List tasks feature (#4)

This PR contains the work done to implement the **List Tasks** feature, and to integrate it into the main content view of the app.

Reviewed-on: rock-n-code/todos-app#4
Co-authored-by: Javier Cicchelli <javier@rock-n-code.com>
Co-committed-by: Javier Cicchelli <javier@rock-n-code.com>

App/Previews/Modifiers/SampleTaskDataModifier.swift

@@ -37,48 +37,45 @@ struct SampleTaskDataModifier: PreviewModifier {
         )
 
         let calendar: Calendar = .current
-        let today: Date = .now
-        let tomorrow: Date = calendar.date(byAdding: .day, value: 1, to: today) ?? today
-        let yesterday = calendar.date(byAdding: .day, value: -1, to: today) ?? today
 
         let tasks: [Todo] = [
             .init(
-                title: "Today task 1",
+                title: "Today task #1",
-                due: today
+                due: .now
             ),
             .init(
-                title: "Today task 2",
+                title: "Today task #2",
                 note: "This is some random note attached to the task.",
-                due: today
+                due: .now
             ),
             .init(
                 title: "Tomorrow task",
-                due: tomorrow
+                due: calendar.date(byAdding: .day, value: 1, to: .now) ?? .now
             ),
             .init(
                 title: "Next week task",
                 note: "This is some random note attached to the task.",
-                due: calendar.date(byAdding: .day, value: 7, to: today) ?? today
+                due: calendar.date(byAdding: .day, value: 7, to: .now) ?? .now
             ),
             .init(
                 title: "Yesterday task",
-                due: yesterday
+                due: calendar.date(byAdding: .day, value: -1, to: .now) ?? .now
             ),
             .init(
                 title: "Last week task",
                 note: "This is some random note attached to the task.",
-                due: calendar.date(byAdding: .day, value: -7, to: today) ?? today
+                due: calendar.date(byAdding: .day, value: -7, to: .now) ?? .now
             ),
             .init(
-                title: "Completed task 1",
+                title: "Completed task #1",
-                due: today,
+                due: calendar.date(byAdding: .day, value: 1, to: .now) ?? .now,
-                completed: today
+                completed: .now
             ),
             .init(
-                title: "Completed task 2",
+                title: "Completed task #2",
                 note: "This is some random note attached to the task.",
-                due: yesterday,
+                due: calendar.date(byAdding: .day, value: -1, to: .now) ?? .now,
-                completed: today
+                completed: .now
             ),
         ]
 

App/Resources/Localizable.xcstrings

@@ -121,6 +121,49 @@
           }
         }
       }
+    "view.task-list-item.placeholder.completed" : {
+      "extractionState" : "manual",
+      "localizations" : {
+        "en" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "Tap to complete or not your task"
+          }
+        }
+      }
+    },
+    "view.task-list-item.placeholder.note" : {
+      "extractionState" : "manual",
+      "localizations" : {
+        "en" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "Add extra notes to your task (if needed)"
+          }
+        }
+      }
+    },
+    "view.task-list-item.placeholder.title" : {
+      "extractionState" : "manual",
+      "localizations" : {
+        "en" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "Give a title to your task"
+          }
+        }
+      }
+    },
+    "view.task-list.content-unavailable.title" : {
+      "extractionState" : "manual",
+      "localizations" : {
+        "en" : {
+          "stringUnit" : {
+            "state" : "translated",
+            "value" : "All Tasks Completed"
+          }
+        }
+      }
     }
   },
   "version" : "1.1"

App/Sources/Extensions/TodoFetchDescriptor+Inits.swift

@@ -0,0 +1,54 @@
+import Foundation
+import SwiftData
+
+/// Extension providing convenient initializers for fetching todos by group category.
+///
+/// This extension allows creating fetch descriptors that automatically filter and sort todos
+/// based on their completion status and due dates according to the specified `TodoGroup`.
+extension FetchDescriptor where T == Todo {
+
+    /// Creates a fetch descriptor for todos filtered and sorted by a specific group.
+    ///
+    /// This initializer provides a convenient way to fetch todos categorized by their temporal
+    /// relevance and completion status. Each group applies appropriate predicates and sort orders:
+    ///
+    /// - **Completed**: All tasks marked as done, sorted by completion date (most recent first)
+    /// - **Overdue**: Incomplete tasks with due dates before today, sorted by due date (most recent first)
+    /// - **Today**: Incomplete tasks due today, sorted by due date (earliest first)
+    /// - **Upcoming**: Incomplete tasks due after today, sorted by due date (earliest first)
+    ///
+    /// - Parameters:
+    ///   - group: The todo group category to filter by.
+    ///   - calendar: The calendar to use for date calculations. Defaults to `.current`.
+    init(
+        group: TodoGroup,
+        calendar: Calendar = .current
+    ) {
+        let today = calendar.startOfDay(for: .now)
+        let tomorrow = calendar.date(byAdding: .day, value: 1, to: today) ?? today
+
+        switch group {
+            case .completed:
+                self.init(
+                    predicate: #Predicate { $0.completed != nil },
+                    sortBy: [.init(\.completed, order: .reverse)]
+                )
+            case .overdue:
+                self.init(
+                    predicate: #Predicate { $0.completed == nil && $0.due < today },
+                    sortBy: [.init(\.due, order: .reverse)]
+                )
+            case .today:
+                self.init(
+                    predicate: #Predicate { $0.completed == nil && $0.due >= today && $0.due < tomorrow },
+                    sortBy: [.init(\.due, order: .forward)]
+                )
+            case .upcoming:
+                self.init(
+                    predicate: #Predicate { $0.completed == nil && $0.due >= tomorrow },
+                    sortBy: [.init(\.due, order: .forward)]
+                )
+        }
+    }
+
+}

App/Sources/Styles/CompletionToggleStyle.swift

@@ -0,0 +1,77 @@
+import SwiftUI
+
+/// A custom toggle style designed for task completion indication.
+///
+/// This style renders a circular checkbox that visually represents completion state:
+/// - **Off state**: An empty circle with a secondary-colored stroke border
+/// - **On state**: A circle with a primary-colored stroke border containing a filled inner circle
+///
+/// ## Usage
+///
+/// Apply this style to any `Toggle` view using the `.completion` static accessor:
+///
+/// ```swift
+/// Toggle("Complete task", isOn: $isCompleted)
+///     .toggleStyle(.completion)
+/// ```
+struct CompletionToggleStyle: ToggleStyle {
+
+    // MARK: Functions
+
+    func makeBody(configuration: Configuration) -> some View {
+        Button {
+            configuration.isOn.toggle()
+        } label: {
+            HStack(alignment: .top, spacing: 12) {
+                ZStack {
+                    Circle()
+                        .strokeBorder(
+                            configuration.isOn ? .primary : .secondary,
+                            lineWidth: 2
+                        )
+                        .frame(width: 24, height: 24)
+
+                    if configuration.isOn {
+                        Circle()
+                            .fill(.primary)
+                            .frame(width: 16, height: 16)
+                    }
+                }
+            }
+        }
+        .animation(
+            .easeInOut,
+            value: configuration.isOn
+        )
+        .buttonStyle(.plain)
+    }
+
+}
+
+// MARK: - Toggle Style Extension
+
+extension ToggleStyle where Self == CompletionToggleStyle {
+
+    /// A toggle style for task completion with a circular checkbox design.
+    ///
+    /// This convenience accessor provides easy access to the ``CompletionToggleStyle``
+    /// for use with SwiftUI's toggle style modifier.
+    static var completion: CompletionToggleStyle {
+        CompletionToggleStyle()
+    }
+
+}
+
+// MARK: - Previews
+
+#Preview("Completion toggle style") {
+    @Previewable
+    @State
+    var isOn = false
+
+    Toggle(
+        "Unchecked task",
+        isOn: $isOn
+    )
+    .toggleStyle(.completion)
+}

App/Sources/View Models/TaskListViewModel.swift

@@ -0,0 +1,43 @@
+import SwiftData
+import SwiftUI
+
+extension TaskListView {
+
+    /// View model for managing the logic for the task list view.
+    ///
+    /// This observable class encapsulates the state and business logic for the task list view.
+    /// It follows the MVVM pattern to separate presentation logic from the view layer.
+    ///
+    /// ## Responsibilities
+    /// - Providing the navigation title for the current group
+    @Observable
+    final class ViewModel {
+
+        // MARK: Properties
+
+        /// The task group to display tasks for.
+        ///
+        /// This property determines which tasks are fetched and displayed in the list.
+        private let group: TodoGroup
+
+        // MARK: Initialization
+
+        /// Initializes a new view model instance for a specific task group.
+        ///
+        /// - Parameter group: The task group to display tasks for.
+        init(group: TodoGroup) {
+            self.group = group
+        }
+
+        // MARK: Computed
+
+        /// The navigation title for the current task group.
+        ///
+        /// This computed property provides the localized title for the current group,
+        /// suitable for display in a navigation bar.
+        ///
+        /// - Returns: The localized title key for the current group.
+        var navigationTitle: LocalizedStringKey { group.title }
+
+    }
+}

App/Sources/Views/TaskList/TaskListItem.swift

@@ -0,0 +1,148 @@
+import SwiftUI
+
+extension TaskListView {
+
+    /// A view that displays a single editable todo task in a list.
+    ///
+    /// This view provides a comprehensive interface for viewing and editing task information,
+    /// including:
+    /// - A completion toggle using a circular checkbox design
+    /// - An editable title field with multi-line support
+    /// - An optional note field that appears when the task has notes
+    /// - A date picker for selecting the task's due date
+    ///
+    /// The view automatically adjusts its appearance based on completion state, dimming
+    /// completed tasks to provide visual feedback. All text fields support automatic
+    /// capitalization and keyboard correction for improved user experience.
+    struct Item: View {
+
+        // MARK: Properties
+
+        /// The todo task to display.
+        @Bindable
+        private var item: Todo
+
+        // MARK: Initializers
+
+        /// Creates a new task list item view for the specified todo.
+        ///
+        /// The item is wrapped in a `@Bindable` property wrapper to enable two-way
+        /// data binding for editing task properties directly within the view.
+        ///
+        /// - Parameter item: The todo task to display and edit.
+        init(_ item: Todo) {
+            _item = Bindable(item)
+        }
+
+        // MARK: Body
+
+        /// The content and behavior of the view.
+        ///
+        /// Renders an editable task list item with a completion toggle, title field,
+        /// optional note field, and date picker. The view's foreground color automatically
+        /// adjusts based on completion state, and changes animate smoothly.
+        var body: some View {
+            HStack(
+                alignment: .top,
+                spacing: 16
+            ) {
+                Toggle(
+                    "view.task-list-item.placeholder.completed",
+                    isOn: isCompleted
+                )
+                .toggleStyle(.completion)
+
+                VStack(
+                    alignment: .leading,
+                    spacing: 8
+                ) {
+                    TextField(
+                        "view.task-list-item.placeholder.title",
+                        text: $item.title,
+                        axis: .vertical
+                    )
+                    .font(.headline)
+
+                    if showNote {
+                        TextField(
+                            "view.task-list-item.placeholder.note",
+                            text: note,
+                            axis: .vertical
+                        )
+                        .font(.subheadline)
+                    }
+
+                    DatePicker(selection: $item.due, displayedComponents: .date) {
+                        Image(systemName: "calendar")
+                    }
+                    .frame(width: 160)
+                    .disabled(isCompleted.wrappedValue)
+                }
+                .autocapitalization(.sentences)
+                .autocorrectionDisabled(false)
+                .foregroundStyle(foregroundColor)
+                .keyboardType(.asciiCapable)
+            }
+            .animation(
+                .easeInOut,
+                value: item.completed
+            )
+        }
+    }
+
+}
+
+// MARK: - Helpers
+
+private extension TaskListView.Item {
+
+    // MARK: Bindings
+
+    var isCompleted: Binding<Bool> {
+        .init {
+            item.completed != nil
+        } set: {
+            item.completed = $0 ? .now : nil
+        }
+    }
+
+    var note: Binding<String> {
+        .init {
+            item.note ?? ""
+        } set: {
+            item.note = $0.isEmpty ? nil : $0
+        }
+    }
+
+    // MARK: Computed
+
+    var foregroundColor: Color {
+        item.completed == nil ? .primary : .secondary
+    }
+
+    var showNote: Bool {
+        guard let note = item.note else {
+            return false
+        }
+
+        return note.trimmingCharacters(in: .whitespacesAndNewlines).isEmpty == false
+    }
+
+}
+
+// MARK: - Previews
+
+#Preview("Task list item") {
+    @Previewable
+    var todo: Todo = .init(
+        title: "Complete project documentation",
+        note: "Add detailed comments and README",
+        due: .now,
+        completed: nil
+    )
+
+    List {
+        TaskListView.Item(todo)
+    }
+    .listStyle(.grouped)
+}

App/Sources/Views/TaskListView.swift

@@ -0,0 +1,99 @@
+import SwiftData
+import SwiftUI
+
+/// A view that displays all todo tasks for a specific task group.
+///
+/// This view shows a filtered list of tasks based on the selected group (today, upcoming, past, or completed).
+/// The view uses a view model to separate business logic from presentation.
+struct TaskListView: View {
+    
+    // MARK: Properties
+    
+    /// Query to fetch todos filtered by the current group.
+    @Query
+    private var tasks: [Todo]
+    
+    /// The view model managing the business logic for this view.
+    @State
+    private var viewModel: ViewModel
+
+    // MARK: Initialization
+    
+    /// Creates a new task list view for a specific group.
+    /// - Parameter group: The todo group to display tasks for.
+    init(group: TodoGroup) {
+        _tasks = .init(FetchDescriptor<Todo>(group: group))
+        _viewModel = .init(initialValue: ViewModel(group: group))
+    }
+    
+    // MARK: Body
+    
+    /// The content and behavior of the view.
+    ///
+    /// Displays a list of tasks filtered by the current group.
+    var body: some View {
+        Group {
+            if tasks.isEmpty {
+                ContentUnavailableView(
+                    "view.task-list.content-unavailable.title",
+                    systemImage: "checkmark.circle"
+                )
+            } else {
+                List {
+                    ForEach(tasks) { todo in
+                        Item(todo)
+                    }
+                }
+                .listStyle(.grouped)
+            }
+        }
+        .navigationTitle(viewModel.navigationTitle)
+    }
+}
+
+// MARK: - Previews
+
+#Preview(
+    "Task list with empty tasks",
+    traits: .emptyContainer
+) {
+    NavigationStack {
+        TaskListView(group: .today)
+    }
+}
+
+#Preview(
+    "Task list - today",
+    traits: .sampleTasks
+) {
+    NavigationStack {
+        TaskListView(group: .today)
+    }
+}
+
+#Preview(
+    "Task list - upcoming",
+    traits: .sampleTasks
+) {
+    NavigationStack {
+        TaskListView(group: .upcoming)
+    }
+}
+
+#Preview(
+    "Task list - overdue",
+    traits: .sampleTasks
+) {
+    NavigationStack {
+        TaskListView(group: .overdue)
+    }
+}
+
+#Preview(
+    "Task list - completed",
+    traits: .sampleTasks
+) {
+    NavigationStack {
+        TaskListView(group: .completed)
+    }
+}

UnitTests/Tests/Extensions/TodoFetchDescriptorTests.swift

@@ -0,0 +1,130 @@
+import Foundation
+import SwiftData
+import Testing
+
+@testable import Todos
+
+@Suite("FetchDescriptor<Todo> extension tests")
+struct TodoFetchDescriptorTests {
+
+    // MARK: Initialization tests
+    
+    @Test(
+        "initializes with group when empty tasks",
+        arguments: TodoGroup.allCases
+    )
+    @MainActor
+    func initializationWhenEmptyTasks(for group: TodoGroup) throws {
+        // GIVEN
+        let container = try modelContainer
+        let context = container.mainContext
+        
+        // WHEN
+        let descriptor = FetchDescriptor<Todo>(group: .today)
+        let results = try context.fetch(descriptor)
+        
+        // THEN
+        #expect(results.isEmpty)
+    }
+    
+    @Test(
+        "initializes with group when filled tasks",
+        arguments: TodoGroup.allCases
+    )
+    @MainActor
+    func initializationWhenFilledTasks(for group: TodoGroup) throws {
+        // GIVEN
+        let container = try modelContainer
+        let context = container.mainContext
+        
+        insert(into: context)
+        
+        // WHEN
+        let descriptor = FetchDescriptor<Todo>(group: group)
+        let results = try context.fetch(descriptor)
+        
+        // THEN
+        #expect(results.count == 2)
+        
+        switch group {
+        case .completed:
+            #expect(results[0].title == "Completed task #2")
+            #expect(results[1].title == "Completed task #1")
+        case .overdue:
+            #expect(results[0].title == "Overdue task #2")
+            #expect(results[1].title == "Overdue task #1")
+        case .today:
+            #expect(results[0].title == "Today task #1")
+            #expect(results[1].title == "Today task #2")
+        case .upcoming:
+            #expect(results[0].title == "Upcoming task #1")
+            #expect(results[1].title == "Upcoming task #2")
+        }
+    }
+
+}
+
+// MARK: - Helpers
+
+private extension TodoFetchDescriptorTests {
+
+    // MARK: Computed
+
+    var modelContainer: ModelContainer {
+        get throws {
+            try ModelContainer(
+                for: Todo.self,
+                configurations: .init(isStoredInMemoryOnly: true)
+            )
+        }
+    }
+
+    // MARK: Functions
+
+    func insert(
+        into context: ModelContext,
+        calendar: Calendar = .current
+    ) {
+        let tasks: [Todo] = [
+            .init(
+                title: "Today task #1",
+                due: .now
+            ),
+            .init(
+                title: "Today task #2",
+                due: .now
+            ),
+            .init(
+                title: "Upcoming task #1",
+                due: calendar.date(byAdding: .day, value: 1, to: .now) ?? .now
+            ),
+            .init(
+                title: "Upcoming task #2",
+                due: calendar.date(byAdding: .day, value: 1, to: .now) ?? .now
+            ),
+            .init(
+                title: "Overdue task #1",
+                due: calendar.date(byAdding: .day, value: -1, to: .now) ?? .now
+            ),
+            .init(
+                title: "Overdue task #2",
+                due: calendar.date(byAdding: .day, value: -1, to: .now) ?? .now
+            ),
+            .init(
+                title: "Completed task #1",
+                due: calendar.date(byAdding: .day, value: -1, to: .now) ?? .now,
+                completed: .now
+            ),
+            .init(
+                title: "Completed task #2",
+                due: calendar.date(byAdding: .day, value: 1, to: .now) ?? .now,
+                completed: .now
+            )
+        ]
+        
+        for task in tasks {
+            context.insert(task)
+        }
+    }
+
+}

UnitTests/Tests/View Models/NewTaskViewModelTests.swift

@@ -124,10 +124,7 @@ struct NewTaskViewModelTests {
     @MainActor
     func saveWithAllProperties() throws {
         // GIVEN
-        let container = try ModelContainer(
+        let container = try modelContainer
-            for: Todo.self,
-            configurations: .init(isStoredInMemoryOnly: true)
-        )
         let context = container.mainContext
         let viewModel = NewTaskView.ViewModel()
 
@@ -153,10 +150,7 @@ struct NewTaskViewModelTests {
     @MainActor
     func saveWithEmptyNote() throws {
         // GIVEN
-        let container = try ModelContainer(
+        let container = try modelContainer
-            for: Todo.self,
-            configurations: .init(isStoredInMemoryOnly: true)
-        )
         let context = container.mainContext
         let viewModel = NewTaskView.ViewModel()
 
@@ -182,10 +176,7 @@ struct NewTaskViewModelTests {
     @MainActor
     func saveWithWhitespaceNote() throws {
         // GIVEN
-        let container = try ModelContainer(
+        let container = try modelContainer
-            for: Todo.self,
-            configurations: .init(isStoredInMemoryOnly: true)
-        )
         let context = container.mainContext
         let viewModel = NewTaskView.ViewModel()
 
@@ -211,10 +202,7 @@ struct NewTaskViewModelTests {
     @MainActor
     func saveMultipleTodos() throws {
         // GIVEN
-        let container = try ModelContainer(
+        let container = try modelContainer
-            for: Todo.self,
-            configurations: .init(isStoredInMemoryOnly: true)
-        )
         let context = container.mainContext
         let viewModelFirst = NewTaskView.ViewModel()
         let viewModelSecond = NewTaskView.ViewModel()
@@ -237,3 +225,20 @@ struct NewTaskViewModelTests {
     }
 
 }
+
+// MARK: - Helpers
+
+private extension NewTaskViewModelTests {
+    
+    // MARK: Computed
+    
+    var modelContainer: ModelContainer {
+        get throws {
+            try ModelContainer(
+                for: Todo.self,
+                configurations: .init(isStoredInMemoryOnly: true)
+            )
+        }
+    }
+    
+}

UnitTests/Tests/View Models/TaskGroupListViewModelTests.swift

@@ -37,11 +37,10 @@ struct TaskGroupListViewModelTests {
     )
     func countWhenEmptyData(for group: TodoGroup) throws {
         // GIVEN
-        let tasks: [Todo] = []
         let viewModel = TaskGroupListView.ViewModel()
 
         // WHEN
-        let count = viewModel.count(tasks, for: group)
+        let count = viewModel.count(emptyTasks, for: group)
 
         // THEN
         #expect(count == 0)
@@ -53,13 +52,33 @@ struct TaskGroupListViewModelTests {
     )
     func countWhenFilledData(for group: TodoGroup) throws {
         // GIVEN
+        let viewModel = TaskGroupListView.ViewModel()
+
+        // WHEN
+        let count = viewModel.count(sampleTasks, for: group)
+
+        // THEN
+        #expect(count == 2)
+    }
+
+}
+
+// MARK: - Helpers
+
+private extension TaskGroupListViewModelTests {
+
+    // MARK: Computed
+    
+    var emptyTasks: [Todo] { [] }
+
+    var sampleTasks: [Todo] {
         let today: Date = .now
         let tomorrow = calendar.date(byAdding: .day, value: 1, to: today) ?? today
         let yesterday = calendar.date(byAdding: .day, value: -1, to: today) ?? today
         let nextWeek = calendar.date(byAdding: .day, value: 7, to: today) ?? today
         let lastWeek = calendar.date(byAdding: .day, value: -7, to: today) ?? today
 
-        let tasks = [
+        return [
             Todo(title: "Today task #1", due: today),
             Todo(title: "Today task #2", due: today),
             Todo(title: "Tomorrow task #1", due: tomorrow),
@@ -67,16 +86,8 @@ struct TaskGroupListViewModelTests {
             Todo(title: "Yesterday task #1", due: yesterday),
             Todo(title: "Last week task #1", due: lastWeek),
             Todo(title: "Completed task #1", due: tomorrow, completed: today),
-            Todo(title: "Completed task #2", due: yesterday, completed: today)
+            Todo(title: "Completed task #2", due: yesterday, completed: today),
         ]
-
-        let viewModel = TaskGroupListView.ViewModel()
-
-        // WHEN
-        let count = viewModel.count(tasks, for: group)
-
-        // THEN
-        #expect(count == 2)
     }
 
 }

UnitTests/Tests/View Models/TaskListViewModelTests.swift

@@ -0,0 +1,27 @@
+import Foundation
+import SwiftData
+import Testing
+
+@testable import Todos
+
+@Suite("TaskList view model tests")
+struct TaskListViewModelTests {
+
+    // MARK: Computed tests
+
+    @Test(
+        "navigationTitle returns correct title for each and every group",
+        arguments: TodoGroup.allCases
+    )
+    func navigationTitle(for group: TodoGroup) {
+        // GIVEN
+        let viewModel = TaskListView.ViewModel(group: group)
+
+        // WHEN
+        let title = viewModel.navigationTitle
+
+        // THEN
+        #expect(title == group.title)
+    }
+
+}