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   *  distributed with this work for additional information
   *  regarding copyright ownership.  The ASF licenses this file
   *  to you under the Apache License, Version 2.0 (the
   *  "License"); you may not use this file except in compliance
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   *
   *    https://www.apache.org/licenses/LICENSE-2.0
   *
   *  Unless required by applicable law or agreed to in writing,
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  package org.apache.cayenne.modeler.util;
  
  import java.io.File;
  
  /**
   * CayenneUserDir represents a directory where all Cayenne-related information is stored
   * on the user machine. This is normally a <code>$HOME/.cayenne</code> directory.
   */
  public class CayenneUserDir {
  
      protected static CayenneUserDir sharedInstance;
  
      public static final String CAYENNE_DIR = ".cayenne";
  
      /**
       * A property name for the property that allows to define an alternative location of
       * Cayenne User Directory (instead of default "$HOME/.cayenne").
       * 
       * @since 1.1
       */
      public static final String ALT_USER_DIR_PROPERTY = "cayenne.userdir";
  
      protected File cayenneUserDir;
  
      public static CayenneUserDir getInstance() {
          if (sharedInstance == null) {
              sharedInstance = new CayenneUserDir();
          }
          return sharedInstance;
      }
  
      /**
       * Constructor for CayenneUserDir.
       */
      protected CayenneUserDir() {
          super();
  
          File tmpDir = null;
          String dirName = System.getProperty(ALT_USER_DIR_PROPERTY);
  
          if (dirName != null) {
              tmpDir = new File(dirName);
          }
          else {
              File homeDir = new File(System.getProperty("user.home"));
              tmpDir = new File(homeDir, CAYENNE_DIR);
          }
  
          if (tmpDir.exists() && !tmpDir.isDirectory()) {
              tmpDir = null;
          }
          else if (tmpDir.exists() && !tmpDir.canRead()) {
              tmpDir = null;
          }
          else if (!tmpDir.exists()) {
              tmpDir.mkdirs();
              if (!tmpDir.exists()) {
                  tmpDir = null;
              }
          }
  
          cayenneUserDir = tmpDir;
      }
  
      /**
       * Returns a directory object where all user Cayenne-related configuration is stored.
       * May return null if the directory is not accessible for whatever reason.
       */
      public File getDirectory() {
          return cayenneUserDir;
      }
  
      /**
       * Return false if the directory is not accessible for any reason at least for
       * reading.
       */
      public boolean canRead() {
          return cayenneUserDir != null;
      }
  
      /**
       * Return false if the directory is not accessible for any reason at least for
       * reading.
       */
      public boolean canWrite() {
          return cayenneUserDir != null && cayenneUserDir.canWrite();
      }
  
      public File resolveFile(String name) {
          return new File(cayenneUserDir, name);
      }
  }
  