cpphibernate/include/cpphibernate/driver/mariadb/impl/_context.h

#pragma once







namespace cpphibernate {
namespace mariadb {

    /**
     * @brief Base class for all mariadb driver context classes.
     */
    struct base_context
    {
        const schema_t&             schema;     //!< schema to use for the operation
        ::cppmariadb::connection&   connection; //!< mariadb connection to use for executing queries

        /**
         * @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 base_context(
            const schema_t&             p_schema,
            ::cppmariadb::connection&   p_connection);
    };

    /**
     * @brief Mariadb driver context for initializing the database.
     */
    struct init_context
        : public base_context
    {
        bool recreate;  //!< Drop existing tables before createing new once.

        /**
         * @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_recreate    Drop existing tables before createing new once.
         */
        inline init_context(
            const schema_t&             p_schema,
            ::cppmariadb::connection&   p_connection,
            bool                        p_recreate);
    };

    /**
     * @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

        friend __impl::change_context_builder;

    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;

    private:
        /**
         * @brief Set the dataset that is stored in this context.
         */
        template<typename T_dataset>
        inline void set(T_dataset& dataset);
    };



    namespace __impl
    {

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

    }

    /**
     * @brief Change the stored dataset of any data_context.
     *
     * @param[in] context   Any data_context.
     * @param[in] dataset   New dataset of the context.
     *
     * @return              The new conext that stores the passed dataset.
     */
    constexpr decltype(auto) change_context = cppmp::generic_predicate<__impl::change_context_builder> { };


#if 0

    /* filter_context */

    struct filter_context
        : public data_context
    {
        const filter_t& filter;

        inline filter_context(
                const schema_t&             p_schema,
                ::cppmariadb::connection&   p_connection,
                const filter_t&             p_filter)
            : data_context  (p_schema, p_connection)
            , filter        (p_filter)
            { }

        template<typename T_data>
        inline filter_context(
                T_data&                     p_data,
                const schema_t&             p_schema,
                ::cppmariadb::connection&   p_connection,
                const filter_t&             p_filter)
            : data_context  (p_data, p_schema, p_connection)
            , filter        (p_filter)
            { }
    };

    /* create_update_context */

    struct create_update_context
        : public filter_context
    {
        bool            is_update;
        const table_t*  derived_table;
        const field_t*  owner_field;
        std::string     owner_key;
        ssize_t         index;

        template<typename T_data>
        inline create_update_context(
                T_data&                     p_data,
                const schema_t&             p_schema,
                ::cppmariadb::connection&   p_connection,
                const filter_t&             p_filter,
                bool                        p_is_update)
            : filter_context(p_data, p_schema, p_connection, p_filter)
            , is_update     (p_is_update)
            , derived_table (nullptr)
            , owner_field   (nullptr)
            , index         (-1)
            { }
    };

    /* read_context */

    struct read_context
        : public filter_context
    {
    protected:
        size_t      base_dataset_id;

    public:
        bool        is_dynamic;
        std::string where;
        std::string limit;
        std::string order_by;

    protected:
        inline read_context(
                const schema_t&             p_schema,
                ::cppmariadb::connection&   p_connection,
                const filter_t&             p_filter)
            : filter_context    (p_schema, p_connection, p_filter)
            , is_dynamic        (false)
            , base_dataset_id   (0)
            { }

    public:
        virtual ~read_context() = default;

        template<typename T_dataset>
        inline T_dataset& emplace(const table_t* table = nullptr) const;

        void emplace() const
            { emplace_intern(nullptr, 0); }

        void finish() const
            { finish_intern(); }

    private:
        virtual void* emplace_intern(void* data, size_t dataset_id) const = 0;
        virtual void  finish_intern () const = 0;
    };

    using read_context_ptr = std::unique_ptr<read_context>;

    /* destroy_context */

    struct destroy_context
        : public data_context
    {
        std::string where;

        template<typename T_data>
        inline destroy_context(
                T_data&                     p_data,
                const schema_t&             p_schema,
                ::cppmariadb::connection&   p_connection)
            : data_context(
                p_data,
                p_schema,
                p_connection)
            { }
    };
#endif
} }