/*
 * Entagged Audio Tag library
 
 * 
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *  
 * This library 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
 * Lesser General Public License for more details.
 * 
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */
package entagged.audioformats.generic;

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

import entagged.audioformats.AudioFile;
import entagged.audioformats.Tag;
import entagged.audioformats.EncodingInfo;
import entagged.audioformats.exceptions.CannotReadException;

/*
 * This abstract class is the skeleton for tag readers. It handles the creation/closing of
 * the randomaccessfile objects and then call the subclass method getEncodingInfo and getTag.
 * These two method have to be implemented in te subclass.
 * 
 *@author	Raphael Slinckx
 *@version	$Id: AudioFileReader.java,v 1.9 2006/01/17 09:51:29 liree Exp $
 *@since	v0.02
 */
public abstract class AudioFileReader {
	
	/*
	 * Returns the encoding info object associated wih the current File.
	 * The subclass can assume the RAF pointer is at the first byte of the file.
	 * The RandomAccessFile must be kept open after this function, but can point
	 * at any offset in the file.
	 * 
	 * @param raf The RandomAccessFile associtaed with the current file
	 * @exception IOException is thrown when the RandomAccessFile operations throw it (you should never throw them manually)
	 * @exception CannotReadException when an error occured during the parsing of the encoding infos
	 */
	protected abstract EncodingInfo getEncodingInfo( RandomAccessFile raf )  throws CannotReadException, IOException;
	
	/*
	 * Same as above but returns the Tag contained in the file, or a new one.
	 * 
	 * @param raf The RandomAccessFile associted with the current file
	 * @exception IOException is thrown when the RandomAccessFile operations throw it (you should never throw them manually)
	 * @exception CannotReadException when an error occured during the parsing of the tag
	 */
	protected abstract Tag getTag( RandomAccessFile raf )  throws CannotReadException, IOException;
	
	/*
	 * Reads the given file, and return an AudioFile object containing the Tag
	 * and the encoding infos present in the file. If the file has no tag, an
	 * empty one is returned. If the encodinginfo is not valid , an error is thrown.
	 * 
	 * @param f The file to read
	 * @exception CannotReadException If anything went bad during the read of this file 
	 */
	public AudioFile read(File f) throws CannotReadException {
		if (!f.canRead())
			throw new CannotReadException("Can't read file \""+f.getAbsolutePath()+"\"");
		
		if(f.length() <= 150)
			throw new CannotReadException("Less than 150 byte \""+f.getAbsolutePath()+"\"");
		
		RandomAccessFile raf = null;
		try{
			raf = new RandomAccessFile( f, "r" );
			raf.seek( 0 );
			
			EncodingInfo info = getEncodingInfo(raf);
		
			Tag tag;
			try {
				raf.seek( 0 );
				tag = getTag(raf);
			} catch (CannotReadException e) {
				System.err.println(e.getMessage());
				tag = new GenericTag();
			}
		
			return new AudioFile(f, info, tag);
			
		} catch ( Exception e ) {
			throw new CannotReadException("\""+f+"\" :"+e,e);
		}
		finally {
				try{
					if(raf != null)
							raf.close();
				}catch(Exception ex){
					System.err.println("\""+f+"\" :"+ex);
				}
		}
	}
}