From 2edc191b1cc33eb81d6aa6e1274ea4aa2dbb61d2 Mon Sep 17 00:00:00 2001
From: =?utf8?q?Tim=20D=C3=BCsterhus?= <duesterhus@woltlab.com>
Date: Mon, 29 Jun 2020 14:18:51 +0200
Subject: [PATCH] Add support for the List-Unsubscribe header to Email

see #3379
---
 .../files/lib/system/email/Email.class.php    | 57 +++++++++++++++++++
 1 file changed, 57 insertions(+)

diff --git a/wcfsetup/install/files/lib/system/email/Email.class.php b/wcfsetup/install/files/lib/system/email/Email.class.php
index 71ec1ac093..e1bb8979ea 100644
--- a/wcfsetup/install/files/lib/system/email/Email.class.php
+++ b/wcfsetup/install/files/lib/system/email/Email.class.php
@@ -71,6 +71,20 @@ class Email {
 	 */
 	protected $listIdHuman = null;
 	
+	/**
+	 * List-Unsubscribe URI
+	 * @var	string
+	 * @since 5.3
+	 */
+	protected $listUnsubscribe = null;
+	
+	/**
+	 * Whether the listUnsubscribe URI has One-Click support
+	 * @var	boolean
+	 * @since 5.3
+	 */
+	protected $listUnsubscribeOneClick = false;
+	
 	/**
 	 * Date header
 	 * @var	\DateTime
@@ -301,6 +315,37 @@ class Email {
 		return ($this->listIdHuman ? $this->listIdHuman.' ' : '').'<'.$this->listId.'.list-id.'.self::getHost().'>';
 	}
 	
+	/**
+	 * Sets the URI for the 'List-Unsubscribe' header.
+	 * 
+	 * If $supportsOneClick is set to true the 'List-Unsubscribe-Post' header
+	 * with the value 'List-Unsubscribe=One-Click' is added.
+	 * 
+	 * @param	string		$uri
+	 * @param	boolean		$supportsOneClick
+	 * @since 5.3
+	 */
+	public function setListUnsubscribe($uri, $supportsOneClick = false) {
+		if ($uri === null) {
+			$this->listUnsubscribe = null;
+			return;
+		}
+		
+		$this->listUnsubscribe = $uri;
+		$this->listUnsubscribeOneClick = $supportsOneClick;
+	}
+	
+	/**
+	 * Returns the email's full 'List-Id' including the host. Returns 'null'
+	 * if no 'List-Id' is set.
+	 * 
+	 * @return	?string
+	 * @since 5.3
+	 */
+	public function getListUnsubscribeUri() {
+		return $this->listUnsubscribe;
+	}
+	
 	/**
 	 * Sets the email's 'From'.
 	 * 
@@ -457,6 +502,12 @@ class Email {
 		if ($this->getListID()) {
 			$headers[] = ['list-id', $this->getListID()];
 		}
+		if ($this->getListUnsubscribeUri()) {
+			$headers[] = ['list-unsubscribe', '<'.$this->getListUnsubscribeUri().'>'];
+			if ($this->listUnsubscribeOneClick) {
+				$headers[] = ['list-unsubscribe-post', 'List-Unsubscribe=One-Click'];
+			}
+		}
 		$headers[] = ['mime-version', '1.0'];
 		
 		if (!$this->body) {
@@ -491,6 +542,12 @@ class Email {
 				case 'list-id':
 					$name = 'List-ID';
 					break;
+				case 'list-unsubscribe-post':
+					// This case is identical to the default case below.
+					// It is special cased, because the grammar of this header is defined
+					// to be pretty tight.
+					$name = 'List-Unsubscribe-Post';
+					break;
 				case 'mime-version':
 					$name = 'MIME-Version';
 					break;
-- 
2.20.1