DatabaseLock.hpp

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/*
 *
 * ---
 *
 *  Copyright (C) 2021 Anselm Schmidt (ans[ät]ohai.su)
 *
 *  This program is free software: you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation, either version 3 of the License, or
 *  (at your option) any later version in addition to the terms of any
 *  licences already herein identified.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program. If not, see <https://www.gnu.org/licenses/>.
 *
 * ---
 *
 * DatabaseLock.hpp
 *
 * Template class for safe in-scope database locks.
 *
 *  Created on: Mar 7, 2019
 *      Author: ans
 */

#ifndef WRAPPER_DATABASELOCK_HPP_
#define WRAPPER_DATABASELOCK_HPP_

#include <functional>   // std::function
#include <string>       // std::string
#include <utility>      // std::move

namespace crawlservpp::Wrapper {


    template<class DB>
    class DatabaseLock {
        // for convenience
        using IsRunningCallback = std::function<bool()>;

    public:



        DatabaseLock(DB& db, const std::string& lockName, IsRunningCallback isRunningCallback)
                : ref(db), name(lockName), locked(false) {
            this->ref.addDatabaseLock(this->name, isRunningCallback);

            this->locked = true;
        }


        virtual ~DatabaseLock() {
            if(this->locked) {
                this->ref.removeDatabaseLock(this->name);

                this->locked = false;
            }
        }



        [[nodiscard]] bool isActive() const noexcept {
            return this->locked;
        }



        DatabaseLock(DatabaseLock&) = delete;

        DatabaseLock& operator=(DatabaseLock&) = delete;


        DatabaseLock(DatabaseLock&& other) noexcept
                : ref(other.ref), name(other.name), locked(other.locked) {
            other.locked = false;
        }


        DatabaseLock& operator=(DatabaseLock&& other) noexcept {
            if(&other != this) {
                if(this->locked) {
                    this->ref.removeDatabaseLock(this->name);

                    this->locked = false;
                }

                this->ref = std::move(other.ref);
                this->name = std::move(other.name);
                this->locked = other.locked;
            }

            return *this;
        }


    private:
        // internal reference to a database connection
        DB& ref;

        // internal lock state
        std::string name;
        bool locked;
    };

} /* namespace crawlservpp::Wrapper */

#endif /* WRAPPER_DATABASELOCK_HPP_ */