# V1 Block 22 — OS-Notification Package

**Purpose**: Desktop notification implementation.

> **Note for Codex**: Follow tasks exactly; avoid exploratory calls when tasks specify names/files/tests.

## Chunk 22.1 — Desktop notification adapter
Recommended level: **HIGH**

Status: Complete on 2026-06-26.

### Tasks
1. Create package **`packages/scheduler_notifications_desktop`**.
2. Implement adapters per platform with conditional import using `dart:io` Platform.
3. For Linux use `notify-send` via `Process.run`; for macOS use `osascript`; for Windows use `win32` Toast via `windows_notification` package.
4. Implement fallback to write to stdout if unsupported.
5. Add adapter factory `DesktopNotificationAdapter.defaultInstance()`.
6. Write integration test using `FakeNotificationAdapter` mocks to assert scheduling logic; skip on CI if platform not supported.

### Acceptance criteria
1. Desktop adapter compiles on all OS; tests skip rather than fail on unsupported.
2. Adapter passes NotificationAdapter contract tests.

### Completed implementation
1. Added package `packages/scheduler_notifications_desktop` with public entry points `desktop_notifications.dart` and `scheduler_notifications_desktop.dart`.
2. Added `DesktopNotificationAdapter.defaultInstance()` and injectable backend support.
3. Added conditional export for IO vs non-IO environments.
4. Added Linux `notify-send` backend via `Process.run`.
5. Added macOS `osascript` backend via `Process.run`.
6. Added stdout/log fallback backend for unsupported platforms and Windows.
7. Added desktop adapter tests covering delegation, Linux/macOS command selection, fallback behavior, fake-adapter scheduling workflow, and default adapter construction.
8. Wired desktop adapter tests into the root test wrapper.

### Notes
1. Windows currently uses the stdout fallback. Adding `windows_notification` would pull Flutter SDK dependencies into this pure Dart package; a true Windows toast adapter should be revisited if the desktop packaging layer already depends on Flutter.

### Verification
1. `dart pub get`: passed.
2. `dart format test/scheduler_core_test.dart packages/scheduler_notifications_desktop`: passed.
3. `cd packages/scheduler_notifications_desktop && dart analyze`: passed, no issues found.
4. `cd packages/scheduler_notifications_desktop && dart test`: passed, 6 tests.
5. `dart analyze`: passed, no issues found.
6. `dart test`: passed, 324 tests.
7. `scripts/test.sh`: not present or not executable.

---