/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License, Version 1.0 only
 * (the "License").  You may not use this file except in compliance
 * with the License.
 *
 * You can obtain a copy of the license at
 * trunk/opends/resource/legal-notices/OpenDS.LICENSE
 * or https://OpenDS.dev.java.net/OpenDS.LICENSE.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at
 * trunk/opends/resource/legal-notices/OpenDS.LICENSE.  If applicable,
 * add the following below this CDDL HEADER, with the fields enclosed
 * by brackets "[]" replaced with your own identifying information:
 *      Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 *
 *
 *      Copyright 2009 Sun Microsystems, Inc.
 */

package org.opends.sdk;



/**
 * The result of a tri-state logical expression. Condition results are
 * used to represent the result of a conditional evaluation that can
 * yield three possible values: {@code FALSE} (i.e. "no"), {@code TRUE}
 * (i.e. "yes"), or {@code UNDEFINED} (i.e. "maybe"). A result of
 * {@code UNDEFINED} indicates that further investigation may be
 * required.
 */
public enum ConditionResult
{
  /**
   * Indicates that the condition evaluated to {@code false}.
   */
  FALSE("false"),

  /**
   * Indicates that the condition could not be evaluated and its result
   * is undefined.
   */
  UNDEFINED("undefined"),

  /**
   * Indicates that the condition evaluated to {@code true}.
   */
  TRUE("true");

  // Boolean -> ConditionResult map.
  private static final boolean[] booleanMap = { false, false, true };

  // AND truth table.
  private static final ConditionResult[][] logicalAND =
      { { FALSE, FALSE, FALSE }, { FALSE, UNDEFINED, UNDEFINED },
          { FALSE, UNDEFINED, TRUE }, };

  // NOT truth table.
  private static final ConditionResult[] logicalNOT =
      { TRUE, UNDEFINED, FALSE };

  // OR truth table.
  private static final ConditionResult[][] logicalOR =
      { { FALSE, UNDEFINED, TRUE }, { UNDEFINED, UNDEFINED, TRUE },
          { TRUE, TRUE, TRUE }, };



  /**
   * Returns the logical AND of zero condition results, which is always
   * {@code TRUE}.
   *
   * @return The logical OR of zero condition results, which is always
   *         {@code TRUE}.
   */
  public static ConditionResult and()
  {
    return TRUE;
  }



  /**
   * Returns the logical AND of the provided condition result, which is
   * always {@code r}.
   *
   * @param r
   *          The condition result.
   * @return The logical AND of the provided condition result, which is
   *         always {@code r}.
   */
  public static ConditionResult and(ConditionResult r)
  {
    return r;
  }



  /**
   * Returns the logical AND of the provided condition results, which is
   * {@code TRUE} if all of the provided condition results are {@code
   * TRUE}, {@code FALSE} if at least one of them is {@code FALSE}, and
   * {@code UNDEFINED} otherwise. Note that {@code TRUE} is returned if
   * the provided list of results is empty.
   *
   * @param results
   *          The condition results to be compared.
   * @return The logical AND of the provided condition results.
   */
  public static ConditionResult and(ConditionResult... results)
  {
    ConditionResult finalResult = TRUE;
    for (ConditionResult result : results)
    {
      finalResult = and(finalResult, result);
      if (finalResult == FALSE)
        break;
    }
    return finalResult;
  }



  /**
   * Returns the logical AND of the provided condition results, which is
   * {@code TRUE} if both of the provided condition results are {@code
   * TRUE}, {@code FALSE} if at least one of them is {@code FALSE} , and
   * {@code UNDEFINED} otherwise.
   *
   * @param r1
   *          The first condition result to be compared.
   * @param r2
   *          The second condition result to be compared.
   * @return The logical AND of the provided condition results.
   */
  public static ConditionResult and(ConditionResult r1,
      ConditionResult r2)
  {
    return logicalAND[r1.ordinal()][r2.ordinal()];
  }



  /**
   * Returns the logical NOT of the provided condition result, which is
   * {@code TRUE} if the provided condition result is {@code FALSE},
   * {@code TRUE} if it is {@code FALSE}, and {@code UNDEFINED}
   * otherwise.
   *
   * @param r
   *          The condition result to invert.
   * @return The logical NOT of the provided condition result.
   */
  public static ConditionResult not(ConditionResult r)
  {
    return logicalNOT[r.ordinal()];
  }



  /**
   * Returns the logical OR of zero condition results, which is always
   * {@code FALSE}.
   *
   * @return The logical OR of zero condition results, which is always
   *         {@code FALSE}.
   */
  public static ConditionResult or()
  {
    return FALSE;
  }



  /**
   * Returns the logical OR of the provided condition result, which is
   * always {@code r}.
   *
   * @param r
   *          The condition result.
   * @return The logical OR of the provided condition result, which is
   *         always {@code r}.
   */
  public static ConditionResult or(ConditionResult r)
  {
    return r;
  }



  /**
   * Returns the logical OR of the provided condition results, which is
   * {@code FALSE} if all of the provided condition results are {@code
   * FALSE}, {@code TRUE} if at least one of them is {@code TRUE}, and
   * {@code UNDEFINED} otherwise. Note that {@code FALSE} is returned if
   * the provided list of results is empty.
   *
   * @param results
   *          The condition results to be compared.
   * @return The logical OR of the provided condition results.
   */
  public static ConditionResult or(ConditionResult... results)
  {
    ConditionResult finalResult = FALSE;
    for (ConditionResult result : results)
    {
      finalResult = and(finalResult, result);
      if (finalResult == TRUE)
        break;
    }
    return finalResult;
  }



  /**
   * Returns the logical OR of the provided condition results, which is
   * {@code FALSE} if both of the provided condition results are {@code
   * FALSE}, {@code TRUE} if at least one of them is {@code TRUE} , and
   * {@code UNDEFINED} otherwise.
   *
   * @param r1
   *          The first condition result to be compared.
   * @param r2
   *          The second condition result to be compared.
   * @return The logical OR of the provided condition results.
   */
  public static ConditionResult or(ConditionResult r1,
      ConditionResult r2)
  {
    return logicalOR[r1.ordinal()][r2.ordinal()];
  }



  /**
   * Returns the condition result which is equivalent to the provided
   * boolean value.
   *
   * @param b
   *          The boolean value.
   * @return {@code TRUE} if {@code b} was {@code true}, otherwise
   *         {@code FALSE}.
   */
  public static ConditionResult valueOf(boolean b)
  {
    return b ? TRUE : FALSE;
  }

  // The human-readable name for this result.
  private final String resultName;



  // Prevent instantiation.
  private ConditionResult(String resultName)
  {
    this.resultName = resultName;
  }



  /**
   * Converts this condition result to a boolean value. {@code FALSE}
   * and {@code UNDEFINED} are both converted to {@code false}, and
   * {@code TRUE} is converted to {@code true}.
   *
   * @return The boolean equivalent of this condition result.
   */
  public boolean toBoolean()
  {
    return booleanMap[ordinal()];
  }



  /**
   * Returns the string representation of this condition result.
   *
   * @return The string representation of his condition result.
   */
  @Override
  public String toString()
  {
    return resultName;
  }
}