package com.tesora.dve.lockmanager;

/*
 * #%L
 * Tesora Inc.
 * Database Virtualization Engine
 * %%
 * Copyright (C) 2011 - 2014 Tesora Inc.
 * %%
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License, version 3,
 * as published by the Free Software Foundation.
 * 
 * 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 Affero General Public License for more details.
 * 
 * You should have received a copy of the GNU Affero General Public License
 * along with this program. If not, see <http://www.gnu.org/licenses/>.
 * #L%
 */

import java.util.LinkedHashMap;

import com.tesora.dve.singleton.Singletons;

// we now acquire table locks (read or exclusive) during parsing, which means we may end up
// acquiring the lock first as exclusive and then as shared - but the cluster lock manager will consider
// the second lock to be blocked.  This class arranges to avoid that.
public class AcquiredLockSet {

	private final LinkedHashMap<LockSpecification,AcquiredLock> acquired;
	
	public AcquiredLockSet() {
		acquired = new LinkedHashMap<LockSpecification,AcquiredLock>();
	}
	
	public void acquire(LockClient conn, LockSpecification ls, LockType lt) {
		AcquiredLock already = acquired.get(ls);
		if (already != null) {
			if (lt.isStrongerThan(already.getType())) {
				getLockManager().release(already);
				already = getLockManager().acquire(conn, ls, lt);
				acquired.put(ls,already);
			}
			return;
		}
		already = getLockManager().acquire(conn, ls, lt);
		acquired.put(ls, already);
	}

    public void release() {
		for(AcquiredLock al : acquired.values())
			getLockManager().release(al);
		acquired.clear();
	}

    protected LockManager getLockManager() {
        return Singletons.lookup(LockManager.class);
    }

}