import 'dart:convert';

import 'package:signals/signals.dart';

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

/// The reader's presentation choices (spec 8.2) plus the per-app limits they
/// move within. Values persist through ReaderSettings in the database.
class ReaderSettingsController {
  ReaderSettingsController(this._db);

  final MewsDatabase _db;

  static const minScale = 0.75;
  static const maxScale = 2.0;
  static const scaleStep = 0.125;

  /// The accepted values, in the order the settings page offers them. A
  /// setting arrives as a link the reader can also type, so a value outside
  /// these lists is refused rather than stored.
  static const themeModes = ['light', 'dark', 'system'];
  static const variants = ['site', 'warm', 'cool', 'green', 'mono'];

  final font = signal('Atkinson Hyperlegible');
  final fontScale = signal(1.0);
  final themeMode = signal('system');
  final variant = signal('site');

  Future<void> load() async {
    final settings = await _db.readSettings();
    if (settings == null) return;
    font.value = settings.font;
    fontScale.value = settings.fontScale;
    themeMode.value = settings.themeMode;
    variant.value = settings.variant;
  }

  Future<bool> setFont(String family) async {
    if (family.isEmpty || family == font.value) return false;
    font.value = family;
    await _persist();
    return true;
  }

  Future<bool> decreaseSize() => _setScale(fontScale.value - scaleStep);
  Future<bool> increaseSize() => _setScale(fontScale.value + scaleStep);

  Future<bool> _setScale(double value) async {
    if (value < minScale || value > maxScale) return false;
    fontScale.value = value;
    await _persist();
    return true;
  }

  Future<bool> setThemeMode(String mode) async {
    if (!themeModes.contains(mode) || mode == themeMode.value) return false;
    themeMode.value = mode;
    await _persist();
    return true;
  }

  Future<bool> setVariant(String variant) async {
    if (!variants.contains(variant) || variant == this.variant.value) {
      return false;
    }
    this.variant.value = variant;
    await _persist();
    return true;
  }

  Future<void> _persist() => _db.saveSettings(
        font: font.value,
        fontScale: fontScale.value,
        themeMode: themeMode.value,
        variant: variant.value,
      );
}

/// Bookmarks and subscriptions. Signals expose derived state (which URLs are
/// bookmarked or subscribed); subscription refreshes piggyback on page loads,
/// comparing the page's dated links against the known entry URLs.
class LibraryController {
  LibraryController(this._db);

  final MewsDatabase _db;

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

  /// New posts found on the most recent refresh of a subscribed site, keyed by
  /// site URL. Empty when there is nothing to report.
  final newEntries = signal(<String, List<MewsEntry>>{});

  Future<void> load() async {
    final bookmarks = await _db.allBookmarks();
    bookmarkedUrls.value = bookmarks.map((b) => b.url).toSet();
    final subs = await _db.allSubscriptions();
    subscribedUrls.value = subs.map((s) => s.url).toSet();
  }

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

  Future<void> toggleBookmark(String url, String? title) async {
    if (isBookmarked(url)) {
      await _db.removeBookmark(url);
      bookmarkedUrls.value = {...bookmarkedUrls.value}..remove(url);
    } else {
      await _db.addBookmark(url, title);
      bookmarkedUrls.value = {...bookmarkedUrls.value, url};
    }
  }

  Future<void> toggleSubscription(String url, String? title, List<MewsEntry> entries) async {
    if (isSubscribed(url)) {
      await _db.removeSubscription(url);
      subscribedUrls.value = {...subscribedUrls.value}..remove(url);
      newEntries.value = {...newEntries.value}..remove(url);
    } else {
      await _db.addSubscription(url, title, entries.map((e) => e.url).toList());
      subscribedUrls.value = {...subscribedUrls.value, url};
      newEntries.value = {...newEntries.value}..remove(url);
    }
  }

  /// Revalidates every subscribed page and reports entries the reader has not
  /// seen yet (spec 6.1). Called when a subscribed page is opened.
  Future<void> refreshSubscription(MewsPage page) async {
    final subs = await _db.allSubscriptions();
    final sub = subs.where((s) => s.url == page.url).firstOrNull;
    if (sub == null) return;

    final known = (jsonDecode(sub.entryUrls) as List).cast<String>().toSet();
    final fresh = page.entries.where((e) => !known.contains(e.url)).toList();
    if (fresh.isEmpty) {
      // Nothing new this time, so the site stops being flagged.
      newEntries.value = {...newEntries.value}..remove(sub.url);
      await _db.updateSubscription(sub.url, lastCheckedAt: DateTime.now());
      return;
    }

    newEntries.value = {...newEntries.value, page.url: fresh};
    await _db.updateSubscription(
      sub.url,
      entryUrls: [...known, ...fresh.map((e) => e.url)],
      lastCheckedAt: DateTime.now(),
    );
  }
}