/*

  * Entagged Audio Tag library

  * Copyright (c) 2003-2005 Rapha�l Slinckx <raphael@slinckx.net>

  * 

  * 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 org.jaudiotagger.audio.mp4.atom;

 import org.jaudiotagger.audio.generic.Utils;

 import org.jaudiotagger.audio.exceptions.NullBoxIdException;

 import org.jaudiotagger.audio.exceptions.InvalidBoxHeaderException;

 import org.jaudiotagger.logging.ErrorMessage;

 import java.io.IOException;

 import java.io.RandomAccessFile;

 import java.io.UnsupportedEncodingException;

 import java.nio.ByteBuffer;

 import java.util.logging.Logger;

 /**

  * Everything in MP4s are held in boxes (formally known as atoms), they are held as a hierachial tree within the MP4.

  * <p/>

  * We are most interested in boxes that are used to hold metadata, but we have to know about some other boxes

  * as well in order to find them.

  * <p/>

  * All boxes consist of a 4 byte box length (big Endian), and then a 4 byte identifier, this is the header

  * which is model in this class.

  * <p/>

  * The length includes the length of the box including the identifier and the length itself.

  * Then they may contain data and/or sub boxes, if they contain subboxes they are known as a parent box. Parent boxes

  * shouldn't really contain data, but sometimes they do.

  * <p/>

  * Parent boxes length includes the length of their immediate sub boxes

  * <p/>

  * This class is normally used by instantiating with the empty constructor, then use the update method

  * to pass the header data which is used to read the identifier and the the size of the box

  */

 public class Mp4BoxHeader

 {

     // Logger Object

     public static Logger logger = Logger.getLogger("org.jaudiotagger.audio.mp4.atom");

     public static final int OFFSET_POS = 0;

     public static final int IDENTIFIER_POS = 4;

     public static final int OFFSET_LENGTH = 4;

     public static final int IDENTIFIER_LENGTH = 4;

     public static final int HEADER_LENGTH = OFFSET_LENGTH + IDENTIFIER_LENGTH;

     //Box identifier

     private String id;

     //Box length

     protected int length;

     //If reading from file , this can be used to hold the headers position in the file

     private long filePos;

     //Raw Header data

     protected ByteBuffer dataBuffer;

     //Mp4 uses UTF-8 for all text

     public static final String CHARSET_UTF_8 = "UTF-8";

     /**

      * Construct empty header

      * <p/>

      * Can be populated later with update method

      */

     public Mp4BoxHeader()

     {

     }

      /**

      * Construct header to allow manual creation of header for writing to file

      * <p/>

      */

     public Mp4BoxHeader(String id)

     {

         if(id.length()!=IDENTIFIER_LENGTH)

         {

             throw new RuntimeException("Invalid length:atom idenifier should always be 4 characters long");

         }

         dataBuffer = ByteBuffer.allocate(HEADER_LENGTH);

         try

         {

             this.id    = id;

             dataBuffer.put(4, id.getBytes("ISO-8859-1")[0]);

             dataBuffer.put(5, id.getBytes("ISO-8859-1")[1]);

             dataBuffer.put(6, id.getBytes("ISO-8859-1")[2]);

             dataBuffer.put(7, id.getBytes("ISO-8859-1")[3]);

         }

         catch(UnsupportedEncodingException uee)

         {

             //Should never happen

             throw new RuntimeException(uee);

         }

     }

     /**

      * Construct header

      * <p/>

      * Create header using headerdata, expected to find header at headerdata current position

      * <p/>

      * Note after processing adjusts position to immediately after header

      *

      * @param headerData

      */

     public Mp4BoxHeader(ByteBuffer headerData)

     {

         update(headerData);

     }

     /**

      * Create header using headerdata, expected to find header at headerdata current position

      * <p/>

      * Note after processing adjusts position to immediately after header

      *

      * @param headerData

      */

     public void update(ByteBuffer headerData)

     {

         //Read header data into byte array

         byte[] b = new byte[HEADER_LENGTH];

         headerData.get(b);

         //Keep reference to copy of RawData

         dataBuffer = ByteBuffer.wrap(b);

         //Calculate box size

         this.length = Utils.getIntBE(b, OFFSET_POS, OFFSET_LENGTH - 1);

         //Calculate box id

         this.id = Utils.getString(b, IDENTIFIER_POS, IDENTIFIER_LENGTH, "ISO-8859-1");

         logger.finest("Mp4BoxHeader id:"+id+":length:"+length);

         if (id.equals("\0\0\0\0"))

         {

             throw new NullBoxIdException(ErrorMessage.MP4_UNABLE_TO_FIND_NEXT_ATOM_BECAUSE_IDENTIFIER_IS_INVALID.getMsg(id));

         }

         if(length<HEADER_LENGTH)

         {

             throw new InvalidBoxHeaderException(ErrorMessage.MP4_UNABLE_TO_FIND_NEXT_ATOM_BECAUSE_IDENTIFIER_IS_INVALID.getMsg(id,length));

         }

     }

     /**

      * @return the box identifier

      */

     public String getId()

     {

         return id;

     }

     /**

      * @return the length of the boxes data (includes the header size)

      */

     public int getLength()

     {

         return length;

     }

     /**

      * Set the length.

      * <p/>

      * This will modify the databuffer accordingly

      *

      * @param length

      */

     public void setLength(int length)

     {

         byte[] headerSize = Utils.getSizeBEInt32(length);

         dataBuffer.put(0, headerSize[0]);

         dataBuffer.put(1, headerSize[1]);

         dataBuffer.put(2, headerSize[2]);

         dataBuffer.put(3, headerSize[3]);

         this.length = length;

     }

     /**

      * Set the Id.

      * <p/>

      * Allows you to manully create a header

      * This will modify the databuffer accordingly

      *

      * @param length

      */

     public void setId(int length)

     {

         byte[] headerSize = Utils.getSizeBEInt32(length);

         dataBuffer.put(5, headerSize[0]);

         dataBuffer.put(6, headerSize[1]);

         dataBuffer.put(7, headerSize[2]);

         dataBuffer.put(8, headerSize[3]);

         this.length = length;

     }

     /**

      * @return the 8 byte header buffer

      */

     public ByteBuffer getHeaderData()

     {

         dataBuffer.rewind();

         return dataBuffer;

     }

     /**

      * @return the length of the data only (does not include the header size)

      */

     public int getDataLength()

     {

         return length - HEADER_LENGTH;

     }

     public String toString()

     {

         return "Box " + id + ":length" + length + ":filepos:" + filePos;

     }

     /**

      * @return UTF_8 (always used by Mp4)

      */

     public String getEncoding()

     {

         return CHARSET_UTF_8;

     }

     /**

      * Seek for box with the specified id starting from the current location of filepointer,

      * <p/>

      * Note it wont find the box if it is contained with a level below the current level, nor if we are

      * at a parent atom that also contains data and we havent yet processed the data. It will work

      * if we are at the start of a child box even if it not the required box as long as the box we are

      * looking for is the same level (or the level above in some cases).

      *

      * @param raf

      * @param id

      * @throws java.io.IOException

      */

     public static Mp4BoxHeader seekWithinLevel(RandomAccessFile raf, String id) throws IOException

     {

         logger.finer("Started searching for:" + id + " in file at:" + raf.getChannel().position());

         Mp4BoxHeader boxHeader = new Mp4BoxHeader();

         ByteBuffer headerBuffer = ByteBuffer.allocate(HEADER_LENGTH);

         int bytesRead = raf.getChannel().read(headerBuffer);

         if (bytesRead != HEADER_LENGTH)

         {

             return null;

         }

         headerBuffer.rewind();

         boxHeader.update(headerBuffer);

         while (!boxHeader.getId().equals(id))

         {

             logger.finer("Found:" + boxHeader.getId() + " Still searching for:" + id + " in file at:" + raf.getChannel().position());

             //Something gone wrong probably not at the start of an atom so return null;

             if (boxHeader.getLength() < Mp4BoxHeader.HEADER_LENGTH)

             {

                 return null;

             }

             int noOfBytesSkipped = raf.skipBytes(boxHeader.getDataLength());

             logger.finer("Skipped:" + noOfBytesSkipped);

             if (noOfBytesSkipped < boxHeader.getDataLength())

             {

                 return null;

             }

             headerBuffer.rewind();

             bytesRead = raf.getChannel().read(headerBuffer);

             logger.finer("Header Bytes Read:" + bytesRead);

             headerBuffer.rewind();

             if (bytesRead == Mp4BoxHeader.HEADER_LENGTH)

             {

                 boxHeader.update(headerBuffer);

             }

             else

             {

                 return null;

             }

         }

         return boxHeader;

     }

     /**

      * Seek for box with the specified id starting from the current location of filepointer,

      * <p/>

      * Note it won't find the box if it is contained with a level below the current level, nor if we are

      * at a parent atom that also contains data and we havent yet processed the data. It will work

      * if we are at the start of a child box even if it not the required box as long as the box we are

      * looking for is the same level (or the level above in some cases).

      *

      * @param data

      * @param id

      * @throws java.io.IOException

      */

     public static Mp4BoxHeader seekWithinLevel(ByteBuffer data, String id) throws IOException

     {

         logger.finer("Started searching for:" + id + " in bytebuffer at" + data.position());

         Mp4BoxHeader boxHeader = new Mp4BoxHeader();

         if (data.remaining() >= Mp4BoxHeader.HEADER_LENGTH)

         {

             boxHeader.update(data);

         }

         else

         {

             return null;

         }

         while (!boxHeader.getId().equals(id))

         {

             logger.finer("Found:" + boxHeader.getId() + " Still searching for:" + id + " in bytebuffer at" + data.position());

             //Something gone wrong probably not at the start of an atom so return null;

             if (boxHeader.getLength() < Mp4BoxHeader.HEADER_LENGTH)

             {

                 return null;

             }

             if(data.remaining()<(boxHeader.getLength() - HEADER_LENGTH))

             {

                 //i.e Could happen if Moov header had size incorrectly recorded

                 return null;    

             }

             data.position(data.position() + (boxHeader.getLength() - HEADER_LENGTH));

             if (data.remaining() >= Mp4BoxHeader.HEADER_LENGTH)

             {

                 boxHeader.update(data);

             }

             else

             {

                 return null;

             }

         }

         logger.finer("Found:" + id + " in bytebuffer at" + data.position());

         return boxHeader;

     }

     /**

      * @return location in file of the start of file header (i.e where the 4 byte length field starts)

      */

     public long getFilePos()

     {

         return filePos;

     }

     /**

      * Set location in file of the start of file header (i.e where the 4 byte length field starts)

      *

      * @param filePos

      */

     public void setFilePos(long filePos)

     {

         this.filePos = filePos;

     }

 }