/*
 * 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.kernel.impl.coreapi;

import org.neo4j.graphdb.Entity;
import org.neo4j.graphdb.Lock;
import org.neo4j.graphdb.Node;
import org.neo4j.graphdb.Relationship;
import org.neo4j.kernel.api.KernelTransaction;

/**
 * Manages user-facing locks.
 */
final class EntityLocker {
    private EntityLocker() {}

    static Lock exclusiveLock(KernelTransaction ktx, Entity entity) {
        long id = entity.getId();
        if (entity instanceof Node) {
            ktx.locks().acquireExclusiveNodeLock(id);
            return new CoreAPILock(() -> ktx.locks().releaseExclusiveNodeLock(id));
        } else if (entity instanceof Relationship) {
            ktx.locks().acquireExclusiveRelationshipLock(id);
            return new CoreAPILock(() -> ktx.locks().releaseExclusiveRelationshipLock(id));
        } else {
            throw new UnsupportedOperationException("Only relationships and nodes can be locked.");
        }
    }

    static Lock sharedLock(KernelTransaction ktx, Entity entity) {
        long id = entity.getId();
        if (entity instanceof Node) {
            ktx.locks().acquireSharedNodeLock(id);
            return new CoreAPILock(() -> ktx.locks().releaseSharedNodeLock(id));
        } else if (entity instanceof Relationship) {
            ktx.locks().acquireSharedRelationshipLock(id);
            return new CoreAPILock(() -> ktx.locks().releaseSharedRelationshipLock(id));
        } else {
            throw new UnsupportedOperationException("Only relationships and nodes can be locked.");
        }
    }

    private static class CoreAPILock implements Lock {
        private boolean released;
        private final Runnable release;

        CoreAPILock(Runnable release) {
            this.release = release;
        }

        @Override
        public void release() {
            if (released) {
                throw new IllegalStateException("Already released");
            }
            released = true;
            release.run();
        }
    }
}
