/*

 * Copyright (c) 2003, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code 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 General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

package sun.management;

import java.lang.management.MemoryUsage;

import java.util.Iterator;

import java.util.Map;

import java.util.HashMap;

/**

 * An abstract sensor.

 *

 * <p>

 * An {@code AbstractSensor} object consists of two attributes:

 * <ul>

 *   <li>{@code on} is a boolean flag indicating if a sensor is

 *       triggered. This flag will be set or cleared by the

 *       component that owns the sensor.</li>

 *   <li>{@code count} is the total number of times that a sensor

 *       has been triggered.</li>

 * </ul>

 *

 * @author  Mandy Chung

 * @since   1.5

 */

public abstract class Sensor {

    private final Object lock = new Object();

    private final String name;

    private long count;                 // VM-initialized to 0

    private boolean on;                 // VM-initialized to false

    /**

     * Constructs a {@code Sensor} object.

     *

     * @param name The name of this sensor.

     */

    public Sensor(String name) {

        this.name = name;

    }

    /**

     * Returns the name of this sensor.

     *

     * @return the name of this sensor.

     */

    public String getName() {

        return name;

    }

    /**

     * Returns the total number of times that this sensor has been triggered.

     *

     * @return the total number of times that this sensor has been triggered.

     */

    public long getCount() {

        synchronized (lock) {

            return count;

        }

    }

    /**

     * Tests if this sensor is currently on.

     *

     * @return {@code true} if the sensor is currently on;

     *         {@code false} otherwise.

     *

     */

    public boolean isOn() {

        synchronized (lock) {

            return on;

        }

    }

    /**

     * Triggers this sensor. This method first sets this sensor on

     * and increments its sensor count.

     */

    public void trigger() {

        synchronized (lock) {

            on = true;

            count++;

        }

        triggerAction();

    }

    /**

     * Triggers this sensor. This method sets this sensor on

     * and increments the count with the input {@code increment}.

     */

    public void trigger(int increment) {

        synchronized (lock) {

            on = true;

            count += increment;

            // Do something here...

        }

        triggerAction();

    }

    /**

     * Triggers this sensor piggybacking a memory usage object.

     * This method sets this sensor on

     * and increments the count with the input {@code increment}.

     */

    public void trigger(int increment, MemoryUsage usage) {

        synchronized (lock) {

            on = true;

            count += increment;

            // Do something here...

        }

        triggerAction(usage);

    }

    /**

     * Clears this sensor.

     */

    public void clear() {

        synchronized (lock) {

            on = false;

        }

        clearAction();

    }

    /**

     * Clears this sensor

     * and increments the count with the input {@code increment}.

     */

    public void clear(int increment) {

        synchronized (lock) {

            on = false;

            count += increment;

        }

        clearAction();

    }

    public String toString() {

        return "Sensor - " + getName() +

            (isOn() ? " on " : " off ") +

            " count = " + getCount();

    }

    abstract void triggerAction();

    abstract void triggerAction(MemoryUsage u);

    abstract void clearAction();

}