/**
 * Manage rd5 diff-file creation
 *
 * @author ab
 */
package btools.mapaccess;

import java.io.BufferedInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.security.DigestInputStream;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

final public class Rd5DiffManager
{
  public static void main( String[] args ) throws Exception
  {
    calcDiffs( new File( args[0] ),new File( args[1] ) );
  }

  /**
   * Compute diffs for all RD5 files
   */
  public static void calcDiffs( File oldDir, File newDir ) throws Exception
  {
    File oldDiffDir = new File( oldDir, "diff" );
    File newDiffDir = new File( newDir, "diff" );

    File[] filesNew = newDir.listFiles();
    
    for( File fn : filesNew )
    {
      String name = fn.getName();
      if ( !name.endsWith( ".rd5" ) )
      {
        continue;
      }
      if ( fn.length() < 1024*1024 )
      {
        continue; // exclude very small files from diffing
      }
      String basename = name.substring( 0, name.length() - 4 );
      File fo = new File( oldDir, name );
      if ( !fo.isFile() )
      {
        continue;
      }
      
      // calculate MD5 of old file
      String md5 = getMD5( fo );

      String md5New = getMD5( fn );
      
      System.out.println( "name=" + name + " md5=" + md5 );
      
      File specificNewDiffs = new File( newDiffDir, basename );
      specificNewDiffs.mkdirs();
      
      String diffFileName = md5 + ".df5";
      File diffFile = new File( specificNewDiffs, diffFileName );
      
      String dummyDiffFileName = md5New + ".df5";
      File dummyDiffFile = new File( specificNewDiffs, dummyDiffFileName );
      dummyDiffFile.createNewFile();

      // calc the new diff
      Rd5DiffTool.diff2files( fo, fn, diffFile  );
      
      // ... and add that to old diff files
      File specificOldDiffs = new File( oldDiffDir, basename );
      if ( specificOldDiffs.isDirectory() )
      {
        File[] oldDiffs = specificOldDiffs.listFiles();
        for( File od : oldDiffs )
        {
          if ( !od.getName().endsWith( ".df5" ) )
          {
            continue;
          }
          if ( System.currentTimeMillis() - od.lastModified() > 9*86400000L )
          {
            continue; // limit diff history to 9 days
          }
          
          File updatedDiff = new File( specificNewDiffs, od.getName() );
          if ( !updatedDiff.exists() )
          {        
            Rd5DiffTool.addDeltas( od, diffFile, updatedDiff  );
            updatedDiff.setLastModified( od.lastModified() );
          }
        }
      }
    }
  }

  public static String getMD5( File f ) throws IOException
  {
    try {
      MessageDigest md = MessageDigest.getInstance("MD5");
      BufferedInputStream bis = new BufferedInputStream(new FileInputStream(f));
      DigestInputStream dis = new DigestInputStream(bis, md);
      byte[] buf = new byte[8192];
      for (; ; ) {
        int len = dis.read(buf);
        if (len <= 0) {
          break;
        }
      }
      dis.close();
      byte[] bytes = md.digest();

      StringBuilder sb = new StringBuilder();
      for (int j = 0; j < bytes.length; j++) {
        int v = bytes[j] & 0xff;
        sb.append(hexChar(v >>> 4)).append(hexChar(v & 0xf));
      }
      return sb.toString();
    } catch (NoSuchAlgorithmException e) {
      throw new IOException("MD5 algorithm not available", e);
    }
  }
  
  private static char hexChar( int v )
  {
    return (char) ( v > 9 ? 'a' + (v-10) : '0' + v );
  }
}