package org.apache.lucene.util.automaton;

/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file 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 with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import java.util.Random;

import org.apache.lucene.util.LuceneTestCase;

/**
 * Not thorough, but tries to test determinism correctness
 * somewhat randomly.
 */
public class TestDeterminism extends LuceneTestCase {
  private Random random;
  
  @Override
  protected void setUp() throws Exception {
    super.setUp();
    random = newRandom();
  }
  
  /** test a bunch of random regular expressions */
  public void testRegexps() throws Exception {
      int num = 500 * RANDOM_MULTIPLIER;
      for (int i = 0; i < num; i++)
        assertAutomaton(AutomatonTestUtil.randomRegexp(random).toAutomaton());
  }
  
  private static void assertAutomaton(Automaton a) {
    Automaton clone = a.clone();
    // complement(complement(a)) = a
    Automaton equivalent = BasicOperations.complement(BasicOperations.complement(a));
    assertTrue(BasicOperations.sameLanguage(a, equivalent));
    
    // a union a = a
    equivalent = BasicOperations.union(a, clone);
    assertTrue(BasicOperations.sameLanguage(a, equivalent));
    
    // a intersect a = a
    equivalent = BasicOperations.intersection(a, clone);
    assertTrue(BasicOperations.sameLanguage(a, equivalent));
    
    // a minus a = empty
    Automaton empty = BasicOperations.minus(a, clone);
    assertTrue(BasicOperations.isEmpty(empty));
    
    // as long as don't accept the empty string
    // then optional(a) - empty = a
    if (!BasicOperations.run(a, "")) {
      //System.out.println("test " + a);
      Automaton optional = BasicOperations.optional(a);
      //System.out.println("optional " + optional);
      equivalent = BasicOperations.minus(optional, BasicAutomata.makeEmptyString());
      //System.out.println("equiv " + equivalent);
      assertTrue(BasicOperations.sameLanguage(a, equivalent));
    }
  } 
}