parameter.hpp

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// SPDX-FileCopyrightText: 2026 Klaus Reimer <k@ailis.de>
// SPDX-License-Identifier: MIT
 
#pragma once
 
#include <any>
#include <cstddef>
#include <format>
#include <optional>
#include <span>
#include <string>
#include <string_view>
#include <utility>
 
#include <kaycxx/cli/parameter_base.hpp>
#include <kaycxx/cli/parse_error.hpp>
#include <kaycxx/cli/parse_value.hpp>
 
namespace kaycxx::cli {
 
template <parseable_value T>
class parameter : public parameter_base {
public:
    explicit parameter(std::string_view name, std::optional<std::string_view> description = std::nullopt)
        : parameter_base(name, description)
    {}
 
    void default_value(T value) {
        default_value_ = std::move(value);
    }
 
    [[nodiscard]] std::string usage() const override {
        return std::format("<{}>", name());
    }
 
    [[nodiscard]] std::size_t min_count() const noexcept override {
        return default_value_ ? 0 : 1;
    }
 
    [[nodiscard]] std::size_t max_count() const noexcept override {
        return 1;
    }
 
    [[nodiscard]] std::any parse_values(std::span<std::string_view const> values) const override {
        if (values.empty()) {
            if (default_value_) {
                return *default_value_;
            }
 
            throw parse_error(std::format("Missing parameter <{}>", name()));
        }
 
        try {
            return detail::parse_value<T>(values.front());
        } catch (parse_error const& error) {
            throw parse_error(std::format("{} for parameter <{}>", error.what(), name()));
        }
    }
 
private:
    std::optional<T> default_value_;
};
 
} // namespace kaycxx::cli