package org.cass;

import java.io.*;
import java.util.regex.*;

/** A class containing useful parsing tools, file pattern generation and
    filtration, and a host of other utilities.
    @author Zachary Vaughan
    @version 1.1 07/14/06 */
public class Utilities
{
   /** Extracts the parent directory portion of the given file pattern. The
       final directory path separator character is also included (typically
       the forward or backward slash).
       <p>Note that this method assumes the directory portion is made up of
          legal directory name characters for the underlying filesystem and no
          wildcard characters. No warnings or exceptions are thrown if this is
          violated. It is up to the user to determine the validity of the string
          beforehand and he or she sees fit.</p>
       @param pstr the pattern string to parse.
       @throws NullPointerException if str is <b>null</b>.
       @return the parent directory portion of the given pattern string, or
          the empty string if none is present in the pattern.
       @see #parsePattern(String) parsePattern(str) */
   public static String parseDirectory(String pstr)
   {
      int i = pstr.lastIndexOf(File.separator);
      return i == -1 ? "." + File.separator : pstr.substring(0, i + 1);
   }

   /** Extracts the pattern portion of the given file pattern by trimming off
       the preceding directory portion. In effect this method extracts the
       opposite from the given pattern as the <i>parseDirectory()</i> method.
       <p>Note that this method assumes the pattern portion is made up of
          legal file name characters for the underlying filesystem and
          legal wildcard characters. No warnings or exceptions are thrown if
          this is violated. It is up to the user to determine the validity of
          the string beforehand and he or she sees fit.</p>
       @param pstr the pattern string to parse.
       @throws NullPointerException if str is <b>null</b>.
       @return the pattern portion of the given pattern string.
       @see #parseDirectory(String) parseDirectory(str) */
   public static String parsePattern(String pstr)
   {
      return pstr.substring(pstr.lastIndexOf(File.separator) + 1);
   }

   /** Gets the set of files matching the given file pattern string.
       @param pstr the file pattern string to use.
       @return an array of files matching the given pattern string, in no
          particular order, or <b>null</b> if the given pattern string
          does not denote a valid directory to search. */
   public static File[] getFiles(String pstr)
   {
      File dir = new File(parseDirectory(pstr));
      String pat = parsePattern(pstr);
      final Pattern p = Pattern.compile(
         pat.replace(".", "\\.").replace("*", ".*"));
      return dir.listFiles(new FilenameFilter()
      {
         public boolean accept(File dir, String name)
         {
            return p.matcher(name).matches();
         }
      });
   }



   private Utilities() {}
}