libcruft-util/cruft/util/registrar.hpp

/*
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/.
 *
 * Copyright 2019 Danny Robson <danny@nerdcruft.net>
 */

#pragma once

#include "log/log.hpp"
#include "introspection/name.hpp"

#include <map>
#include <stdexcept>

namespace cruft {
    template <typename KeyT, typename FactoryT>
    class registry {
    public:
        struct cookie {
        private:
            KeyT m_key;

        public:
            explicit cookie (KeyT const &_key)
                : m_key (_key)
            { ; }

            explicit cookie (KeyT &&_key)
                : m_key (std::move (_key))
            { ; }

            cookie (cookie &&rhs) noexcept
                : m_key (std::move (rhs.m_key))
            { ; }

            cookie& operator= (cookie &&rhs) noexcept
            {
                std::swap (rhs.m_key, m_key);
                return *this;
            }

            cookie (cookie const&) = delete;
            cookie& operator= (cookie const&) = delete;

            ~cookie ()
            {
                try {
                    registry::remove (m_key);
                } catch (std::exception const &err) {
                    LOG_ERROR ("Unable to remove registration for {}", m_key);
                }
            }
        };


        static cookie
        add [[nodiscard]] (KeyT key, FactoryT &&factory)
        {
            auto const &[pos, success] = store ().insert (
                { key, std::move (factory) }
            );

            if (success) {
                LOG_INFO (
                    "Registered {} for {}",
                    key,
                    cruft::introspection::name::full<FactoryT> ()
                );
                return cookie { key };
            } {
                LOG_ERROR (
                    "Unable to register {} for {}",
                    key,
                    cruft::introspection::name::full<FactoryT> ()
                );
                throw std::runtime_error ("Unable to register type");
            }
        }


        static FactoryT remove (KeyT const &key)
        {
            auto &s_factory = store ();

            auto pos = s_factory.find (key);
            if (pos == s_factory.cend ())
                throw std::invalid_argument ("Key not found");

            auto val = s_factory.extract (pos);
            return std::move (val.mapped ());
        }


        static FactoryT& at (KeyT const &key)
        {
            return store ().at (key);
        }

    private:
        static auto&
        store (void)
        {
            static std::map<KeyT,FactoryT> s_factory;
            return s_factory;
        }
    };
}