/*
 * Copyright Red Hat, Inc. and/or its affiliates
 * and other contributors as indicated by the @author tags and
 * the COPYRIGHT.txt file distributed with this work.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.teiid.dqp.internal.datamgr;

import java.lang.management.ManagementFactory;
import java.lang.management.ThreadMXBean;

import org.teiid.logging.LogConstants;
import org.teiid.logging.LogManager;
import org.teiid.logging.MessageLevel;

/**
 * Timer class that uses the ThreadMXBean for CPU timing
 */
public class ThreadCpuTimer {
	
	private static ThreadMXBean threadMXBean = ManagementFactory.getThreadMXBean();
	private int totalTime = -1;
	private long lastTime = -1;
	private boolean active;
	
	public ThreadCpuTimer() {
		active = threadMXBean.isThreadCpuTimeSupported() 
				&& threadMXBean.isThreadCpuTimeEnabled()
				&& LogManager.isMessageToBeRecorded(LogConstants.CTX_COMMANDLOGGING, MessageLevel.DETAIL);
	}
	
	public void start() {
		if (!active) {
			return;
		}
		try {
			lastTime = threadMXBean.getCurrentThreadCpuTime();
		} catch (UnsupportedOperationException e) {
			inactivate();
		}
		
	}

	private void inactivate() {
		active = false;
		lastTime = -1;
		totalTime = -1;
	}
	
	public long stop() {
		if (!active) {
			return -1;
		}
		if (lastTime != -1) {
			try {
				long time = threadMXBean.getCurrentThreadCpuTime();
				if (time != -1) {
					if (totalTime == -1) {
						totalTime = 0;
					}
					totalTime += (time - lastTime);
				} else {
					inactivate();
				}
			} catch (UnsupportedOperationException e) {
				inactivate();
			}
		}
		lastTime = -1;
		return totalTime;
	}

}
