[GitHub] [james-project] Arsnael commented on a diff in pull request #1175: JAMES-3812 Provide a ToPlainText mailet

[GitBox <gi...@apache.org>]

Arsnael commented on code in PR #1175:
URL: https://github.com/apache/james-project/pull/1175#discussion_r973848984


##########
server/mailet/mailets/src/main/java/org/apache/james/transport/mailets/ToPlainText.java:
##########
@@ -0,0 +1,144 @@
+/****************************************************************
+ * Licensed to the Apache Software Foundation (ASF) under one   *
+ * or more contributor license agreements.  See the NOTICE file *
+ * distributed with this work for additional information        *
+ * regarding copyright ownership.  The ASF licenses this file   *
+ * to you under the Apache License, Version 2.0 (the            *
+ * "License"); you may not use this file except in compliance   *
+ * with the License.  You may obtain a copy of the License at   *
+ *                                                              *
+ *   http://www.apache.org/licenses/LICENSE-2.0                 *
+ *                                                              *
+ * Unless required by applicable law or agreed to in writing,   *
+ * software distributed under the License is distributed on an  *
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY       *
+ * KIND, either express or implied.  See the License for the    *
+ * specific language governing permissions and limitations      *
+ * under the License.                                           *
+ ****************************************************************/
+
+package org.apache.james.transport.mailets;
+
+import java.io.IOException;
+
+import javax.inject.Inject;
+import javax.mail.BodyPart;
+import javax.mail.MessagingException;
+import javax.mail.Multipart;
+import javax.mail.internet.MimeMessage;
+
+import org.apache.commons.io.IOUtils;
+import org.apache.james.util.html.HtmlTextExtractor;
+import org.apache.mailet.Mail;
+import org.apache.mailet.base.GenericMailet;
+
+/**
+ * This mailet converts HTML parts of a message into Plain text.
+ *
+ * It starts looking for multipart/alternative containing a text/plain and a text/html part
+ * and only keep the text/plain part. Then in a second pass replaces remaining text/html by
+ * their textual content, infered by parsing the HTML content and handling common tags.
+ *
+ * Eg:
+ *
+ * <mailet matcher="All" class="ToPlainText"/>
+ *
+ * Only available for servers having JMAP, not available for JPA.
+ */
+public class ToPlainText extends GenericMailet {
+    private final HtmlTextExtractor htmlTextExtractor;
+
+    @Inject
+    public ToPlainText(HtmlTextExtractor htmlTextExtractor) {
+        this.htmlTextExtractor = htmlTextExtractor;
+    }
+
+    @Override
+    public void service(Mail mail) throws MessagingException {
+        try {
+            if (removeHtmlFromMultipartAlternative(mail.getMessage())
+                    || convertRemainingHtmlToPlainText(mail.getMessage())) {
+                mail.getMessage().saveChanges();
+            }
+        } catch (Exception e) {
+            throw new MessagingException("Exception while extracting HTML", e);
+        }
+    }
+
+    // true if the message content is mutated
+    private boolean removeHtmlFromMultipartAlternative(MimeMessage mimeMessage) throws IOException, MessagingException {
+        if (mimeMessage.getContent() instanceof Multipart) {
+            Multipart multipart = (Multipart) mimeMessage.getContent();
+            return removeHtmlFromMultipartAlternativeForContent(multipart);
+        }
+        return false;
+    }
+
+    // true if the message content is mutated
+    private boolean removeHtmlFromMultipartAlternative(BodyPart bodyPart) throws IOException, MessagingException {
+        if (bodyPart.getContent() instanceof Multipart) {
+            Multipart multipart = (Multipart) bodyPart.getContent();
+            return removeHtmlFromMultipartAlternativeForContent(multipart);
+        }
+        return false;
+    }
+
+    // true if the message content is mutated
+    private boolean removeHtmlFromMultipartAlternativeForContent(Multipart multipart) throws MessagingException, IOException {
+        boolean mutated = false;
+        if (multipart.getContentType().startsWith("multipart/alternative")) {
+            int removedParts = 0;
+            for (int i = 0; i < multipart.getCount(); i++) {
+                if (multipart.getBodyPart(i + removedParts).getContentType().startsWith("text/html")) {
+                    multipart.removeBodyPart(i + removedParts);
+                    removedParts++;
+                    mutated = true;
+                }
+            }
+        } else {
+            for (int i = 0; i < multipart.getCount(); i++) {
+                mutated = removeHtmlFromMultipartAlternative(multipart.getBodyPart(i));
+            }
+        }
+        return mutated;
+    }
+
+    // true if the message content is mutated
+    private boolean convertRemainingHtmlToPlainText(MimeMessage mimeMessage) throws IOException, MessagingException {
+        if (mimeMessage.getContentType().startsWith("text/html")) {
+            mimeMessage.setContent(htmlTextExtractor.toPlainText(IOUtils.toString(mimeMessage.getInputStream())), "text/plain");
+            return true;
+        }
+        if (mimeMessage.getContent() instanceof Multipart) {
+            boolean mutated = false;
+            Multipart multipart = (Multipart) mimeMessage.getContent();
+            for (int i = 0; i < multipart.getCount(); i++) {
+                mutated = convertRemainingHtmlToPlainText(multipart.getBodyPart(i));
+            }
+            return mutated;
+        }
+        return false;
+    }
+
+    // true if the message content is mutated
+    private boolean convertRemainingHtmlToPlainText(BodyPart bodyPart) throws IOException, MessagingException {
+        if (bodyPart.getContent() instanceof Multipart) {

Review Comment:
   This if clause and the one in line 112 are exactly the same code inside. Extracting it into a private method maybe would be better? 



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