import '../../database/database.dart';
import '../../l10n/strings.dart';
import '../../mews/document.dart';
import 'controllers/reader_settings_controller.dart'
    show LibraryController;

/// Builds the internal History, Bookmarks and Subscriptions pages as real
/// [MewsPage]s: they render like any other page and take part in the walk
/// history, so swiping and back/forward treat them like visited pages.
class InternalPages {
  InternalPages(
      {required MewsDatabase db,
      required LibraryController library,
      required Strings strings})
      : _db = db,
        _library = library,
        _strings = strings;

  static const historyUrl = 'mews:history';
  static const bookmarksUrl = 'mews:bookmarks';
  static const subscriptionsUrl = 'mews:subscriptions';

  final MewsDatabase _db;
  final LibraryController _library;
  final Strings _strings;

  /// Whether [url] is one of the internal pages.
  bool handles(String url) => isInternal(url);

  /// Whether [url] belongs to the internal mews: scheme.
  static bool isInternal(String url) =>
      Uri.tryParse(url)?.scheme == 'mews';

  /// The internal page for [url], or null when the name is unknown.
  Future<MewsPage?> pageFor(String url) async {
    // mews:history is an opaque URI: the page name is the path, not a host.
    switch (Uri.tryParse(url)?.path) {
      case 'history':
        return _history(url);
      case 'bookmarks':
        return _bookmarks(url);
      case 'subscriptions':
        return _subscriptions(url);
      default:
        return null;
    }
  }

  Future<MewsPage> _history(String url) async {
    final visits = await _db.recentVisits();
    return _page(
      url: url,
      title: _strings.t('history-title'),
      empty: _strings.t('history-empty'),
      entries: [
        for (final visit in visits)
          _Entry(
            url: visit.url,
            // Dated links are the Mews posts pattern, so history reads like
            // any other entry list.
            label: '${_day(visit.visitedAt)} ${_clock(visit.visitedAt)}',
            title: visit.title ?? visit.url,
          ),
      ],
    );
  }

  Future<MewsPage> _bookmarks(String url) async {
    final bookmarks = await _db.bookmarksByDate();
    return _page(
      url: url,
      title: _strings.t('bookmarks-title'),
      empty: _strings.t('bookmarks-empty'),
      entries: [
        for (final bookmark in bookmarks)
          _Entry(
            url: bookmark.url,
            label: _day(bookmark.createdAt),
            title: bookmark.title ?? bookmark.url,
          ),
      ],
    );
  }

  Future<MewsPage> _subscriptions(String url) async {
    final subscriptions = await _db.allSubscriptions();
    return _page(
      url: url,
      title: _strings.t('subscriptions-title'),
      empty: _strings.t('subscriptions-empty'),
      entries: [
        for (final subscription in subscriptions)
          _Entry(
            url: subscription.url,
            label: _day(subscription.createdAt),
            title: (subscription.title ?? subscription.url) +
                _newPostsNote(subscription.url),
          ),
      ],
    );
  }

  String _newPostsNote(String siteUrl) {
    final count = _library.newEntries.value[siteUrl]?.length ?? 0;
    if (count == 0) return '';
    final note = count == 1
        ? _strings.t('subscriptions-new-one')
        : _strings.t('subscriptions-new-many', {'count': count});
    return ' \u2014 $note';
  }

  MewsPage _page({
    required String url,
    required String title,
    required String empty,
    required List<_Entry> entries,
  }) {
    final blocks = <MewsBlock>[
      HeadingBlock(1, [MewsText(title)]),
      if (entries.isEmpty)
        ParagraphBlock([MewsText(empty)])
      else
        ListBlock(
          ordered: false,
          start: 1,
          items: [
            for (final entry in entries)
              MewsListItem([
                ParagraphBlock([
                  MewsLink(entry.url, [MewsText('${entry.label} ${entry.title}')]),
                ]),
              ]),
          ],
        ),
    ];

    return MewsPage(
      url: url,
      // Internal pages carry a marker so they render as Mews pages, not as
      // plainly-shown external ones.
      specVersion: 'internal',
      title: title,
      body: blocks,
      lang: 'en',
      direction: TextDirection.ltr,
      variant: MewsVariant.plain,
      entries: const [],
    );
  }

  String _day(DateTime date) =>
      '${date.year.toString().padLeft(4, '0')}-${_two(date.month)}-${_two(date.day)}';

  String _clock(DateTime date) => '${_two(date.hour)}:${_two(date.minute)}';

  String _two(int value) => value.toString().padLeft(2, '0');
}

class _Entry {
  const _Entry({required this.url, required this.label, required this.title});

  final String url;
  final String label;
  final String title;
}