text: //  Copyright (C) 2015-2021 Virgil Security, Inc.
  //
  //  All rights reserved.
  //
  //  Redistribution and use in source and binary forms, with or without
  //  modification, are permitted provided that the following conditions are
  //  met:
  //
  //      (1) Redistributions of source code must retain the above copyright
  //      notice, this list of conditions and the following disclaimer.
  //
  //      (2) Redistributions in binary form must reproduce the above copyright
  //      notice, this list of conditions and the following disclaimer in
  //      the documentation and/or other materials provided with the
  //      distribution.
  //
  //      (3) Neither the name of the copyright holder nor the names of its
  //      contributors may be used to endorse or promote products derived from
  //      this software without specific prior written permission.
  //
  //  THIS SOFTWARE IS PROVIDED BY THE AUTHOR ''AS IS'' AND ANY EXPRESS OR
  //  IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
  //  WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  //  DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT,
  //  INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
  //  (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
  //  SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  //  HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
  //  STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
  //  IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  //  POSSIBILITY OF SUCH DAMAGE.
  //
  //  Lead Maintainer: Virgil Security Inc. <support@virgilsecurity.com>
  
  #ifndef VM_MESSAGES_QUEUE_LISTENERS_H
  #define VM_MESSAGES_QUEUE_LISTENERS_H
  
  #include "OperationQueueListener.h"
  
  #include <QLoggingCategory>
  #include <QMutex>
  
  Q_DECLARE_LOGGING_CATEGORY(lcMessagesQueueListener);
  
  namespace vm {
  //
  // Listener that skips non-unique message download operations
  //
  class UniqueMessageDownloadOperationFilter : public OperationQueueListener
  {
      Q_OBJECT
  
  public:
      using OperationQueueListener::OperationQueueListener;
  
  private:
      bool preRun(OperationSourcePtr source) override;
      void postRun(OperationSourcePtr source) override;
  
      QStringList m_ids;
      QMutex m_mutex;
  };
  } // namespace vm
  
  #endif // VM_MESSAGES_QUEUE_LISTENERS_H
  