/* 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.Set;
import java.util.HashSet;

/** 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;
   }
}