import 'package:signals/signals.dart';

import '../../database/database.dart';
import '../../mews/document.dart';

/// Which sites the reader subscribes to (spec 6). The posts themselves live in
/// the database, so an unread post survives a restart; only the set of
/// addresses is held here, because that is what the chrome watches.
class SubscriptionsController {
  SubscriptionsController(this._db);

  final MewsDatabase _db;

  final subscribedUrls = signal(<String>{});

  Future<void> load() async {
    final rows = await _db.allSubscriptions();
    subscribedUrls.value = rows.map((row) => row.url).toSet();
  }

  bool isSubscribed(String url) => subscribedUrls.value.contains(url);

  Future<void> toggle(MewsPage page) async {
    if (isSubscribed(page.url)) {
      await remove(page.url);
      return;
    }
    await _db.addSubscription(page.url, page.title, page.atomFeedHref);
    subscribedUrls.value = {...subscribedUrls.value, page.url};
    // The posts already on the page are the site's back catalogue, not news,
    // so they are stored read and only later posts are flagged.
    await _db.addEntries(page.url, page.entries, read: true);
  }

  Future<void> remove(String siteUrl) async {
    await _db.removeSubscription(siteUrl);
    subscribedUrls.value = {...subscribedUrls.value}..remove(siteUrl);
  }

  /// Records the posts on a subscribed page the reader just opened, and
  /// returns the ones that are new. Does nothing for a site not subscribed to.
  Future<List<MewsEntry>> refreshSite(MewsPage page) async {
    if (!isSubscribed(page.url)) return const [];
    await _db.describeSubscription(page.url,
        title: page.title, atomHref: page.atomFeedHref);
    final fresh = await _db.addEntries(page.url, page.entries);
    await _db.touchSubscription(page.url, DateTime.now());
    return fresh;
  }
}