/*
 * Copyright (C) 2019-present ScyllaDB
 */

/*
 * SPDX-License-Identifier: LicenseRef-ScyllaDB-Source-Available-1.1
 */

#pragma once

#include <seastar/core/semaphore.hh>
#include <seastar/core/shared_ptr.hh>

class service_permit {
    seastar::lw_shared_ptr<seastar::semaphore_units<>> _permit;
    service_permit(seastar::semaphore_units<>&& u) : _permit(seastar::make_lw_shared<seastar::semaphore_units<>>(std::move(u))) {}
    friend service_permit make_service_permit(seastar::semaphore_units<>&& permit);
    friend service_permit empty_service_permit();
public:
    size_t count() const { return _permit ? _permit->count() : 0; };
    // Merge additional semaphore units into this permit.
    // Used to grow the permit after the actual resource cost is known.
    void adopt(seastar::semaphore_units<>&& units) {
        if (_permit) {
            _permit->adopt(std::move(units));
        }
    }
};

inline service_permit make_service_permit(seastar::semaphore_units<>&& permit) {
    return service_permit(std::move(permit));
}

inline service_permit empty_service_permit() {
    return make_service_permit(seastar::semaphore_units<>());
}