cppcore/include/cppcore/conversion/string.inl

#pragma once

#include <cppcore/misc/exception.h>
#include <cppcore/misc/type_helper.h>

#include "enum.h"
#include "string.h"

#ifdef _GLIBCXX_VECTOR
#define CPPCORE_HAS_VECTOR
#endif

#ifdef _GLIBCXX_LIST
#define CPPCORE_HAS_LIST
#endif

namespace cppcore
{

    /* global */

    template<typename T, typename T_traits>
    inline std::string to_string(const T& value)
        { return string_conversion_t<T_traits>::template to_string<T>(value); }

    template<typename T, typename T_traits>
    inline void to_string(std::ostream& os, const T& value)
        { string_conversion_t<T_traits>::template to_string<T>(os, value); }

    template<typename T, typename T_traits>
    inline bool try_from_string(const std::string& s, T& value)
        { return string_conversion_t<T_traits>::template try_from_string<T>(s, value); }

    template<typename T, typename T_traits>
    inline T from_string(const std::string& s)
        { return string_conversion_t<T_traits>::template from_string<T>(s); }

    template<typename T, typename T_traits>
    inline T from_string_default(const std::string& s, const T& default_value)
        { return string_conversion_t<T_traits>::template from_string_default<T>(s, default_value); }

    template<typename T_predicate>
    inline bool string_split(const std::string& str, char seperator, T_predicate&& predicate)
    {
        auto* i = str.c_str();
        auto* e = str.c_str() + str.size();
        auto* s = i;
        while (i <= e)
        {
            if (    s != e
                && (    *i == seperator
                    ||  *i == '\0'))
            {
                std::string tmp(s, static_cast<size_t>(i - s));
                if (!predicate(tmp))
                    return false;
                s = i + 1;
            }
            ++i;
        }
        return true;
    }

    /* string_conversion */

    template<typename T_traits>
    template<typename T>
    inline std::string string_conversion_t<T_traits>
        ::to_string(const T& value)
    {
        using predicate_type = typename traits_type::template to_string_predicate_type<T>;
        return predicate_type { } (value);
    }

    template<typename T_traits>
    template<typename T>
    inline void string_conversion_t<T_traits>
        ::to_string(std::ostream& os, const T& value)
    {
        using predicate_type = typename traits_type::template to_stream_predicate_type<T>;
        predicate_type { } (os, value);
    }

    template<typename T_traits>
    template<typename T>
    inline bool string_conversion_t<T_traits>
        ::try_from_string(const std::string& s, T& value)
    {
        using predicate_type = typename traits_type::template from_string_predicate_type<T>;
        return predicate_type { } (s, value);
    }

    template<typename T_traits>
    template<typename T>
    inline T string_conversion_t<T_traits>
        ::from_string(const std::string& s)
    {
        using namespace ::std;
        T ret;
        if (!try_from_string(s, ret))
            throw convert_exception("unable to convert '"s + s + "' to '"s + type_helper<T>::name() + "'"s);
        return ret;
    }

    template<typename T_traits>
    template<typename T>
    inline T string_conversion_t<T_traits>
        ::from_string_default(const std::string& s, const T& default_value)
    {
        T ret;
        return try_from_string(s, ret)
            ? ret
            : default_value;
    }

    namespace __impl
    {

        /* op_to_string */

        template<typename T, typename Enable>
        struct op_to_string
        {
            inline std::string operator()(const T& v) const
                { return std::to_string(v); }
        };

        template<typename T>
        struct op_to_string<T, std::enable_if_t<std::is_enum_v<T>>>
        {
            inline std::string operator()(const T& v) const
                { return enum_conversion<T>::to_string(v); }
        };

        template<typename T>
        struct op_to_string<T, std::enable_if_t<std::is_floating_point_v<T>>>
        {
            inline std::string operator()(const T& v) const
            {
                std::stringstream os;
                op_to_stream<T> { } (os, v);
                return os.str();
            }
        };

        template<>
        struct op_to_string<std::string, void>
        {
            inline std::string operator()(const std::string& v) const
                { return v; }
        };

        template<typename T, size_t N>
        struct op_to_string<T[N], std::enable_if_t<std::is_same_v<std::decay_t<T>, char>>>
        {
            using value_type = T[N];

            inline std::string operator()(const value_type& v) const
                { return std::string(v, N-1); }
        };

        template<typename T>
        struct op_to_string<T*, std::enable_if_t<std::is_same_v<std::decay_t<T>, char>>>
        {
            using value_type = T*;

            inline std::string operator()(const value_type& v) const
                { return std::string(v); }
        };

        template<typename T>
        struct op_to_string<T, decltype(std::declval<T>().to_string(std::declval<std::ostream&>()), void())>
        {
            inline std::string operator()(const T& v) const
            {
                std::ostringstream os;
                v.to_string(os);
                return os.str();
            }
        };

        template<typename T>
        struct op_to_string<T, decltype(std::declval<T>().to_string(), void())>
        {
            inline std::string operator()(const T& v) const
                { return v.to_string(); }
        };

        #ifdef CPPCORE_HAS_VECTOR
        template<typename T>
        struct op_to_string<std::vector<T>, void>
        {
            inline std::string operator()(const std::vector<T>& v) const
            {
                std::ostringstream os;
                op_to_stream<std::vector<T>> { } (os, v);
                return os.str();
            }
        };
        #endif

        #ifdef CPPCORE_HAS_LIST
        template<typename T>
        struct op_to_string<std::list<T>, void>
        {
            inline std::string operator()(const std::list<T>& v) const
            {
                std::ostringstream os;
                op_to_stream<std::list<T>> { } (os, v);
                return os.str();
            }
        };
        #endif

        /* op_to_stream */

        template<typename T, typename Enable>
        struct op_to_stream
        {
            inline void operator()(std::ostream& os, const T& v) const
                { os << v; }
        };

        template<typename T>
        struct op_to_stream<T, std::enable_if_t<std::is_enum_v<T>>>
        {
            inline void operator()(std::ostream& os, const T& v) const
                { os << enum_conversion<T>::to_string(v); }
        };

        template<typename T>
        struct op_to_stream<T, decltype(std::declval<T>().to_string(std::declval<std::ostream&>()), void())>
        {
            inline void operator()(std::ostream& os, const T& v) const
                { v.to_string(os); }
        };

        template<typename T>
        struct op_to_stream<T, decltype(std::declval<T>().to_string(), void())>
        {
            inline void operator()(std::ostream& os, const T& v) const
                { os << v.to_string(); }
        };

        #ifdef CPPCORE_HAS_VECTOR
        template<typename T>
        struct op_to_stream<std::vector<T>, void>
        {
            inline void operator()(std::ostream& os, const std::vector<T>& v) const
            {
                bool first = true;
                for (auto& x : v)
                {
                    if (first)  first = false;
                    else        os << ',';
                    to_string(os, x);
                }
            }
        };
        #endif

        #ifdef CPPCORE_HAS_LIST
        template<typename T>
        struct op_to_stream<std::list<T>, void>
        {
            inline void operator()(std::ostream& os, const std::list<T>& v) const
            {
                bool first = true;
                for (auto& x : v)
                {
                    if (first)  first = false;
                    else        os << ',';
                    to_string(os, x);
                }
            }
        };
        #endif

        /* op_from_string */

        template<typename T, typename Enable>
        struct op_from_string
        {
            inline bool operator()(const std::string& s, T& value) const
            {
                std::istringstream ss(s);
                ss >> value;
                return static_cast<bool>(ss);
            }
        };

        template<>
        struct op_from_string<std::string, void>
        {
            inline bool operator()(const std::string& s, std::string& value) const
            {
                value = s;
                return true;
            }
        };

        template<>
        struct op_from_string<const char*, void>
        {
            inline bool operator()(const std::string& s, const char*& value) const
            {
                value = s.c_str();
                return true;
            }
        };

        template<>
        struct op_from_string<bool, void>
        {
            inline bool operator()(const std::string& s, bool& value) const
            {
                const std::string TRUE_STR("true");
                int i;
                value = s == "T"
                    ||  s == "t"
                    ||  std::equal(
                            s.begin(), s.end(),
                            TRUE_STR.begin(), TRUE_STR.end(),
                            [](char a, char b) {
                                return tolower(a) == tolower(b);
                            })
                    || (    cppcore::try_from_string(s, i)
                        &&  i != 0);
                return true;
            }
        };

        template<typename T>
        struct op_from_string<T, std::enable_if_t<std::is_enum_v<T>>>
        {
            inline bool operator()(const std::string& s, T& v) const
                { return enum_conversion<T>::try_to_enum(s, v); }
        };

        template<typename T>
        struct op_from_string<T, decltype(std::declval<T&>().from_string(std::declval<const std::string&>()), void())>
        {
            inline bool operator()(const std::string& s, T& v) const
                { return v.from_string(s); }
        };

        template<typename T>
        struct op_from_string<T, decltype(T::from_string(std::declval<const std::string&>(), std::declval<T&>()), void())>
        {
            inline bool operator()(const std::string& s, T& v) const
                { return T::from_string(s, v); }
        };

        template<typename T>
        struct op_from_string<T, typename std::enable_if_t<std::is_integral_v<T>>>
        {
            inline bool operator()(const std::string& s, T& v) const
            {
                char *e = nullptr;
                const char *c = s.c_str();
                v = static_cast<T>(std::strtoull(c, &e, 0));
                return (c != e);
            }
        };

        template<typename T>
        struct op_from_string<T, typename std::enable_if_t<std::is_floating_point_v<T>>>
        {
            inline bool operator()(const std::string& s, T& value) const
            {
                char *e = nullptr;
                const char *c = s.c_str();
                value = static_cast<T>(std::strtold(c, &e));
                return (c != e);
            }
        };

        #ifdef CPPCORE_HAS_VECTOR
        template<typename T>
        struct op_from_string<std::vector<T>, void>
        {
            inline bool operator()(const std::string& str, std::vector<T>& value) const
            {
                std::vector<T> tmp;
                auto ret = string_split(str, ',', [&](const std::string& s) {
                    tmp.emplace_back();
                    return try_from_string(s, tmp.back());
                });
                if (ret)
                    value = std::move(tmp);
                return ret;
            }
        };
        #endif

        #ifdef CPPCORE_HAS_LIST
        template<typename T>
        struct op_from_string<std::list<T>, void>
        {
            inline bool operator()(const std::string& str, std::list<T>& value) const
            {
                std::list<T> tmp;
                auto ret = string_split(str, ',', [&tmp](auto& s) {
                    tmp.emplace_back();
                    return try_from_string(s, tmp.back());
                });
                if (ret)
                    value = std::move(tmp);
                return ret;
            }
        };
        #endif
    }

}


namespace std
{

    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>&>())
    {
        std::forward<X>(x).to_string(os);
        return os;
    }

}