Fetch data(preview) from provided url.

fetch_preview_from_web_link.dart

import 'package:html/parser.dart';
import 'package:http/http.dart';

/// Convenient solution for flutter(dart) to fetch data(preview, title etc.) from provided web link.
class FetchPreviewHelper {
  static final titlePreview =  'title';
  static final descriptionPreview = 'description';
  static final imagePreview = 'image';
  static final favIconPreview = 'favIcon';
  static final appleIconPreview = 'appleIcon';

  Future<Map<String, dynamic>> fetch(url) async {
    final client = Client();
    final response = await client.get(_validateUrl(url));
    final document = parse(response.body);

    String? description, title, image, appleIcon, favIcon;

    var elements = document.getElementsByTagName('meta');
    final linkElements = document.getElementsByTagName('link');

    elements.forEach((tmp) {
      /// fetching title
      if (tmp.attributes['property'] == 'og:title') {
        /* fetching seo title */
        title = tmp.attributes['content'];
      }
      /* if seo title is empty then fetch normal title */
      if (title == null || (title != null && title!.isEmpty)) {
        title = document.getElementsByTagName(titlePreview)[0].text;
      }

      /// fetching description
      if (tmp.attributes['property'] == 'og:description') {
        /* fetching seo description */
        description = tmp.attributes['content'];
      }
      /* if seo description is empty then fetch normal description. */
      if (description == null || (description != null && description!.isEmpty)) {
        /* fetching base title */
        if (tmp.attributes['name'] == descriptionPreview) {
          description = tmp.attributes['content'];
        }
      }

      /// fetching image
      if (tmp.attributes['property'] == 'og:image') {
        image = tmp.attributes['content'];
      }
    });

    linkElements.forEach((tmp) {
      if (tmp.attributes['rel'] == 'apple-touch-icon') {
        appleIcon = tmp.attributes['href'];
      }
      if (tmp.attributes['rel']?.contains('icon') == true) {
        favIcon = tmp.attributes['href'];
      }
    });

    return {
      titlePreview: title ?? '',
      descriptionPreview: description ?? '',
      imagePreview: image ?? '',
      appleIconPreview: appleIcon ?? '',
      favIconPreview: favIcon ?? ''
    };
  }

  _validateUrl(String url) {
    if (url.startsWith('http://') == true || url.startsWith('https://') == true) {
      return url;
    }
    else {
      return 'http://$url';
    }
  }
}

//------------------------------------ new file -----------------------------------

//----- some start of the separate StatefulWidget, which is skipped for convenience -----
 
 /// json object of a preview page
  Map<String, dynamic>? previewData;

  @override
  void initState() {
    FetchPreviewHelper().fetch(widget.suggestion.url).then((resultData) {
      setState(() {
        previewData = resultData;
      });
    });
    super.initState();
  }
  
  /* Example of using received data:
  
  //--- somewhere in the middle of the widget  --
  
  Row(
                      children: <Widget>[
                        previewData?[FetchPreviewHelper.favIconPreview] != null ||
                                previewData?[FetchPreviewHelper.favIconPreview] !=
                                    ''
                            ? Image.network(
                                previewData?[FetchPreviewHelper.favIconPreview],
                                height: AppDimens.sizeFavIcon,
                                width: AppDimens.sizeFavIcon,
                                errorBuilder: (BuildContext context,
                                    Object exception, StackTrace? stackTrace) {
                                  return LinkIconWidget();
                                },
                              )
                            : LinkIconWidget(),
                        Text(widget.suggestion.url!,
                            style: AppStyles.styleCaptionNormal.apply(
                                color: AppConfigs.of(context).colors.blueBright))
                      ],
                    ), 
                    
                    */
  
// ----------------  rest of the StatefulWidget, which is skipped for convenience -----