/*-
 * See the file LICENSE for redistribution information.
 *
 * Copyright (c) 2002,2008 Oracle.  All rights reserved.
 *
 * $Id: LockInfo.java,v 1.36 2008/06/10 02:52:14 cwl Exp $
 */

package com.sleepycat.je.txn;

import java.util.Collections;
import java.util.Map;
import java.util.WeakHashMap;

import com.sleepycat.je.utilint.Tracer;

/**
 * LockInfo is a class that embodies information about a lock instance.  The
 * holding thread and the locktype are all contained in the object.
 *
 * This class is public for unit tests.
 */
public class LockInfo implements Cloneable {
    protected Locker locker;
    protected LockType lockType;

    private static boolean deadlockStackTrace = false;
    private static Map<LockInfo, StackTraceAtLockTime> traceExceptionMap =
        Collections.synchronizedMap(new WeakHashMap<LockInfo, 
                                    StackTraceAtLockTime>());
    @SuppressWarnings("serial")
    private static class StackTraceAtLockTime extends Exception {}

    /**
     * Called when the je.txn.deadlockStackTrace property is changed.
     */
    static void setDeadlockStackTrace(boolean enable) {
        deadlockStackTrace = enable;
    }

    /**
     * For unit testing only.
     */
    public static boolean getDeadlockStackTrace() {
        return deadlockStackTrace;
    }

    /**
     * Construct a new LockInfo.  public for Sizeof program.
     */
    public LockInfo(Locker locker, LockType lockType) {
	this.locker = locker;
	this.lockType = lockType;

        if (deadlockStackTrace) {
            traceExceptionMap.put(this, new StackTraceAtLockTime());
        }
    }

    /**
     * Change this lockInfo over to the prescribed locker.
     */
    void setLocker(Locker locker) {
	this.locker = locker;
    }

    /**
     * @return The transaction associated with this Lock.
     */
    Locker getLocker() {
	return locker;
    }

    /**
     * @return The LockType associated with this Lock.
     */
    void setLockType(LockType lockType) {
	this.lockType = lockType;
    }

    /**
     * @return The LockType associated with this Lock.
     */
    LockType getLockType() {
	return lockType;
    }

    @Override
    public Object clone()
        throws CloneNotSupportedException {

        return super.clone();
    }

    /**
     * Debugging
     */
    public void dump() {
	System.out.println(this);
    }

    @Override
    public String toString() {
        StringBuffer buf = new StringBuffer(500);

        buf.append("<LockInfo locker=\"");
        buf.append(locker);
        buf.append("\" type=\"");
        buf.append(lockType);
        buf.append("\"/>");

        if (deadlockStackTrace) {
            Exception traceException = traceExceptionMap.get(this);
            if (traceException != null) {
                buf.append(" lock taken at: ");
                buf.append(Tracer.getStackTrace(traceException));
            }
        }

        return buf.toString();
    }
}
