Add link preview cards for URLs in messages

[Copilot]

Implements rich link previews for HTTP/HTTPS URLs shared in messages. Extracts Open Graph metadata (title, description, image) with HTML fallbacks and displays in Material card below message text.

Implementation

Core components:

• LinkPreviewFetcher - Fetches metadata via HTTP with SOCKS5 proxy support from Delta Chat config
• LinkPreviewCache - Thread-safe LRU cache (100 entries) to avoid redundant fetches
• LinkPreviewExecutor - Fixed thread pool (2 threads) for async fetching
• LinkPreviewView - MaterialCardView component displaying title/description/image/domain
• LinkPreviewUtil - Regex-based URL extraction from message text

Integration:

• ConversationItem.setLinkPreview() - Checks cache, spawns async fetch if needed, updates UI on main thread
• ViewStub pattern in conversation layouts (sent/received) for lazy initialization
• Visibility management ensures preview hidden when other media types shown

Settings:

• Privacy preference pref_link_previews (default: enabled)
• Located in Settings → Privacy → Link Previews

Technical details

• Only processes text messages containing HTTP/HTTPS URLs (first URL used)
• Parses og:title, og:description, og:image with fallback to <title> and <meta name="description">
• 500KB HTML size limit, 10s connect/read timeouts
• Image URLs converted from relative to absolute
• Caches failed fetches to prevent retry storms

Example flow:

// In ConversationItem.bind()
if (Prefs.areLinkPreviewsEnabled(context)) {
  String url = LinkPreviewUtil.extractFirstUrl(messageText);
  LinkPreview cached = LinkPreviewCache.getInstance().get(url);
  if (cached == null) {
    LinkPreviewExecutor.getInstance().execute(() -> {
      LinkPreview preview = new LinkPreviewFetcher(context).fetchPreview(url);
      LinkPreviewCache.getInstance().put(url, preview);
      post(() -> linkPreviewStub.get().bind(preview, glideRequests));
    });
  }
}

No new dependencies. Uses existing Glide for image loading and Material Design components.

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• dl.google.com
  • Triggering command: /usr/lib/jvm/temurin-17-jdk-amd64/bin/java /usr/lib/jvm/temurin-17-jdk-amd64/bin/java --add-opens=java.base/java.lang=ALL-UNNAMED --add-opens=java.base/java.lang.invoke=ALL-UNNAMED --add-opens=java.base/java.util=ALL-UNNAMED --add-opens=java.prefs/java.util.prefs=ALL-UNNAMED --add-exports=jdk.compiler/com.sun.tools.javac.api=ALL-UNNAMED --add-exports=jdk.compiler/com.sun.tools.javac.util=ALL-UNNAMED --add-opens=java.base/java.util=ALL-UNNAMED --add-opens=java.prefs/java.util.prefs=ALL-UNNAMED --add-opens=java.base/java.nio.charset=ALL-UNNAMED --add-opens=java.base/java.net=ALL-UNNAMED --add-opens=java.base/java.util.concurrent.atomic=ALL-UNNAMED --add-opens=java.xml/javax.xml.namespace=ALL-UNNAMED -Xmx4608m -Dfile.encoding=UTF-8 -Duser.country -Duser.language=en -Duser.variant -cp /home/REDACTED/.gradle/wrapper/dists/gradle-8.13-bin/5xuhj0ry160q40clulazy9h7d/gradle-8.13/lib/gradle-daemon-main-8.13.jar (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

Original prompt

---

This section details on the original issue you should resolve

<issue_title>Link previews</issue_title>
<issue_description>### Describe your feature:
Link previews (link cards) like in telegram and other messengers
Example

Why do you think it is useful:

It helps to search for relevant content</issue_description>

Comments on the Issue (you are @copilot in this section)

@adbenitez some notes:

• it should be possible to disable this feature for privacy reasons
• the fetching of the preview should respect the proxy settings in the app</comment_new>

• Fixes Link previews #30

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