<?php
//
//  Pear DB Pager - Retrieve and return information of databases
//                  result sets
//
//  Copyright (C) 2001  Tomas Von Veschler Cox <cox@idecnet.com>
//
//  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., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
//
//
// $Id$

require_once 'PEAR.php';
require_once 'DB.php';

/**
* This class handles all the stuff needed for displaying paginated results
* from a database query of Pear DB, in a very easy way.
* Documentation and examples of use, can be found in:
* http://vulcanonet.com/soft/pager/ (could be outdated)
*
* IMPORTANT!
* Since PEAR DB already support native row limit (more fast and avaible in
* all the drivers), there is no more need to use $pager->build() or
* the $pager->fetch*() methods.
*
* Usage example:
*
*< ?php
* require_once 'DB/Pager.php';
* $db = DB::connect('your DSN string');
* $from = 0;   // The row to start to fetch from (you might want to get this
*              // param from the $_GET array
* $limit = 10; // The number of results per page
* $maxpages = 10; // The number of pages for displaying in the pager (optional)
* $res = $db->limitQuery($sql, $from, $limit);
* $nrows = 0; // Alternative you could use $res->numRows()
* while ($row = $res->fetchrow()) {
*    // XXX code for building the page here
*     $nrows++;
* }
* $data = DB_Pager::getData($from, $limit, $nrows, $maxpages);
* // XXX code for building the pager here
* ? >
*
* @version 0.7
* @author Tomas V.V.Cox <cox@idecnet.com>
* @see http://vulcanonet.com/soft/pager/
*/

class MECON_DB_Pager extends DB_Result
{

    var $currentpage = 0;
    var $current = 0;
    var $to = 0;

    /**
    * Constructor
    *
    * Gets all the data needed to paginate results
    * The object has this properties:
    *
    *    'current' => X,    // current page you are
    *    'numrows' => X,    // total number of results
    *    'next'    => X,    // row number where next page starts
    *    'prev'    => X,    // row number where prev page starts
    *    'remain'  => X,    // number of results remaning *in next page*
    *    'numpages'=> X,    // total number of pages
    *    'from'    => X,    // the row to start fetching
    *    'to'      => X,    // the row to stop fetching
    *    'limit'   => X,    // how many results per page
    *    'maxpages'   => X, // how many pages to show (google style)
    *    'firstpage'  => X, // the row number of the first page
    *    'lastpage'   => X, // the row number where the last page starts
    *    'pages'   => array(    // assoc with page "number => start row"
    *                1 => X,
    *                2 => X,
    *                3 => X
    *                )
    *    );

    * @param object $res  A DB_result object from Pear_DB
    * @param int    $from  The row to start fetching
    * @param int    $limit  How many results per page
    * @param int    $maxpages  Maximum pages to display
    * @param int    $numrows Pager will automatically
    *    find this param if is not given. If your Pear_DB backend extension
    *    doesn't support numrows(), you can manually calculate it
    *    and supply later to the constructor
    * @deprecated
    */
    function MECON_DB_Pager (&$res, $from = 0, $limit = 10, $maxpages = 21, $numrows = null)
    {
        $this->dbh = $res->dbh;
        $this->result = $res->result;
        $this->row_counter = $res->row_counter;
        $this->limit_from = $res->limit_from;
        $this->from = $from;
        $this->limit = $limit;
        $this->numrows = $numrows;
        $this->maxpages = $maxpages;
	$this->build();
    }

    /**
    * Calculates all the data needed by Pager to work
    * @return mixed PEAR_Error if error.
    */
    function build()
    {
        // if there is no numrows given, calculate it
        if ($this->numrows === null) {
            $this->numrows = $this->numrows();
            if (DB::isError($this->numrows)) {
                return $this->numrows;
            }
        }
	// Si no hay resultados no se hace nada.
        if (empty($this->numrows) or ($this->numrows < 0)) {
            return;
        }
        $this->from = empty($this->from) ? 0 : $this->from;

        if ($this->limit <= 0) {
            return PEAR::raiseError (null, 'wrong "limit" param', null,
                                     null, null, 'DB_Error', true);
        }

        // Total number of pages
        $this->numpages = ceil($this->numrows/$this->limit);

        // first & last page
        $this->firstpage = 1;
        $this->lastpage  = $this->numpages;

        // Build pages array
        $this->pages = array();
        for ($i = 1; $i <= $this->numpages; $i++) {
            $offset = $this->limit * ($i - 1);
            $this->pages[$i] = $offset;
            // $from must point to one page
            if ($this->from == $offset) {
                // The current page we are
                $this->currentpage = $i;
            }
        }
        if (!isset($this->currentpage)) {
            return PEAR::raiseError (null, 'wrong "from" param', null,
                                     null, null, 'DB_Error', true);
        }

        // Limit number of pages (goole algoritm)
        if ($this->maxpages) {
            $radio = floor($this->maxpages/2);
            $this->firstpage = $this->currentpage - $radio;
            if (!($this->maxpages % 2)) {
                $this->firstpage++;
            }
            if ($this->firstpage < 1) {
                $this->firstpage = 1;
            }
            $this->lastpage = $this->currentpage + $radio;
            if ($this->lastpage > $this->numpages) {
                $this->lastpage = $this->numpages;
            }
            foreach (range($this->firstpage, $this->lastpage) as $page) {
                $tmp[$page] = $this->pages[$page];
            }
            $this->pages = $tmp;
        }

        // Prev link
        $this->prev = $this->from - $this->limit;
        $this->prev = ($this->prev >= 0) ? $this->prev : null;

        // Next link
        $this->next = $this->from + $this->limit;
        $this->next = ($this->next < $this->numrows) ? $this->next : null;

        // Results remaining in next page & Last row to fetch
        if ($this->currentpage == $this->numpages) {
            $this->remain = 0;
            $this->to = $this->numrows;
        } else {
            if ($this->currentpage == ($this->numpages - 1)) {
                $this->remain = $this->numrows - ($this->limit * ($this->numpages - 1));
            } else {
                $this->remain = $this->limit;
            }
            $this->to = $this->currentpage * $this->limit;
        }

        // Current item (when fetching).
        $this->current = $this->from - 1;
    }

    function fetchRow($mode=DB_FETCHMODE_DEFAULT, $rownum=null)
    {
        $this->current++;
        if ($this->current >= $this->to) {
            return null;
        }
        return parent::fetchRow($mode, $this->current);
    }

    function fetchInto(&$arr, $mode=DB_FETCHMODE_DEFAULT)
    {
        $this->current++;
        if ($this->current >= $this->to) {
            return null;
        }
        return parent::fetchInto($arr, $mode, $this->current);
    }
}
?>