<?php
/**
 * Simple datasource decorator: Median
 *
 * $Id$
 *
 * @author gERD Schaufelberger <gerd@php-tools.net>
 * @license PHP License
 * @package WB
 * @subpackage db
 */

WBClass::load('WBDatasource_Decorator');

/**
 * Simple datasource decorator: Median
 *
 * @version 0.1.0
 * @package WB
 * @subpackage db
 */
class WBDatasource_Decorator_Median extends WBDatasource_Decorator
{
    /**
     * decorator's parameter list
     *
     * Parameters:
     * - columns: list of columns to decorate
     * - span: number of items to calculate average of
     * - format: number format as in sprintf()
     *
     * @var array
     */
    protected $parameter    =   array(
                                'span'      =>  7,
                                'column'    =>  array(),
                                'format'    =>  '%d'
                            );

    /**
     * store values for each column to calculate average
     * @var array
     */
    private $buffer =   array();

    /**
     * location of median values
     * @var array
     */
    private $idx    =   array();

    /**
     * setup column buffers
     */
    public function onStart(&$item)
    {
        $this->parameter['span']  = intval($this->parameter['span']);
        foreach ($this->parameter['column'] as $c) {#
            $this->buffer[$c]   =   array();
            $item[$c . '_med']  =   null;
        }

        $this->pos[]    =   ceil($this->parameter['span'] / 2);
        if ($this->parameter['span'] % 2 == 0) {
            $this->pos[]    =   floor($this->parameter['span'] / 2);
        }
    }

    /**
     * actually decorate list item
     *
     * @param array $item
     * @return void
     */
    public function decorate(&$item)
    {
        foreach ($this->buffer as $c => &$b) {
            if (count($b) >= $this->parameter['span']) {
                array_shift($b);
            }

            $b[]    =   $item[$c];
            if (count($b) != $this->parameter['span']) {
                $item[$c . '_med']  =   null;
                continue;
            }

            $x  =   $b[$this->pos[0]];
            if (isset($this->pos[1])) {
                $x  +=  $this->pos[1];
                $x  /=  2;
            }
            $item[$c . '_med']  =   sprintf($this->parameter['format'], $x);
        }
    }
}
?>