package org.farng.mp3.id3;

import java.io.IOException;
import java.io.RandomAccessFile;

import org.farng.mp3.InvalidTagException;
import org.farng.mp3.object.ObjectStringFixedLength;
import org.farng.mp3.object.ObjectStringNullTerminated;
import org.farng.mp3.object.ObjectStringSizeTerminated;

/**
 * <h3>4.20.   Linked information</h3>
 * <p/>
 * <p>   To keep information duplication as low as possible this frame may be<br>    used to link
 * information from another ID3v2 tag that might reside in<br>    another audio file or alone in a binary
 * file. It is RECOMMENDED that<br>
 * <p/>
 *    this method is only used when the files are stored on a CD-ROM or<br>    other circumstances
 * when the risk of file separation is low. The<br>    frame contains a frame identifier, which is the frame
 * that should be<br>    linked into this tag, a URL [URL] field, where a reference to the<br>   
 * file where the frame is given, and additional ID data, if needed.<br>
 * <p/>
 *    Data should be retrieved from the first tag found in the file to<br>    which this link
 * points. There may be more than one "LINK" frame in a<br>    tag, but only one with the same
 * contents. A linked frame is to be<br>    considered as part of the tag and has the same restrictions as if
 * it<br>
 * <p/>
 *    was a physical part of the tag (i.e. only one "RVRB" frame allowed,<br>    whether
 * it's linked or not).</p>
 * <p/>
 * <p>     <Header for 'Linked information', ID: "LINK"><br>
 * <p/>
 *      Frame identifier        $xx xx xx xx<br>
 *      URL                    
 * <text string> $00<br>      ID and additional data  <text string(s)></p>
 * <p/>
 * <p>   Frames that may be linked and need no additional data are "ASPI",<br>   
 * "ETCO", "EQU2", "MCID", "MLLT", "OWNE", "RVA2",
 * "RVRB", "SYTC", the<br>
 * <p/>
 *    text information frames and the URL link frames.</p>
 * <p/>
 * <p>   The "AENC", "APIC", "GEOB" and "TXXX" frames may be linked
 * with<br>
 * <p/>
 *    the content descriptor as additional ID data.</p>
 * <p/>
 * <p>   The "USER" frame may be linked with the language field as additional<br>    ID
 * data.<br>    </p>
 * <p/>
 * <p>   The "PRIV" frame may be linked with the owner identifier as<br>    additional ID
 * data.</p>
 * <p/>
 * <p>   The "COMM", "SYLT" and "USLT"
 * <p/>
 * frames may be linked with three bytes<br>    of language descriptor directly followed by a content
 * descriptor as<br>    additional ID data.<br> </p>
 *
 * @author Eric Farng
 * @version $Revision: 2374 $
 */
public class FrameBodyLINK extends AbstractID3v2FrameBody {

    /**
     * Creates a new FrameBodyLINK object.
     */
    public FrameBodyLINK() {
        super();
    }

    /**
     * Creates a new FrameBodyLINK object.
     */
    public FrameBodyLINK(final FrameBodyLINK body) {
        super(body);
    }

    /**
     * Creates a new FrameBodyLINK object.
     */
    public FrameBodyLINK(final String frameIdentifier, final String url, final String additionalData) {
        setObject("Frame Identifier", frameIdentifier);
        setObject("URL", url);
        setObject("ID and Additional Data", additionalData);
    }

    /**
     * Creates a new FrameBodyLINK object.
     */
    public FrameBodyLINK(final RandomAccessFile file) throws IOException, InvalidTagException {
        this.read(file);
    }

    public String getAdditionalData() {
        return (String) getObject("ID and Additional Data");
    }

    public void getAdditionalData(final String additionalData) {
        setObject("ID and Additional Data", additionalData);
    }

    public String getFrameIdentifier() {
        return (String) getObject("Frame Identifier");
    }

    public void getFrameIdentifier(final String frameIdentifier) {
        setObject("Frame Identifier", frameIdentifier);
    }

    public String getIdentifier() {
        return "LINK" + ((char) 0) + getFrameIdentifier() + ((char) 0) + getAdditionalData();
    }

    protected void setupObjectList() {
        appendToObjectList(new ObjectStringFixedLength("Frame Identifier", 4));
        appendToObjectList(new ObjectStringNullTerminated("URL"));
        appendToObjectList(new ObjectStringSizeTerminated("ID and Additional Data"));
    }
}