voyagehandbook/lib/util/render.dart

import 'package:cached_network_image/cached_network_image.dart';
import 'package:flutter/material.dart';
import 'package:html/parser.dart';
import 'package:html/dom.dart' as dom;
import 'package:url_launcher/url_launcher.dart';
import 'package:voyagehandbook/api/classes.dart';
import 'package:voyagehandbook/util/styles.dart';
import 'package:voyagehandbook/util/widgets/warning.dart';
import 'package:html_unescape/html_unescape_small.dart';
import 'package:zoom_pinch_overlay/zoom_pinch_overlay.dart';

/*
        Voyage Handbook - The open-source WikiVoyage reader
        Copyright (C) 2023 Matyáš Caras

        This program is free software: you can redistribute it and/or modify
        it under the terms of the GNU General Public License version 3 as published by
        the Free Software Foundation.

        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 General Public License for more details.

        You should have received a copy of the GNU General Public License
        along with this program.  If not, see <https://www.gnu.org/licenses/>.
*/
final _ignoredTags = ["style", "script"];

class PageRenderer {
  final ColorScheme scheme;
  final double height;
  final double width;

  PageRenderer(this.scheme, this.height, this.width);

  /// Used to create Widgets from raw HTML from WM API
  ListView renderFromPageHTML(RawPage page) {
    var out = <Widget>[
      const SizedBox(
        height: 10,
      ),
      Text(
        page.title,
        textAlign: TextAlign.center,
        style: PageStyles.h1,
      ),
      const SizedBox(
        height: 10,
      ),
      Row(
        mainAxisAlignment: MainAxisAlignment.center,
        children: [
          const Text("From"),
          const SizedBox(
            width: 5,
          ),
          GestureDetector(
            onTap: () => launchUrl(
                Uri.parse("https://en.wikivoyage.org/wiki/${page.key}"),
                mode: LaunchMode.externalApplication),
            child: const Text(
              "WikiVoyage",
              style: TextStyle(
                decoration: TextDecoration.underline,
                fontWeight: FontWeight.bold,
              ),
            ),
          ),
        ],
      ),
      Row(
        children: [
          const Text("under"),
          const SizedBox(
            width: 5,
          ),
          GestureDetector(
            onTap: () => launchUrl(Uri.parse(page.license.url),
                mode: LaunchMode.externalApplication),
            child: Text(
              page.license.title,
              style: const TextStyle(
                decoration: TextDecoration.underline,
              ),
            ),
          )
        ],
      )
    ];
    var document = parse(page.html);
    var sections = document.body!.getElementsByTagName("section");
    for (var sec in sections) {
      if (sec.localName == "section") {
        out.addAll(_renderSection(sec));
      }
    }
    var l = ListView.builder(
      padding: EdgeInsets.zero,
      itemBuilder: (c, i) => out[i],
      itemCount: out.length,
    );
    return l;
  }

  List<Widget> _renderSection(dom.Element sec) {
    var out = <Widget>[];
    // Get Section Title
    var headings = sec.children.where(
        (element) => ["h2", "h3", "h4", "h5"].contains(element.localName));
    var sectionTitle = (headings.isNotEmpty) ? headings.first : null;
    if (sectionTitle != null) {
      switch (sectionTitle.localName) {
        case "h2":
          out.add(
            const SizedBox(
              height: 10,
            ),
          );
          out.add(Text(
            sectionTitle.text,
            style: PageStyles.h2,
            textAlign: TextAlign.center,
          ));
          break;
        case "h3":
          out.add(
            Align(
              alignment: Alignment.centerLeft,
              child: Text(
                sectionTitle.text,
                style: PageStyles.h3,
              ),
            ),
          );
          break;
        case "h4":
          out.add(
            Align(
              alignment: Alignment.centerLeft,
              child: Text(sectionTitle.text, style: PageStyles.h4),
            ),
          );
          break;
        case "h5":
          out.add(
            Align(
              alignment: Alignment.centerLeft,
              child: Text(sectionTitle.text, style: PageStyles.h5),
            ),
          );
          break;
        default:
          out.add(
            Align(
              alignment: Alignment.centerLeft,
              child: Text(sectionTitle.text),
            ),
          );
          break;
      }
      // out.add(
      //   const SizedBox(
      //     height: 5,
      //   ),
      // );
    }

    // create TextSpans from text content
    for (var element in sec.children) {
      // Go through all section's children
      for (var t in _ignoredTags) {
        var ignored = element.getElementsByTagName(t);
        if (ignored.isNotEmpty) {
          // Remove ignored tags
          for (var element in ignored) {
            element.remove();
          }
        }
      }

      switch (element.localName) {
        case "p":
        case "link":
          out.add(
            RichText(
              text: TextSpan(children: _renderText(element.innerHtml)),
              textAlign: TextAlign.justify,
            ),
          ); // add paragraph spans as single rich text
          out.add(
            const SizedBox(
              height: 5,
            ),
          ); // space paragraphs
          break;
        case "figure":
          out.addAll(_renderImageFigure(element));
          out.add(
            const SizedBox(
              height: 10,
            ),
          );
          break;
        case "section":
          out.addAll(_renderSection(element));
          break;
        case "div":
          if (element.attributes["class"] != null &&
              element.attributes["class"] == "pp_cautionbox") {
            out.add(_renderWarning(element));
            out.add(
              const SizedBox(
                height: 10,
              ),
            );
          } else if (element.id == "region_list") {
            var inner = parse(
              element.innerHtml.replaceAll(RegExp(r'<\/?span.+?>'), ""),
            );
            for (var e in inner.body!.children) {
              if (e.localName == "figure") {
                // render image
                out.addAll(_renderImageFigure(e));
                out.add(
                  const SizedBox(
                    height: 5,
                  ),
                );
              } else if (e.localName == "table") {
                Color? boxColor;
                var text = <TextSpan>[];
                for (var td in e
                    .getElementsByTagName("tr")
                    .first
                    .getElementsByTagName("td")) {
                  if (td.attributes["style"] != null) {
                    var colorMatch = RegExp(r'background-color:#(.+?);')
                        .firstMatch(td.attributes["style"]!);
                    boxColor = Color(int.parse("0xff${colorMatch!.group(1)}"));
                  } else {
                    text.addAll(_renderText(td.innerHtml));
                  }
                }
                out.add(
                  const SizedBox(
                    height: 10,
                  ),
                );
                out.add(
                  Row(
                    crossAxisAlignment: CrossAxisAlignment.center,
                    children: [
                      if (boxColor != null)
                        Container(
                          color: boxColor,
                          width: 25,
                          height: 25,
                        ),
                      const SizedBox(
                        width: 10,
                      ),
                      Flexible(
                        child: RichText(
                          text: TextSpan(children: text),
                        ),
                      )
                    ],
                  ),
                );
              }
            }
            out.add(
              const SizedBox(
                height: 10,
              ),
            );
          }
          break;
        default:
          break;
      }
      element.remove();
    }

    out.add(
      const SizedBox(
        height: 5,
      ),
    );
    return out;
  }

  List<Widget> _renderImageFigure(dom.Element element) {
    var out = <Widget>[];

    /// Image figure
    var imgs = element.getElementsByTagName("img");
    if (imgs.isEmpty) return [];
    var img = imgs.first; // get image element
    if (img.attributes["src"] == null || img.attributes["src"] == "") return [];
    var figcap = element.getElementsByTagName("figcaption"); // get caption
    String? caption;
    if (figcap.isNotEmpty) {
      caption = figcap.first.text; // TODO: handle links
    }
    out.add(const SizedBox(
      height: 10,
    ));
    out.add(
      SizedBox(
        // TODO: open wikimedia page?
        width: width * 0.8,
        height: height * 0.3,
        child: ZoomOverlay(
          child: CachedNetworkImage(
            imageUrl: img.attributes["src"]!.replaceAll("//", "https://"),
            progressIndicatorBuilder: (context, url, downloadProgress) =>
                LinearProgressIndicator(value: downloadProgress.progress),
            errorWidget: (context, url, error) => Icon(
              Icons.error,
              color: scheme.error,
            ),
          ),
        ),
      ),
    ); // load image
    if (caption != null) {
      // Add caption when available
      out.add(
        const SizedBox(
          height: 3,
        ),
      );
      out.add(
        Text(
          caption,
          textAlign: TextAlign.center,
        ),
      );
    }

    return out;
  }

// used to render warning box
  Widget _renderWarning(dom.Element element) {
    var content = <TextSpan>[];
    for (var tr in element
        .getElementsByTagName("table")
        .first
        .getElementsByTagName("tbody")
        .first
        .getElementsByTagName("tr")) {
      for (var e in tr.getElementsByTagName("td")) {
        // Get to table data
        content.addAll(
          _renderText(
            e.innerHtml.replaceAll(RegExp(r'<img.+?\/?>'), ""),
          ),
        );
      }
    }
    return Warning(content: content);
  }

  /// Used to render basic text with bold and italic formatting
  List<TextSpan> _renderText(String innerHtml) {
    var unescape = HtmlUnescape();
    innerHtml = unescape.convert(innerHtml);
    var content = <TextSpan>[];
    var input = innerHtml
        .replaceAll(RegExp(r"<(?!(?:\/b)|(?:\/i)|b|i).+?>", dotAll: true), "")
        .replaceAll("\\n", "\n")
        .replaceAll("<br>", "\n");
    var noFormatting =
        input.split(RegExp(r"(?:<b.*?>.+?<\/b>)|<i.*?>.+?<\/i>", dotAll: true));
    var needToFormat =
        RegExp(r"(?:<b.*?>.+?<\/b>)|<i.*?>.+?<\/i>", dotAll: true)
            .allMatches(input)
            .toList();
    for (var s in needToFormat) {
      content.add(TextSpan(
          text:
              noFormatting[needToFormat.indexOf(s)])); // add text before styled
      var raw = s.group(0)!;
      content.add(
        TextSpan(
          text: RegExp(r">(?!<)(.+?)<").firstMatch(raw)!.group(1),
          style: TextStyle(
            fontWeight: (raw.contains("<b")) ? FontWeight.bold : null,
            fontStyle: (raw.contains("<i")) ? FontStyle.italic : null,
          ),
        ),
      ); // add styled
    }
    content.add(TextSpan(text: noFormatting.last)); // add last
    return content;
  }
}