import 'dart:convert';

import 'package:html/dom.dart';
import 'package:html/parser.dart' as parser;

import '../../channels/channel_video.dart';
import '../../exceptions/exceptions.dart';
import '../../retry.dart';
import '../../videos/videos.dart';
import '../youtube_http_client.dart';
import 'generated/channel_upload_page_id.g.dart';

///
class ChannelUploadPage {
  ///
  final String channelId;
  final Document _root;

  late final _InitialData _initialData = _getInitialData();

  ///
  _InitialData _getInitialData() {
    final scriptText = _root
        .querySelectorAll('script')
        .map((e) => e.text)
        .toList(growable: false);

    var initialDataText = scriptText.firstWhere(
        (e) => e.contains('window["ytInitialData"] ='),
        orElse: () => '');
    if (initialDataText.isNotEmpty) {
      return _InitialData(ChannelUploadPageId.fromRawJson(
          _extractJson(initialDataText, 'window["ytInitialData"] =')));
    }

    initialDataText = scriptText.firstWhere(
        (e) => e.contains('var ytInitialData = '),
        orElse: () => '');
    if (initialDataText.isNotEmpty) {
      return _InitialData(ChannelUploadPageId.fromRawJson(
          _extractJson(initialDataText, 'var ytInitialData = ')));
    }

    throw TransientFailureException(
        'Failed to retrieve initial data from the channel upload page, please report this to the project GitHub page.'); // ignore: lines_longer_than_80_chars
  }

  String _extractJson(String html, String separator) {
    return _matchJson(
        html.substring(html.indexOf(separator) + separator.length));
  }

  String _matchJson(String str) {
    var bracketCount = 0;
    late int lastI;
    for (var i = 0; i < str.length; i++) {
      lastI = i;
      if (str[i] == '{') {
        bracketCount++;
      } else if (str[i] == '}') {
        bracketCount--;
      } else if (str[i] == ';') {
        if (bracketCount == 0) {
          return str.substring(0, i);
        }
      }
    }
    return str.substring(0, lastI + 1);
  }

  ///
  ChannelUploadPage(this._root, this.channelId, [_InitialData initialData])
      : _initialData = initialData;

  ///
  Future<ChannelUploadPage> nextPage(YoutubeHttpClient httpClient) {
    if (initialData.continuation.isEmpty) {
      return Future.value(null);
    }
    var url =
        'https://www.youtube.com/browse_ajax?ctoken=${initialData.continuation}&continuation=${initialData.continuation}&itct=${initialData.clickTrackingParams}';
    return retry(() async {
      var raw = await httpClient.getString(url);
      return ChannelUploadPage(null, channelId,
          _InitialData(ChannelUploadPageId.fromJson(json.decode(raw)[1])));
    });
  }

  ///
  static Future<ChannelUploadPage> get(
      YoutubeHttpClient httpClient, String channelId, String sorting) {
    assert(sorting != null);
    var url =
        'https://www.youtube.com/channel/$channelId/videos?view=0&sort=$sorting&flow=grid';
    return retry(() async {
      var raw = await httpClient.getString(url);
      return ChannelUploadPage.parse(raw, channelId);
    });
  }

  ///
  ChannelUploadPage.parse(String raw, this.channelId)
      : _root = parser.parse(raw);
}

class _InitialData {
  // Json parsed map
  final ChannelUploadPageId root;

  _InitialData(this.root);

  /* Cache results */

  List<ChannelVideo> _uploads;
  String _continuation;
  String _clickTrackingParams;

  List<GridRendererItem> getContentContext() {
    if (root.contents != null) {
      return root.contents.twoColumnBrowseResultsRenderer.tabs
          .map((e) => e.tabRenderer)
          .firstWhere((e) => e.selected)
          .content
          .sectionListRenderer
          .contents
          .first
          .itemSectionRenderer
          .contents
          .first
          .gridRenderer
          .items;
    }
    if (root.response != null) {
      return root.response.continuationContents.gridContinuation.items;
    }
    throw FatalFailureException('Failed to get initial data context.');
  }

  NextContinuationData getContinuationContext() {
    if (root.contents != null) {
      return root.contents?.twoColumnBrowseResultsRenderer?.tabs
          ?.map((e) => e.tabRenderer)
          ?.firstWhere((e) => e.selected)
          ?.content
          ?.sectionListRenderer
          ?.contents
          ?.first
          ?.itemSectionRenderer
          ?.contents
          ?.first
          ?.gridRenderer
          ?.continuations
          ?.first
          ?.nextContinuationData;
    }
    if (root.response != null) {
      return root?.response?.continuationContents?.gridContinuation
          ?.continuations?.first?.nextContinuationData;
    }
    return null;
  }

  List<ChannelVideo> get uploads => _uploads ??= getContentContext()
      ?.map(_parseContent)
      ?.where((e) => e != null)
      ?.toList();

  String get continuation =>
      _continuation ??= getContinuationContext()?.continuation ?? '';

  String get clickTrackingParams => _clickTrackingParams ??=
      getContinuationContext()?.clickTrackingParams ?? '';

  ChannelVideo _parseContent(GridRendererItem content) {
    if (content == null || content.gridVideoRenderer == null) {
      return null;
    }
    var video = content.gridVideoRenderer;
    return ChannelVideo(
        VideoId(video.videoId),
        video.title?.simpleText ??
            video.title?.runs?.map((e) => e.text)?.join() ??
            '');
  }
}