cpphibernate/include/cpphibernate/driver/mariadb/context/data_context.h

#pragma once

#include <cpphibernate/config.h>

#include "base_context.h"

namespace cpphibernate {
namespace mariadb {

    namespace __impl
    {

        /**
         * @brief Helper class to create the change_context predicate.
         */
        template<typename X, typename = void>
        struct change_context_builder;

    }

    struct table_t;

    /**
     * @brief Predicate to change the stored dataset of any data_context.
     */
    constexpr decltype(auto) change_context = cppmp::generic_predicate<__impl::change_context_builder> { };

    /**
     * @brief Mariadb driver context that helds a specific dataset.
     */
    struct data_context
        : public base_context
    {
    private:
        mutable size_t          _dataset_id;    //!< Unique type id of the dataset that is stored in this context.
        mutable void *          _dataset;       //!< Pointer to the stored dataset.
        mutable const table_t * _table;         //!< Table this context/dataset belongs to

        template<typename X, typename T_enable>
        friend struct __impl::change_context_builder;

    protected:
        /**
         * @brief Constructor.
         *
         * @param[in] p_schema      Mariadb driver schema to use for the operation.
         * @param[in] p_connection  Mariadb connection to execute queries with.
         */
        inline data_context(
            const schema_t&             p_schema,
            ::cppmariadb::connection&   p_connection);

    public:
        /**
         * @brief Constructor.
         *
         * @param[in] p_schema      Mariadb driver schema to use for the operation.
         * @param[in] p_connection  Mariadb connection to execute queries with.
         * @param[in] p_dataset     Dataset to store in the context.
         */
        template<typename T_dataset>
        inline data_context(
            const schema_t&             p_schema,
            ::cppmariadb::connection&   p_connection,
            T_dataset&                  p_dataset);

        /**
         * @brief Get a reference to the stored dataset if the type matches.
         *        If an invalid type is requested an exception is thrown.
         */
        template<typename T_dataset>
        inline decltype(auto) get() const;

    protected:
        /**
         * @brief Set the dataset that is stored in this context.
         *
         * @param[in] dataset       Dataset to store in the context.
         * @param[in] dataset_id    Unique id of the dataset stored in the context.
         *
         * @return Pointer to the stored dataset.
         */
        template<typename T_dataset>
        inline void * set(T_dataset& dataset, size_t dataset_id = 0) const;

        /**
         * @brief Clear the context (set the stored dataset to nullptr).
         */
        inline void clear() const;
    };

} }