expression.h

#ifndef _EXPRESSION_H
#define _EXPRESSION_H
/*
 * Fledge storage client.
 *
 * Copyright (c) 2018 OSisoft, LLC
 *
 * Released under the Apache 2.0 Licence
 *
 * Author: Mark Riddoch
 */
#include <string>
#include <sstream>
#include <iostream>
#include <vector>
#include <resultset.h>


class Expression {
    public:
        Expression(const std::string& column, const std::string& op, int value) :
            m_column(column), m_op(op), m_type(INT_COLUMN)
        {
            m_value.ival = value;
        };
        Expression(const std::string& column, const std::string& op, double value) :
            m_column(column), m_op(op), m_type(NUMBER_COLUMN)
        {
            m_value.fval = value;
        };
        const std::string   toJSON() const
        {
        std::ostringstream json;

            json << "{ \"column\" : \"" << m_column << "\", ";
            json << "\"operator\" : \"" << m_op << "\", ";
            json << "\"value\" : ";
            switch (m_type)
            {
            case JSON_COLUMN:
            case BOOL_COLUMN:
            case STRING_COLUMN:
            case NULL_COLUMN:
                break;
            case INT_COLUMN:
                json << m_value.ival;
                break;
            case NUMBER_COLUMN:
                json << m_value.fval;
                break;
            }
            json << "}";
            return json.str();
        }
    private:
        const std::string   m_column;
        const std::string   m_op;
        ColumnType      m_type;
        union {
            long    ival;
            double  fval;
            }       m_value;
};

class ExpressionValues : public std::vector<Expression>
{
    public:
        const std::string   toJSON() const
        {
        std::ostringstream json;

            json << "[ ";
            for (std::vector<Expression>::const_iterator it = this->cbegin();
                 it != this->cend(); ++it)

            {
                json << it->toJSON();
                if (it + 1 != this->cend())
                    json << ", ";
                else
                    json << " ";
            }
            json << "]";
            return json.str();
        };
};
#endif