implemented adding targets to links in markdown

Signed-off-by: Stephan Richter <s.richter@srsoftware.de>

backend/src/main/java/de/srsoftware/umbrella/backend/Application.java

@@ -80,7 +80,7 @@ public class Application {
 			new DocumentApi(config).bindPath("/api/document").on(server);
 			new UserLegacy(config).bindPath("/legacy/user").on(server);
 			new NotesLegacy(config).bindPath("/legacy/notes").on(server);
-			new MarkdownApi().bindPath("/api/markdown").on(server);
+			new MarkdownApi(config).bindPath("/api/markdown").on(server);
 			new NoteModule(config).bindPath("/api/notes").on(server);
 			new StockModule(config).bindPath("/api/stock").on(server);
 			new PollModule(config).bindPath("/api/poll").on(server);

markdown/src/main/java/de/srsoftware/umbrella/markdown/MarkdownApi.java

@@ -3,21 +3,34 @@ package de.srsoftware.umbrella.markdown;
 
 import static de.srsoftware.tools.MimeType.MIME_HTML;
 import static de.srsoftware.umbrella.core.ModuleRegistry.userService;
+import static de.srsoftware.umbrella.core.constants.Field.BASE_URL;
+import static de.srsoftware.umbrella.core.exceptions.UmbrellaException.missingField;
 
 import com.sun.net.httpserver.HttpExchange;
+import de.srsoftware.configuration.Configuration;
 import de.srsoftware.tools.Path;
 import de.srsoftware.umbrella.core.BaseHandler;
 import de.srsoftware.umbrella.core.ModuleRegistry;
 import de.srsoftware.umbrella.core.Util;
 import de.srsoftware.umbrella.core.api.MarkdownService;
+import de.srsoftware.umbrella.core.constants.Field;
 import de.srsoftware.umbrella.core.exceptions.UmbrellaException;
 import java.io.IOException;
+import java.util.Optional;
+import java.util.regex.Pattern;
 
 public class MarkdownApi extends BaseHandler implements MarkdownService {
 
+	private static Pattern ANCHOR = Pattern.compile("(?is)<a\\b[^>]*>.*?</a>");
+	private static Pattern HREF   = Pattern.compile("(?i)\\bhref\\s*=\\s*(?:\"([^\"]*)\"|'([^']*)'|([^\\s>]+))");
+	private static Pattern TARGET = Pattern.compile("(?i)\\btarget\\s*=");
+	private final String baseUrl;
 
-	public MarkdownApi() {
+	public MarkdownApi(Configuration config) {
 		super();
+		Optional<String> baseUrl = config.get(BASE_URL);
+		if (baseUrl.isEmpty()) throw missingField(BASE_URL);
+		this.baseUrl = baseUrl.get();
 		ModuleRegistry.add(this);
 	}
 
@@ -29,6 +42,24 @@ public class MarkdownApi extends BaseHandler implements MarkdownService {
 
 			if (user.isEmpty()) throw UmbrellaException.forbidden("You must be logged in to use the markdown renderer!");
 			var rendered = Util.markdown(body(ex));
+			var anchors = ANCHOR.matcher(rendered);
+			while (anchors.find()){
+				String anchor = anchors.group();
+				var urls = HREF.matcher(anchor);
+				if (!urls.find()) continue; // no url → nothing to do
+
+				var href = urls.group(1) != null ? urls.group(1) : (urls.group(2) != null ? urls.group(2) : urls.group(3));
+				var target = TARGET.matcher(anchor);
+				if (target.find()) continue; // target already set → leave untouched
+
+				if (!href.startsWith("http")) continue; // relative url? good!
+
+				if (!href.startsWith(baseUrl)) { // add target
+					var replacement = "<a target=\"_blank\""+anchor.substring(2);
+					rendered = rendered.replace(anchor, replacement);
+					anchors.reset(rendered);
+				}
+			}
 			ex.getResponseHeaders().add(CONTENT_TYPE,MIME_HTML);
 			return sendContent(ex,rendered);
 		} catch (UmbrellaException e){