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• Pageable.java

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org.cp.elements.util.paging.Pageable Maven / Gradle / Ivy

/*
 * Copyright (c) 2011-Present. Codeprimate, LLC and authors.  All Rights Reserved.
 * 

 * This software is licensed under the Codeprimate End User License Agreement (EULA).
 * This software is proprietary and confidential in addition to an intellectual asset
 * of the aforementioned authors.
 * 

 * By using the software, the end-user implicitly consents to and agrees to be in compliance
 * with all terms and conditions of the EULA.  Failure to comply with the EULA will result in
 * the maximum penalties permissible by law.
 * 

 * In short, this software may not be reverse engineered, reproduced, copied, modified
 * or distributed without prior authorization of the aforementioned authors, permissible
 * and expressed only in writing.  The authors grant the end-user non-exclusive, non-negotiable
 * and non-transferable use of the software "as is" without expressed or implied WARRANTIES,
 * EXTENSIONS or CONDITIONS of any kind.
 * 

 * For further information on the software license, the end user is encouraged to read
 * the EULA @ ...
 */

package org.cp.elements.util.paging;

import static java.util.stream.StreamSupport.stream;
import static org.cp.elements.lang.ElementsExceptionsFactory.newPageNotFoundException;

import java.util.Comparator;

import org.cp.elements.lang.Assert;

/**
 * The {@link Pageable} interface defines a contract for implementing objects that support paging
 * over the contents of the object, such as a {@link Iterable}.
 *
 * @author John J. Blum
 * @param  {@link Class type} of the elements or items contained in the {@link Page pages}
 * of this {@link Pageable} object.
 * @see java.lang.Iterable
 * @see org.cp.elements.util.paging.Page
 * @since 1.0.0
 */
@SuppressWarnings("unused")
public interface Pageable extends Iterable> {

  /**
   * Determines whether this {@link Pageable} object contains any {@link Page Pages}.
   *
   * @return a boolean value indicating whether this {@link Pageable} object contains any {@link Page Pages}.
   * @see #count()
   */
  default boolean isEmpty() {
    return count() < 1;
  }

  /**
   * Get the total number of {@link Page pages} in this {@link Pageable} object.
   *
   * @return an int value indicating the total number of {@link Page pages} in this {@link Pageable} object.
   */
  default int count() {
    return (int) stream(this.spliterator(), false).count();
  }

  /**
   * Jump to the first {@link Page} in this {@link Pageable} collection of {@link Page Pages}.
   *
   * @return the first {@link Page}.
   * @throws PageNotFoundException if no {@link Page Pages} are available.
   * @see #getPage(int)
   */
  default Page firstPage() {

    try {
      return getPage(1);
    }
    catch (Exception cause) {
      throw newPageNotFoundException(cause, "No first page");
    }
  }

  /**
   * Gets the {@link Page} for the given page {@link Integer#TYPE number}, starting with page one.
   *
   * @param number integer value indicating the page number of the {@link Page} to return.
   * @return the {@link Page} with {@link Integer#TYPE number}.
   * @throws IllegalArgumentException if the {@link Integer#TYPE page number} is less than equal to 0.
   * @throws PageNotFoundException if a {@link Page} with {@link Integer#TYPE number} is not found.
   * @see org.cp.elements.util.paging.Page
   */
  default Page getPage(int number) {

    Assert.isTrue(number > 0, "Page number [%d] must be greater than 0", number);

    int count = 0;

    for (Page page : this) {
      if (++count == number) {
        return page;
      }
    }

    throw newPageNotFoundException("Page with number [%d] not found", number);
  }

  /**
   * Jump to the last {@link Page} in this {@link Pageable} collection of {@link Page Pages}.
   *
   * @return the last {@link Page}.
   * @throws PageNotFoundException if no {@link Page Pages} are available.
   * @see #getPage(int)
   */
  default Page lastPage() {

    try {
      return getPage(count());
    }
    catch (Exception cause) {
      throw newPageNotFoundException(cause, "No last page");
    }
  }

  /**
   * Sorts (orders) all the elements across all the {@link Page Pages} contained by this {@link Pageable}.
   *
   * @param orderBy {@link Comparator} used to sort (order) all the elements across all the {@link Page Pages}
   * contained by this {@link Pageable}.
   * @see java.util.Comparator
   */
  void sort(Comparator orderBy);

}