Prevent duplicate send operations

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

@@ -113,6 +113,9 @@ public interface DaoOperation {
     @Query("SELECT * FROM operation WHERE id = :id")
     EntityOperation getOperation(long id);
 
+    @Query("SELECT * FROM operation WHERE message = :message AND name = :name")
+    EntityOperation getOperation(long message, String name);
+
     @Query("SELECT * FROM operation WHERE error IS NOT NULL")
     List<EntityOperation> getOperationsError();
 
@@ -149,9 +152,4 @@ public interface DaoOperation {
 
     @Query("DELETE FROM operation WHERE id = :id")
     int deleteOperation(long id);
-
-    @Query("DELETE FROM operation" +
-            " WHERE folder = :folder" +
-            " AND state <> 'executing'")
-    int deletePendingOperations(long folder);
 }

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

@@ -436,28 +436,35 @@ public class ServiceSend extends ServiceBase implements SharedPreferences.OnShar
     }
 
     private void onSync(EntityFolder outbox) {
-        DB db = DB.getInstance(this);
+        NotificationManager nm = (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);
 
+        DB db = DB.getInstance(this);
         try {
             db.beginTransaction();
 
             db.folder().setFolderError(outbox.id, null);
 
-            // Delete pending operations
-            db.operation().deletePendingOperations(outbox.id);
-
-            // Requeue operations
-            NotificationManager nm = (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);
+            // Requeue non executing operations
             for (long id : db.message().getMessageByFolder(outbox.id)) {
                 EntityMessage message = db.message().getMessage(id);
-                if (message != null) {
+                if (message == null)
+                    continue;
+
+                EntityOperation op = db.operation().getOperation(message.id, EntityOperation.SEND);
+                if (op != null) {
+                    if ("executing".equals(op.state))
+                        continue;
+                    db.operation().deleteOperation(op.id);
+                }
+
+                db.message().setMessageError(message.id, null);
                 nm.cancel("send:" + message.id, 1);
+
                 if (message.ui_snoozed == null)
                     EntityOperation.queue(this, message, EntityOperation.SEND);
                 else
                     EntityMessage.snooze(this, message.id, message.ui_snoozed);
             }
-            }
 
             db.setTransactionSuccessful();
         } finally {