JsonWriter.hpp

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#ifndef _AV_TRANSCODER_MEDIA_PROPERTY_JSONWRITER_HPP_
#define _AV_TRANSCODER_MEDIA_PROPERTY_JSONWRITER_HPP_

#include <AvTranscoder/common.hpp>

#include <iostream>
#include <sstream>

namespace avtranscoder
{
namespace json
{

/**
 * @brief To manage 'null' element in JSON
 */
struct JsonNull
{
};

/**
 * @brief Based class to write element to a stream.
 */
class AvExport JsonStreamWriter
{
public:
    JsonStreamWriter()
        : first(true)
    {
    }
    virtual ~JsonStreamWriter() {}

    virtual std::string build()
    {
        finish();
        return stream.str();
    }

protected:
    friend class JsonObjectStreamWriter;
    friend class JsonArrayStreamWriter;
    std::ostringstream stream;
    bool first;

    template <typename T>
    JsonStreamWriter& operator<<(T value)
    {
        stream << value;
        return *this;
    }

    JsonStreamWriter& addSep()
    {
        if(first)
        {
            first = false;
        }
        else
        {
            stream << ',';
        }
        return *this;
    }

    virtual std::ostream& finish() = 0;

    // Escape strings accordingly to the JSON standard
    std::string escapeJsonString(const std::string& input);
};

// Write a boolean to the stream.
template <>
JsonStreamWriter& JsonStreamWriter::operator<<(bool value);
// Write a string to the stream.
template <>
JsonStreamWriter& JsonStreamWriter::operator<<(const char* string);
// Write null (empty value) to the stream.
template <>
JsonStreamWriter& JsonStreamWriter::operator<<(JsonNull);

/**
 * @brief Write an object to a stream.
 */
class AvExport JsonObjectStreamWriter : public JsonStreamWriter
{
public:
    JsonObjectStreamWriter() { stream << '{'; }

    template <typename T>
    JsonObjectStreamWriter& operator<<(const std::pair<const char*, T> pair)
    {
        addSep() << pair.first << ':' << pair.second;
        return *this;
    }

protected:
    virtual std::ostream& finish() { return stream << '}'; }
};

template <>
JsonObjectStreamWriter& JsonObjectStreamWriter::operator<<(const std::pair<const char*, const char*> pair);

/**
 * @brief Write an array to a stream.
 */
class AvExport JsonArrayStreamWriter : public JsonStreamWriter
{
public:
    JsonArrayStreamWriter() { stream << '['; }

    template <typename T>
    JsonArrayStreamWriter& operator<<(T value)
    {
        addSep() << value;
        return *this;
    }

protected:
    virtual std::ostream& finish() { return stream << ']'; }
};
}
}

#endif