cppcore/include/cppcore/conversion/string.h

#pragma once

#include <string>
#include <iostream>

namespace cppcore
{

    namespace __impl
    {

        /**
         * @brief Predicate class to convert any type to a string using a stream.
         */
        template<typename T, typename Enable = void>
        struct op_to_stream;

        /**
         * @brief Predicate class to convert any type to a string.
         */
        template<typename T, typename Enable = void>
        struct op_to_string;

        /**
         * @brief Predicate class to convert a string to any type.
         */
        template<typename T, typename Enable = void>
        struct op_from_string;

        /**
         * @brief Traits class to store needed data types.
         */
        struct string_conversion_traits
        {
            template<typename T>
            using to_stream_predicate_type = op_to_stream<T>;

            template<typename T>
            using to_string_predicate_type = op_to_string<T>;

            template<typename T>
            using from_string_predicate_type = op_from_string<T>;
        };

    }

    /**
     * @brief Convert the passed value to string.
     *
     * @tparam T            Type of the passed value.
     * @tparam T_traits     Traits type to use for conversion.
     *
     * @param[in] value     Value to convert to string.
     *
     * @return              Converted value.
     */
    template<typename T, typename T_traits = __impl::string_conversion_traits>
    inline std::string to_string(const T& value);

    /**
     * @brief Write the passed value as string representation to a stream.
     *
     * @tparam T            Type of the passed value.
     * @tparam T_traits     Traits type to use for conversion.
     *
     * @param[in] value     Value to convert to write to stream.
     */
    template<typename T, typename T_traits = __impl::string_conversion_traits>
    inline void to_string(std::ostream& os, const T& value);

    /**
     * @brief Try to convert the given string to the passed value.
     *
     * @tparam T            Type of the value to convert the stirng to.
     * @tparam T_traits     Traits type to use for conversion.
     *
     * @param[in]  s        String to convert to value.
     * @param[out] value    Parameter to store vconverted value in.
     *
     * @retval true         If the conversion was successful.
     * @retval false        If the conversion failed.
     */
    template<typename T, typename T_traits = __impl::string_conversion_traits>
    inline bool try_from_string(const std::string& s, T& value);

    /**
     * @brief Try to convert the given string to the passed type. Throws exception if conversion was failed.
     *
     * @tparam T            Type of the value to convert the stirng to.
     * @tparam T_traits         Traits type to use for conversion.
     *
     * @param[in]  s        String to convert to value.
     *
     * @return              Converted value.
     */
    template<typename T, typename T_traits = __impl::string_conversion_traits>
    inline T from_string(const std::string& s);

    /**
     * @brief Try to convert the given string to the passed type. Returns the passed default value if conversion was failed.
     *
     * @tparam T                Type of the value to convert the stirng to.
     * @tparam T_traits         Traits type to use for conversion.
     *
     * @param[in] s             String to convert to value.
     * @param[in] default_value Default value to return if the conversion failed.
     *
     * @return                  Converted value.
     */
    template<typename T, typename T_traits = __impl::string_conversion_traits>
    inline T from_string_default(const std::string& s, const T& default_value);

    /**
     * @brief Split string at the passed seperator and calls the passed predicate for each element.
     *
     * @tparam T_predicate  Type of predicate to execute for each element.
     *
     * @param s             String to split.
     * @param seperator     Seperator to split string at.
     * @param predicate     Predicate to execute for each element.
     *
     * @return              Value returned from the predicate.
     */
    template<typename T_predicate>
    inline bool string_split(const std::string& s, char seperator, const T_predicate& predicate);

    /**
     * @brief Class to handle string conversions.
     *
     * @tparam T_traits     Traits to use for converting.
     */
    template<typename T_traits>
    struct string_conversion_t
    {
        using traits_type = T_traits;

        /**
         * @brief Convert the passed value to string.
         *
         * @tparam T        Type of the passed value.
         *
         * @param[in] value Value to convert to string.
         *
         * @return          Converted value.
         */
        template<typename T>
        static inline std::string to_string(const T& value);

        /**
         * @brief Write the passed value as string representation to a stream.
         *
         * @tparam T        Type of the passed value.
         *
         * @param[in] value Value to convert to write to stream.
         */
        template<typename T>
        static inline void to_string(std::ostream& os, const T& value);

        /**
         * @brief Try to convert the given string to the passed value.
         *
         * @tparam T            Type of the value to convert the stirng to.
         *
         * @param[in]  s        String to convert to value.
         * @param[out] value    Parameter to store vconverted value in.
         *
         * @retval true         If the conversion was successful.
         * @retval false        If the conversion failed.
         */
        template<typename T>
        static inline bool try_from_string(const std::string& s, T& value);

        /**
         * @brief Try to convert the given string to the passed type. Throws exception if conversion was failed.
         *
         * @tparam T            Type of the value to convert the stirng to.
         *
         * @param[in]  s        String to convert to value.
         *
         * @return              Converted value.
         */
        template<typename T>
        static inline T from_string(const std::string& s);

        /**
         * @brief Try to convert the given string to the passed type. Returns the passed default value if conversion was failed.
         *
         * @tparam T                Type of the value to convert the stirng to.
         *
         * @param[in] s             String to convert to value.
         * @param[in] default_value Default value to return if the conversion failed.
         *
         * @return                  Converted value.
         */
        template<typename T>
        static inline T from_string_default(const std::string& s, const T& default_value);
    };

    /**
     * @brief String conversion class with default traits.
     */
    struct string_conversion
        : public string_conversion_t<__impl::string_conversion_traits>
        { };

}


namespace std
{

    /**
     * @brief Operator overload to write value to stream that supports the to_string method, with stream parameter.
     */
    template<typename T_char, typename T_traits, typename X>
    inline auto operator<<(basic_ostream<T_char, T_traits>& os, X&& x)
        -> decltype(
            std::forward<X>(x).to_string(std::declval<basic_ostream<T_char, T_traits>&>()),
            std::declval<basic_ostream<T_char, T_traits>&>());

    /**
     * @brief Operator overload to write value to stream that supports the to_string method, with stream parameter.
     */
    template<typename T_char, typename T_traits, typename X>
    inline auto operator<<(basic_ostream<T_char, T_traits>& os, X&& x)
        -> decltype(
            std::forward<X>(x).to_string(),
            std::declval<basic_ostream<T_char, T_traits>&>());

}

#include "string.inl"