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/*
 * JBoss, Home of Professional Open Source.
 * Copyright 2012, Red Hat, Inc., and individual contributors
 * as indicated by the @author tags. See the copyright.txt file in the
 * distribution for a full listing of individual contributors.
 *
 * This 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 software 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 software; if not, write to the Free
 * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
 * 02110-1301 USA, or see the FSF site: http://www.fsf.org.
 */

package org.gatein.api.common;

import org.gatein.api.internal.ObjectToStringBuilder;

import java.io.Serializable;

/**
 * A pagination object to be used to describe pagination (offset, limit) which can be used in queries.
 *
 * @author Nick Scavelli
 */
public class Pagination implements Serializable {
    private final int offset;
    private final int limit;

    public Pagination(int offset, int limit) {
        if (limit == 0)
            throw new IllegalArgumentException("limit cannot be 0 for pagination.");

        this.offset = offset;
        this.limit = limit;
    }

    /**
     * The current page number this pagination object represents
     *
     * @return the page number
     */
    public int getPageNumber() {
        if (offset < limit || limit == 0)
            return 1;

        return (offset / limit) + 1;
    }

    /**
     * The offset for this pagination object. The offset determines what index (0 index) to start retrieving results from.
     *
     * @return the offset
     */
    public int getOffset() {
        return offset;
    }

    /**
     * The limit for this pagination object. The limit determines the maximum amount of results to return.
     *
     * @return the limit
     */
    public int getLimit() {
        return limit;
    }

    /**
     * Creates a new pagination object representing the next page
     *
     * @return new pagination object with offset shifted by offset+limit
     */
    public Pagination getNext() {
        return new Pagination(offset + limit, limit);
    }

    /**
     * Creates a new pagination object representing the previous page
     *
     * @return new pagination object with offset shifted by offset-limit
     */
    public Pagination getPrevious() {
        if (limit >= offset) {
            return new Pagination(0, limit);
        } else {
            return new Pagination(offset - limit, limit);
        }
    }

    @Override
    public String toString() {
        return ObjectToStringBuilder.toStringBuilder().add("offset", getOffset()).add("limit", getLimit())
                .add("pageNumber", getPageNumber()).toString();
    }

    @Override
    public boolean equals(Object o) {
        if (this == o)
            return true;
        if (!(o instanceof Pagination))
            return false;

        Pagination pagination = (Pagination) o;

        return (limit == pagination.limit) && (offset == pagination.offset);
    }

    @Override
    public int hashCode() {
        int result = offset;
        result = 31 * result + limit;
        return result;
    }
}