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)]
+                )
+        }
+    }
+
+}

UnitTests/Tests/Extensions/TodoFetchDescriptorTests.swift

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+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)
+        }
+    }
+
+}