argparser/src/union-type.h

#ifndef ARGPARSER_UNION_TYPE_H
#define ARGPARSER_UNION_TYPE_H

#include "distinct-types.h"
#include "errors.h"
#include "tuple-iteration.h"
#include "type.h"
#include <any>
#include <string>
#include <tuple>
#include <vector>

namespace argparser {
    namespace internal {
        template<typename... Ts>
        std::string construct_string_type_name_list_from_tuple(std::tuple<Ts...> types) {
            std::string expected_types;
            expected_types = std::get<0>(types)->get_name();
            if (std::tuple_size_v<decltype(types)> > 1) {
                internal::tuple_foreach(types, [&expected_types]<typename T>(type_handle_impl<T> &type, auto idx) {
                    if (idx == std::tuple_size_v<decltype(types)> - 1 || idx == 0) {
                        return;
                    }
                    expected_types += ", " + type->get_name();
                });
                expected_types += " or " + std::get<std::tuple_size_v<decltype(types)> - 1>(types)->get_name();
            }
            return expected_types;
        }
    }// namespace internal

    template<typename... Ts>
    class union_type;

    template<typename... Ts>
        requires(std::tuple_size<internal::distinct_types_tuple<Ts...>>::value > 1)
    class union_type<Ts...> : public type_impl<internal::distinct_types_variant<Ts...>> {
        using variant_type = internal::distinct_types_variant<Ts...>;
    public:
        union_type(std::string name, std::tuple<type_handle_impl<Ts>...> types) : type_impl<variant_type>(std::move(name)), types(std::move(types)) {}

        variant_type parse(const char *begin, const char *end, const char *&parse_end, internal::parser_allow_undelimited allow_undelimited) override {
            std::vector<variant_type> results{};
            std::vector<std::string> result_types{};
            size_t length = 0;

            internal::tuple_foreach(types, [&begin, &end, &length, &results, &result_types, &allow_undelimited]<typename T>(type_handle_impl<T> &type, auto) {
                const char *this_parse_end;
                try {
                    auto val = type->parse(begin, end, this_parse_end, allow_undelimited);
                    size_t this_length = this_parse_end - begin;
                    if (this_length >= length) {
                        variant_type variant_wrapped_val = val;
                        if (this_length == length) {
                            results.push_back(variant_wrapped_val);
                            result_types.push_back(type->get_name());
                        } else {
                            length = this_length;
                            results = {variant_wrapped_val};
                            result_types = {type->get_name()};
                        }
                    }
                } catch (errors::type_parsing_error &e) {
                    // ignore errors
                }
            });
            if (length == 0) {
                std::string expected_types = internal::construct_string_type_name_list_from_tuple(types);
                throw errors::type_parsing_error(this->name, std::string(begin, end), 0, std::format("expected {}", expected_types));
            }
            if (results.size() > 1) {
                throw errors::ambiguous_parse_error(this->name, std::string(begin, end), 0, result_types);
            }
            parse_end = begin + length;
            return results[0];
        }

    private:
        std::tuple<type_handle_impl<Ts>...> types;
    };

    template<typename T, typename... Ts>
        requires(std::tuple_size<internal::distinct_types_tuple<T, Ts...>>::value == 1)
    class union_type<T, Ts...> : public type_impl<T> {
    public:
        union_type(std::string name, std::tuple<type_handle_impl<T>, type_handle_impl<Ts>...> types) : type_impl<T>(std::move(name)), types(std::move(types)) {}

        T parse(const char *begin, const char *end, const char *&parse_end, internal::parser_allow_undelimited) override {
            std::vector<T> results{};
            std::vector<std::string> result_types{};
            size_t length = 0;

            internal::tuple_foreach(types, [&begin, &end, &length, &results, &result_types](type_handle_impl<T> &type, auto) {
                const char *this_parse_end;
                try {
                    auto val = type->parse(begin, end, this_parse_end);
                    size_t this_length = this_parse_end - begin;
                    if (this_length >= length) {
                        if (this_length == length) {
                            results.push_back(val);
                            result_types.push_back(type->get_name());
                        } else {
                            length = this_length;
                            results = {val};
                            result_types = {type->get_name()};
                        }
                    }
                } catch (errors::type_parsing_error &e) {
                    // ignore errors
                }
            });

            if (length == 0) {
                std::string expected_types = internal::construct_string_type_name_list_from_tuple(types);
                throw errors::type_parsing_error(this->name, std::string(begin, end), 0, std::format("expected {}", expected_types));
            }
            if (results.size() > 1 && !std::equal(results.begin() + 1, results.end(), results.begin())) {
                throw errors::ambiguous_parse_error(this->name, std::string(begin, end), 0, result_types);
            }
            parse_end = begin + length;
            return results[0];
        }

    private:
        std::tuple<type_handle_impl<T>, type_handle_impl<Ts>...> types;
    };

}// namespace argparser


#endif//ARGPARSER_UNION_TYPE_H