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

/// 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 ReaderSettingsController settings,
    required Strings strings,
  })  : _db = db,
        _library = library,
        _settings = settings,
        _strings = strings;

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

  final MewsDatabase _db;
  final LibraryController _library;
  final ReaderSettingsController _settings;
  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);
      case 'settings':
        return _settingsPage(url);
      default:
        return null;
    }
  }

  /// Whether [url] changes a setting instead of visiting a page, e.g.
  /// mews:setting/theme/light.
  static bool isSettingUrl(String url) =>
      Uri.tryParse(url)?.path.startsWith('setting/') ?? false;

  /// Applies the setting encoded in [url]; the page stays where it is and
  /// rerenders with the new value.
  Future<void> applySetting(String url) async {
    final segments =
        Uri.tryParse(url)?.path.split('/') ?? const <String>[];
    if (segments.length < 3) return;
    final value = Uri.decodeComponent(segments.last);
    switch (segments[1]) {
      case 'font':
        await _settings.setFont(value);
      case 'size':
        if (value == 'decrease') {
          await _settings.decreaseSize();
        } else if (value == 'increase') {
          await _settings.increaseSize();
        }
      case 'theme':
        await _settings.setThemeMode(value);
      case 'colors':
        await _settings.setVariant(value);
    }
  }

  MewsPage _settingsPage(String url) {
    return _page(
      url: url,
      title: _strings.t('settings-page-title'),
      empty: '',
      entries: const [],
      extraBlocks: [
        // Typeface: the current choice is plain text; alternatives are links.
        HeadingBlock(2, [MewsText(_strings.t('settings-font-heading'))]),
        ..._options('font', [
          _Option(_strings.t('settings-font-atkinson'), 'Atkinson Hyperlegible'),
        ], current: _settings.font.value),
        // Text size steps between the configured bounds; the current value
        // stays plain text between the two actions.
        HeadingBlock(2, [MewsText(_strings.t('settings-size-heading'))]),
        ListBlock(
          ordered: false,
          start: 1,
          items: [
            if (_settings.fontScale.value > ReaderSettingsController.minScale)
              MewsListItem([
                ParagraphBlock([
                  _link('mews:setting/size/decrease',
                      _strings.t('settings-size-decrease')),
                ]),
              ]),
            MewsListItem([
              ParagraphBlock([
                MewsEmphasis(EmphasisStyle.strong, [
                  MewsText('${(_settings.fontScale.value * 100).round()}%'),
                ]),
              ]),
            ]),
            if (_settings.fontScale.value < ReaderSettingsController.maxScale)
              MewsListItem([
                ParagraphBlock([
                  _link('mews:setting/size/increase',
                      _strings.t('settings-size-increase')),
                ]),
              ]),
          ],
        ),
        HeadingBlock(2, [MewsText(_strings.t('settings-theme-heading'))]),
        ..._options('theme', [
          _Option(_strings.t('settings-theme-light'), 'light'),
          _Option(_strings.t('settings-theme-dark'), 'dark'),
          _Option(_strings.t('settings-theme-system'), 'system'),
        ], current: _settings.themeMode.value),
        HeadingBlock(2, [MewsText(_strings.t('settings-variant-heading'))]),
        ..._options('colors', [
          _Option(_strings.t('settings-variant-site'), 'site'),
          _Option(_strings.t('settings-variant-warm'), 'warm'),
          _Option(_strings.t('settings-variant-cool'), 'cool'),
          _Option(_strings.t('settings-variant-green'), 'green'),
          _Option(_strings.t('settings-variant-mono'), 'mono'),
        ], current: _settings.variant.value),
        HeadingBlock(2, [MewsText(_strings.t('settings-library-heading'))]),
        ListBlock(
          ordered: false,
          start: 1,
          items: [
            for (final entry in [
              (historyUrl, _strings.t('settings-history')),
              (bookmarksUrl, _strings.t('settings-bookmarks')),
              (subscriptionsUrl, _strings.t('settings-subscriptions')),
            ])
              MewsListItem([
                ParagraphBlock([_link(entry.$1, entry.$2)]),
              ]),
          ],
        ),
      ],
    );
  }

  /// One item per option: the current value in bold, the others as links.
  List<MewsBlock> _options(String group, List<_Option> options,
      {required String current}) {
    return [
      ListBlock(
        ordered: false,
        start: 1,
        items: [
          for (final option in options)
            MewsListItem([
              if (option.value == current)
                ParagraphBlock([
                  MewsEmphasis(
                      EmphasisStyle.strong, [MewsText(option.label)]),
                ])
              else
                ParagraphBlock([
                  _link('mews:setting/$group/${option.value}', option.label),
                ]),
            ]),
        ],
      ),
    ];
  }

  MewsLink _link(String href, String label) =>
      MewsLink(href, [MewsText(label)]);

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

    blocks.addAll(extraBlocks);

    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;
}

/// One selectable value in a settings option group.
class _Option {
  const _Option(this.label, this.value);

  final String label;
  final String value;
}