/*
 * Copyright 2010-2012 Luca Garulli (l.garulli--at--orientechnologies.com)
 *
 * Licensed 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.
 */
package com.orientechnologies.common.comparator;

import java.util.Comparator;

/**
 * Creates comparators for classes that does not implement {@link Comparable} but logically can be compared.
 * 
 * @author Andrey Lomakin
 * @since 03.07.12
 */
public class OComparatorFactory {
  public static final OComparatorFactory INSTANCE = new OComparatorFactory();

  private static final boolean           unsafeWasDetected;

  static {
    boolean unsafeDetected = false;

    try {
      Class<?> sunClass = Class.forName("sun.misc.Unsafe");
      unsafeDetected = sunClass != null;
    } catch (ClassNotFoundException cnfe) {
      // Ignore
    }

    unsafeWasDetected = unsafeDetected;
  }

  /**
   * Returns {@link Comparator} instance if applicable one exist or <code>null</code> otherwise.
   * 
   * @param clazz
   *          Class of object that is going to be compared.
   * @param <T>
   *          Class of object that is going to be compared.
   * @return {@link Comparator} instance if applicable one exist or <code>null</code> otherwise.
   */
  @SuppressWarnings("unchecked")
  public <T> Comparator<T> getComparator(Class<T> clazz) {
    boolean useUnsafe = Boolean.valueOf(System.getProperty("memory.useUnsafe"));

    if (clazz.equals(byte[].class)) {
      if (useUnsafe && unsafeWasDetected)
        return (Comparator<T>) OUnsafeByteArrayComparator.INSTANCE;

      return (Comparator<T>) OByteArrayComparator.INSTANCE;
    }

    return null;
  }
}
