/*
 * Copyright (c) 2024-2026 Fabian Freund.
 *
 * This file is part of WebLibre
 * (see https://weblibre.eu).
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as
 * published by the Free Software Foundation, either version 3 of the
 * License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program. If not, see <http://www.gnu.org/licenses/>.
 */
import 'package:collection/collection.dart';
import 'package:nullability/nullability.dart';
import 'package:rss_dart/dart_rss.dart';
import 'package:rss_dart/domain/rss1_feed.dart';
import 'package:weblibre/features/web_feed/data/database/definitions.drift.dart';
import 'package:weblibre/features/web_feed/data/models/feed_article.dart';
import 'package:weblibre/features/web_feed/data/models/feed_author.dart';
import 'package:weblibre/features/web_feed/data/models/feed_link.dart';
import 'package:weblibre/features/web_feed/extensions/atom.dart';
import 'package:weblibre/features/web_feed/extensions/rss.dart';

class FeedParser {
  final Uri url;
  late Object _feed;

  FeedParser._(this.url, this._feed);

  factory FeedParser.parse({required Uri url, required String xmlString}) {
    final rssVersion = WebFeed.detectRssVersion(xmlString);
    final feed = switch (rssVersion) {
      RssVersion.rss1 => Rss1Feed.parse(xmlString),
      RssVersion.rss2 => RssFeed.parse(xmlString),
      RssVersion.atom => AtomFeed.parse(xmlString),
      RssVersion.unknown => throw Error.safeToString(
        'Invalid XML String? We cannot detect RSS/Atom version.',
      ),
    };

    return FeedParser._(url, feed);
  }

  FeedData readGeneralData() {
    switch (_feed) {
      case final Rss1Feed feed:
        return FeedData(
          url: url,
          title: feed.title.whenNotEmpty ?? feed.dc?.title,
          description: feed.description.whenNotEmpty ?? feed.dc?.description,
          siteLink: feed.link.mapNotNull(Uri.tryParse),
          authors: feed.dc?.creator.whenNotEmpty.mapNotNull(
            (creator) => [FeedAuthor(name: creator)],
          ),
          tags: feed.dc?.toFeedCategories(),
        );
      case final RssFeed feed:
        final categories = feed.categories.toFeedCategories();

        return FeedData(
          url: url,
          title: feed.title.whenNotEmpty ?? feed.dc?.title,
          description: feed.description.whenNotEmpty ?? feed.dc?.description,
          siteLink: feed.link.mapNotNull(Uri.tryParse),
          authors: (feed.author.whenNotEmpty ?? feed.dc?.creator.whenNotEmpty)
              .mapNotNull((creator) => [FeedAuthor(name: creator)]),
          tags: categories.isNotEmpty
              ? categories
              : feed.dc?.toFeedCategories(),
        );
      case final AtomFeed feed:
        final authors = feed.authors.toFeedAuthors();
        final tags = feed.categories.toFeedCategories();

        return FeedData(
          url: url,
          title: feed.title.whenNotEmpty,
          icon: feed.icon.mapNotNull(Uri.tryParse),
          siteLink: feed.links
              .toFeedLinks()
              .getRelation(FeedLinkRelation.alternate)
              ?.uri,
          description: feed.subtitle.whenNotEmpty,
          authors: authors.isNotEmpty ? authors : null,
          tags: tags,
        );
      default:
        throw Exception(
          'Unknown feed type in readGeneralData: ${_feed.runtimeType}',
        );
    }
  }

  List<FeedArticle> readArticles() {
    final fetchDate = DateTime.now();

    switch (_feed) {
      case final Rss1Feed feed:
        return feed.items.mapIndexed((i, item) {
          final title = item.title.whenNotEmpty ?? item.dc?.title.whenNotEmpty;

          final itemId = item.dc?.identifier.whenNotEmpty ?? title;
          final uniqueId =
              '${item.link.whenNotEmpty ?? feed.link.whenNotEmpty ?? url}#$itemId';
          final date = SafeParseDateTime.safeParse(item.dc?.date);
          final link = item.link.mapNotNull(Uri.tryParse);

          return FeedArticle(
            id: uniqueId,
            feedId: url,
            title: title,
            fetched: fetchDate,
            created: date,
            authors: item.dc?.creator.whenNotEmpty.mapNotNull(
              (creator) => [FeedAuthor(name: creator)],
            ),
            summaryHtml:
                item.description.whenNotEmpty ??
                item.dc?.description.whenNotEmpty,
            links: link.mapNotNull(
              (link) => [
                FeedLink(uri: link, relation: FeedLinkRelation.alternate),
              ],
            ),
            tags: item.dc?.toFeedCategories(),
            contentHtml: item.content?.value.whenNotEmpty,
          );
        }).toList();
      case final RssFeed feed:
        return feed.items.mapIndexed((i, item) {
          final title = item.title.whenNotEmpty ?? item.dc?.title.whenNotEmpty;

          final itemId =
              item.guid.whenNotEmpty ??
              item.dc?.identifier.whenNotEmpty ??
              title;

          final uniqueId =
              '${item.link.whenNotEmpty ?? feed.link.whenNotEmpty ?? url}#$itemId';
          final date = SafeParseDateTime.safeParse(
            item.pubDate.whenNotEmpty ?? item.dc?.date,
          );
          final link = item.link.mapNotNull(Uri.tryParse);
          final author =
              item.author.whenNotEmpty ?? item.dc?.creator.whenNotEmpty;

          final categories = item.categories.toFeedCategories();

          return FeedArticle(
            id: uniqueId,
            feedId: url,
            title: title,
            fetched: fetchDate,
            created: date,
            authors: author.mapNotNull(
              (creator) => [FeedAuthor(name: creator)],
            ),
            summaryHtml:
                item.description.whenNotEmpty ??
                item.dc?.description.whenNotEmpty,
            links: link.mapNotNull(
              (link) => [
                FeedLink(uri: link, relation: FeedLinkRelation.alternate),
              ],
            ),
            tags: categories.isNotEmpty
                ? categories
                : item.dc?.toFeedCategories(),
            contentHtml: item.content?.value.whenNotEmpty,
          );
        }).toList();
      case final AtomFeed feed:
        final feedLink = feed.links.toFeedLinks().getRelation(
          FeedLinkRelation.self,
        );

        return feed.items.mapIndexed((i, item) {
          final authors = item.authors.toFeedAuthors();

          final tags = item.categories.toFeedCategories();

          final itemLinks = item.links.toFeedLinks();
          final articleLink = itemLinks.getRelation(FeedLinkRelation.alternate);

          final itemId = item.id.whenNotEmpty ?? item.title;
          final uniqueId =
              '${articleLink?.uri ?? feedLink?.uri ?? url}#$itemId';

          final published = SafeParseDateTime.safeParse(item.published);
          final updated = SafeParseDateTime.safeParse(item.updated);

          return FeedArticle(
            id: uniqueId,
            feedId: url,
            title: item.title.whenNotEmpty,
            summaryHtml: item.summary.whenNotEmpty,
            links: itemLinks,
            authors: authors.isNotEmpty ? authors : null,
            tags: tags,
            fetched: fetchDate,
            created: published,
            updated: updated,
            contentHtml: item.content.whenNotEmpty,
          );
        }).toList();
      default:
        throw Exception(
          'Unknown feed type in readArticles: ${_feed.runtimeType}',
        );
    }
  }
}