/**
 * This file Copyright (c) 2011-2012 Magnolia International
 * Ltd.  (http://www.magnolia-cms.com). All rights reserved.
 *
 *
 * This file is dual-licensed under both the Magnolia
 * Network Agreement and the GNU General Public License.
 * You may elect to use one or the other of these licenses.
 *
 * This file is distributed in the hope that it will be
 * useful, but AS-IS and WITHOUT ANY WARRANTY; without even the
 * implied warranty of MERCHANTABILITY or FITNESS FOR A
 * PARTICULAR PURPOSE, TITLE, or NONINFRINGEMENT.
 * Redistribution, except as permitted by whichever of the GPL
 * or MNA you select, is prohibited.
 *
 * 1. For the GPL license (GPL), you can redistribute and/or
 * modify this file under the terms of the GNU General
 * Public License, Version 3, as published by the Free Software
 * Foundation.  You should have received a copy of the GNU
 * General Public License, Version 3 along with this program;
 * if not, write to the Free Software Foundation, Inc., 51
 * Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * 2. For the Magnolia Network Agreement (MNA), this file
 * and the accompanying materials are made available under the
 * terms of the MNA which accompanies this distribution, and
 * is available at http://www.magnolia-cms.com/mna.html
 *
 * Any modifications to this file must keep this entire header
 * intact.
 *
 */
package info.magnolia.module;

import com.google.inject.ProvisionException;

import javax.inject.Inject;
import javax.inject.Provider;

/**
 * Provider for the module instance of a module.
 *
 * @param <T> the type of the module class
 * @version $Id$
 */
public class ModuleInstanceProvider<T> implements Provider<T> {

    @Inject
    private ModuleRegistry moduleRegistry;
    public String moduleName;

    public ModuleInstanceProvider(String moduleName) {
        this.moduleName = moduleName;
    }

    @Override
    @SuppressWarnings("unchecked")
    public synchronized T get() {
        T moduleInstance = (T) moduleRegistry.getModuleInstance(moduleName);
        if (moduleInstance == null) {
            throw new ProvisionException(
                    "Module instance for module [" + moduleName + "] not available, most likely because the module has not yet been started. " +
                    "Inject a Provider<> instead to get access to the module instance when it's available.");
        }
        return moduleInstance;
    }
}