/*
    $Id: FitsStreamReader.java,v 1.2 2004/10/06 21:41:01 mch Exp $
   
    Copyright (c) etc
    */
   
   package org.astrogrid.datacenter.fits;
   
   import java.io.BufferedInputStream;
  import java.io.File;
  import java.io.FileInputStream;
  import java.io.IOException;
  import java.io.InputStream;
  import java.net.URL;
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  import org.astrogrid.datacenter.fits.FitsReader;
  
  /***
   * A set of routines for reading a fits image
   * <p>
   * FITS images are binary representations of tables or pixel images, and are
   * well known in the astronomical community (in 2003!).  They consist of
   * a number of 'lines' of 80 characters of ASCII keyword/value pairs, then
   * the binary data itself.
   * <p>
   * (Should say more or give reference)
   * <p>
   * This particular class handles streamable fits images for reading purposes.
   * Therefore you can pass it a remote url and call methods to process that url.
   * However you can't do random access or writes on a url referenced file...
   * <p>
   * This is a 'lazy loader' - it only reads when required, but caches everything
   * as it does.
   */
  public class FitsStreamReader implements FitsReader
  {
     String fitsName = null;
     InputStream in = null;
     //int dataOffset = -1; //how big is the header. -1 = not loaded yet.
     //   Hashtable header = null; //header key/value pairs. null = not loaded yet
     Log log = LogFactory.getLog(FitsReader.class);
     
     /* total number of bytes read */
     long totBytesRead = 0;
  
     public FitsStreamReader(URL url) throws IOException
     {
        fitsName = url.toString();
        InputStream urlIn = url.openStream();
        assert urlIn != null : "Stream to URL "+url+" returned null";
        in = new BufferedInputStream(urlIn);
     }
     
     public FitsStreamReader(File file) throws IOException
     {
        fitsName = file.toString();
        in = new BufferedInputStream(new FileInputStream(file));
     }
     
     public FitsStreamReader(InputStream inStream)
     {
        if (inStream == null)
        {
           throw new IllegalArgumentException("InputStream cannot be null");
        }
              
        this.in = inStream;
     }
     
     /***
      * Loads the header into a set of key/value pairs.  NB this reads up to the
      * END marker, or the optionally given stop keyword.  This means that, if
      * we know something of the file and only want to read useful information, we
      * can stop before having to read the whole thing.
      * <p>
      * For example, some of the JBO fits files have huge HISTORY blocks, so we
      * can specify "HISTORY AIP" as an 'endWord' and when they are encountered,
      * the reader will stop reading.
      * <p>
      * To read the whole thing, right up to the end of the 2880 block boundary (ie
      * ready to read the data block) see readHeader
      */
     public void readHeaderKeywords(FitsHeader header, String endWord) throws IOException
     {
        log.trace("Loading image header...");
  
        //read a line (80 bytes) at a time until we reach END
        byte[] block = new byte[80];
        //for (int j=0;j<block.length;j++) block[j]=5;  //debug to check for nulls
        int lineNum = 0;
        FitsKeyword keyword = null;
        
        do {
           lineNum++;
           
           int bytesRead = in.read(block);
           int lineBytesRead = bytesRead;
           
          //must read the complete 80 bytes - bear in mind we might be
          //loading off a remote link
          while ((lineBytesRead <80) && (bytesRead != -1))
          {
             bytesRead = in.read(block, lineBytesRead, 80-lineBytesRead);
             lineBytesRead = lineBytesRead + bytesRead;
          }
          totBytesRead = totBytesRead + lineBytesRead;
          
          //debug
          //String t="";
          //for (int j=0;j<block.length;j++) t=t+"["+block[j]+"] ";
          //Log.trace(t);
          
          //quick check for binary data, just in case there is something
          //wrong with the header we don't want to have to read the whole
          // image
          //you get some nulls in some text lines, on the other hand you also get some complete 0 blocks...
          for (int i=0;i<block.length;i++)
          {
             if ( ((block[i] >128) || (block[i] <32)) && (block[i] != 0)   )
             {
                StringBuffer msg= new StringBuffer(
                   "Binary data encountered before header END in image "+fitsName+"\n"+
                   new String(block)+"\n");
                for (int j=0;j<block.length;j++) msg.append("["+block[j]+"] ");
                
                throw new FitsFormatException(msg.toString());
             }
          }
          boolean isNuls = true;
          for (int i=0;i<block.length;i++) {
             if (block[i] != 0) {
                isNuls = false;
                break;
             }
          }
          if (isNuls) throw new FitsFormatException("All-Nuls block in header of "+fitsName+", line "+lineNum);
 
          //parse keyword
          keyword = new FitsKeyword(block);
 
          //add keyword if not null - *do* want to add END so that we can check that
          //the whole lot has been read
          if ( (keyword.getKey() != null) && (keyword.getKey().length() >0))
          {
             header.add(keyword);
             log.trace("Line="+new String(block)+", Key="+keyword.getKey()+", Value='"+keyword.getValue()+"'");
          }
          
       } while ((keyword.getKey() == null) || !(keyword.getKey().toUpperCase().startsWith("END") || ((endWord != null) && (keyword.getKey().toUpperCase().startsWith(endWord.toUpperCase())))));
    }
 
    
    /***
     * Read data block (actually just skips it for the moment)
     * @todo there's a bug about - I've added a bit to skip an extra 28 cards
     * because that's what seems to need to be done, but I have no idea why.
     */
    public void readData(FitsHdu hdu) throws IOException
    {
       log.trace("Skipping data (pos="+totBytesRead+")...");
       //first make sure we have read up to the header END keyword
       if (hdu.getHeader().get("END") == null) {
          
          readHeaderKeywords(hdu.getHeader(), null);
       }
       
       //then make up to nearest 2880 block
       long r = totBytesRead % 2880;
       skipTo(totBytesRead + r);
       
       //now read data
       long size = hdu.getHeader().getDataSize();
       log.trace("data size="+size);
       
 //    hdu.setData(new FitsData());
       //skip data block.  NB sometimes one single 'skip' read is not sufficient
       skipTo(totBytesRead+size);
       
       //then make up to nearest 2880 block
       r = totBytesRead % 2880;
       skipTo(totBytesRead + r);
 
       if (size >0) skipTo(totBytesRead + 2880);
       
       log.trace("read to pos "+totBytesRead);
       
       
    }
 
    /***
     * Skips bytes up to given position in stream.  A single 'skip()' call does
     * not always skip that number of bytes, presumably depending on
     */
    public void skipTo(long targetPos) throws IOException
    {
       while (totBytesRead <targetPos)
       {
          long bytesRead = in.skip(targetPos - totBytesRead);
          
          if (bytesRead == -1) {
             throw new IOException("End of file");
          }
          
          totBytesRead = totBytesRead + bytesRead;
       }
    }
    
 }
 
 /*
  $Log: FitsStreamReader.java,v $
  Revision 1.2  2004/10/06 21:41:01  mch
  Removed string appending in loop
 
  Revision 1.1  2004/09/28 15:02:13  mch
  Merged PAL and server packages
 
  Revision 1.6  2004/09/07 14:52:00  mch
  Fixes etc for SEC
 
  Revision 1.5  2004/09/07 01:39:27  mch
  Moved email keys from TargetIndicator to Slinger
 
  Revision 1.4  2004/07/12 23:25:58  mch
  Better error reporting
 
  Revision 1.3  2004/03/12 04:45:26  mch
  It05 MCH Refactor
 
  Revision 1.2  2004/01/13 00:33:14  nw
  Merged in branch providing
  * sql pass-through
  * replace Certification by User
  * Rename _query as Query
 
  Revision 1.1.10.1  2004/01/08 09:43:40  nw
  replaced adql front end with a generalized front end that accepts
  a range of query languages (pass-thru sql at the moment)
 
  Revision 1.1  2003/11/28 18:21:03  mch
  Stream implementation of FitsReader
 
  Revision 1.2  2003/11/26 18:46:55  mch
  First attempt to generate index from FITS files
 
  Revision 1.1  2003/11/25 11:04:11  mch
  New FITS io package
 
  Revision 1.1.1.1  2003/08/25 18:36:27  mch
  Reimported to fit It02 source structure
 
  Revision 1.1  2003/07/03 18:14:51  mch
  Fits file handling
 
  */