/*

 * 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

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 * questions.

 */

package javax.management;

import java.io.IOException;

import java.io.ObjectInputStream;

import java.io.ObjectOutputStream;

import java.io.Serializable;

import java.io.StreamCorruptedException;

import java.util.Objects;

/**

 * <p>Provides general information for an MBean descriptor object.

 * The feature described can be an attribute, an operation, a

 * parameter, or a notification.  Instances of this class are

 * immutable.  Subclasses may be mutable but this is not

 * recommended.</p>

 *

 * @since 1.5

 */

public class MBeanFeatureInfo implements Serializable, DescriptorRead {

    /* Serial version */

    static final long serialVersionUID = 3952882688968447265L;

    /**

     * The name of the feature.  It is recommended that subclasses call

     * {@link #getName} rather than reading this field, and that they

     * not change it.

     *

     * @serial The name of the feature.

     */

    protected String name;

    /**

     * The human-readable description of the feature.  It is

     * recommended that subclasses call {@link #getDescription} rather

     * than reading this field, and that they not change it.

     *

     * @serial The human-readable description of the feature.

     */

    protected String description;

    /**

     * @serial The Descriptor for this MBeanFeatureInfo.  This field

     * can be null, which is equivalent to an empty Descriptor.

     */

    private transient Descriptor descriptor;

    /**

     * Constructs an <CODE>MBeanFeatureInfo</CODE> object.  This

     * constructor is equivalent to {@code MBeanFeatureInfo(name,

     * description, (Descriptor) null}.

     *

     * @param name The name of the feature.

     * @param description A human readable description of the feature.

     */

    public MBeanFeatureInfo(String name, String description) {

        this(name, description, null);

    }

    /**

     * Constructs an <CODE>MBeanFeatureInfo</CODE> object.

     *

     * @param name The name of the feature.

     * @param description A human readable description of the feature.

     * @param descriptor The descriptor for the feature.  This may be null

     * which is equivalent to an empty descriptor.

     *

     * @since 1.6

     */

    public MBeanFeatureInfo(String name, String description,

                            Descriptor descriptor) {

        this.name = name;

        this.description = description;

        this.descriptor = descriptor;

    }

    /**

     * Returns the name of the feature.

     *

     * @return the name of the feature.

     */

    public String getName() {

        return name;

    }

    /**

     * Returns the human-readable description of the feature.

     *

     * @return the human-readable description of the feature.

     */

    public String getDescription() {

        return description;

    }

    /**

     * Returns the descriptor for the feature.  Changing the returned value

     * will have no affect on the original descriptor.

     *

     * @return a descriptor that is either immutable or a copy of the original.

     *

     * @since 1.6

     */

    public Descriptor getDescriptor() {

        return (Descriptor) ImmutableDescriptor.nonNullDescriptor(descriptor).clone();

    }

    /**

     * Compare this MBeanFeatureInfo to another.

     *

     * @param o the object to compare to.

     *

     * @return true if and only if <code>o</code> is an MBeanFeatureInfo such

     * that its {@link #getName()}, {@link #getDescription()}, and

     * {@link #getDescriptor()}

     * values are equal (not necessarily identical) to those of this

     * MBeanFeatureInfo.

     */

    public boolean equals(Object o) {

        if (o == this)

            return true;

        if (!(o instanceof MBeanFeatureInfo))

            return false;

        MBeanFeatureInfo p = (MBeanFeatureInfo) o;

        return (Objects.equals(p.getName(), getName()) &&

                Objects.equals(p.getDescription(), getDescription()) &&

                Objects.equals(p.getDescriptor(), getDescriptor()));

    }

    public int hashCode() {

        return getName().hashCode() ^ getDescription().hashCode() ^

               getDescriptor().hashCode();

    }

    /**

     * Serializes an {@link MBeanFeatureInfo} to an {@link ObjectOutputStream}.

     * @serialData

     * For compatibility reasons, an object of this class is serialized as follows.

     * <p>

     * The method {@link ObjectOutputStream#defaultWriteObject defaultWriteObject()}

     * is called first to serialize the object except the field {@code descriptor}

     * which is declared as transient. The field {@code descriptor} is serialized

     * as follows:

     *     <ul>

     *     <li>If {@code descriptor} is an instance of the class

     *        {@link ImmutableDescriptor}, the method {@link ObjectOutputStream#write

     *        write(int val)} is called to write a byte with the value {@code 1},

     *        then the method {@link ObjectOutputStream#writeObject writeObject(Object obj)}

     *        is called twice to serialize the field names and the field values of the

     *        {@code descriptor}, respectively as a {@code String[]} and an

     *        {@code Object[]};</li>

     *     <li>Otherwise, the method {@link ObjectOutputStream#write write(int val)}

     * is called to write a byte with the value {@code 0}, then the method

     * {@link ObjectOutputStream#writeObject writeObject(Object obj)} is called

     * to serialize directly the field {@code descriptor}.

     *     </ul>

     *

     * @since 1.6

     */

    private void writeObject(ObjectOutputStream out) throws IOException {

        out.defaultWriteObject();

        if (descriptor != null &&

            descriptor.getClass() == ImmutableDescriptor.class) {

            out.write(1);

            final String[] names = descriptor.getFieldNames();

            out.writeObject(names);

            out.writeObject(descriptor.getFieldValues(names));

        } else {

            out.write(0);

            out.writeObject(descriptor);

        }

    }

    /**

     * Deserializes an {@link MBeanFeatureInfo} from an {@link ObjectInputStream}.

     * @serialData

     * For compatibility reasons, an object of this class is deserialized as follows.

     * <p>

     * The method {@link ObjectInputStream#defaultReadObject defaultReadObject()}

     * is called first to deserialize the object except the field

     * {@code descriptor}, which is not serialized in the default way. Then the method

     * {@link ObjectInputStream#read read()} is called to read a byte, the field

     * {@code descriptor} is deserialized according to the value of the byte value:

     *    <ul>

     *    <li>1. The method {@link ObjectInputStream#readObject readObject()}

     *       is called twice to obtain the field names (a {@code String[]}) and

     *       the field values (a {@code Object[]}) of the {@code descriptor}.

     *       The two obtained values then are used to construct

     *       an {@link ImmutableDescriptor} instance for the field

     *       {@code descriptor};</li>

     *    <li>0. The value for the field {@code descriptor} is obtained directly

     *       by calling the method {@link ObjectInputStream#readObject readObject()}.

     *       If the obtained value is null, the field {@code descriptor} is set to

     *       {@link ImmutableDescriptor#EMPTY_DESCRIPTOR EMPTY_DESCRIPTOR};</li>

     *    <li>-1. This means that there is no byte to read and that the object is from

     *       an earlier version of the JMX API. The field {@code descriptor} is set

     *       to {@link ImmutableDescriptor#EMPTY_DESCRIPTOR EMPTY_DESCRIPTOR}</li>

     *    <li>Any other value. A {@link StreamCorruptedException} is thrown.</li>

     *    </ul>

     *

     * @since 1.6

     */

    private void readObject(ObjectInputStream in)

        throws IOException, ClassNotFoundException {

        in.defaultReadObject();

        switch (in.read()) {

        case 1:

            final String[] names = (String[])in.readObject();

            final Object[] values = (Object[]) in.readObject();

            descriptor = (names.length == 0) ?

                ImmutableDescriptor.EMPTY_DESCRIPTOR :

                new ImmutableDescriptor(names, values);

            break;

        case 0:

            descriptor = (Descriptor)in.readObject();

            if (descriptor == null) {

                descriptor = ImmutableDescriptor.EMPTY_DESCRIPTOR;

            }

            break;

        case -1: // from an earlier version of the JMX API

            descriptor = ImmutableDescriptor.EMPTY_DESCRIPTOR;

            break;

        default:

            throw new StreamCorruptedException("Got unexpected byte.");

        }

    }

}