Create a multipart/related message for html, text and inline images

Signed-off-by: Daniel Kesselberg <mail@danielkesselberg.de>

2 files changed, 181 insertions, 73 deletions

diff --git a/lib/Service/MailTransmission.php b/lib/Service/MailTransmission.php
index 79c65bcd8..73b50c8c1 100644
--- a/lib/Service/MailTransmission.php
+++ b/lib/Service/MailTransmission.php
@@ -38,8 +38,6 @@ use Horde_Mime_Headers_MessageId;
 use Horde_Mime_Headers_Subject;
 use Horde_Mime_Mail;
 use Horde_Mime_Mdn;
-use Horde_Mime_Part;
-use Horde_Text_Filter;
 use OCA\Mail\Account;
 use OCA\Mail\Address;
 use OCA\Mail\AddressList;
@@ -59,7 +57,6 @@ use OCA\Mail\Events\MessageSentEvent;
 use OCA\Mail\Events\SaveDraftEvent;
 use OCA\Mail\Exception\AttachmentNotFoundException;
 use OCA\Mail\Exception\ClientException;
-use OCA\Mail\Exception\InvalidDataUriException;
 use OCA\Mail\Exception\SentMailboxNotSetException;
 use OCA\Mail\Exception\ServiceException;
 use OCA\Mail\IMAP\IMAPClientFactory;
@@ -191,59 +188,16 @@ class MailTransmission implements IMailTransmission {
 
 		$mail = new Horde_Mime_Mail();
 		$mail->addHeaders($headers);
-		if ($messageData->isHtml()) {
-			$doc = new \DOMDocument();
-			$doc->loadHTML($message->getContent(), LIBXML_HTML_NODEFDTD | LIBXML_HTML_NOIMPLIED);
-
-			$uriParser = new DataUriParser();
-
-			$images = $doc->getElementsByTagName('img');
-			for ($i = 0; $i < $images->count(); $i++) {
-				$image = $images->item($i);
-				if ($image === null) {
-					continue;
-				}
-
-				$src = $image->getAttribute('src');
-				if ($src === '') {
-					continue;
-				}
-
-				try {
-					$dataUri = $uriParser->parse($src);
-				} catch (InvalidDataUriException $e) {
-					continue;
-				}
-
-				$part = new Horde_Mime_Part();
-				$part->setCharset($dataUri->getParameters()['charset']);
-				$part->setDisposition('inline');
-				$part->setName('embedded_image_' . $i);
-				$part->setContents($dataUri->getData());
-				$part->setType($dataUri->getMediaType());
-				if ($dataUri->isBase64()) {
-					$part->setTransferEncoding('base64');
-				}
-
-				$cid = $part->setContentId();
-				$mail->addMimePart($part);
-
-				$image->setAttribute('src', 'cid:' . $cid);
-			}
-
-			$htmlContent = $doc->saveHTML();
 
-			$mail->setHtmlBody($htmlContent, null, false);
-			$mail->setBody(Horde_Text_Filter::filter($htmlContent, 'Html2text',
-				['callback' => [$this, 'htmlToTextCallback']]));
-		} else {
-			$mail->setBody($message->getContent());
-		}
+		$mimeMessage = new MimeMessage(
+			new DataUriParser()
+		);
 
-		// Append local attachments
-		foreach ($message->getAttachments() as $attachment) {
-			$mail->addMimePart($attachment);
-		}
+		$mail->setBasePart($mimeMessage->build(
+			$messageData->isHtml(),
+			$message->getContent(),
+			$message->getAttachments()
+		));
 
 		$this->eventDispatcher->dispatchTyped(
 			new BeforeMessageSentEvent($account, $messageData, $repliedToMessageId, $draft, $message, $mail)
@@ -326,25 +280,6 @@ class MailTransmission implements IMailTransmission {
 	}
 
 	/**
-	 * A callback for Horde_Text_Filter.
-	 *
-	 * The purpose of this callback is to overwrite the default behaviour
-	 * of html2text filter to convert <p>Hello</p> => Hello\n\n with
-	 * <p>Hello</p> => Hello\n.
-	 *
-	 * @param \DOMDocument $doc
-	 * @param \DOMNode $node
-	 * @return string|null non-null, add this text to the output and skip further processing of the node.
-	 */
-	public function htmlToTextCallback(\DOMDocument $doc, \DOMNode $node) {
-		if ($node instanceof \DOMElement && strtolower($node->tagName) === 'p') {
-			return $node->textContent . "\n";
-		}
-
-		return null;
-	}
-
-	/**
 	 * @param NewMessageData $message
 	 * @param Message|null $previousDraft
 	 *
diff --git a/lib/Service/MimeMessage.php b/lib/Service/MimeMessage.php
new file mode 100644
index 000000000..bc5d8a0e7
--- /dev/null
+++ b/lib/Service/MimeMessage.php
@@ -0,0 +1,173 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * @author Daniel Kesselberg <mail@danielkesselberg.de>
+ *
+ * Mail
+ *
+ * This code is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License, version 3,
+ * as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License, version 3,
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>
+ *
+ */
+
+namespace OCA\Mail\Service;
+
+use DOMDocument;
+use DOMNode;
+use Horde_Mime_Part;
+use Horde_Text_Filter;
+use OCA\Mail\Exception\InvalidDataUriException;
+use OCA\Mail\Service\DataUri\DataUriParser;
+
+class MimeMessage {
+	private DataUriParser $uriParser;
+
+	public function __construct(DataUriParser $uriParser) {
+		$this->uriParser = $uriParser;
+	}
+
+	/**
+	 * @param bool $isHtml
+	 * @param string $content
+	 * @param Horde_Mime_Part[] $attachments
+	 * @return void
+	 */
+	public function build(bool $isHtml, string $content, array $attachments): Horde_Mime_Part {
+		if ($isHtml) {
+			$doc = new DOMDocument();
+			$doc->loadHTML($content, LIBXML_HTML_NODEFDTD | LIBXML_HTML_NOIMPLIED);
+
+			$images = $doc->getElementsByTagName('img');
+			$imageParts = [];
+
+			for ($i = 0; $i < $images->count(); $i++) {
+				$image = $images->item($i);
+				if ($image === null) {
+					continue;
+				}
+
+				$src = $image->getAttribute('src');
+				if ($src === '') {
+					continue;
+				}
+
+				try {
+					$dataUri = $this->uriParser->parse($src);
+				} catch (InvalidDataUriException $e) {
+					continue;
+				}
+
+				$part = new Horde_Mime_Part();
+				$part->setType($dataUri->getMediaType());
+				$part->setCharset($dataUri->getParameters()['charset']);
+				$part->setName('embedded_image_' . $i);
+				$part->setDisposition('inline');
+				if ($dataUri->isBase64()) {
+					$part->setTransferEncoding('base64');
+				}
+				$part->setContents($dataUri->getData());
+
+				$cid = $part->setContentId();
+				$imageParts[] = $part;
+
+				$image->setAttribute('src', 'cid:' . $cid);
+			}
+
+			$htmlContent = $doc->saveHTML();
+			$textContent = Horde_Text_Filter::filter($htmlContent, 'Html2text', ['callback' => [$this, 'htmlToTextCallback']]);
+
+			$alternativePart = new Horde_Mime_Part();
+			$alternativePart->setType('multipart/alternative');
+
+			$htmlPart = new Horde_Mime_Part();
+			$htmlPart->setType('text/html');
+			$htmlPart->setCharset('UTF-8');
+			$htmlPart->setContents($htmlContent);
+			$htmlPart->setDescription('HTML Version of Message');
+
+			$textPart = new Horde_Mime_Part();
+			$textPart->setType('text/plain');
+			$textPart->setCharset('UTF-8');
+			$textPart->setContents($textContent);
+			$textPart->setDescription('Plaintext Version of Message');
+
+			/*
+			 * RFC1341: In general, user agents that compose multipart/alternative entities should place the
+			 * body parts in increasing order of preference, that is, with the preferred format last.
+			 */
+			$alternativePart[] = $textPart;
+			$alternativePart[] = $htmlPart;
+
+			/*
+			 * Wrap the multipart/alternative parts in multipart/related when inline images are found.
+			 */
+			if (count($imageParts) > 0) {
+				$bodyPart = new Horde_Mime_Part();
+				$bodyPart->setType('multipart/related');
+				$bodyPart[] = $alternativePart;
+				foreach ($imageParts as $imagePart) {
+					$bodyPart[] = $imagePart;
+				}
+			} else {
+				$bodyPart = $alternativePart;
+			}
+		} else {
+			$bodyPart = new Horde_Mime_Part();
+			$bodyPart->setType('text/plain');
+			$bodyPart->setCharset('UTF-8');
+			$bodyPart->setContents($content);
+		}
+
+		/*
+		 * For attachments wrap the body (multipart/related, multipart/alternative or text/plain) in
+		 * a multipart/mixed part.
+		 */
+		if (count($attachments) > 0) {
+			$basePart = new Horde_Mime_Part();
+			$basePart->setType('multipart/mixed');
+			$basePart[] = $bodyPart;
+			foreach ($attachments as $attachment) {
+				$basePart[] = $attachment;
+			}
+		} else {
+			$basePart = $bodyPart;
+		}
+
+		/*
+		 * To add the Mime-Version-Header
+		 */
+		$basePart->isBasePart(true);
+
+		return $basePart;
+	}
+
+	/**
+	 * A callback for Horde_Text_Filter.
+	 *
+	 * The purpose of this callback is to overwrite the default behaviour
+	 * of html2text filter to convert <p>Hello</p> => Hello\n\n with
+	 * <p>Hello</p> => Hello\n.
+	 *
+	 * @param DOMDocument $doc
+	 * @param DOMNode $node
+	 * @return string|null non-null, add this text to the output and skip further processing of the node.
+	 */
+	public function htmlToTextCallback(DOMDocument $doc, DOMNode $node) {
+		if ($node instanceof \DOMElement && strtolower($node->tagName) === 'p') {
+			return $node->textContent . "\n";
+		}
+
+		return null;
+	}
+}