package com.renxo.cms.util;

import java.io.Serializable;
import java.util.concurrent.locks.Lock;

import org.jgroups.JChannel;
import org.jgroups.blocks.locking.LockService;

/**
 * A <code>LockManager</code> implementation for distributed environments based
 * on JGroups' {@link LockService}.
 * 
 * @param <K>
 *            the type of the lock key.
 */
public class DistributedJGroupsLockManager<K extends Serializable> extends
		AbstractJdkLockManager<K> {

	// ----------------------------------------------------------------------
	// Constants
	// ----------------------------------------------------------------------

	private static final long DEFAULT_TRY_LOCK_TIMEOUT = 5 * 1000L;

	// ----------------------------------------------------------------------
	// Fields
	// ----------------------------------------------------------------------

	private String configurationFile;

	private String locksGroupsName = "locks";

	private JChannel jChannel;

	private LockService lockService;

	// ----------------------------------------------------------------------
	// Setters for IoC
	// ----------------------------------------------------------------------

	/**
	 * Sets the JGroups configuration file to use. A locking protocol should be
	 * configured towards the top of the stack.
	 * 
	 * @param configurationFile
	 *            the JGroups configuration file to set.
	 * @see LockService
	 */
	public void setConfigurationFile(String configurationFile) {
		this.configurationFile = configurationFile;
	}

	/**
	 * Configures the locks group name. This will be used as the JChannel
	 * cluster name. Default is <code>locks</code>.
	 * 
	 * @param locksGroupsName
	 *            the locks group name to set.
	 */
	public void setLocksGroupsName(String locksGroupsName) {
		this.locksGroupsName = locksGroupsName;
	}

	// ----------------------------------------------------------------------
	// AbstractJdkLockManager implementations
	// ----------------------------------------------------------------------

	@Override
	protected Lock getLock(K key) {
		return lockService.getLock(String.valueOf(key));
	}

	@Override
	protected long defaultTryLockTimeout() {
		return DEFAULT_TRY_LOCK_TIMEOUT;
	}

	// ----------------------------------------------------------------------
	// Lifecycle methods
	// ----------------------------------------------------------------------

	/**
	 * Initializes the JChannel.
	 * 
	 * @throws Exception
	 *             if the JChannel cannot be initialized.
	 */
	public void init() throws Exception {

		jChannel = new JChannel(configurationFile);
		jChannel.connect(locksGroupsName);
		lockService = new LockService(jChannel);
	}

	/**
	 * Shuts down the JChannel.
	 */
	public void shutdown() {

		if (jChannel != null && jChannel.isConnected()) {
			jChannel.close();
		}
	}
}