Communication: Fix announcement emails not rendering correctly

src/main/java/de/tum/cit/aet/artemis/communication/service/notifications/MailService.java

@@ -5,6 +5,8 @@
 import static de.tum.cit.aet.artemis.core.config.Constants.PROFILE_CORE;
 
 import java.net.URL;
+import java.util.HashMap;
+import java.util.List;
 import java.util.Locale;
 import java.util.Set;
 
@@ -64,6 +66,8 @@ public class MailService implements InstantNotificationService {
 
     private final MailSendingService mailSendingService;
 
+    private final List<MarkdownCustomRendererService> markdownCustomRendererServices;
+
     // notification related variables
 
     private static final String NOTIFICATION = "notification";
@@ -89,11 +93,16 @@ public class MailService implements InstantNotificationService {
 
     private static final String WEEKLY_SUMMARY_NEW_EXERCISES = "weeklySummaryNewExercises";
 
-    public MailService(MessageSource messageSource, SpringTemplateEngine templateEngine, TimeService timeService, MailSendingService mailSendingService) {
+    private final HashMap<Long, String> renderedPosts;
+
+    public MailService(MessageSource messageSource, SpringTemplateEngine templateEngine, TimeService timeService, MailSendingService mailSendingService,
+            MarkdownCustomLinkRendererService markdownCustomLinkRendererService, MarkdownCustomReferenceRendererService markdownCustomReferenceRendererService) {
         this.messageSource = messageSource;
         this.templateEngine = templateEngine;
         this.timeService = timeService;
         this.mailSendingService = mailSendingService;
+        markdownCustomRendererServices = List.of(markdownCustomLinkRendererService, markdownCustomReferenceRendererService);
+        renderedPosts = new HashMap<>();
     }
 
     /**
@@ -266,14 +275,30 @@ public void sendNotification(Notification notification, User user, Object notifi
 
             // Render markdown content of post to html
             try {
-                Parser parser = Parser.builder().build();
-                HtmlRenderer renderer = HtmlRenderer.builder().build();
-                String postContent = post.getContent();
-                String renderedPostContent = renderer.render(parser.parse(postContent));
+                String renderedPostContent;
+
+                // To avoid having to re-render the same post multiple times we store it in a hash map
+                if (renderedPosts.containsKey(post.getId())) {
+                    renderedPostContent = renderedPosts.get(post.getId());
+                }
+                else {
+                    Parser parser = Parser.builder().build();
+                    HtmlRenderer renderer = HtmlRenderer.builder()
+                            .attributeProviderFactory(attributeContext -> new MarkdownRelativeToAbsolutePathAttributeProvider(artemisServerUrl.toString()))
+                            .nodeRendererFactory(new MarkdownImageBlockRendererFactory(artemisServerUrl.toString())).build();
+                    String postContent = post.getContent();
+                    renderedPostContent = markdownCustomRendererServices.stream().reduce(renderer.render(parser.parse(postContent)), (s, service) -> service.render(s),
+                            (s1, s2) -> s2);
+                    if (post.getId() != null) {
+                        renderedPosts.put(post.getId(), renderedPostContent);
+                    }
+                }
+
                 post.setContent(renderedPostContent);
             }
             catch (Exception e) {
                 // In case something goes wrong, leave content of post as-is
+                log.error("Error while parsing post content", e);
             }
         }
         else {

src/main/java/de/tum/cit/aet/artemis/communication/service/notifications/MarkdownCustomLinkRendererService.java

@@ -0,0 +1,71 @@
+package de.tum.cit.aet.artemis.communication.service.notifications;
+
+import static de.tum.cit.aet.artemis.core.config.Constants.PROFILE_CORE;
+
+import java.net.URL;
+import java.util.Set;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.beans.factory.annotation.Value;
+import org.springframework.context.annotation.Profile;
+import org.springframework.stereotype.Service;
+import org.springframework.web.util.UriComponentsBuilder;
+
+/**
+ * This service implements the rendering of markdown tags that represent a link.
+ * It takes the tag, transforms it into an <a></a> tag, and sets the corresponding href.
+ */
+@Profile(PROFILE_CORE)
+@Service
+public class MarkdownCustomLinkRendererService implements MarkdownCustomRendererService {
+
+    private static final Logger log = LoggerFactory.getLogger(MarkdownCustomLinkRendererService.class);
+
+    private final Set<String> supportedTags;
+
+    @Value("${server.url}")
+    private URL artemisServerUrl;
+
+    public MarkdownCustomLinkRendererService() {
+        this.supportedTags = Set.of("programming", "modeling", "quiz", "text", "file-upload", "lecture", "attachment", "lecture-unit", "slide", "faq");
+    }
+
+    /**
+     * Takes a string and replaces all occurrences of custom markdown tags (e.g. [programming], [faq], etc.) with a link
+     *
+     * @param content string to render
+     *
+     * @return the newly rendered string.
+     */
+    public String render(String content) {
+        String tagPattern = String.join("|", supportedTags);
+        // The pattern checks for the occurrence of any tag and then extracts the link from it
+        Pattern pattern = Pattern.compile("\\[(" + tagPattern + ")\\](.*?)\\((.*?)\\)(.*?)\\[/\\1\\]");
+        Matcher matcher = pattern.matcher(content);
+        String parsedContent = content;
+
+        while (matcher.find()) {
+            try {
+                String textStart = matcher.group(2);
+                String link = matcher.group(3);
+                String textEnd = matcher.group(4);
+                String text = (textStart + " " + textEnd).trim();
+
+                String absoluteUrl = UriComponentsBuilder.fromUri(artemisServerUrl.toURI()).path(link).build().toUriString();
+
+                parsedContent = parsedContent.substring(0, matcher.start()) + "<a href=\"" + absoluteUrl + "\">" + text + "</a>" + parsedContent.substring(matcher.end());
+            }
+            catch (Exception e) {
+                log.error("Not able to render tag. Replacing with empty.", e);
+                parsedContent = parsedContent.substring(0, matcher.start()) + parsedContent.substring(matcher.end());
+            }
+
+            matcher = pattern.matcher(parsedContent);
+        }
+
+        return parsedContent;
+    }
+}

src/main/java/de/tum/cit/aet/artemis/communication/service/notifications/MarkdownCustomReferenceRendererService.java

@@ -0,0 +1,72 @@
+package de.tum.cit.aet.artemis.communication.service.notifications;
+
+import static de.tum.cit.aet.artemis.core.config.Constants.PROFILE_CORE;
+
+import java.util.HashMap;
+import java.util.Set;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.context.annotation.Profile;
+import org.springframework.stereotype.Service;
+
+/**
+ * This service implements the rendering of markdown tags that represent a reference (to e.g. a user).
+ * These references cannot directly represent a link, so they are rendered as their text only.
+ */
+@Profile(PROFILE_CORE)
+@Service
+public class MarkdownCustomReferenceRendererService implements MarkdownCustomRendererService {
+
+    private static final Logger log = LoggerFactory.getLogger(MarkdownCustomReferenceRendererService.class);
+
+    private final Set<String> supportedTags;
+
+    private final HashMap<String, String> startingCharacters;
+
+    public MarkdownCustomReferenceRendererService() {
+        supportedTags = Set.of("user", "channel");
+        startingCharacters = new HashMap<>();
+        startingCharacters.put("user", "@");
+        startingCharacters.put("channel", "#");
+    }
+
+    /**
+     * Takes a string and replaces all occurrences of custom markdown tags (e.g. [user], [channel], etc.) with text.
+     * To make it better readable, it prepends an appropriate character. (e.g. for users an @, for channels a #)
+     *
+     * @param content string to render
+     *
+     * @return the newly rendered string.
+     */
+    @Override
+    public String render(String content) {
+        String tagPattern = String.join("|", supportedTags);
+        Pattern pattern = Pattern.compile("\\[(" + tagPattern + ")\\](.*?)\\((.*?)\\)(.*?)\\[/\\1\\]");
+        Matcher matcher = pattern.matcher(content);
+        String parsedContent = content;
+
+        while (matcher.find()) {
+            try {
+                String tag = matcher.group(1);
+                String startingCharacter = startingCharacters.get(tag);
+                startingCharacter = startingCharacter == null ? "" : startingCharacter;
+                String textStart = matcher.group(2);
+                String textEnd = matcher.group(4);
+                String text = startingCharacter + (textStart + " " + textEnd).trim();
+
+                parsedContent = parsedContent.substring(0, matcher.start()) + text + parsedContent.substring(matcher.end());
+            }
+            catch (Exception e) {
+                log.error("Not able to render tag. Replacing with empty.", e);
+                parsedContent = parsedContent.substring(0, matcher.start()) + parsedContent.substring(matcher.end());
+            }
+
+            matcher = pattern.matcher(parsedContent);
+        }
+
+        return parsedContent;
+    }
+}

src/main/java/de/tum/cit/aet/artemis/communication/service/notifications/MarkdownCustomRendererService.java

@@ -0,0 +1,6 @@
+package de.tum.cit.aet.artemis.communication.service.notifications;
+
+public interface MarkdownCustomRendererService {
+
+    String render(String content);
+}

src/main/java/de/tum/cit/aet/artemis/communication/service/notifications/MarkdownImageBlockRenderer.java

@@ -0,0 +1,44 @@
+package de.tum.cit.aet.artemis.communication.service.notifications;
+
+import java.util.Map;
+import java.util.Set;
+
+import org.commonmark.node.Image;
+import org.commonmark.node.Node;
+import org.commonmark.node.Text;
+import org.commonmark.renderer.NodeRenderer;
+import org.commonmark.renderer.html.HtmlNodeRendererContext;
+import org.commonmark.renderer.html.HtmlWriter;
+
+public class MarkdownImageBlockRenderer implements NodeRenderer {
+
+    private final String baseUrl;
+
+    private final HtmlWriter html;
+
+    MarkdownImageBlockRenderer(HtmlNodeRendererContext context, String baseUrl) {
+        html = context.getWriter();
+        this.baseUrl = baseUrl;
+    }
+
+    @Override
+    public Set<Class<? extends Node>> getNodeTypes() {
+        return Set.of(Image.class);
+    }
+
+    @Override
+    public void render(Node node) {
+        Image image = (Image) node;
+
+        html.tag("a", Map.of("href", baseUrl + image.getDestination()));
+
+        try {
+            html.text(((Text) image.getFirstChild()).getLiteral());
+        }
+        catch (Exception e) {
+            html.text(image.getDestination());
+        }
+
+        html.tag("/a");
+    }
+}

src/main/java/de/tum/cit/aet/artemis/communication/service/notifications/MarkdownImageBlockRendererFactory.java

@@ -0,0 +1,19 @@
+package de.tum.cit.aet.artemis.communication.service.notifications;
+
+import org.commonmark.renderer.NodeRenderer;
+import org.commonmark.renderer.html.HtmlNodeRendererContext;
+import org.commonmark.renderer.html.HtmlNodeRendererFactory;
+
+public class MarkdownImageBlockRendererFactory implements HtmlNodeRendererFactory {
+
+    private final String baseUrl;
+
+    public MarkdownImageBlockRendererFactory(String baseUrl) {
+        this.baseUrl = baseUrl;
+    }
+
+    @Override
+    public NodeRenderer create(HtmlNodeRendererContext context) {
+        return new MarkdownImageBlockRenderer(context, baseUrl);
+    }
+}

src/main/java/de/tum/cit/aet/artemis/communication/service/notifications/MarkdownRelativeToAbsolutePathAttributeProvider.java

@@ -0,0 +1,32 @@
+package de.tum.cit.aet.artemis.communication.service.notifications;
+
+import java.util.Map;
+
+import org.commonmark.node.Node;
+import org.commonmark.renderer.html.AttributeProvider;
+
+public class MarkdownRelativeToAbsolutePathAttributeProvider implements AttributeProvider {
+
+    private final String baseUrl;
+
+    public MarkdownRelativeToAbsolutePathAttributeProvider(String baseUrl) {
+        this.baseUrl = baseUrl;
+    }
+
+    /**
+     * We store images and attachments with relative urls, so when rendering we need to replace them with absolute ones
+     *
+     * @param node       rendered Node, if Image or Link we try to replace the source
+     * @param attributes of the Node
+     * @param tagName    of the html element
+     */
+    @Override
+    public void setAttributes(Node node, String tagName, Map<String, String> attributes) {
+        if ("a".equals(tagName)) {
+            String href = attributes.get("href");
+            if (href != null && href.startsWith("/")) {
+                attributes.put("href", baseUrl + href);
+            }
+        }
+    }
+}

src/test/java/de/tum/cit/aet/artemis/communication/notifications/service/MailServiceTest.java

@@ -31,6 +31,8 @@
 import de.tum.cit.aet.artemis.communication.domain.notification.NotificationConstants;
 import de.tum.cit.aet.artemis.communication.service.notifications.MailSendingService;
 import de.tum.cit.aet.artemis.communication.service.notifications.MailService;
+import de.tum.cit.aet.artemis.communication.service.notifications.MarkdownCustomLinkRendererService;
+import de.tum.cit.aet.artemis.communication.service.notifications.MarkdownCustomReferenceRendererService;
 import de.tum.cit.aet.artemis.core.domain.Course;
 import de.tum.cit.aet.artemis.core.domain.User;
 import de.tum.cit.aet.artemis.core.service.TimeService;
@@ -115,7 +117,8 @@ void setUp() throws MalformedURLException, URISyntaxException {
 
         mailSendingService = new MailSendingService(jHipsterProperties, javaMailSender);
 
-        mailService = new MailService(messageSource, templateEngine, timeService, mailSendingService);
+        mailService = new MailService(messageSource, templateEngine, timeService, mailSendingService, new MarkdownCustomLinkRendererService(),
+                new MarkdownCustomReferenceRendererService());
         ReflectionTestUtils.setField(mailService, "artemisServerUrl", new URI("http://localhost:8080").toURL());
     }