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0169-uikit-navigation-pt1/README.md

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+## [Point-Free](https://www.pointfree.co)
+
+> #### This directory contains code from Point-Free Episode: [UIKit Navigation: Part 1](https://www.pointfree.co/episodes/ep169-uikit-navigation-part-1)
+>
+> What does all the work we’ve done with navigation in SwiftUI have to say about UIKit? Turns out a lot! Without making a single change to the view models we can rewrite the entire view layer in UIKit, and the application will work exactly as it did before, deep-linking and all!

0169-uikit-navigation-pt1/SwiftUINavigation/SwiftUINavigation.xcodeproj/project.xcworkspace/xcshareddata/IDEWorkspaceChecks.plist

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+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+<plist version="1.0">
+<dict>
+	<key>IDEDidComputeMac32BitWarning</key>
+	<true/>
+</dict>
+</plist>

0169-uikit-navigation-pt1/SwiftUINavigation/SwiftUINavigation/Assets.xcassets/AccentColor.colorset/Contents.json

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+{
+  "colors" : [
+    {
+      "idiom" : "universal"
+    }
+  ],
+  "info" : {
+    "author" : "xcode",
+    "version" : 1
+  }
+}

0169-uikit-navigation-pt1/SwiftUINavigation/SwiftUINavigation/Assets.xcassets/AppIcon.appiconset/Contents.json

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+{
+  "images" : [
+    {
+      "idiom" : "iphone",
+      "scale" : "2x",
+      "size" : "20x20"
+    },
+    {
+      "idiom" : "iphone",
+      "scale" : "3x",
+      "size" : "20x20"
+    },
+    {
+      "idiom" : "iphone",
+      "scale" : "2x",
+      "size" : "29x29"
+    },
+    {
+      "idiom" : "iphone",
+      "scale" : "3x",
+      "size" : "29x29"
+    },
+    {
+      "idiom" : "iphone",
+      "scale" : "2x",
+      "size" : "40x40"
+    },
+    {
+      "idiom" : "iphone",
+      "scale" : "3x",
+      "size" : "40x40"
+    },
+    {
+      "idiom" : "iphone",
+      "scale" : "2x",
+      "size" : "60x60"
+    },
+    {
+      "idiom" : "iphone",
+      "scale" : "3x",
+      "size" : "60x60"
+    },
+    {
+      "idiom" : "ipad",
+      "scale" : "1x",
+      "size" : "20x20"
+    },
+    {
+      "idiom" : "ipad",
+      "scale" : "2x",
+      "size" : "20x20"
+    },
+    {
+      "idiom" : "ipad",
+      "scale" : "1x",
+      "size" : "29x29"
+    },
+    {
+      "idiom" : "ipad",
+      "scale" : "2x",
+      "size" : "29x29"
+    },
+    {
+      "idiom" : "ipad",
+      "scale" : "1x",
+      "size" : "40x40"
+    },
+    {
+      "idiom" : "ipad",
+      "scale" : "2x",
+      "size" : "40x40"
+    },
+    {
+      "idiom" : "ipad",
+      "scale" : "1x",
+      "size" : "76x76"
+    },
+    {
+      "idiom" : "ipad",
+      "scale" : "2x",
+      "size" : "76x76"
+    },
+    {
+      "idiom" : "ipad",
+      "scale" : "2x",
+      "size" : "83.5x83.5"
+    },
+    {
+      "idiom" : "ios-marketing",
+      "scale" : "1x",
+      "size" : "1024x1024"
+    }
+  ],
+  "info" : {
+    "author" : "xcode",
+    "version" : 1
+  }
+}

0169-uikit-navigation-pt1/SwiftUINavigation/SwiftUINavigation/Assets.xcassets/Contents.json

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+{
+  "info" : {
+    "author" : "xcode",
+    "version" : 1
+  }
+}

0169-uikit-navigation-pt1/SwiftUINavigation/SwiftUINavigation/ContentView.swift

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+import Parsing
+import SwiftUI
+
+struct DeepLinkRequest {
+  var pathComponents: ArraySlice<Substring>
+  var queryItems: [String: ArraySlice<Substring?>]
+}
+
+extension DeepLinkRequest {
+  init(url: URL) {
+    let queryItems = URLComponents(url: url, resolvingAgainstBaseURL: false)?.queryItems ?? []
+
+    self.init(
+      pathComponents: url.path.split(separator: "/")[...],
+      queryItems: queryItems.reduce(into: [:]) { dictionary, item in
+        dictionary[item.name, default: []].append(item.value?[...])
+      }
+    )
+  }
+}
+
+struct PathComponent<ComponentParser>: Parser
+where
+  ComponentParser: Parser,
+  ComponentParser.Input == Substring
+{
+  let component: ComponentParser
+  init(_ component: ComponentParser) {
+    self.component = component
+  }
+
+  func parse(_ input: inout DeepLinkRequest) -> ComponentParser.Output? {
+    guard
+      var firstComponent = input.pathComponents.first,
+      let output = self.component.parse(&firstComponent),
+      firstComponent.isEmpty
+    else { return nil }
+
+    input.pathComponents.removeFirst()
+    return output
+  }
+}
+
+struct PathEnd: Parser {
+  func parse(_ input: inout DeepLinkRequest) -> Void? {
+    guard input.pathComponents.isEmpty
+    else { return nil }
+    return ()
+  }
+}
+
+struct QueryItem<ValueParser>: Parser
+where
+  ValueParser: Parser,
+  ValueParser.Input == Substring
+{
+  let name: String
+  let valueParser: ValueParser
+
+  init(_ name: String, _ valueParser: ValueParser) {
+    self.name = name
+    self.valueParser = valueParser
+  }
+
+  init(_ name: String) where ValueParser == Rest<Substring> {
+    self.init(name, Rest())
+  }
+
+  func parse(_ input: inout DeepLinkRequest) -> ValueParser.Output? {
+    guard
+      let wrapped = input.queryItems[self.name]?.first,
+      var value = wrapped,
+      let output = self.valueParser.parse(&value),
+      value.isEmpty
+    else { return nil }
+
+    input.queryItems[self.name]?.removeFirst()
+    return output
+  }
+}
+
+enum AppRoute {
+  case one
+  case inventory(InventoryRoute?)
+  case three
+}
+
+enum InventoryRoute {
+  case add(Item, ItemRoute? = nil)
+  case row(Item.ID, RowRoute)
+
+  enum RowRoute {
+    case delete
+    case duplicate
+    case edit
+  }
+}
+
+enum ItemRoute {
+  case colorPicker
+}
+
+let item = QueryItem("name").orElse(Always(""))
+  .take(QueryItem("quantity", Int.parser()).orElse(Always(1)))
+  .map { name, quantity in
+    Item(name: String(name), status: .inStock(quantity: quantity))
+  }
+
+let inventoryDeepLinker = PathEnd()
+  .map { AppRoute.inventory(nil) }
+  .orElse(
+    PathComponent("add")
+      .skip(PathEnd())
+      .take(item)
+      .map { .inventory(.add($0)) }
+  )
+  .orElse(
+    PathComponent("add")
+      .skip(PathComponent("colorPicker"))
+      .skip(PathEnd())
+      .take(item)
+      .map { .inventory(.add($0, .colorPicker)) }
+  )
+  .orElse(
+    PathComponent(UUID.parser())
+      .skip(PathComponent("edit"))
+      .skip(PathEnd())
+      .map { id in .inventory(.row(id, .edit)) }
+  )
+  .orElse(
+    PathComponent(UUID.parser())
+      .skip(PathComponent("delete"))
+      .skip(PathEnd())
+      .map { id in .inventory(.row(id, .delete)) }
+  )
+
+let deepLinker = PathComponent("one")
+  .skip(PathEnd())
+  .map { AppRoute.one }
+  .orElse(
+    PathComponent("inventory")
+      .take(inventoryDeepLinker)
+  )
+  .orElse(
+    PathComponent("three")
+      .skip(PathEnd())
+      .map { .three }
+  )
+
+enum Tab {
+  case one, inventory, three
+}
+
+class AppViewModel: ObservableObject {
+  @Published var inventoryViewModel: InventoryViewModel
+  @Published var selectedTab: Tab
+
+  init(
+    inventoryViewModel: InventoryViewModel = .init(),
+    selectedTab: Tab = .one
+  ) {
+    self.inventoryViewModel = inventoryViewModel
+    self.selectedTab = selectedTab
+  }
+
+  func open(url: URL) {
+    var request = DeepLinkRequest(url: url)
+    if let route = deepLinker.parse(&request) {
+      switch route {
+      case .one:
+        self.selectedTab = .one
+
+      case let .inventory(inventoryRoute):
+        self.selectedTab = .inventory
+        self.inventoryViewModel.navigate(to: inventoryRoute)
+
+      case .three:
+        self.selectedTab = .three
+      }
+    }
+  }
+}
+
+extension InventoryViewModel {
+  func navigate(to route: InventoryRoute?) {
+    switch route {
+    case let .add(item, .none):
+      self.route = .add(.init(item: item))
+
+    case let .add(item, .colorPicker):
+      self.route = .add(.init(item: item, route: .colorPicker))
+
+    case let .row(id, rowRoute):
+      guard let viewModel = self.inventory[id: id]
+      else { break }
+      viewModel.navigate(to: rowRoute)
+
+    case .none:
+      self.route = nil
+    }
+  }
+}
+
+extension ItemRowViewModel {
+  func navigate(to route: InventoryRoute.RowRoute) {
+    switch route {
+    case .delete:
+      self.route = .deleteAlert
+    case .duplicate:
+      self.route = .duplicate(.init(item: self.item))
+    case .edit:
+      self.route = .edit(.init(item: self.item))
+    }
+  }
+}
+
+struct ContentView: View {
+  @ObservedObject var viewModel: AppViewModel
+
+  var body: some View {
+    TabView(selection: self.$viewModel.selectedTab) {
+      Button("Go to 2nd tab") {
+        self.viewModel.selectedTab = .inventory
+      }
+        .tabItem { Text("One") }
+        .tag(Tab.one)
+
+      NavigationView {
+        InventoryView(viewModel: self.viewModel.inventoryViewModel)
+      }
+        .tabItem { Text("Inventory") }
+        .tag(Tab.inventory)
+
+      Text("Three")
+        .tabItem { Text("Three") }
+        .tag(Tab.three)
+    }
+    .onOpenURL { url in
+      self.viewModel.open(url: url)
+    }
+  }
+}
+
+struct ContentView_Previews: PreviewProvider {
+  static var previews: some View {
+    ContentView(viewModel: .init(selectedTab: .inventory))
+  }
+}