/*
 * Copyright (C) 2009 The Guava Authors
 *
 * 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.google.common.collect;

import com.google.common.annotations.Beta;
import com.google.common.annotations.GwtCompatible;

import java.util.NoSuchElementException;

/**
 * A descriptor for a <i>discrete</i> {@code Comparable} domain such as all
 * {@link Integer}s. A discrete domain is one that supports the three basic
 * operations: {@link #next}, {@link #previous} and {@link #distance}, according
 * to their specifications. The methods {@link #minValue} and {@link #maxValue}
 * should also be overridden for bounded types.
 *
 * <p>A discrete domain always represents the <i>entire</i> set of values of its
 * type; it cannot represent partial domains such as "prime integers" or
 * "strings of length 5."
 *
 * <p>See the Guava User Guide section on <a href=
 * "http://code.google.com/p/guava-libraries/wiki/RangesExplained#Discrete_Domains">
 * {@code DiscreteDomain}</a>.
 *
 * @author Kevin Bourrillion
 * @since 10.0
 * @see DiscreteDomains
 */
@GwtCompatible
@Beta
public abstract class DiscreteDomain<C extends Comparable> {
  /** Constructor for use by subclasses. */
  protected DiscreteDomain() {}

  /**
   * Returns the unique least value of type {@code C} that is greater than
   * {@code value}, or {@code null} if none exists. Inverse operation to {@link
   * #previous}.
   *
   * @param value any value of type {@code C}
   * @return the least value greater than {@code value}, or {@code null} if
   *     {@code value} is {@code maxValue()}
   */
  public abstract C next(C value);

  /**
   * Returns the unique greatest value of type {@code C} that is less than
   * {@code value}, or {@code null} if none exists. Inverse operation to {@link
   * #next}.
   *
   * @param value any value of type {@code C}
   * @return the greatest value less than {@code value}, or {@code null} if
   *     {@code value} is {@code minValue()}
   */
  public abstract C previous(C value);

  /**
   * Returns a signed value indicating how many nested invocations of {@link
   * #next} (if positive) or {@link #previous} (if negative) are needed to reach
   * {@code end} starting from {@code start}. For example, if {@code end =
   * next(next(next(start)))}, then {@code distance(start, end) == 3} and {@code
   * distance(end, start) == -3}. As well, {@code distance(a, a)} is always
   * zero.
   *
   * <p>Note that this function is necessarily well-defined for any discrete
   * type.
   *
   * @return the distance as described above, or {@link Long#MIN_VALUE} or
   *     {@link Long#MAX_VALUE} if the distance is too small or too large,
   *     respectively.
   */
  public abstract long distance(C start, C end);

  /**
   * Returns the minimum value of type {@code C}, if it has one. The minimum
   * value is the unique value for which {@link Comparable#compareTo(Object)}
   * never returns a positive value for any input of type {@code C}.
   *
   * <p>The default implementation throws {@code NoSuchElementException}.
   *
   * @return the minimum value of type {@code C}; never null
   * @throws NoSuchElementException if the type has no (practical) minimum
   *     value; for example, {@link java.math.BigInteger}
   */
  public C minValue() {
    throw new NoSuchElementException();
  }

  /**
   * Returns the maximum value of type {@code C}, if it has one. The maximum
   * value is the unique value for which {@link Comparable#compareTo(Object)}
   * never returns a negative value for any input of type {@code C}.
   *
   * <p>The default implementation throws {@code NoSuchElementException}.
   *
   * @return the maximum value of type {@code C}; never null
   * @throws NoSuchElementException if the type has no (practical) maximum
   *     value; for example, {@link java.math.BigInteger}
   */
  public C maxValue() {
    throw new NoSuchElementException();
  }
}