/*
 * ====================================================================
 *
 * The Apache Software License, Version 1.1
 *
 * Copyright (c) 1999-2003 The Apache Software Foundation.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The end-user documentation included with the redistribution, if
 *    any, must include the following acknowledgement:
 *       "This product includes software developed by the
 *        Apache Software Foundation (http://www.apache.org/)."
 *    Alternately, this acknowledgement may appear in the software itself,
 *    if and wherever such third-party acknowledgements normally appear.
 *
 * 4. The names "The Jakarta Project", "Commons", and "Apache Software
 *    Foundation" must not be used to endorse or promote products derived
 *    from this software without prior written permission. For written
 *    permission, please contact apache@apache.org.
 *
 * 5. Products derived from this software may not be called "Apache"
 *    nor may "Apache" appear in their names without prior written
 *    permission of the Apache Software Foundation.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation.  For more
 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 *
 */

package org.exoplatform.services.document.impl.diff;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;
import java.util.Random;

import org.exoplatform.services.document.diff.DiffAlgorithm;
import org.exoplatform.services.document.diff.DiffService;
import org.exoplatform.services.document.diff.Revision;

public class DiffServiceImpl extends ToStringImpl implements DiffService {

  /** The differencing algorithm to use. */
  protected DiffAlgorithm algorithm;

  public DiffServiceImpl(DiffAlgorithm algorithm) {
    this.algorithm = algorithm;
  }

  /**
   * compute the difference between an original and a revision.
   * 
   * @param orig the original
   * @param rev the revision to compare with the original.
   * @return a Revision describing the differences
   */
  public Revision diff(Object[] orig, Object[] rev) throws Exception {
    if (orig == null || rev == null) {
      throw new IllegalArgumentException();
    }
    return algorithm.diff(orig, rev);
  }

  /**
   * Compares the two input sequences.
   * 
   * @param orig The original sequence.
   * @param rev The revised sequence.
   * @return true if the sequences are identical. False otherwise.
   */
  public boolean compare(Object[] orig, Object[] rev) {
    if (orig.length != rev.length) {
      return false;
    } else {
      for (int i = 0; i < orig.length; i++) {
        if (!orig[i].equals(rev[i])) {
          return false;
        }
      }
      return true;
    }
  }

  /**
   * Converts an array of {@link Object Object} to a string using
   * {@link DiffServiceImpl#NL Diff.NL} as the line separator.
   * 
   * @param o the array of objects.
   */
  public String arrayToString(Object[] o) {
    return arrayToString(o, NL);
  }

  /**
   * Edits all of the items in the input sequence.
   * 
   * @param text The input sequence.
   * @return A sequence of the same length with all the lines differing from the
   *         corresponding ones in the input.
   */
  public Object[] editAll(Object[] text) {
    Object[] result = new String[text.length];

    for (int i = 0; i < text.length; i++)
      result[i] = text[i] + " <edited>";

    return result;
  }

  /**
   * Performs random edits on the input sequence. Useful for testing.
   * 
   * @param text The input sequence.
   * @return The sequence with random edits performed.
   */
  public Object[] randomEdit(Object[] text) {
    return randomEdit(text, text.length);
  }

  /**
   * Performs random edits on the input sequence. Useful for testing.
   * 
   * @param text The input sequence.
   * @param seed A seed value for the randomizer.
   * @return The sequence with random edits performed.
   */
  public Object[] randomEdit(Object[] text, long seed) {
    List result = new ArrayList(Arrays.asList(text));
    Random r = new Random(seed);
    int nops = r.nextInt(10);
    for (int i = 0; i < nops; i++) {
      boolean del = r.nextBoolean();
      int pos = r.nextInt(result.size() + 1);
      int len = Math.min(result.size() - pos, 1 + r.nextInt(4));
      if (del && result.size() > 0) { // delete
        result.subList(pos, pos + len).clear();
      } else {
        for (int k = 0; k < len; k++, pos++) {
          result.add(pos, "[" + i + "] random edit[" + i + "][" + i + "]");
        }
      }
    }
    return result.toArray();
  }

  /**
   * Shuffles around the items in the input sequence.
   * 
   * @param text The input sequence.
   * @return The shuffled sequence.
   */
  public Object[] shuffle(Object[] text) {
    return shuffle(text, text.length);
  }

  /**
   * Shuffles around the items in the input sequence.
   * 
   * @param text The input sequence.
   * @param seed A seed value for randomizing the suffle.
   * @return The shuffled sequence.
   */
  public Object[] shuffle(Object[] text, long seed) {
    List result = new ArrayList(Arrays.asList(text));
    Collections.shuffle(result);
    return result.toArray();
  }

  /**
   * Generate a random sequence of the given size.
   * 
   * @param The size of the sequence to generate.
   * @return The generated sequence.
   */
  public Object[] randomSequence(int size) {
    return randomSequence(size, size);
  }

  /**
   * Generate a random sequence of the given size.
   * 
   * @param The size of the sequence to generate.
   * @param seed A seed value for randomizing the generation.
   * @return The generated sequence.
   */
  public Object[] randomSequence(int size, long seed) {
    Integer[] result = new Integer[size];
    Random r = new Random(seed);
    for (int i = 0; i < result.length; i++) {
      result[i] = new Integer(r.nextInt(size));
    }
    return result;
  }

}