/*
    * Fsgrep is a simple Java application which allows a user to
    * search all files in a directory structure for lines matching
    * a given pattern.  Its functionality is a combination of the
    * Unix 'find' and 'grep' utilities.
    * Visit [http://fsgrep.sourceforge.net/] for more information.
    * 
    * Copyright (C) 2003-2006 Murali Krishnan [murali_ca_us@users.sourceforge.net]
    * 
   * Fsgrep is free software; you can redistribute it and/or modify
   * it under the terms of version 2 of the GNU General Public
   * License as published by the Free Software Foundation.
   * 
   * Fsgrep 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 General Public License for more details.
   * 
   * You should have received a copy of the GNU General Public License
   * along with Fsgrep (see the file named LICENSE.txt); if not, write
   * to the Free Software Foundation, Inc., 59 Temple Place, Suite 330,
   * Boston, MA  02111-1307  USA
   */
  
  package mk.fsgrep.util;
  
  
  import java.io.*;
  import java.util.*;
  
  
  /***
   * A simple persistent data store using the Java Properties framework.
   * This gives crude support for collection storage by key prefix
   * identification.
   * 
   * @author  Murali Krishnan
   *
   */
  public class PersistentData extends Properties {
  
      //------------------------------------------------------------
      //- Class Variables
  
  
      /***
       * The singleton instance.
       */
      private static PersistentData sInstance = null;
  
  
      /***
       * The file where this object is persisted.
       */
      protected static final File DATA_FILE = new File(AppProperties.APP_DIR + File.separator + "pdata.properties");
  
  
      //------------------------------------------------------------
      //- Class Functions
  
      /***
       * @return the singleton, created lazily.
       */
      public static synchronized PersistentData getInstance() {
          if (sInstance == null) {
              sInstance = new PersistentData();
          }
  
          return sInstance;
      }
  
  
      //------------------------------------------------------------
      //- Instance Variables
  
  
  
      //------------------------------------------------------------
      //- Constructors
  
      /***
       * The default constructor loads the file.
       */
      protected PersistentData() {
          load();
      }
  
  
      //------------------------------------------------------------
      //- Accessors
  
  
  
      //------------------------------------------------------------
      //- Settors
  
  
  
      //------------------------------------------------------------
     //- Private/Protected Utility Functions
 
     /***
      * Read the data file to populate this object.
      * It should only be called by the (default) constructor.
      */
     protected synchronized void load() {
         if (DATA_FILE.exists()) {
             try {
                 FileInputStream fis = new FileInputStream(DATA_FILE);
                 load(fis);
                 fis.close();
             } catch (IOException ioe) {
                 System.err.println("Could not read persistent data.");
                 ioe.printStackTrace();
             }
         } else {
             System.out.println("Creating default persistent data file.");
             store();
         }
     }
 
 
     //------------------------------------------------------------
     //- Public Interface Functions
 
     /***
      * Lookup the value for the given key and convert it to a boolean.
      * If it is not found, return false.
      * 
      * @return  The property value converted to a boolean value.
      * @param  key  The association key.
      */
     public boolean getBooleanProperty(String key) {
         String value = getProperty(key);
 
         boolean result = Boolean.TRUE.toString().equals(value);
 
         return result;
     }
 
     /***
      * Save this objects values to the file.
      */
     public synchronized void store() {
         AppProperties.ensureAppDir();
 
         try {
             FileOutputStream fos = new FileOutputStream(DATA_FILE);
             store(fos, "fsgrep persistent data");
             fos.close();
         } catch (IOException ioe) {
             System.err.println("Could not save persistent data.");
             ioe.printStackTrace();
         }
     }
 
 
     /***
      * Return the sorted set of all keys that have the give prefix.
      *
      * @param prefix  The string begining of the keys to be extracted.
      * @return all the property keys with the given prefix.
      */
     public synchronized Collection<String> getKeysPrefixed(String prefix) {
         // Note: Numeric sorting is only valid if the number of digits is
         // consistent.
         Collection<String> result = new TreeSet<String>();
 
         for (Object o : keySet()) {
             String key = (String) o;
             if (key.startsWith(prefix)) {
                 result.add(key);
             }
         }
         return result;
     }
 
 
     /***
      * Remove all keys that have the give prefix.
      * 
      * @param prefix  The string begining of the keys to be removed.
      */
     public synchronized void removeKeysPrefixed(String prefix) {
         // Note: Numeric sorting is only valid if the number of digits is
         // consistent.
         Collection<String> keys = getKeysPrefixed(prefix);
 
         for (String key : keys) {
             remove(key);
         }
     }
 
 
     /***
      * Save the key/value mapping where the key is a prefix/index.
      * 
      * @param  prefix  The key prefix.
      * @param  index   The index (numeric) part of the key.
      * @param  value   The value associated with the key.
      */
     public void put(String prefix, int index, String value) {
         StringBuffer indexPart = new StringBuffer(String.valueOf(index));
         while (indexPart.length() < 3) {
             indexPart.insert(0, "0");
         }
 
         String key = prefix + indexPart;
 
         setProperty(key, value);
     }
 
     //------------------------------------------------------------
     //- Class Interface Functions
 
 
 
     //------------------------------------------------------------
     //- Inner Classes
 
 
 
     //------------------------------------------------------------
     //- Main
 
 
 
 }