Prepare one click unsubscribe

app/src/main/java/eu/faircode/email/Core.java

@@ -3418,6 +3418,8 @@ class Core {
                         String[] authentication = helper.getAuthentication();
                         MessageHelper.MessageParts parts = helper.getMessageParts();
 
+                        Pair<String, Boolean> unsubscribe = helper.getListUnsubscribe();
+
                         EntityMessage message = new EntityMessage();
                         message.account = folder.account;
                         message.folder = folder.id;
@@ -3451,7 +3453,7 @@ class Core {
                         message.bcc = helper.getBcc();
                         message.reply = helper.getReply();
                         message.list_post = helper.getListPost();
-                        message.unsubscribe = helper.getListUnsubscribe();
+                        message.unsubscribe = (unsubscribe == null ? null : unsubscribe.first);
                         message.headers = helper.getHeaders();
                         message.infrastructure = helper.getInfrastructure();
                         message.subject = helper.getSubject();
@@ -4554,6 +4556,8 @@ class Core {
             String[] authentication = helper.getAuthentication();
             MessageHelper.MessageParts parts = helper.getMessageParts();
 
+            Pair<String, Boolean> unsubscribe = helper.getListUnsubscribe();
+
             message = new EntityMessage();
             message.account = folder.account;
             message.folder = folder.id;
@@ -4600,7 +4604,7 @@ class Core {
             message.bcc = helper.getBcc();
             message.reply = helper.getReply();
             message.list_post = helper.getListPost();
-            message.unsubscribe = helper.getListUnsubscribe();
+            message.unsubscribe = (unsubscribe == null ? null : unsubscribe.first);
             message.autocrypt = helper.getAutocrypt();
             if (download_headers)
                 message.headers = helper.getHeaders();

app/src/main/java/eu/faircode/email/MessageHelper.java

@@ -2761,13 +2761,12 @@ public class MessageHelper {
         }
     }
 
-    String getListUnsubscribe() throws MessagingException {
+    Pair<String, Boolean> getListUnsubscribe() throws MessagingException {
         ensureHeaders();
 
-        String list;
         try {
             // https://www.ietf.org/rfc/rfc2369.txt
-            list = imessage.getHeader("List-Unsubscribe", null);
+            String list = imessage.getHeader("List-Unsubscribe", null);
             if (list == null)
                 return null;
 
@@ -2777,6 +2776,15 @@ public class MessageHelper {
             if (list == null || list.startsWith("NO"))
                 return null;
 
+            // https://datatracker.ietf.org/doc/html/rfc8058
+            boolean onclick = false;
+            String post = imessage.getHeader("List-Unsubscribe-Post", null);
+            if (post != null) {
+                post = MimeUtility.unfold(post);
+                post = decodeMime(post);
+                onclick = "List-Unsubscribe=One-Click".equalsIgnoreCase(post.trim());
+            }
+
             String link = null;
             String mailto = null;
             int s = list.indexOf('<');
@@ -2821,9 +2829,9 @@ public class MessageHelper {
             }
 
             if (link != null)
-                return link;
+                return new Pair<>(link, onclick);
             if (mailto != null)
-                return mailto;
+                return new Pair<>(mailto, onclick);
 
             if (!BuildConfig.PLAY_STORE_RELEASE)
                 Log.i(new IllegalArgumentException("List-Unsubscribe: " + list));