WordPress - Replace comment notification email with Mandrill template

replace-comment-notification-email-with-mandrill-template.php

<?php
define( 'ABC_NEW_COMMENT_EMAIL_MARKER', '|||abcNewComment||' );

add_filter( "comment_notification_text", "abc_comment_notification_text", 10, 2 );
/**
 * Filter for changing the content of the email notification sent upon new comment.
 *
 * This function replaces the original comment email with a prefix + the comment_id.
 * Later it will be extracted and inserted into Mandrill template as variables by abc_replace_mandrill_template.
 *
 * See the other function abc_replace_mandrill_template for full reference.
 *
 * @param $notify_message the original email message
 * @param $comment_id the comment id
 *
 * @return string the new message structured as |||abcNewComment||comment_id
 */
function abc_comment_notification_text( $message_template, $comment_id ) {
	$message_template = ABC_NEW_COMMENT_EMAIL_MARKER . $comment_id;

	return $message_template;
}

add_filter( 'mandrill_payload', 'abc_replace_mandrill_template' );
/**
 * Replace default Mandrill email template with the corresponding one
 *
 * @param $message Mandrill message object as defined in https://mandrillapp.com/api/docs/messages.html#method=send-template
 *
 * @return object the filtered $message object
 */
function abc_replace_mandrill_template( $message ) {
	// convenience variable
	$autoTags = $message['tags']['automatic'];

	// If this is a new comment notification email (to author) and
	// the email body has been prepared by abc_comment_notification_text function by
	// inserting "|||abcNewComment||comment_id" into the message body, then we
	// - replace the template with the template for comment emails
	// - insert the corresponding variables into the template
	if ( in_array( 'wp_wp_notify_postauthor', $autoTags )
	         && false !== strpos( $message['template']['content'][0]['content'], ABC_NEW_COMMENT_EMAIL_MARKER )
	) {
		// Get the comment id from email
		$comment_id = (int) substr( $message['template']['content'][0]['content'], strlen( ABC_NEW_COMMENT_EMAIL_MARKER ) );

		// We've got a valid $comment_id
		if ( $comment_id > 0 ) {
			// Extract the needed variables for template
			$comment = get_comment( $comment_id );
			if ( empty( $comment ) ) {
				$comment_content = "";
			} else {
				$comment_content = nl2br($comment->comment_content);
			}

			$post        = get_post( $comment->comment_post_ID );
			$author      = get_userdata( $post->post_author );
			$author_name = $author->first_name . " " . $author->last_name;
			if ( ! trim( $author_name ) ) {
				$author_name = $author->user_login;
			}

			$slug = $post->post_name;

			// Insert the vars into the template
			$message['template']['content'][] =
				array('name' => 'author_name',
				      'content' => "Hello " . $author_name . ",<br><br>");

			$message['template']['content'][] =
				array('name' => 'comment_content',
				      'content' => $comment_content);

			$message['template']['content'][] =
				array('name' => 'task_link',
				      'content' => '<a href="' . site_url() . "/task/{$slug}/#comments" .
							'" style="color: black;text-decoration:none;padding:5px 60px;margin:10px;font-size:28px;line-height: 28px;">Reply Here</a>');
			// Change the template
			$message['template']['name'] = 'New Comment Email';
		}
	}

	return $message;
}

See this Gist for Mandrill template:
https://gist.github.com/mariusvetrici/986fa6d350d4b6ebfcaa