// This example is from _Java Examples in a Nutshell_. (http://www.oreilly.com)
// Copyright (c) 1997 by David Flanagan
// This example is provided WITHOUT ANY WARRANTY either expressed or implied.
// You may study, use, modify, and distribute it for non-commercial purposes.
// For any commercial use, see http://www.davidflanagan.com/javaexamples

import java.io.*;
import java.util.zip.*;

/**
 * This class defines two static methods for gzipping files and zipping
 * directories.  It also defines a demonstration program as a nested class.
 **/
public class Compress {
  /** Gzip the contents of the from file and save in the to file. */
  public static void gzipFile(String from, String to) throws IOException {
    // Create stream to read from the from file
    FileInputStream in = new FileInputStream(from);
    // Create stream to compress data and write it to the to file.
    GZIPOutputStream out = new GZIPOutputStream(new FileOutputStream(to));
    // Copy bytes from one stream to the other
    byte[] buffer = new byte[4096];
    int bytes_read;
    while((bytes_read = in.read(buffer)) != -1) 
      out.write(buffer, 0, bytes_read);
    // And close the streams
    in.close();
    out.close();
  }

  /** Zip the contents of the directory, and save it in the zipfile */
  public static void zipDirectory(String dir, String zipfile) 
       throws IOException, IllegalArgumentException {
    // Check that the directory is a directory, and get its contents
    File d = new File(dir);
    if (!d.isDirectory())
      throw new IllegalArgumentException("Compress: not a directory:  " + dir);
    String[] entries = d.list();
    byte[] buffer = new byte[4096];  // Create a buffer for copying 
    int bytes_read;

    // Create a stream to compress data and write it to the zipfile
    ZipOutputStream out = new ZipOutputStream(new FileOutputStream(zipfile));

    // Loop through all entries in the directory
    for(int i = 0; i < entries.length; i++) {
      File f = new File(d, entries[i]);
      if (f.isDirectory()) continue;               // Don't zip sub-directories
      FileInputStream in = new FileInputStream(f); // Stream to read file
      ZipEntry entry = new ZipEntry(f.getPath());  // Make a ZipEntry
      out.putNextEntry(entry);                     // Store entry in zipfile
      while((bytes_read = in.read(buffer)) != -1)  // Copy bytes to zipfile
        out.write(buffer, 0, bytes_read);
      in.close();                                  // Close input stream
    }
    // When we're done with the whole loop, close the output stream
    out.close();
  }

  /**
   * This nested class is a test program that demonstrates the use of the
   * static methods defined above.
   **/
  public static class Test {
    /**
     * Compress a specified file or directory.  If no destination name is
     * specified, append .gz to a file name or .zip to a directory name
     **/
    public static void main(String args[]) throws IOException {
      if ((args.length != 1) && (args.length != 2)) {  // check arguments
        System.err.println("Usage: java Compress$Test <from> [<to>]");
        System.exit(0);
      }
      String from = args[0], to;
      File f = new File(from);
      boolean directory = f.isDirectory();   // Is it a file or directory?
      if (args.length == 2) to = args[1];    
      else {                                 // If destination not specified
        if (directory) to = from + ".zip";   //   use a .zip suffix
        else to = from + ".gz";              //   or a .gz suffix
      }

      if ((new File(to)).exists()) { // Make sure not to overwrite anything
        System.err.println("Compress: won't overwrite existing file: " + to);
        System.exit(0);
      }

      // Finally, call one of the methods defined above to do the work.
      if (directory) Compress.zipDirectory(from, to);
      else Compress.gzipFile(from, to);
    }
  }
}