[feat] enable-background-download

ONBOARDING.md

@@ -115,7 +115,7 @@ The detailed docs live in `docs/`. Read them in this order if you're new:
 1. **[docs/content-rendering.md](docs/content-rendering.md)** — HTML rendering, the `sanitize()` workarounds, `flutter_html_table` filter in `main.dart`.
 1. **[docs/onboarding-flow.md](docs/onboarding-flow.md)** — the three onboarding pages and their persistence side-effects.
 1. **[docs/features.md](docs/features.md)** — pages, widgets, drawer, share menu, language switcher.
-1. **[docs/background-tasks.md](docs/background-tasks.md)** — `workmanager` isolate, the result-sync trick, why parts are commented out.
+1. **[docs/background-tasks.md](docs/background-tasks.md)** — `workmanager` isolate, the two-phase check/download flow, the settings matrix, and the result-sync trick.
 1. **[docs/localization.md](docs/localization.md)** — `.arb` workflow, `context.l10n` extension, in-app language vs. content language.
 1. **[docs/testing.md](docs/testing.md)** — unit/widget tests, fixtures, integration test, CI.
 1. **[docs/conventions.md](docs/conventions.md)** — coding conventions, lints, do/don't.
@@ -131,7 +131,7 @@ These are the load-bearing oddities — read these before changing code in their
 - **`LanguageDownloader`** (`lib/data/language_downloader.dart`) is the in-house module that downloads + unzips a language's HTML + PDF into a staging directory and swaps it into place atomically. Failed downloads never destroy prior offline content, concurrent `download()` calls are serialized (peak memory bounded by two zips), and a `.staging` leftover from a crashed run is cleaned up on the next attempt. It replaced the third-party `download_assets` package and is wired up in `main.dart` and the background isolate via `languageDownloaderProvider.overrideWithValue(...)`.
 - **`flutter_html` error filter.** `main.dart` installs a `FlutterError.onError` shim that swallows four specific assertions thrown by `flutter_html_table` 3.0.0. Read the long docstring there before touching it — the four assertion variants are documented in detail.
 - **HTML pre-processing.** `widgets/html_view.dart` calls `sanitize()` to fix bugs in `flutter_html` (e.g. percent table widths, fuzzy translations, stylized subtitles). Some workarounds are also in the HTML generator (`pywikitools`) upstream.
-- **Background task is half-disabled.** Big chunks of `BackgroundScheduler.schedule()` and `Workmanager().initialize` in `main.dart` are commented out, gated on a "version 0.9" milestone. Don't delete them — they are the working scaffolding for the next release.
+- **Background task is enabled and settings-driven.** `BackgroundScheduler.schedule()` registers a periodic `workmanager` task at the `CheckFrequency` interval (or cancels it when `never`), and `backgroundMain()` runs a two-phase flow: `backgroundCheck` then a settings-gated `backgroundDownload` (see the `AutomaticUpdates` × connectivity matrix in `docs/background-tasks.md`). Scheduling is owned by `BackgroundScheduler`, triggered from startup / onboarding step 3 / the check-frequency setting — `main.dart` only calls `Workmanager().initialize(backgroundTask)`.
 - **No package on pub.dev.** `pubspec.yaml` has `publish_to: 'none'`.
 - **License is AGPL** with an Apple App Store exception. See `LICENSE` and `COPYING.iOS`.
 - **`test` is pinned to ^1.29.0** because 1.30+ needs a newer `test_api` than `flutter_test` allows.
@@ -170,8 +170,8 @@ ______________________________________________________________________
 
 ## 8. Roadmap context (from README)
 
-- **0.9**: enable automatic background updates (scaffolding present but commented out).
+- **0.9**: enable automatic background updates — **done**: the periodic task is
+  scheduled from `CheckFrequency` and downloads per `AutomaticUpdates` (see
+  `docs/background-tasks.md`).
 - **1.0**: solid release.
 - iOS planned for 2024.
-
-If you see code with `TODO for version 0.9`, that's why.

android/app/src/main/AndroidManifest.xml

@@ -6,6 +6,8 @@
     <uses-permission android:name="android.permission.READ_MEDIA_VIDEO" tools:node="remove" />
     <uses-permission android:name="android.permission.READ_MEDIA_AUDIO" tools:node="remove" />
     <uses-permission android:name="android.permission.INTERNET" />
+    <!-- connectivity_plus: query WiFi/mobile connection type for onlyOnWifi -->
+    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
    <application
         android:label="4training.net"
         android:name="${applicationName}"

android/gradle.properties

@@ -1,3 +1,7 @@
 org.gradle.jvmargs=-Xmx1536M
 android.useAndroidX=true
 android.enableJetifier=false
+# This builtInKotlin flag was added automatically by Flutter migrator
+android.builtInKotlin=false
+# This newDsl flag was added automatically by Flutter migrator
+android.newDsl=false

docs/architecture.md

@@ -19,11 +19,14 @@ There is no app-owned backend; all content comes from public GitHub repos and th
 - **Background isolate**:
   - Spawned by `workmanager`. Runs `backgroundTask()` in `lib/background/background_task.dart`,
     builds its own `ProviderContainer`, checks each downloaded language for new GitHub commits,
-    persists results to `SharedPreferences`.
+    persists results to `SharedPreferences`, and — depending on the `AutomaticUpdates` setting and
+    connectivity — downloads the languages that have updates.
     The main isolate later detects the activity by reloading shared prefs (see `BackgroundResultNotifier.checkForActivity`).
 
-> **Note:** Currently the periodic registration of the background task is **commented out** (gated behind "version 0.9").
-> The task is wired up and tested in the integration test, but is not actually being scheduled at app launch.
+> **Note:** The periodic task is scheduled by `BackgroundScheduler.schedule()`
+> at the `CheckFrequency` interval (not scheduled when `never`), and its run is
+> gated by the `AutomaticUpdates` setting (check-only, or download on WiFi /
+> always). See `docs/background-tasks.md`.
 
 ## Layered overview
 

docs/background-tasks.md

@@ -1,6 +1,10 @@
 # Background Tasks
 
-The app has a `workmanager`-based periodic background task that **checks** for content updates while the app is closed. Note: as of v0.8 the *scheduling* of this task is **disabled** (commented out, gated for v0.9). The task implementation is complete and integration-tested; only the registration is dormant.
+The app has a `workmanager`-based periodic background task that **checks** for
+content updates while the app is closed and, when the user's settings allow it,
+**downloads** the languages that have updates. The task is scheduled at the
+`CheckFrequency` interval (and not scheduled at all when the user picks
+`never`); what it does once it runs is driven by the `AutomaticUpdates` setting.
 
 ## What runs in the background
 
@@ -25,49 +29,103 @@ void backgroundTask() {
 ### `backgroundMain()`
 1. Gets a fresh `SharedPreferences` instance (the background isolate has its own memory).
 2. Resolves `getApplicationDocumentsDirectory()` and builds a real `LanguageDownloaderImpl` with a fresh `Dio` and the local `FileSystem`.
-3. Builds a new `ProviderContainer` with `sharedPrefsProvider` **and** `languageDownloaderProvider` overridden — the background isolate has the same atomicity and concurrency guarantees as the foreground path.
-4. Calls `backgroundCheck(ref)`.
-5. Currently, the task only checks for updates, never auto-downloads.
+3. Builds a new `ProviderContainer` with `sharedPrefsProvider`, `languageDownloaderProvider` **and** `connectivityServiceProvider` overridden — the background isolate has the same atomicity and concurrency guarantees as the foreground path, plus a way to check the connection type without a `BuildContext`.
+4. Runs the two-phase flow: **`backgroundCheck(ref)`** (phase 1) then **`backgroundDownload(ref)`** (phase 2).
 
-### `backgroundCheck(ProviderContainer ref)`
+### `backgroundCheck(ProviderContainer ref)` — phase 1
 For each language code in `availableLanguagesProvider`:
 1. `languageProvider(code).notifier.lazyInit()` — minimal disk check, no JSON parse.
 2. Skip if not downloaded.
-3. `languageStatusProvider(code).check()` — same GitHub Commits API call as the foreground.
+3. `languageStatusProvider(code).check()` — same GitHub Commits API call as the foreground. This refreshes `updatesAvailable-<lang>` / `lastChecked-<lang>` in prefs.
 4. Bail out of the loop if the rate limit (`apiRateLimitExceeded`) is hit.
 
+### `backgroundDownload(ProviderContainer ref)` — phase 2
+Reads `automaticUpdatesProvider` (from the isolate's own prefs) and decides
+whether to download the languages that phase 1 flagged with `updatesAvailable`:
+
+| `AutomaticUpdates`    | metered (mobile) | unmetered (WiFi/ethernet) |
+| --------------------- | ---------------- | ------------------------- |
+| `never`               | no download      | no download               |
+| `requireConfirmation` | no download¹     | no download¹              |
+| `onlyOnWifi`          | no download      | download                  |
+| `yesAlways`           | download         | download                  |
+
+¹ `requireConfirmation` deliberately leaves `updatesAvailable` set so the
+foreground can surface it — see [Confirming updates in the foreground](#confirming-updates-in-the-foreground).
+
+For `onlyOnWifi`, connectivity is queried via `connectivityServiceProvider`
+(`ConnectivityService.isUnmetered()`). "Unmetered" means WiFi **or** ethernet —
+the user's real intent behind `onlyOnWifi` is "don't burn mobile data". When
+downloading, each language with `updatesAvailable` is re-downloaded via
+`languageDownloader.download(code)` in a per-language `try`/`catch`, so one
+language's failure never aborts the whole run. After each download the language's
+`languageStatusProvider` is invalidated so `updatesAvailable` resets to false.
+
+### Connectivity (`lib/data/connectivity_service.dart`)
+`ConnectivityService.isUnmetered()` wraps the `connectivity_plus` package
+(Android needs the `ACCESS_NETWORK_STATE` permission). It is exposed as
+`connectivityServiceProvider`, a `MustOverrideProvider` — the real
+`ConnectivityServiceImpl` is wired up in `main.dart` and in `backgroundMain()`,
+and tests inject `FakeConnectivityService` (a controllable `unmetered` flag,
+living in `lib/background/background_test.dart` next to `FakeLanguageDownloader`).
+
 ### Debug logging
 `writeLog(message)` appends to `<docDir>/background.log` so the integration test (and human debuggers) can confirm the task ran. Marked `TODO: Remove later`.
 
 ## Scheduling (`lib/background/background_scheduler.dart`)
 
-The current code is essentially:
+`BackgroundScheduler.schedule()` registers (or cancels) the periodic task
+according to the `CheckFrequency` setting:
 
 ```dart
-class BackgroundScheduler extends Notifier<bool> {
-  @override
-  bool build() => false;
-
-  Future<void> schedule() async {
-    /* TODO Enable this with version 0.9
-       cancelByUniqueName('backgroundTask')
-       interval = checkFrequency.getDuration()  // null if 'never'
-       if interval == null: state = false; return
-       Workmanager().registerPeriodicTask('backgroundTask', 'backgroundTask',
-           constraints: Constraints(networkType: NetworkType.connected),
-           initialDelay: interval ~/ 2)
-       state = true
-    */
+Future<void> schedule() async {
+  // idempotent re-scheduling: always cancel the prior registration first
+  await Workmanager().cancelByUniqueName('backgroundTask');
+  final interval = ref.read(checkFrequencyProvider).getDuration(); // null == never
+  if (interval == null) {
+    state = false;          // CheckFrequency.never -> task stays cancelled
+    return;
   }
+  await Workmanager().registerPeriodicTask('backgroundTask', 'backgroundTask',
+      constraints: Constraints(networkType: NetworkType.connected),
+      initialDelay: interval ~/ 2);
+  state = true;
 }
 ```
 
-`schedule()` is called from three places (and is currently a no-op):
+- The provider's `bool` state reflects whether the task is currently scheduled.
+- `CheckFrequency.never` → nothing registered, `state = false`.
+- The `NetworkType.connected` constraint guarantees *some* connection when the
+  task fires (which is why `yesAlways` can download without a connectivity check).
+- The `task` name `'backgroundTask'` is what reaches `executeTask` and selects
+  the `backgroundMain` branch (kept distinct from `'testTask'`).
+
+`schedule()` is called from three places:
 - `StartupPage.init()` after a successful startup,
 - `SetUpdatePrefsPage` after the user submits onboarding step 3,
 - `CheckFrequencyNotifier.setCheckFrequency` whenever the user changes the frequency.
 
-The `Workmanager().initialize(backgroundTask, isInDebugMode: false)` call in `main()` is also commented out behind the same `TODO enable in version 0.9`.
+`main()` calls `Workmanager().initialize(backgroundTask)` to register the isolate
+entry point; the periodic scheduling itself is owned entirely by
+`BackgroundScheduler` (there is no one-off registration on launch).
+
+Unit tests can't touch the `workmanager` platform channel, so `schedule()`'s
+branching logic is mirrored by `TestBackgroundScheduler`
+(`test/background_scheduler_test.dart`), which is asserted across every
+`CheckFrequency` and for cancel-before-register re-scheduling.
+
+## Confirming updates in the foreground
+
+Under `AutomaticUpdates.requireConfirmation` the background task finds updates but
+does not download them. `updatesNeedConfirmationProvider`
+(`lib/data/updates.dart`) is true exactly when that setting is active **and**
+updates are available. It drives a **persistent indicator**:
+- a red dot next to the Settings entry in the drawer (`MainDrawer`), and
+- a `ConfirmUpdatesPrompt` on the settings page with a "download now" button that
+  runs the normal foreground download path for every language with updates.
+
+After a successful foreground download, `updatesAvailable` resets via the usual
+`LanguageStatusNotifier` rebuild, so the indicator and prompt disappear.
 
 ## How the foreground learns about background work
 
@@ -90,15 +148,20 @@ There's a comment in `BackgroundResultNotifier.checkForActivity`: "*languageStat
 Two tests, both running on a real Android emulator (CI uses `reactivecircus/android-emulator-runner@v2`, API level 29):
 
 1. **"Test that background task gets executed"**
-   - `Workmanager().initialize(backgroundTask, isInDebugMode: false)`.
+   - `Workmanager().initialize(backgroundTask)`.
    - `registerOneOffTask(..., 'testTask', initialDelay: 2s)` — `task` argument is what gets passed to `executeTask` and what selects the `backgroundTestMain()` branch.
    - Main isolate registers a port via `IsolateNameServer.registerPortWithName(port.sendPort, 'test')`.
    - `backgroundTask` sends `'success'` via `IsolateNameServer.lookupPortByName('test')`.
    - Main isolate awaits the port message with a 10-second timeout.
 
 2. **"Test synchronization with main isolate"** — full happy-path: mount `App4Training` with `appLanguage='de'`, open settings to warm `languageStatusProvider`, fire the background task, then open a worksheet and verify the `foundBgActivity` snackbar appears.
 
-The fixtures use `MemoryFileSystem` and `FakeLanguageDownloader` from `lib/background/background_test.dart`.
+`backgroundTestMain()` mirrors `backgroundMain()`'s two-phase flow
+(`backgroundCheck` then `backgroundDownload`) with a `FakeConnectivityService`,
+so the integration test exercises the full check-then-download path
+deterministically. The fixtures use `MemoryFileSystem`,
+`FakeLanguageDownloader` and `FakeConnectivityService` from
+`lib/background/background_test.dart`.
 
 ## Why the test fixtures live in `lib/`
 

docs/conventions.md

@@ -57,14 +57,12 @@ The repo's existing code is sparing with comments — but where comments exist,
 - Don't write comments that restate the code.
 - **Do** write comments when the *why* is non-obvious — e.g. why an internal Riverpod import is needed, why a button is intentionally clickable while looking disabled.
 - `// FIXME` is used to mark workarounds that should ideally move upstream (`pywikitools`, `flutter_html`).
-- `// TODO for version 0.9` marks the v0.9 milestone code.
 
 ## Don'ts
 
 - **Don't** add a service/repository layer. Riverpod notifiers ARE the repository.
 - **Don't** reintroduce `custom_lint` (removed for analyzer-version conflict).
 - **Don't** unpin `test` without first reading the comments in `pubspec.yaml`.
 - **Don't** reintroduce `download_assets` (replaced by the in-house `LanguageDownloader` in `lib/data/language_downloader.dart`, which gives atomic staging-and-swap downloads, a concurrency cap, and no same-filename workaround).
-- **Don't** delete commented-out v0.9 code without project agreement — it's the working scaffold for the next release.
 - **Don't** introduce a navigation library (`go_router`, etc.) — Navigator 1.0 is intentional and it interplays cleanly with the URL-mirroring `/view/<page>/<lang>` scheme.
 - **Don't** delete the `flutter_html_table` error filter — the four assertion variants are real and well-documented.

docs/features.md

@@ -25,7 +25,7 @@ The main reading screen.
 Three sections:
 1. **App language** — `DropdownButtonAppLanguage`.
 2. **`LanguageSettings`** — title + explanation text + `LanguagesTable` (the per-language download/update/delete table).
-3. **`UpdateSettings`** — "Last check" timestamp + `CheckNowButton`. The check-frequency and automatic-updates dropdowns are commented out (for v0.9).
+3. **`UpdateSettings`** — the `DropdownButtonCheckFrequency` (how often the background task runs) and `DropdownButtonAutomaticUpdates` (whether/when it downloads), "Last check" timestamp, `CheckNowButton`, and a `ConfirmUpdatesPrompt` shown under `requireConfirmation` when updates are waiting.
 
 ### `AboutPage` (`/about`)
 Static text + version. Renders localized strings via `flutter_linkify` so URLs in the strings become tappable (`url_launcher`).