Prevent too long IMAP commands

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

@@ -1029,25 +1029,29 @@ class Core {
                 MessagingException ex = (MessagingException) ifolder.doCommand(new IMAPFolder.ProtocolCommand() {
                     @Override
                     public Object doCommand(IMAPProtocol protocol) {
-                        Log.i("Executing uid fetch count=" + uids.size());
-                        Response[] responses = protocol.command(
-                                "UID FETCH " + TextUtils.join(",", uids) + " (UID)", null);
-
-                        if (responses.length > 0 && responses[responses.length - 1].isOK()) {
-                            for (Response response : responses)
-                                if (response instanceof FetchResponse) {
-                                    FetchResponse fr = (FetchResponse) response;
-                                    UID uid = fr.getItem(UID.class);
-                                    if (uid != null)
-                                        uids.remove(uid.uid);
-                                }
-                            return null;
-                        } else {
-                            for (Response response : responses)
-                                if (response.isNO() || response.isBAD() || response.isBYE())
-                                    return new MessagingException(response.toString());
-                            return new MessagingException("UID FETCH failed");
+                        Log.i(folder.name + " executing uid fetch count=" + uids.size());
+                        List<List<Long>> chunked = Helper.chunkList(new ArrayList<>(uids), 25);
+                        for (int c = 0; c < chunked.size(); c++) {
+                            Log.i(folder.name + " chunk #" + c + " size=" + chunked.get(c).size());
+                            Response[] responses = protocol.command(
+                                    "UID FETCH " + TextUtils.join(",", chunked.get(c)) + " (UID)", null);
+
+                            if (responses.length > 0 && responses[responses.length - 1].isOK()) {
+                                for (Response response : responses)
+                                    if (response instanceof FetchResponse) {
+                                        FetchResponse fr = (FetchResponse) response;
+                                        UID uid = fr.getItem(UID.class);
+                                        if (uid != null)
+                                            uids.remove(uid.uid);
+                                    }
+                            } else {
+                                for (Response response : responses)
+                                    if (response.isNO() || response.isBAD() || response.isBYE())
+                                        return new MessagingException(response.toString());
+                                return new MessagingException("UID FETCH failed");
+                            }
                         }
+                        return null;
                     }
                 });
                 if (ex != null)

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

@@ -576,6 +576,13 @@ public class Helper {
         return PreferenceManager.getDefaultSharedPreferences(context).getBoolean("pro", false);
     }
 
+    public static <T> List<List<T>> chunkList(List<T> list, int size) {
+        List<List<T>> result = new ArrayList<>(list.size() / size);
+        for (int i = 0; i < list.size(); i += size)
+            result.add(list.subList(i, i + size < list.size() ? i + size : list.size()));
+        return result;
+    }
+
     static long[] toLongArray(List<Long> list) {
         long[] result = new long[list.size()];
         for (int i = 0; i < list.size(); i++)