package org.jaudiotagger.audio.flac;

 import org.jaudiotagger.audio.exceptions.CannotReadException;

 import org.jaudiotagger.logging.ErrorMessage;

 import org.jaudiotagger.tag.id3.AbstractID3v2Tag;

 import org.jaudiotagger.tag.id3.ID3v22Tag;

 import org.jaudiotagger.tag.id3.ID3v23Tag;

 import org.jaudiotagger.tag.id3.ID3v24Tag;

 import java.io.IOException;

 import java.io.RandomAccessFile;

 import java.nio.ByteBuffer;

 /**

  * Flac Stream

  * <p/>

  * Reader files and identifies if this is in fact a flac stream

  */

 public class FlacStreamReader

 {

     public static final int FLAC_STREAM_IDENTIFIER_LENGTH = 4;

     public static final String FLAC_STREAM_IDENTIFIER = "fLaC";

     private RandomAccessFile raf;

     private int startOfFlacInFile;

     /**

      * Create instance for holding stream info

      * @param raf

      */

     public FlacStreamReader(RandomAccessFile raf)

     {

         this.raf = raf;

     }

     /**

      * Reads the stream block to ensure it is a flac file

      *

      * @throws IOException

      * @throws CannotReadException

      */

     public void findStream() throws IOException, CannotReadException

     {

         //Begins tag parsing

         if (raf.length() == 0)

         {

             //Empty File

             throw new CannotReadException("Error: File empty");

         }

         raf.seek(0);

         //FLAC Stream at start

         if (isFlacHeader())

         {

             startOfFlacInFile = 0;

             return;

         }

         //Ok maybe there is an ID3v24tag first

         if (isId3v24Tag())

         {

             startOfFlacInFile = (int) (raf.getFilePointer() - FLAC_STREAM_IDENTIFIER_LENGTH);

             return;

         }

         //Ok maybe there is an ID3v23tag first

         if (isId3v23Tag())

         {

             startOfFlacInFile = (int) (raf.getFilePointer() - FLAC_STREAM_IDENTIFIER_LENGTH);

             return;

         }

         //Ok maybe there is an ID3v22tag first

         if (isId3v22Tag())

         {

             startOfFlacInFile = (int) (raf.getFilePointer() - FLAC_STREAM_IDENTIFIER_LENGTH);

             return;

         }

         throw new CannotReadException(ErrorMessage.FLAC_NO_FLAC_HEADER_FOUND.getMsg());

     }

     private boolean isId3v24Tag() throws IOException

     {

         int id3tagsize;

         ID3v24Tag id3tag = new ID3v24Tag();

         ByteBuffer bb = ByteBuffer.allocate(AbstractID3v2Tag.TAG_HEADER_LENGTH);

         raf.seek(0);

         raf.getChannel().read(bb);

         if (id3tag.seek(bb))

         {

             id3tagsize = id3tag.readSize(bb);

             raf.seek(id3tagsize);

             //FLAC Stream immediately after end of id3 tag

             if (isFlacHeader())

             {

                 return true;

             }

         }

         return false;

     }

     private boolean isId3v23Tag() throws IOException

     {

         int id3tagsize;

         ID3v23Tag id3tag = new ID3v23Tag();

         ByteBuffer bb = ByteBuffer.allocate(AbstractID3v2Tag.TAG_HEADER_LENGTH);

         raf.seek(0);

         raf.getChannel().read(bb);

         if (id3tag.seek(bb))

         {

             id3tagsize = id3tag.readSize(bb);

             raf.seek(id3tagsize);

             //FLAC Stream immediately after end of id3 tag

             if (isFlacHeader())

             {

                 return true;

             }

         }

         return false;

     }

     private boolean isId3v22Tag() throws IOException

     {

         int id3tagsize;

         ID3v22Tag id3tag = new ID3v22Tag();

         ByteBuffer bb = ByteBuffer.allocate(AbstractID3v2Tag.TAG_HEADER_LENGTH);

         raf.seek(0);

         raf.getChannel().read(bb);

         if (id3tag.seek(bb))

         {

             id3tagsize = id3tag.readSize(bb);

             raf.seek(id3tagsize);

             //FLAC Stream immediately after end of id3 tag

             if (isFlacHeader())

             {

                 return true;

             }

         }

         return false;

     }

     private boolean isFlacHeader() throws IOException

     {

         //FLAC Stream at start

         byte[] b = new byte[FLAC_STREAM_IDENTIFIER_LENGTH];

         raf.read(b);

         String flac = new String(b);

         return flac.equals(FLAC_STREAM_IDENTIFIER);

     }

     /**

      * Usually flac header is at start of file, but unofficially and ID3 tag is allowed at the start of the file.

      *

      * @return the start of the Flac within file

      */

     public int getStartOfFlacInFile()

     {

         return startOfFlacInFile;

     }

 }