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// -*- c++ -*-
// Distributed under the BSD 2-Clause License.
// See accompanying file LICENSE for details.
#pragma once
#include <functional>
#include <variant>
#include <optional>
#include <string>
#include <type_traits>
#include <iostream>
namespace arg
{
struct noarg {};
template<typename T>
struct Opt
{
std::string shortopt;
std::string longopt;
std::function<int(T)> cb;
std::string help;
T t{};
};
template<>
struct Opt<noarg>
{
std::string shortopt;
std::string longopt;
std::function<int()> cb;
std::string help;
noarg t{};
};
template<typename... Ts>
class Parser
{
public:
struct missing_arg{};
int parse(int argc, const char* const argv[])
{
if(argc < 1)
{
return 1;
}
for(int i = 1; i < argc; ++i) // skip argv[0] which is program name
{
bool was_handled{false};
for(const auto& option : options)
{
enum class state { handled, unhandled };
std::pair<int, state> ret =
std::visit([&](auto&& opt) -> std::pair<int, state>
{
if(opt.shortopt != argv[i] &&
opt.longopt != argv[i])
{
return {0, state::unhandled};
}
try
{
using T = std::decay_t<decltype(opt)>;
if constexpr (std::is_same_v<T, Opt<noarg>>)
{
return {opt.cb(), state::handled};
}
else
{
auto arg = convert(argc, argv, i, opt.t);
return {opt.cb(arg), state::handled};
}
}
catch(std::invalid_argument&)
{
std::cout << argv[0] <<
": invalid argument for option '" <<
opt.shortopt << "'\n";
std::cout << "Type '" << argv[0] <<
" -h' for more information.\n";
return {1, state::handled};
}
catch(missing_arg&)
{
std::cout << argv[0] <<
": option requires and argument '" <<
opt.shortopt << "'\n";
std::cout << "Type '" << argv[0] <<
" -h' for more information.\n";
std::cout << opt.help << "\n";
return {1, state::handled};
}
},
option);
if(ret.second == state::handled && ret.first != 0)
{
return ret.first;
}
was_handled |= ret.second == state::handled;
if(was_handled)
{
break;
}
}
if(!was_handled)
{
std::cout << argv[0] << ": invalid option '" << argv[i] << "'\n";
std::cout << "Type '" << argv[0] << " -h' for more information.\n";
return 1;
}
}
return 0;
}
template<typename T>
void add(const std::string& shortopt,
const std::string& longopt,
std::function<int(T)> cb,
const std::string& help)
{
options.emplace_back(Opt<T>{shortopt, longopt, cb, help});
}
void add(const std::string& shortopt,
const std::string& longopt,
std::function<int()> cb,
const std::string& help)
{
options.emplace_back(Opt<noarg>{shortopt, longopt, cb, help});
}
private:
template<typename T>
T convert(int argc, const char* const argv[], int& i, T)
{
auto opt = convert(argc, argv, i, std::optional<T>{});
if(!opt)
{
throw missing_arg{};
}
return *opt;
}
template<typename T>
std::optional<T> convert(int argc, const char* const argv[], int& i,
std::optional<T>)
{
std::string arg;
bool has_arg{false};
if(i+1 < argc)
{
arg = argv[i+1];
has_arg = !arg.starts_with("-");
if(has_arg)
{
++i;
}
}
if(!has_arg)
{
return {};
}
if constexpr (std::is_same_v<T, int>)
{
return std::stoi(arg);
}
else if constexpr (std::is_same_v<T, double>)
{
return std::stod(arg);
}
else if constexpr (std::is_same_v<T, std::string>)
{
return arg;
}
else
{
static_assert(std::is_same_v<T, void>, "missing");
}
return {};
}
using Opts = std::variant<Opt<noarg>, Opt<Ts>...>;
std::vector<Opts> options;
};
} // arg::
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