/**

  *  @author : Paul Taylor

  *

  *  Version @version:$Id: MP3AudioHeader.java 836 2009-11-12 15:44:07Z paultaylor $

  *

  *  MusicTag Copyright (C)2003,2004

  *

  *  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,

  *  you can get a copy from http://www.opensource.org/licenses/lgpl-license.php or write to the Free Software

  *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA

  */

 package org.jaudiotagger.audio.mp3;

 import org.jaudiotagger.audio.AudioHeader;

 import org.jaudiotagger.audio.exceptions.InvalidAudioFrameException;

 import org.jaudiotagger.logging.Hex;

 import java.io.EOFException;

 import java.io.File;

 import java.io.FileInputStream;

 import java.io.IOException;

 import java.nio.ByteBuffer;

 import java.nio.channels.FileChannel;

 import java.text.ParseException;

 import java.text.SimpleDateFormat;

 import java.util.Date;

 import java.util.Locale;

 import java.util.logging.Level;

 import java.util.logging.Logger;

 /**

  * Represents the audio header of an MP3 File

  * <p/>

  * <p>The audio header consists of a number of

  * audio frames. Because we are not trying to play the audio but only extract some information

  * regarding the audio we only need to read the first  audio frames to ensure that we have correctly

  * identified them as audio frames and extracted the metadata we reuire.

  * <p/>

  * <p>Start of Audio id 0xFF (11111111) and then second byte anded with 0xE0(11100000).

  * For example 2nd byte doesnt have to be 0xE0 is just has to have the top 3 signicant

  * bits set. For example 0xFB (11111011) is a common occurence of the second match. The 2nd byte

  * defines flags to indicate various mp3 values.

  * <p/>

  * <p>Having found these two values we then read the header which comprises these two bytes plus a further

  * two to ensure this really is a MP3Header, sometimes the first frame is actually a dummy frame with summary information

  * held within about the whole file, typically using a Xing Header or LAme Header. This is most useful when the file

  * is variable bit rate, if the file is variable bit rate but does not use a summary header it will not be correctly

  * identified as a VBR frame and the track length will be incorrectly calculated. Strictly speaking MP3 means

  * Layer III file but MP2 Layer II), MP1 Layer I) and MPEG-2 files are sometimes used and named with

  * the .mp3 suffix so this library attempts to supports all these formats.

  */

 public class MP3AudioHeader implements AudioHeader

 {

     protected MPEGFrameHeader mp3FrameHeader;

     protected XingFrame mp3XingFrame;

     protected VbriFrame mp3VbriFrame;

     private long fileSize;

     private long startByte;

     private double timePerFrame;

     private double trackLength;

     private long numberOfFrames;

     private long numberOfFramesEstimate;

     private long bitrate;

     private String encoder = "";

     private static final SimpleDateFormat timeInFormat = new SimpleDateFormat("ss", Locale.UK);

     private static final SimpleDateFormat timeOutFormat = new SimpleDateFormat("mm:ss",Locale.UK);

     private static final SimpleDateFormat timeOutOverAnHourFormat = new SimpleDateFormat("kk:mm:ss",Locale.UK);

     private static final char isVbrIdentifier = '~';

     private static final int CONVERT_TO_KILOBITS = 1000;

     private static final String TYPE_MP3 = "mp3";

     private static final int CONVERTS_BYTE_TO_BITS = 8;

     //Logger

     public static Logger logger = Logger.getLogger("org.jaudiotagger.audio.mp3");

     /**

      * After testing the average location of the first MP3Header bit was at 5000 bytes so this is

      * why chosen as a default.

      */

     private final static int FILE_BUFFER_SIZE = 5000;

     private final static int MIN_BUFFER_REMAINING_REQUIRED = MPEGFrameHeader.HEADER_SIZE + XingFrame.MAX_BUFFER_SIZE_NEEDED_TO_READ_XING;

     private static final int NO_SECONDS_IN_HOUR = 3600;

     public MP3AudioHeader()

     {

     }

     /**

      * Search for the first MP3Header in the file

      * <p/>

      * The search starts from the start of the file, it is usually safer to use the alternative constructor that

      * allows you to provide the length of the tag header as a parameter so the tag can be skipped over.

      *

      * @param seekFile

      * @throws IOException

      * @throws InvalidAudioFrameException

      */

     public MP3AudioHeader(final File seekFile) throws IOException, InvalidAudioFrameException

     {

         if (!seek(seekFile, 0))

         {

             throw new InvalidAudioFrameException("No audio header found within" + seekFile.getName());

         }

     }

     /**

      * Search for the first MP3Header in the file

      * <p/>

      * Starts searching from location startByte, this is because there is likely to be an ID3TagHeader

      * before the start of the audio. If this tagHeader contains unsynchronized information there is a

      * possibility that it might be inaccurately identified as the start of the Audio data. Various checks

      * are done in this code to prevent this happening but it cannot be guaranteed.

      * <p/>

      * Of course if the startByte provided overstates the length of the tag header, this could mean the

      * start of the MP3AudioHeader is missed, further checks are done within the MP3 class to recognize

      * if this has occurred and take appropriate action.

      *

      * @param seekFile

      * @param startByte

      * @throws IOException

      * @throws InvalidAudioFrameException

      */

     public MP3AudioHeader(final File seekFile, long startByte) throws IOException, InvalidAudioFrameException

     {

         if (!seek(seekFile, startByte))

         {

             throw new InvalidAudioFrameException("No audio header found within" + seekFile.getName());

         }

     }

     /**

      * Returns true if the first MP3 frame can be found for the MP3 file

      * <p/>

      * This is the first byte of  music data and not the ID3 Tag Frame.     *

      *

      * @param seekFile  MP3 file to seek

      * @param startByte if there is an ID3v2tag we dont want to start reading from the start of the tag

      * @return true if the first MP3 frame can be found

      * @throws IOException on any I/O error

      * @noinspection NestedTryStatement

      */

     public boolean seek(final File seekFile, long startByte) throws IOException

     {

         //This is substantially faster than updating the filechannels position

         long filePointerCount;

         final FileInputStream fis = new FileInputStream(seekFile);

         final FileChannel fc = fis.getChannel();

         //Read into Byte Buffer in Chunks

         ByteBuffer bb = ByteBuffer.allocateDirect(FILE_BUFFER_SIZE);

         //Move FileChannel to the starting position (skipping over tag if any)

         fc.position(startByte);

         //Update filePointerCount

         filePointerCount = startByte;

         //Read from here into the byte buffer , doesn't move location of filepointer

         fc.read(bb, startByte);

         bb.flip();

         boolean syncFound = false;

         try

         {

             do

             {

                 //TODO remaining() is quite an expensive operation, isn't there a way we can work this out without

                 //interrogating the bytebuffer. Also this is rarely going to be true, and could be made less true

                 //by increasing FILE_BUFFER_SIZE

                 if (bb.remaining() <= MIN_BUFFER_REMAINING_REQUIRED)

                 {

                     bb.clear();

                     fc.position(filePointerCount);

                     fc.read(bb, fc.position());

                     bb.flip();

                     if (bb.limit() <= MIN_BUFFER_REMAINING_REQUIRED)

                     {

                         //No mp3 exists

                         return false;

                     }

                 }

                 //MP3File.logger.finest("fc:"+fc.position() + "bb"+bb.position());

                 if (MPEGFrameHeader.isMPEGFrame(bb))

                 {

                     try

                     {

                         if (MP3AudioHeader.logger.isLoggable(Level.FINEST))

                         {

                             MP3AudioHeader.logger.finest("Found Possible header at:" + filePointerCount);

                         }

                         mp3FrameHeader = MPEGFrameHeader.parseMPEGHeader(bb);

                         syncFound = true;

                         //if(2==1) use this line when you want to test getting the next frame without using xing

                         if (XingFrame.isXingFrame(bb, mp3FrameHeader))

                         {

                             if (MP3AudioHeader.logger.isLoggable(Level.FINEST))

                             {

                                 MP3AudioHeader.logger.finest("Found Possible XingHeader");

                             }

                             try

                             {

                                 //Parses Xing frame without modifying position of main buffer

                                 mp3XingFrame = XingFrame.parseXingFrame();

                             }

                             catch (InvalidAudioFrameException ex)

                             {

                                 // We Ignore because even if Xing Header is corrupted

                                 //doesn't mean file is corrupted

                             }

                             break;

                         }

                         else if (VbriFrame.isVbriFrame(bb, mp3FrameHeader))

                         {

                             if (MP3AudioHeader.logger.isLoggable(Level.FINEST))

                             {

                                 MP3AudioHeader.logger.finest("Found Possible VbriHeader");

                             }

                             try

                             {

                                 //Parses Vbri frame without modifying position of main buffer

                                 mp3VbriFrame = VbriFrame.parseVBRIFrame();

                             }

                             catch (InvalidAudioFrameException ex)

                             {

                                 // We Ignore because even if Vbri Header is corrupted

                                 //doesn't mean file is corrupted

                             }

                             break;

                         }

                         // There is a small but real chance that an unsynchronised ID3 Frame could fool the MPEG

                         // Parser into thinking it was an MPEG Header. If this happens the chances of the next bytes

                         // forming a Xing frame header are very remote. On the basis that  most files these days have

                         // Xing headers we do an additional check for when an apparent frame header has been found

                         // but is not followed by a Xing Header:We check the next header this wont impose a large

                         // overhead because wont apply to most Mpegs anyway ( Most likely to occur if audio

                         // has an  APIC frame which should have been unsynchronised but has not been) , or if the frame

                         // has been encoded with as Unicode LE because these have a BOM of 0xFF 0xFE

                         else

                         {

                             syncFound = isNextFrameValid(seekFile, filePointerCount, bb, fc);

                             if (syncFound)

                             {

                                 break;

                             }

                         }

                     }

                     catch (InvalidAudioFrameException ex)

                     {

                         // We Ignore because likely to be incorrect sync bits ,

                         // will just continue in loop

                     }

                 }

                 //TODO position() is quite an expensive operation, isn't there a way we can work this out without

                 //interrogating the bytebuffer

                 bb.position(bb.position() + 1);

                 filePointerCount++;

             }

             while (!syncFound);

         }

         catch (EOFException ex)

         {

             MP3AudioHeader.logger.log(Level.WARNING, "Reached end of file without finding sync match", ex);

             syncFound = false;

         }

         catch (IOException iox)

         {

             MP3AudioHeader.logger.log(Level.SEVERE, "IOException occurred whilst trying to find sync", iox);

             syncFound = false;

             throw iox;

         }

         finally

         {

             if (fc != null)

             {

                 fc.close();

             }

             if (fis != null)

             {

                 fis.close();

             }

         }

         //Return to start of audio header

         if (MP3AudioHeader.logger.isLoggable(Level.FINEST))

         {

             MP3AudioHeader.logger.finer("Return found matching mp3 header starting at" + filePointerCount);

         }

         setFileSize(seekFile.length());

         setMp3StartByte(filePointerCount);

         setTimePerFrame();

         setNumberOfFrames();

         setTrackLength();

         setBitRate();

         setEncoder();

         /*if((filePointerCount - startByte )>0)

         {

             logger.severe(seekFile.getName()+"length:"+startByte+"Difference:"+(filePointerCount - startByte));

         }

         */

         return syncFound;

     }

     /**

      * Called in some circumstances to check the next frame to ensure we have the correct audio header

      *

      * @param seekFile

      * @param filePointerCount

      * @param bb

      * @param fc

      * @return true if frame is valid

      * @throws java.io.IOException

      */

     private boolean isNextFrameValid(File seekFile, long filePointerCount, ByteBuffer bb, FileChannel fc) throws IOException

     {

         if (MP3AudioHeader.logger.isLoggable(Level.FINEST))

         {

             MP3AudioHeader.logger.finer("Checking next frame" + seekFile.getName() + ":fpc:" + filePointerCount + "skipping to:" + (filePointerCount + mp3FrameHeader.getFrameLength()));

         }

         boolean result = false;

         int currentPosition = bb.position();

         //Our buffer is not large enough to fit in the whole of this frame, something must

         //have gone wrong because frames are not this large, so just return false

         //bad frame header

         if (mp3FrameHeader.getFrameLength() > (FILE_BUFFER_SIZE - MIN_BUFFER_REMAINING_REQUIRED))

         {

             MP3AudioHeader.logger.finer("Frame size is too large to be a frame:" + mp3FrameHeader.getFrameLength());

             return false;

         }

         //Check for end of buffer if not enough room get some more

         if (bb.remaining() <= MIN_BUFFER_REMAINING_REQUIRED + mp3FrameHeader.getFrameLength())

         {

             MP3AudioHeader.logger.finer("Buffer too small, need to reload, buffer size:" + bb.remaining());

             bb.clear();

             fc.position(filePointerCount);

             fc.read(bb, fc.position());

             bb.flip();

             //So now original buffer has been replaced, so set current position to start of buffer

             currentPosition = 0;

             //Not enough left

             if (bb.limit() <= MIN_BUFFER_REMAINING_REQUIRED)

             {

                 //No mp3 exists

                 MP3AudioHeader.logger.finer("Nearly at end of file, no header found:");

                 return false;

             }

             //Still Not enough left for next alleged frame size so giving up

             if (bb.limit() <= MIN_BUFFER_REMAINING_REQUIRED + mp3FrameHeader.getFrameLength())

             {

                 //No mp3 exists

                 MP3AudioHeader.logger.finer("Nearly at end of file, no room for next frame, no header found:");

                 return false;

             }

         }

         //Position bb to the start of the alleged next frame

         bb.position(bb.position() + mp3FrameHeader.getFrameLength());

         if (MPEGFrameHeader.isMPEGFrame(bb))

         {

             try

             {

                 MPEGFrameHeader.parseMPEGHeader(bb);

                 MP3AudioHeader.logger.finer("Check next frame confirms is an audio header ");

                 result = true;

             }

             catch (InvalidAudioFrameException ex)

             {

                 MP3AudioHeader.logger.finer("Check next frame has identified this is not an audio header");

                 result = false;

             }

         }

         else

         {

             MP3AudioHeader.logger.finer("isMPEGFrame has identified this is not an audio header");

         }

         //Set back to the start of the previous frame

         bb.position(currentPosition);

         return result;

     }

     /**

      * Set the location of where the Audio file begins in the file

      *

      * @param startByte

      */

     protected void setMp3StartByte(final long startByte)

     {

         this.startByte = startByte;

     }

     /**

      * Returns the byte position of the first MP3 Frame that the

      * <code>file</code> arguement refers to. This is the first byte of music

      * data and not the ID3 Tag Frame.

      *

      * @return the byte position of the first MP3 Frame

      */

     public long getMp3StartByte()

     {

         return startByte;

     }

     /**

      * Set number of frames in this file, use Xing if exists otherwise ((File Size - Non Audio Part)/Frame Size)

      */

     protected void setNumberOfFrames()

     {

         numberOfFramesEstimate = (fileSize - startByte) / mp3FrameHeader.getFrameLength();

         if (mp3XingFrame != null && mp3XingFrame.isFrameCountEnabled())

         {

             numberOfFrames = mp3XingFrame.getFrameCount();

         }

         else if (mp3VbriFrame != null)

         {

             numberOfFrames = mp3VbriFrame.getFrameCount();

         }

         else

         {

             numberOfFrames = numberOfFramesEstimate;

         }

     }

     /**

      * @return The number of frames within the Audio File, calculated as accurrately as possible

      */

     public long getNumberOfFrames()

     {

         return numberOfFrames;

     }

     /**

      * @return The number of frames within the Audio File, calculated by dividing the filesize by

      *         the number of frames, this may not be the most accurate method available.

      */

     public long getNumberOfFramesEstimate()

     {

         return numberOfFramesEstimate;

     }

     /**

      * Set the time each frame contributes to the audio in fractions of seconds, the higher

      * the sampling rate the shorter the audio segment provided by the frame,

      * the number of samples is fixed by the MPEG Version and Layer

      */

     protected void setTimePerFrame()

     {

         timePerFrame = mp3FrameHeader.getNoOfSamples() / mp3FrameHeader.getSamplingRate().doubleValue();

         //Because when calculating framelength we may have altered the calculation slightly for MPEGVersion2

         //to account for mono/stero we seem to have to make a corresponding modification to get the correct time

         if ((mp3FrameHeader.getVersion() == MPEGFrameHeader.VERSION_2) || (mp3FrameHeader.getVersion() == MPEGFrameHeader.VERSION_2_5))

         {

             if ((mp3FrameHeader.getLayer() == MPEGFrameHeader.LAYER_II) || (mp3FrameHeader.getLayer() == MPEGFrameHeader.LAYER_III))

             {

                 if (mp3FrameHeader.getNumberOfChannels() == 1)

                 {

                     timePerFrame = timePerFrame / 2;

                 }

             }

         }

     }

     /**

      * @return the the time each frame contributes to the audio in fractions of seconds

      */

     private double getTimePerFrame()

     {

         return timePerFrame;

     }

     /**

      * Estimate the length of the audio track in seconds

      * Calculation is Number of frames multiplied by the Time Per Frame using the first frame as a prototype

      * Time Per Frame is the number of samples in the frame (which is defined by the MPEGVersion/Layer combination)

      * divided by the sampling rate, i.e the higher the sampling rate the shorter the audio represented by the frame is going

      * to be.

      */

     protected void setTrackLength()

     {

         trackLength = numberOfFrames * getTimePerFrame();

     }

     /**

      * @return Track Length in seconds

      */

     public double getPreciseTrackLength()

     {

         return trackLength;

     }

     public int getTrackLength()

     {

         return (int) getPreciseTrackLength();

     }

     /**

      * Return the length in user friendly format

      * @return

      */

     public String getTrackLengthAsString()

     {

         final Date timeIn;

         try

         {

             final long lengthInSecs = getTrackLength();

             synchronized(timeInFormat)

             {

                 timeIn = timeInFormat.parse(String.valueOf(lengthInSecs));

             }

             if (lengthInSecs < NO_SECONDS_IN_HOUR)

             {

                 synchronized(timeOutFormat)

                 {

                     return timeOutFormat.format(timeIn);

                 }

             }

             else

             {

                 synchronized(timeOutOverAnHourFormat)

                 {

                     return timeOutOverAnHourFormat.format(timeIn);

                 }

             }

         }

         catch (ParseException pe)

         {

             logger.warning("Unable to parse:"+getPreciseTrackLength() +" failed with ParseException:"+pe.getMessage());

             return "";

         }

     }

     /**

      * @return the audio file type

      */

     public String getEncodingType()

     {

         return TYPE_MP3;

     }

     /**

      * Set bitrate in kbps, if Vbr use Xingheader if possible

      */

     protected void setBitRate()

     {

         if (mp3XingFrame != null && mp3XingFrame.isVbr())

         {

             if (mp3XingFrame.isAudioSizeEnabled() && mp3XingFrame.getAudioSize() > 0)

             {

                 bitrate = (long) ((mp3XingFrame.getAudioSize() * CONVERTS_BYTE_TO_BITS) / (timePerFrame * getNumberOfFrames() * CONVERT_TO_KILOBITS));

             }

             else

             {

                 bitrate = (long) (((fileSize - startByte) * CONVERTS_BYTE_TO_BITS) / (timePerFrame * getNumberOfFrames() * CONVERT_TO_KILOBITS));

             }

         }

         else if (mp3VbriFrame != null)

         {

             if (mp3VbriFrame.getAudioSize() > 0)

             {

                 bitrate = (long) ((mp3VbriFrame.getAudioSize() * CONVERTS_BYTE_TO_BITS) / (timePerFrame * getNumberOfFrames() * CONVERT_TO_KILOBITS));

             }

             else

             {

                 bitrate = (long) (((fileSize - startByte) * CONVERTS_BYTE_TO_BITS) / (timePerFrame * getNumberOfFrames() * CONVERT_TO_KILOBITS));

             }

         }

         else

         {

             bitrate = mp3FrameHeader.getBitRate();

         }

     }

     protected void setEncoder()

     {

         if (mp3XingFrame != null)

         {

             if (mp3XingFrame.getLameFrame() != null)

             {

                 encoder = mp3XingFrame.getLameFrame().getEncoder();

             }

         }

         else if (mp3VbriFrame != null)

         {

             encoder = mp3VbriFrame.getEncoder();

         }

     }

     /**

      * @return bitrate in kbps, no indicator is provided as to whether or not it is vbr

      */

     public long getBitRateAsNumber()

     {

         return bitrate;

     }

     /**

      * @return the BitRate of the Audio, to distinguish cbr from vbr we add a '~'

      *         for vbr.

      */

     public String getBitRate()

     {

         if (mp3XingFrame != null && mp3XingFrame.isVbr())

         {

             return isVbrIdentifier + String.valueOf(bitrate);

         }

         else if (mp3VbriFrame != null)

         {

             return isVbrIdentifier + String.valueOf(bitrate);

         }

         else

         {

             return String.valueOf(bitrate);

         }

     }

     /**

      * @return the sampling rate in Hz

      */

     public int getSampleRateAsNumber()

     {

         return mp3FrameHeader.getSamplingRate();

     }

     /**

      * @return the sampling rate as string

      */

     public String getSampleRate()

     {

         return String.valueOf(mp3FrameHeader.getSamplingRate());

     }

     /**

      * @return MPEG Version (1-3)

      */

     public String getMpegVersion()

     {

         return mp3FrameHeader.getVersionAsString();

     }

     /**

      * @return MPEG Layer (1-3)

      */

     public String getMpegLayer()

     {

         return mp3FrameHeader.getLayerAsString();

     }

     /**

      * @return the format of the audio (i.e. MPEG-1 Layer3)

      */

     public String getFormat()

     {

         return mp3FrameHeader.getVersionAsString() + " " + mp3FrameHeader.getLayerAsString();

     }

     /**

      * @return the Channel Mode such as Stero or Mono

      */

     public String getChannels()

     {

         return mp3FrameHeader.getChannelModeAsString();

     }

     /**

      * @return Emphasis

      */

     public String getEmphasis()

     {

         return mp3FrameHeader.getEmphasisAsString();

     }

     /**

      * @return if the bitrate is variable, Xing header takes precedence if we have one

      */

     public boolean isVariableBitRate()

     {

         if (mp3XingFrame != null)

         {

             return mp3XingFrame.isVbr();

         }

         else if (mp3VbriFrame != null)

         {

             return mp3VbriFrame.isVbr();

         }

         else

         {

             return mp3FrameHeader.isVariableBitRate();

         }

     }

     public boolean isProtected()

     {

         return mp3FrameHeader.isProtected();

     }

     public boolean isPrivate()

     {

         return mp3FrameHeader.isPrivate();

     }

     public boolean isCopyrighted()

     {

         return mp3FrameHeader.isCopyrighted();

     }

     public boolean isOriginal()

     {

         return mp3FrameHeader.isOriginal();

     }

     public boolean isPadding()

     {

         return mp3FrameHeader.isPadding();

     }

     /**

      * @return encoder

      */

     public String getEncoder()

     {

         return encoder;

     }

     /**

      * Set the size of the file, required in some calculations

      *

      * @param fileSize

      */

     protected void setFileSize(long fileSize)

     {

         this.fileSize = fileSize;

     }

     /**

      * @return a string represntation

      */

     public String toString()

     {

         String s = "fileSize:" + fileSize + " encoder:" + encoder + " startByte:" + Hex.asHex(startByte) + " numberOfFrames:" + numberOfFrames + " numberOfFramesEst:" + numberOfFramesEstimate + " timePerFrame:" + timePerFrame + " bitrate:" + bitrate + " trackLength:" + getTrackLengthAsString();

         if (this.mp3FrameHeader != null)

         {

             s += mp3FrameHeader.toString();

         }

         if (this.mp3XingFrame != null)

         {

             s += mp3XingFrame.toString();

         }

         return s;

     }

 }