content: /* Alloy Analyzer 4 -- Copyright (c) 2006-2009, Felix Chang
   *
   * Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files
   * (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify,
   * merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is
   * furnished to do so, subject to the following conditions:
   *
   * The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
   *
   * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
   * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
   * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF
   * OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
   */
  
  package edu.mit.csail.sdg.alloy4;
  
  import java.util.HashSet;
  import java.util.Set;
  
  /**
   * This generates unique names based on names provided by the caller.
   * <p>
   * <b>Thread Safety:</b> Safe.
   */
  
  public final class UniqueNameGenerator {
  
      /** This stores the set of names we've generated so far. */
      private final Set<String> names = new HashSet<String>();
  
      /** Construct a UniqueNameGenerator with a blank history. */
      public UniqueNameGenerator() {}
  
      /**
       * Regard the provided name as "seen".
       * <p>
       * For convenience, it returns the argument as the return value.
       */
      public synchronized String seen(String name) {
          names.add(name);
          return name;
      }
  
      /**
       * Queries whether the provided name has been "seen" or not.
       */
      public synchronized boolean hasSeen(String name) {
          return names.contains(name);
      }
  
      /** Clear the history of previously generated names. */
      public synchronized void clear() {
          names.clear();
      }
  
      /**
       * Generate a unique name based on the input name.
       * <p>
       * Specifically: if the name has not been generated/seen already by this
       * generator, then it is returned as is. Otherwise, we append ' to it until the
       * name becomes unique.
       */
      public synchronized String make(String name) {
          while (!names.add(name))
              name = name + "'";
          return name;
      }
  }
  