ssp/include/ss/converter.hpp

#pragma once

#include "extract.hpp"
#include "function_traits.hpp"
#include "restrictions.hpp"
#include "type_traits.hpp"
#include <string>
#include <type_traits>
#include <vector>

namespace ss {
INIT_HAS_METHOD(tied);
INIT_HAS_METHOD(ss_valid);
INIT_HAS_METHOD(error);

////////////////
// replace validator
////////////////

// replace 'validator' types with elements they operate on
// eg. no_validator_tup_t<int, ss::nx<char, 'A', 'B'>> <=> std::tuple<int, char>
// where ss::nx<char, 'A', 'B'> is a validator '(n)one e(x)cept' which
// checks if the returned character is either 'A' or 'B', returns error if not
// additionaly if one element is left in the pack, it will be unwraped from
// the tuple eg. no_void_validator_tup_t<int> <=> int instead of std::tuple<int>
template <typename T, typename U = void>
struct no_validator;

template <typename T>
struct no_validator<T, typename std::enable_if_t<has_m_ss_valid_t<T>>> {
    using type = typename member_wrapper<decltype(&T::ss_valid)>::arg_type;
};

template <typename T, typename U>
struct no_validator {
    using type = T;
};

template <typename T>
using no_validator_t = typename no_validator<T>::type;

template <typename... Ts>
struct no_validator_tup {
    using type = typename apply_trait<no_validator, std::tuple<Ts...>>::type;
};

template <typename... Ts>
struct no_validator_tup<std::tuple<Ts...>> {
    using type = typename no_validator_tup<Ts...>::type;
};

template <typename T>
struct no_validator_tup<std::tuple<T>> {
    using type = no_validator_t<T>;
};

template <typename... Ts>
using no_validator_tup_t = typename no_validator_tup<Ts...>::type;

////////////////
// no void tuple
////////////////

template <typename... Ts>
struct no_void_tup {
    using type =
        typename filter_not<std::is_void, no_validator_tup_t<Ts...>>::type;
};

template <typename... Ts>
using no_void_tup_t = filter_not_t<std::is_void, Ts...>;

////////////////
// no void or validator
////////////////

// replace 'validators' and remove void from tuple
template <typename... Ts>
struct no_void_validator_tup {
    using type = no_validator_tup_t<no_void_tup_t<Ts...>>;
};

template <typename... Ts>
struct no_void_validator_tup<std::tuple<Ts...>> {
    using type = no_validator_tup_t<no_void_tup_t<Ts...>>;
};

template <typename... Ts>
using no_void_validator_tup_t = typename no_void_validator_tup<Ts...>::type;

////////////////
// tied class
////////////////

// check if the parameter pack is only one element which is a class and has
// the 'tied' method which is to be used for type deduction when converting
template <typename T, typename... Ts>
struct tied_class {
    constexpr static bool value =
        (sizeof...(Ts) == 0 && std::is_class_v<T> && has_m_tied<T>::value);
};

template <typename... Ts>
constexpr bool tied_class_v = tied_class<Ts...>::value;

// the error can be set inside a string, or a bool
enum class error_mode { String, Bool };

////////////////
// converter
////////////////

class converter {
    using string_range = std::pair<const char*, const char*>;
    constexpr static auto default_delimiter = ',';

public:
    using split_input = std::vector<string_range>;

    // parses line with given delimiter, returns a 'T' object created with
    // extracted values of type 'Ts'
    template <typename T, typename... Ts>
    T convert_object(const char* const line, const std::string& delim = "") {
        return to_object<T>(convert<Ts...>(line, delim));
    }

    // parses line with given delimiter, returns tuple of objects with
    // extracted values of type 'Ts'
    template <typename... Ts>
    no_void_validator_tup_t<Ts...> convert(const char* const line,
                                           const std::string& delim = "") {
        input_ = split(line, delim);
        return convert<Ts...>(input_);
    }

    // parses already split line, returns 'T' object with extracted values
    template <typename T, typename... Ts>
    T convert_object(const split_input& elems) {
        return to_object<T>(convert<Ts...>(elems));
    }

    // parses already split line, returns either a tuple of objects with
    // parsed values (returns raw element (no tuple) if Ts is empty), or if
    // one argument is given which is a class which has a tied
    // method which returns a tuple, returns that type
    template <typename T, typename... Ts>
    no_void_validator_tup_t<T, Ts...> convert(const split_input& elems) {
        if constexpr (sizeof...(Ts) == 0 &&
                      is_instance_of<T, std::tuple>::value) {
            return convert_impl(elems, (T*){});

        } else if constexpr (tied_class_v<T, Ts...>) {
            using arg_ref_tuple =
                typename std::result_of_t<decltype (&T::tied)(T)>;

            using arg_tuple =
                typename apply_trait<std::decay, arg_ref_tuple>::type;

            return to_object<T>(convert_impl(elems, (arg_tuple*){}));
        } else {
            return convert_impl<T, Ts...>(elems);
        }
    }

    bool valid() const {
        return (error_mode_ == error_mode::String) ? string_error_.empty()
                                                   : bool_error_ == false;
    }

    const std::string& error_msg() const {
        return string_error_;
    }

    void set_error_mode(error_mode mode) {
        error_mode_ = mode;
    }

    // 'splits' string by given delimiter, returns vector of pairs which
    // contain the beginings and the ends of each column of the string
    const split_input& split(const char* const line,
                             const std::string& delim = "") {
        input_.clear();
        if (line[0] == '\0') {
            return input_;
        }

        switch (delim.size()) {
        case 0:
            return split_impl(line, ',');
        case 1:
            return split_impl(line, delim[0]);
        default:
            return split_impl(line, delim, delim.size());
        };
    }

private:
    ////////////////
    // error
    ////////////////

    void clear_error() {
        string_error_.clear();
        bool_error_ = false;
    }

    std::string error_sufix(const string_range msg, size_t pos) const {
        std::string error;
        error.reserve(32);
        error.append("at column ")
            .append(std::to_string(pos + 1))
            .append(": \'")
            .append(msg.first, msg.second)
            .append("\'");
        return error;
    }

    void set_error_invalid_conversion(const string_range msg, size_t pos) {
        if (error_mode_ == error_mode::String) {
            string_error_.clear();
            string_error_.append("invalid conversion for parameter ")
                .append(error_sufix(msg, pos));
        } else {
            bool_error_ = true;
        }
    }

    void set_error_validate(const char* const error, const string_range msg,
                            size_t pos) {
        if (error_mode_ == error_mode::String) {
            string_error_.clear();
            string_error_.append(error).append(" ").append(
                error_sufix(msg, pos));
        } else {
            bool_error_ = true;
        }
    }

    void set_error_number_of_colums(size_t expected_pos, size_t pos) {
        if (error_mode_ == error_mode::String) {
            string_error_.clear();
            string_error_.append("invalid number of columns, expected: ")
                .append(std::to_string(expected_pos))
                .append(", got: ")
                .append(std::to_string(pos));
        } else {
            bool_error_ = true;
        }
    }

    ////////////////
    // convert implementation
    ////////////////

    template <typename... Ts>
    no_void_validator_tup_t<Ts...> convert_impl(const split_input& elems) {
        clear_error();
        no_void_validator_tup_t<Ts...> ret{};
        if (sizeof...(Ts) != elems.size()) {
            set_error_number_of_colums(sizeof...(Ts), elems.size());
            return ret;
        }
        return extract_tuple<Ts...>(elems);
    }

    // do not know how to specialize by return type :(
    template <typename... Ts>
    no_void_validator_tup_t<std::tuple<Ts...>> convert_impl(
        const split_input& elems, const std::tuple<Ts...>*) {
        return convert_impl<Ts...>(elems);
    }

    ////////////////
    // substring
    ////////////////

    template <typename Delim>
    const split_input& split_impl(const char* const line, Delim delim,
                                  size_t delim_size = 1) {
        auto range = substring(line, delim);
        input_.push_back(range);
        while (range.second[0] != '\0') {
            range = substring(range.second + delim_size, delim);
            input_.push_back(range);
        }
        return input_;
    }

    bool no_match(const char* end, char delim) const {
        return *end != delim;
    }

    bool no_match(const char* end, const std::string& delim) const {
        return strncmp(end, delim.c_str(), delim.size()) != 0;
    }

    template <typename Delim>
    string_range substring(const char* const begin, Delim delim) const {
        const char* end;
        for (end = begin; *end != '\0' && no_match(end, delim); ++end)
            ;

        return string_range{begin, end};
    }

    ////////////////
    // conversion
    ////////////////

    template <typename T>
    void extract_one(no_validator_t<T>& dst, const string_range msg,
                     size_t pos) {
        if (!valid()) {
            return;
        }

        if (!extract(msg.first, msg.second, dst)) {
            set_error_invalid_conversion(msg, pos);
            return;
        }

        if constexpr (has_m_ss_valid_t<T>) {
            if (T validator; !validator.ss_valid(dst)) {
                if constexpr (has_m_error_t<T>) {
                    set_error_validate(validator.error(), msg, pos);
                } else {
                    set_error_validate("validation error", msg, pos);
                }
                return;
            }
        }
    }

    template <size_t ArgN, size_t TupN, typename... Ts>
    void extract_multiple(no_void_validator_tup_t<Ts...>& tup,
                          const split_input& elems) {
        using elem_t = std::tuple_element_t<ArgN, std::tuple<Ts...>>;

        constexpr bool not_void = !std::is_void_v<elem_t>;
        constexpr bool one_element = count_not<std::is_void, Ts...>::size == 1;

        if constexpr (not_void) {
            if constexpr (one_element) {
                extract_one<elem_t>(tup, elems[ArgN], ArgN);
            } else {
                auto& el = std::get<TupN>(tup);
                extract_one<elem_t>(el, elems[ArgN], ArgN);
            }
        }

        if constexpr (sizeof...(Ts) > ArgN + 1) {
            constexpr size_t NewTupN = (not_void) ? TupN + 1 : TupN;
            extract_multiple<ArgN + 1, NewTupN, Ts...>(tup, elems);
        }
    }

    template <typename... Ts>
    no_void_validator_tup_t<Ts...> extract_tuple(const split_input& elems) {
        static_assert(!all_of<std::is_void, Ts...>::value,
                      "at least one parameter must be non void");
        no_void_validator_tup_t<Ts...> ret;
        extract_multiple<0, 0, Ts...>(ret, elems);
        return ret;
    };

    ////////////////
    // members
    ////////////////

    std::vector<string_range> input_;
    std::string string_error_;
    bool bool_error_;
    enum error_mode error_mode_ { error_mode::Bool };
};

template <>
inline void converter::extract_one<std::string>(std::string& dst,
                                                const string_range msg,
                                                size_t) {
    if (!valid()) {
        return;
    }

    extract(msg.first, msg.second, dst);
}

} /* ss */