AppView.swift

import ComposableArchitecture
import HomeFeature
import RestoreFeature
import SwiftUI
import WelcomeFeature

struct AppView: View {
  let store: Store<AppState, AppAction>

  enum ViewState: Equatable {
    case loading
    case welcome
    case restore
    case home
    case failure(String)

    init(_ state: AppState) {
      switch state.screen {
      case .loading: self = .loading
      case .welcome(_): self = .welcome
      case .restore(_): self = .restore
      case .home(_): self = .home
      case .failure(let failure): self = .failure(failure)
      }
    }
  }

  var body: some View {
    WithViewStore(store.scope(state: ViewState.init)) { viewStore in
      ZStack {
        switch viewStore.state {
        case .loading:
          ProgressView {
            Text("Loading")
          }
          .controlSize(.large)
          .frame(maxWidth: .infinity, maxHeight: .infinity)
          .transition(.opacity)

        case .welcome:
          IfLetStore(
            store.scope(
              state: { (/AppState.Screen.welcome).extract(from: $0.screen) },
              action: AppAction.welcome
            ),
            then: { store in
              WelcomeView(store: store)
                .frame(maxWidth: .infinity, maxHeight: .infinity)
                .transition(.asymmetric(
                  insertion: .move(edge: .trailing),
                  removal: .opacity
                ))
            }
          )

        case .restore:
          IfLetStore(
            store.scope(
              state: { (/AppState.Screen.restore).extract(from: $0.screen) },
              action: AppAction.restore
            ),
            then: { store in
              RestoreView(store: store)
                .frame(maxWidth: .infinity, maxHeight: .infinity)
                .transition(.asymmetric(
                  insertion: .move(edge: .trailing),
                  removal: .opacity
                ))
            }
          )