/*
 * Copyright (c) 2005 Your Corporation. All Rights Reserved.
 */
package net.jetmaven;

import org.hibernate.HibernateException;
import org.hibernate.Query;
import org.hibernate.ScrollableResults;

import java.util.List;

/**
 * Hibernate分頁信息
 */
public class HibernatePage implements Page
{
    private List elements;
    private int pageSize;
    private int pageNumber;
    private int totalElements = 0;

    /**
     * 構建HibernatePage對象，完成Hibernate的Query數據的分頁處理
     *
     * @param query      Hibernate的Query對象
     * @param pageNumber 當前頁編碼，從1開始，如果傳的值為Integer.MAX_VALUE表示獲取最后一頁。
     *                   如果你不知道最后一頁編碼，傳Integer.MAX_VALUE即可。如果當前頁超過總頁數，也表示最后一頁。
     *                   這兩種情況將重新更改當前頁的頁碼，為最后一頁編碼。
     * @param pageSize   每一頁顯示的條目數
     */
    public HibernatePage(Query query, int pageNumber, int pageSize)
    {
        this.pageNumber = pageNumber;
        this.pageSize = pageSize;
        try
        {
            ScrollableResults scrollableResults = query.scroll();
            //get the total elements number
            scrollableResults.last();
            this.totalElements = scrollableResults.getRowNumber();
            if (Integer.MAX_VALUE == this.pageNumber || this.pageNumber > getLastPageNumber())   //last page
            {
                this.pageNumber = getLastPageNumber();
            }
            elements = query.setFirstResult((this.pageNumber - 1) * this.pageSize).setMaxResults(this.pageSize + 1).list();
        } catch (HibernateException e)
        {
            throw new RuntimeException(e);
        }
    }

    public boolean isFirstPage()
    {
        return getThisPageNumber() == 1;
    }

    public boolean isLastPage()
    {
        return getThisPageNumber() >= getLastPageNumber();
    }

    public boolean hasNextPage()
    {
        return getLastPageNumber() > getThisPageNumber();
    }

    public boolean hasPreviousPage()
    {
        return getThisPageNumber() > 1;
    }

    public int getLastPageNumber()
    {
        return totalElements % this.pageSize == 0 ? totalElements / this.pageSize : totalElements / this.pageSize + 1;
    }

    /**
     * 返回List類型數據
     *
     * @return   List數據源
     */
    public Object getThisPageElements()
    {
        return elements;
    }

    public int getTotalNumberOfElements()
    {
        return totalElements;
    }

    public int getThisPageFirstElementNumber()
    {
        return (getThisPageNumber() - 1) * getPageSize() + 1;
    }

    public int getThisPageLastElementNumber()
    {
        int fullPage = getThisPageFirstElementNumber() + getPageSize() - 1;
        return getTotalNumberOfElements() < fullPage ? getTotalNumberOfElements() : fullPage;
    }

    public int getNextPageNumber()
    {
        return getThisPageNumber() + 1;
    }

    public int getPreviousPageNumber()
    {
        return getThisPageNumber() - 1;
    }

    public int getPageSize()
    {
        return pageSize;
    }

    public int getThisPageNumber()
    {
        return pageNumber;
    }
}