// 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 QPDFOBJGEN_HH

#define QPDFOBJGEN_HH

#include <qpdf/DLL.h>

#include <iostream>

#include <set>

#include <string>

class QPDFObjectHandle;

class QPDFObjectHelper;

// This class represents an object ID and generation pair.  It is suitable to use as a key in a map

// or set.

class QPDFObjGen

{

  public:

    QPDFObjGen() = default;

    QPDFObjGen(int obj, int gen) :

        obj(obj),

        gen(gen)

    {

    }

    bool

    operator<(QPDFObjGen const& rhs) const

    {

        return (obj < rhs.obj) || (obj == rhs.obj && gen < rhs.gen);

    }

    bool

    operator==(QPDFObjGen const& rhs) const

    {

        return obj == rhs.obj && gen == rhs.gen;

    }

    bool

    operator!=(QPDFObjGen const& rhs) const

    {

        return !(*this == rhs);

    }

    int

    getObj() const

    {

        return obj;

    }

    int

    getGen() const

    {

        return gen;

    }

    bool

    isIndirect() const

    {

        return obj != 0;

    }

    std::string

    unparse(char separator = ',') const

    {

        return std::to_string(obj) + separator + std::to_string(gen);

    }

    friend std::ostream&

    operator<<(std::ostream& os, QPDFObjGen og)

    {

        os << og.obj << "," << og.gen;

        return os;

    }

    // Convenience class for loop detection when processing objects.

    //

    // The class adds 'add' methods to a std::set<QPDFObjGen> which allows to test whether an

    // QPDFObjGen is present in the set and to insert it in a single operation. The 'add' method is

    // overloaded to take a QPDFObjGen, QPDFObjectHandle or an QPDFObjectHelper as parameter.

    //

    // The erase method is modified to ignore requests to erase QPDFObjGen(0, 0).

    //

    // Usage example:

    //

    // void process_object(QPDFObjectHandle oh, QPDFObjGen::set& seen)

    // {

    //     if (seen.add(oh)) {

    //         // handle first encounter of oh

    //     } else {

    //         // handle loop / subsequent encounter of oh

    //     }

    // }

    class QPDF_DLL_CLASS set: public std::set<QPDFObjGen>

    {

      public:

        // Add 'og' to the set. Return false if 'og' is already present in the set. Attempts to

        // insert QPDFObjGen(0, 0) are ignored.

        bool

        add(QPDFObjGen og)

        {

            if (og.isIndirect()) {

                if (count(og)) {

                    return false;

                }

                emplace(og);

            }

            return true;

        }

        void

        erase(QPDFObjGen og)

        {

            if (og.isIndirect()) {

                std::set<QPDFObjGen>::erase(og);

            }

        }

    };

  private:

    // This class does not use the Members pattern to avoid a memory allocation for every one of

    // these. A lot of these get created and destroyed.

    int obj{0};

    int gen{0};

};

#endif // QPDFOBJGEN_HH