// Copyright (c) 2005-2021 Jay Berkenbilt
// Copyright (c) 2022-2025 Jay Berkenbilt and Manfred Holger
//
// This file is part of qpdf.
//
// Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
// in compliance with the License. You may obtain a copy of the License at
//
//   http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software distributed under the License
// is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
// or implied. See the License for the specific language governing permissions and limitations under
// the License.
//
// Versions of qpdf prior to version 7 were released under the terms of version 2.0 of the Artistic
// License. At your option, you may continue to consider qpdf to be licensed under those terms.
// Please see the manual for additional information.

#ifndef QPDFSTREAMFILTER_HH
#define QPDFSTREAMFILTER_HH

#include <qpdf/DLL.h>
#include <qpdf/Pipeline.hh>
#include <qpdf/QPDFObjectHandle.hh>

class QPDF_DLL_CLASS QPDFStreamFilter
{
  public:
    QPDFStreamFilter() = default;

    virtual ~QPDFStreamFilter() = default;

    // A QPDFStreamFilter class must implement, at a minimum, setDecodeParms() and
    // getDecodePipeline(). QPDF will always call setDecodeParms() before calling
    // getDecodePipeline(). It is expected that you will store any needed information from
    // decode_parms (or the decode_parms object itself) in your instance so that it can be used to
    // construct the decode pipeline.

    // Return a boolean indicating whether your filter can proceed with the given /DecodeParms. The
    // default implementation accepts a null object and rejects everything else.
    QPDF_DLL
    virtual bool setDecodeParms(QPDFObjectHandle decode_parms);

    // Return a pipeline that will decode data encoded with your filter. Your implementation must
    // ensure that the pipeline is deleted when the instance of your class is destroyed.
    QPDF_DLL
    virtual Pipeline* getDecodePipeline(Pipeline* next) = 0;

    // If your filter implements "specialized" compression or lossy compression, override one or
    // both of these methods. The default implementations return false. See comments in QPDFWriter
    // for details. QPDF defines specialized compression as non-lossy compression not intended for
    // general-purpose data. qpdf, by default, doesn't mess with streams that are compressed with
    // specialized compression, the idea being that the decision to use that compression scheme
    // would fall outside of what QPDFWriter would know anything about, so any attempt to decode and
    // re-encode would probably be undesirable.
    QPDF_DLL
    virtual bool isSpecializedCompression();
    QPDF_DLL
    virtual bool isLossyCompression();

  private:
    QPDFStreamFilter(QPDFStreamFilter const&) = delete;
    QPDFStreamFilter& operator=(QPDFStreamFilter const&) = delete;
};

#endif // QPDFSTREAMFILTER_HH
