/*
 *  The Sun Project JXTA(TM) Software License
 *  
 *  Copyright (c) 2001-2007 Sun Microsystems, Inc. All rights reserved.
 *  
 *  Redistribution and use in source and binary forms, with or without 
 *  modification, are permitted provided that the following conditions are met:
 *  
 *  1. Redistributions of source code must retain the above copyright notice,
 *     this list of conditions and the following disclaimer.
 *  
 *  2. Redistributions in binary form must reproduce the above copyright notice, 
 *     this list of conditions and the following disclaimer in the documentation 
 *     and/or other materials provided with the distribution.
 *  
 *  3. The end-user documentation included with the redistribution, if any, must 
 *     include the following acknowledgment: "This product includes software 
 *     developed by Sun Microsystems, Inc. for JXTA(TM) technology." 
 *     Alternately, this acknowledgment may appear in the software itself, if 
 *     and wherever such third-party acknowledgments normally appear.
 *  
 *  4. The names "Sun", "Sun Microsystems, Inc.", "JXTA" and "Project JXTA" must 
 *     not be used to endorse or promote products derived from this software 
 *     without prior written permission. For written permission, please contact 
 *     Project JXTA at http://www.jxta.org.
 *  
 *  5. Products derived from this software may not be called "JXTA", nor may 
 *     "JXTA" appear in their name, without prior written permission of Sun.
 *  
 *  THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED WARRANTIES,
 *  INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND 
 *  FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL SUN 
 *  MICROSYSTEMS OR ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, 
 *  INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 
 *  LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, 
 *  OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF 
 *  LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING 
 *  NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, 
 *  EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *  
 *  JXTA is a registered trademark of Sun Microsystems, Inc. in the United 
 *  States and other countries.
 *  
 *  Please see the license information page at :
 *  <http://www.jxta.org/project/www/license.html> for instructions on use of 
 *  the license in source files.
 *  
 *  ====================================================================

 *  This software consists of voluntary contributions made by many individuals 
 *  on behalf of Project JXTA. For more information on Project JXTA, please see 
 *  http://www.jxta.org.
 *  
 *  This license is based on the BSD license adopted by the Apache Foundation. 
 */

package net.jxta.content;

import net.jxta.document.Document;


/**
 * The common container for managing content (arbitrary binary data) within
 * JXTA.  Content consists of:
 * <ul>
 * <li>Content data for the Content in the form of a JXTA
 * {@link net.jxta.document.Document}.</li>
 * <li>A persistent canonical identifier for the Content in the form of a
 * {@link net.jxta.content.ContentID}.</li>
 * <li>An optional ContentID for an associated Content for which this Content is
 * metadata.</li>
 * </ul>
 *
 * @see net.jxta.content.ContentID
 * @see net.jxta.document.Document
 */
public class Content {

    /**
     * ContentID of this Content instance. A persistent canonical identifier
     * for this Content instance.
     */
    private final ContentID id;

    /**
     * ContentID for an associated Content instance for which this Content
     * instance is metadata.  This may be the ContentId of another Content
     * instance in the same Peer Group or <tt>null</tt>.
     */
    private final ContentID metaId;

    /**
     * Contains the data of this Content instance.
     */
    private final Document doc;

    /**
     * Constructs a Content instance for a existing Content given it's
     * ContentID and a document.
     * <p/>
     * <p/>This implementation does not verify that the ContentID matches the
     * provided Document.
     *
     * @param id       ContentId of the new Content
     * @param about    ContentID of an associated Content for which this
     *  Content is metadata.
     * @param document Document which contains the data for this Content
     */
    public Content(ContentID id, ContentID about, Document document) {
        if (null == id) {
            throw new IllegalArgumentException("ContentID may not be null.");
        }

        if (null == document) {
            throw new IllegalArgumentException("Document may not be null.");
        }

        this.id = id;
        this.metaId = about;
        this.doc = document;
    }

    /**
     * Returns the ContentID of this Content instance.
     *
     * @return ContentID of this Content instance
     */
    public ContentID getContentID() {
        return id;
    }

    /**
     * Returns the ContentID of an associated Content for which this
     * Content is metadata or <tt>null</tt> if there is no associated
     * Content.
     *
     * @return ContentID The ContentID of an associated Content for which this
     *  Content is metadata or <tt>null</tt> if there is no associated Content
     */
    public ContentID getMetaID() {
        return metaId;
    }

    /**
     * Returns a Document containing the data of this Content instance.
     *
     * @return A Document containing the data of this Content instance
     */
    public Document getDocument() {
        return doc;
    }
}