withAnimation {
          self.selectedPageIndex = 1
        }
      }) {
        Text(titleTwo).bold()
      }.modifier(PageSlideButtonStyle())
    }
    .cornerRadius(25.0)
    .shadow(radius: 5.0)
  }
}

struct PageSlide<FirstPage: View, SecondPage: View>: View {

  let firstPage: FirstPage
  let firstPageTitle: String
  let secondPage: SecondPage
  let secondPageTitle: String

  @State var selectedPageIndex = 0

  init(
    @ViewBuilder firstPage: () -> FirstPage,
    firstPageTitle: String,
    @ViewBuilder secondPage: () -> SecondPage,
    secondPageTitle: String
  ) {
    self.firstPage = firstPage()
    self.firstPageTitle = firstPageTitle
    self.secondPage = secondPage()
    self.secondPageTitle = secondPageTitle
  }

  var body: some View {
    ZStack(alignment: .bottom) {
      if selectedPageIndex == 0 {
        firstPage.transition(AnyTransition.slide.animation(.easeInOut))
      } else {
        secondPage.transition(AnyTransition.slide.animation(.easeInOut))
      }
      PageSlideControl(
        selectedPageIndex: $selectedPageIndex,
        titleOne: firstPageTitle,
        titleTwo: secondPageTitle
      )
    }

  }
}

struct PageSlide_Previews: PreviewProvider {
  static var previews: some View {
    PageSlide(
      firstPage: {
        List {
          Text("One")
          Text("Two")
          Text("Three")
        }
      },
      firstPageTitle: "Workouts",
      secondPage: {
        List {
          Text("Four")
          Text("Five")
          Text("Six")
        }
      },
      secondPageTitle: "Stats"
    )
  }
}

This is unfinished.