main.h

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#pragma once
 
#include "di/cli/prelude.h"
#include "di/container/string/prelude.h"
#include "di/container/vector/prelude.h"
#include "di/meta/core.h"
#include "dius/print.h"
 
namespace dius::main::detail {
template<typename T>
concept HasHelp = requires(T const& value) { value->help; };
 
template<typename T>
constexpr auto help_set(T const& result) -> bool {
    if constexpr (HasHelp<T>) {
        return result->help;
    } else {
        return false;
    }
}
}
 
#define DIUS_MAIN(Type, NS)                                                                      \
    auto main(int argc, char** argv) -> int {                                                    \
        auto args = ::di::Vector<::di::TransparentStringView> {};                                \
        for (int i = 0; i < argc; i++) {                                                         \
            char* arg = argv[i];                                                                 \
            size_t len = 0;                                                                      \
            while (arg[len] != '\0') {                                                           \
                len++;                                                                           \
            }                                                                                    \
            args.push_back({ arg, len });                                                        \
        }                                                                                        \
                                                                                                 \
        auto as_span = args.span();                                                              \
        auto parser = ::di::get_cli_parser<Type>();                                              \
        auto result = parser.parse(as_span);                                                     \
        using ParserResult = decltype(result);                                                   \
        constexpr bool has_help = ::dius::main::detail::HasHelp<ParserResult>;                   \
        if (!result) {                                                                           \
            ::dius::eprintln("Failed to parse command line arguments."_sv);                      \
            if constexpr (has_help) {                                                            \
                ::dius::eprintln("Run with '--help' for all list of valid options."_sv);         \
            }                                                                                    \
            return 2;                                                                            \
        }                                                                                        \
                                                                                                 \
        if (::dius::main::detail::help_set(result)) {                                            \
            auto fd_writer = ::dius::SyncFile(::dius::SyncFile::Owned::No, 2);                   \
            parser.write_help(fd_writer);                                                        \
            return 0;                                                                            \
        }                                                                                        \
                                                                                                 \
        using Result = decltype(NS::main(*result));                                              \
        if constexpr (::di::concepts::Expected<Result>) {                                        \
            auto main_result = NS::main(*result);                                                \
            if (!main_result) {                                                                  \
                ::dius::eprintln("Command failed: error: {}"_sv, main_result.error().message()); \
                return 1;                                                                        \
            }                                                                                    \
        } else {                                                                                 \
            (void) NS::main(*result);                                                            \
        }                                                                                        \
        return 0;                                                                                \
    }