Resolve relative URLs within RSS article description

src/gui/rss/rsswidget.cpp

@@ -54,6 +54,8 @@
 #include "feedlistwidget.h"
 #include "ui_rsswidget.h"
 
+void convertRelativePathToAbsolute(QString &html, const QString &basePath);
+
 RSSWidget::RSSWidget(IGUIApplication *app, QWidget *parent)
     : GUIApplicationComponent(app, parent)
     , m_ui {new Ui::RSSWidget}
@@ -610,6 +612,52 @@ void RSSWidget::renderArticle(const RSS::Article *article) const
 
         html += u"<pre>" + description + u"</pre>";
     }
+    // Supplement relative path to absolute path
+
+    const QUrl url {article->link()};
+    const QString basePath = url.scheme() + u"://" + url.host();
+    convertRelativePathToAbsolute(html, basePath);
     html += u"</div>";
     m_ui->textBrowser->setHtml(html);
 }
+
+void convertRelativePathToAbsolute(QString &html, const QString &basePath)
+{
+    QRegularExpression rx;
+    rx.setPatternOptions(QRegularExpression::CaseInsensitiveOption);
+    // href regex
+    rx.setPattern(
+        uR"(((<a\s+[^>]*?href|<img\s+[^>]*?src)\s*=\s*["'])((https?|ftp):)?(\/\/[^\/]*)?(\/?[^\/"].*?)(["']))"_s);
+
+    QString normalizedBasePath = basePath.endsWith(u'/') ? basePath : basePath + u'/';
+    QRegularExpressionMatchIterator iter = rx.globalMatch(html);
+
+    while (iter.hasNext())
+    {
+        const QRegularExpressionMatch match = iter.next();
+        const QString &scheme = match.captured(4);
+        const QString &host = match.captured(5);
+        if (!scheme.isEmpty())
+        {
+            if (host.isEmpty())
+                break; // invalid URL, should never happen
+
+            // already absolute path
+            continue;
+        }
+
+        QString relativePath = match.captured(6);
+        if (relativePath.startsWith(u'/'))
+            relativePath = relativePath.mid(1);
+
+        if (!host.isEmpty())
+            normalizedBasePath = u"http:" + host;
+
+        const QString &fullMatch = match.captured(0);
+        const QString &prefix = match.captured(1);
+        const QString &suffix = match.captured(7);
+        const QString absolutePath = normalizedBasePath + relativePath;
+
+        html.replace(fullMatch, prefix + absolutePath + suffix);
+    }
+}