program_intro.hpp

// Copyright (C) 2022 by Camden Mannett.
// Distributed under the Boost Software License, Version 1.0.
// (See accompanying file LICENSE or copy at https://www.boost.org/LICENSE_1_0.txt)
 
#pragma once
 
#include "arg_router/policy/policy.hpp"
 
namespace arg_router::policy
{
template <typename S>
class program_intro_t
{
public:
    using string_type = S;
 
    constexpr explicit program_intro_t([[maybe_unused]] S str = {}) noexcept {}
 
    [[nodiscard]] constexpr static std::string_view program_intro() noexcept { return S::get(); }
 
private:
    static_assert(utility::utf8::count(program_intro()) > 1,
                  "Program intro must be longer than one character");
};
 
template <typename S>
constexpr auto program_intro = program_intro_t<S>{};
 
template <typename S>
struct is_policy<program_intro_t<S>> : std::true_type {
};
}  // namespace arg_router::policy