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/*
 * Copyright (C) 2005, The Beangle Software.
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published
 * by the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.See the
 * GNU Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this program.  If not, see .
 */

package org.beangle.commons.collection.page

object Page {

  val DefaultPageNo = 1

  val DefaultPageSize = 20

  def empty[T](): Page[T] = EmptyPage.asInstanceOf[Page[T]]

  private object EmptyPage extends Page[Any] {

    def totalPages: Int = 0

    def pageIndex: Int = 0

    def pageSize: Int = 0

    def totalItems: Int = 0

    def hasNext: Boolean = false

    def hasPrevious: Boolean = false

    def next(): Page[Any] = this

    def previous(): Page[Any] = this

    def apply(index: Int): Any = null.asInstanceOf[Any]

    def length: Int = 0

    def moveTo(pageIndex: Int): Page[Any] = this

    def items: Seq[Any] = Nil

    def iterator: Iterator[Any] = Nil.iterator
  }
}

/** 分页对象
  *
  * @author chaostone
  */
trait Page[E] extends collection.immutable.Seq[E] {

  def totalPages: Int

  def pageIndex: Int

  def pageSize: Int

  def totalItems: Int

  def next(): Page[E]

  def hasNext: Boolean

  def previous(): Page[E]

  def hasPrevious: Boolean

  def moveTo(pageIndex: Int): Page[E]

  def items: collection.Seq[E]
}