feat: check every subscription in the background and add the posts page

app/test/controllers_test.dart

@@ -8,6 +8,8 @@ import 'package:mews/application/controllers/subscriptions_controller.dart';
 import 'package:mews/database/database.dart';
 import 'package:mews/mews/document.dart';
 
+import 'fake_fetch.dart';
+
 void main() {
   late MewsDatabase db;
 
@@ -61,7 +63,7 @@ void main() {
   });
 
   test('subscribing takes on the back catalogue without flagging it', () async {
-    final subscriptions = SubscriptionsController(db);
+    final subscriptions = SubscriptionsController(db: db, fetch: FakeFetch(const {}));
     await subscriptions.load();
 
     final firstPost = MewsEntry(
@@ -97,7 +99,7 @@ void main() {
   });
 
   test('unread posts survive a restart', () async {
-    final subscriptions = SubscriptionsController(db);
+    final subscriptions = SubscriptionsController(db: db, fetch: FakeFetch(const {}));
     await subscriptions.load();
     await subscriptions.toggle(_page('https://example.com/', const []));
     await subscriptions.refreshSite(_page('https://example.com/', [
@@ -109,14 +111,14 @@ void main() {
 
     // A fresh controller over the same database sees the same unread post,
     // which the old in-memory count could not do.
-    final restarted = SubscriptionsController(db);
+    final restarted = SubscriptionsController(db: db, fetch: FakeFetch(const {}));
     await restarted.load();
     expect(restarted.isSubscribed('https://example.com/'), isTrue);
     expect(await db.unreadCount(), 1);
   });
 
   test('leaving a site takes its posts with it', () async {
-    final subscriptions = SubscriptionsController(db);
+    final subscriptions = SubscriptionsController(db: db, fetch: FakeFetch(const {}));
     await subscriptions.load();
     await subscriptions.toggle(_page('https://example.com/', const []));
     await subscriptions.refreshSite(_page('https://example.com/', [
@@ -132,6 +134,79 @@ void main() {
     expect(await db.unreadCount(), 0);
   });
 
+  test('a check finds new posts on every subscribed site', () async {
+    const siteA = 'https://a.example/';
+    const siteB = 'https://b.example/';
+    final sources = {
+      siteA: _entriesPage('Site A', const []),
+      siteB: _entriesPage('Site B', const []),
+    };
+    final subscriptions =
+        SubscriptionsController(db: db, fetch: FakeFetch(sources));
+    await subscriptions.load();
+    await subscriptions.toggle(_page(siteA, const []));
+    await subscriptions.toggle(_page(siteB, const []));
+
+    // Both sites publish something after the reader subscribed.
+    sources[siteA] = _entriesPage('Site A', const [
+      ('2026-10-09', 'a-one.html', 'A newer post'),
+    ]);
+    sources[siteB] = _entriesPage('Site B', const [
+      ('2026-10-10', 'b-one.html', 'Another post'),
+      ('2026-10-09', 'b-two.html', 'And one more'),
+    ]);
+
+    await subscriptions.refreshAll();
+    expect(await db.unreadCount(), 3);
+    expect(await db.unreadCount(siteUrl: siteA), 1);
+    expect(subscriptions.refreshing.value, isFalse);
+
+    // Every site was recorded as checked.
+    for (final site in await db.allSubscriptions()) {
+      expect(site.lastCheckedAt, isNotNull);
+    }
+  });
+
+  test('one unreachable site does not stop the rest of the check', () async {
+    const reachable = 'https://a.example/';
+    const unreachable = 'https://down.example/';
+    final subscriptions = SubscriptionsController(
+      db: db,
+      // Only the first site answers; the other has no source at all.
+      fetch: FakeFetch({
+        reachable: _entriesPage('Site A', const [
+          ('2026-10-09', 'a-one.html', 'A newer post'),
+        ]),
+      }),
+    );
+    await subscriptions.load();
+    await subscriptions.toggle(_page(unreachable, const []));
+    await subscriptions.toggle(_page(reachable, const []));
+
+    await subscriptions.refreshAll();
+    expect(await db.unreadCount(siteUrl: reachable), 1);
+    expect(subscriptions.refreshing.value, isFalse);
+    // The site that could not be reached is still marked as checked.
+    final down = (await db.allSubscriptions())
+        .firstWhere((s) => s.url == unreachable);
+    expect(down.lastCheckedAt, isNotNull);
+  });
+
+  test('a check already running is not started again', () async {
+    final subscriptions = SubscriptionsController(
+      db: db,
+      fetch: FakeFetch({'https://a.example/': _entriesPage('Site A', const [])}),
+    );
+    await subscriptions.load();
+    await subscriptions.toggle(_page('https://a.example/', const []));
+
+    var redraws = 0;
+    subscriptions.onChanged = () => redraws++;
+    await Future.wait([subscriptions.refreshAll(), subscriptions.refreshAll()]);
+    // One pass: it starts and finishes once, so two redraws, not four.
+    expect(redraws, 2);
+  });
+
   test('caches pages for offline reopening', () async {
     await db.saveCachedPage(CachedPagesCompanion.insert(
       url: 'https://example.com/page.html',
@@ -161,3 +236,20 @@ MewsPage _page(String url, List<MewsEntry> entries) => MewsPage(
       entries: entries,
       specVersion: '0.1',
     );
+
+/// A Mews page whose list holds dated links (spec 6.1), one per entry given as
+/// (date, file name, title).
+String _entriesPage(
+        String title, List<(String, String, String)> entries) =>
+    '''
+<?xml version="1.0" encoding="UTF-8"?>
+<html xmlns="http://www.w3.org/1999/xhtml">
+  <head><title>$title</title><meta name="mews-profile" content="0.1" /></head>
+  <body>
+    <h1>$title</h1>
+    <ul>
+${entries.map((e) => '      <li><a href="${e.$2}">${e.$1} ${e.$3}</a></li>').join('\n')}
+    </ul>
+  </body>
+</html>
+''';