/*
 * Copyright (c) "Neo4j"
 * Neo4j Sweden AB [http://neo4j.com]
 *
 * This file is part of Neo4j.
 *
 * Neo4j 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.
 *
 * 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 <http://www.gnu.org/licenses/>.
 */
package org.neo4j.capabilities;

import java.util.Objects;
import java.util.function.Supplier;

final class CapabilityInstance<T> {
    private final Capability<T> capability;
    private volatile Supplier<T> value;

    CapabilityInstance(Capability<T> capability) {
        this.capability = Objects.requireNonNull(capability);
        this.value = null;
    }

    Capability<T> capability() {
        return capability;
    }

    T get() {
        var localValue = value;
        if (localValue == null) {
            return null;
        }
        return localValue.get();
    }

    void set(T value) {
        this.value = () -> value;
    }

    void supply(Supplier<T> value) {
        this.value = value;
    }
}
