net.smartlab.web.page.Paginator Maven / Gradle / Ivy

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/*
 * The SmartWeb Framework
 * Copyright (C) 2004-2006
 *
 * This library 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 2.1 of the License, or (at your option) any later version.
 *
 * This library 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 library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
 *
 * For further informations on the SmartWeb Framework please visit
 *
 *                        http://smartweb.sourceforge.net
 */
 
package net.smartlab.web.page;

import java.util.Iterator;
import java.util.NoSuchElementException;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

/**
 * TODO documentation
 * 
 * @author rlogiacco
 */
public abstract class Paginator implements Iterator {

    /* # net.smartlab.web.paging.PaginationException pe */

    /**
     * A constant to identify an unlimited page listing.
     * www.lamiainclinazione.org
     */
    public final static int UNLIMITED_PAGES = 0;

    /**
     * A constant to identify an unlimited item listing.
     */
    public final static int UNLIMITED_ITEMS = 0;

    /**
     * A constant to identify the page was not setted.
     */
    public final static int UNDEFINED_PAGE = -1;

    /**
     * Logging system accessor.
     */
    protected Log logger = LogFactory.getLog(this.getClass());

    /**
     * The elements in the current page.
     */
    protected Object[] array;

    /**
     * The page relative index of the current element.
     */
    private int index;

    /**
     * The actual page index.
     */
    private int page;

    /**
     * The number of items in all pages.
     */
    private int count;

    /**
     * An array of page indexes directly accessibile.
     */
    private int[] pages;

    /**
     * The last page can ever been accessed through this paginator instance.
     */
    private int last;


    /**
     * TODO documentation
     */
    protected Paginator() {
        this(0, 0);
    }

    /**
     * TODO documentation
     * 
     * @param size
     * @param pages
     */
    protected Paginator(int size, int pages) {
        this.array = new Object[size];
        this.pages = new int[pages];
        this.page = UNDEFINED_PAGE;
        this.index = 0;
    }

    /**
     * TODO documentation
     * 
     * @return
     */
    public int getPage() {
        return page;
    }

    /**
     * TODO documentation
     * 
     * @return
     */
    public int[] getPages() {
        return pages;
    }

    /**
     * TODO documentation
     * 
     * @return
     */
    public int getPageCount() {
        return last;
    }

    /**
     * TODO documentation
     * 
     * @param size
     */
    public void setPages(int size) {
        if (array.length > 0) {
            this.last = (count / array.length) + (count % array.length == 0 ? 0 : 1);
            if (size == Paginator.UNLIMITED_PAGES || last <= size) {
                this.pages = new int[last];
            } else {
                this.pages = new int[size];
            }
        }
    }

    /**
     * TODO documentation
     * 
     * @param page
     */
    public void setPage(int page) {
        if (count > 0) {
            if (pages.length != UNLIMITED_PAGES && (page <= 0 || page > last)) {
                throw new IndexOutOfBoundsException("Invalid page " + page);
            }
            if (page < pages[0] || page > pages[pages.length - 1]) {
                for (int i = 0; i < pages.length; i++) {
                    pages[i] = (((page - 1) / pages.length) * pages.length) + i + 1;
                }
                if (pages[pages.length - 1] > last) {
                    int[] tmp = new int[last - pages[0] + 1];
                    System.arraycopy(pages, 0, tmp, 0, tmp.length);
                    this.pages = tmp;
                }
            }
            this.index = 0;
            if (page != this.page) {
                this.page = page;
                this.setArray();
            }
        }
    }

    /**
     * TODO documentation
     * 
     * @return
     */
    public int getNext() {
        if (page >= last || count == 0 || pages[pages.length - 1] >= last) {
            return -1;
        } else {
            return pages[pages.length - 1] + 1;
        }
    }

    /**
     * TODO documentation
     * 
     * @return
     */
    public int getPrev() {
        if (page <= 1 || pages[0] <= 1 || count == 0) {
            return -1;
        } else {
            return pages[0] - 1;
        }
    }

    /**
     * TODO documentation
     * 
     * @param count
     */
    public void setCount(int count) {
        this.count = count;
        if (pages.length > 0) {
            this.setPages(pages.length);
        }
        if (array.length == UNLIMITED_ITEMS) {
            this.setPageSize(count);
        }
    }

    /**
     * TODO documentation
     * 
     * @return
     */
    public int getCount() {
        return count;
    }

    /**
     * TODO documentation
     * 
     * @return
     */
    public int getPageSize() {
        return array.length;
    }

    /**
     * TODO documentation
     * 
     * @param size
     */
    public void setPageSize(int size) {
        if (size == UNLIMITED_ITEMS) {
            this.array = new Object[size];
            this.setPages(1);
        } else {
            this.array = new Object[size];
            this.setPages(UNLIMITED_PAGES);
        }
    }

    /**
     * TODO documentation
     * 
     * @return
     */
    public int getStart() {
        if (pages.length > 0) {
            return ((page - 1) * array.length) + 1;
        } else {
            return 0;
        }
    }

    /**
     * TODO documentation
     * 
     * @return
     */
    public int getStop() {
        if (pages.length > 0) {
            if (page * array.length < count) {
                return page * array.length;
            } else {
                return count;
            }
        } else {
            return 0;
        }
    }

    /**
     * TODO documentation
     */
    abstract protected void setArray();

    /**
     * @see java.util.Iterator#hasNext()
     */
    public boolean hasNext() {
        if (page == UNDEFINED_PAGE) {
            this.setPage(1);
        }
        return index < array.length && array[index] != null;
    }

    /**
     * @see java.util.Iterator#next()
     */
    public Object next() {
        try {
            return array[index++];
        } catch (Exception e) {
            throw new NoSuchElementException();
        }
    }

    /**
     * This operation is not supported.
     * 
     * @see java.util.Iterator#remove()
     * @throws java.lang.UnsupportedOperationException
     */
    public void remove() {
        throw new UnsupportedOperationException();
    }

    /**
     * TODO documentation
     */
    public void reset() {
        this.index = 0;
    }
}