<?php
/**
 * Smarty plugin
 * This plugin is only for Smarty2 BC
 *
 * @package    Smarty
 * @subpackage PluginsFunction
 */

/**
 * Smarty {math} function plugin
 * Type:     function<br>
 * Name:     math<br>
 * Purpose:  handle math computations in template
 *
 * @link     http://www.smarty.net/manual/en/language.function.math.php {math}
 *           (Smarty online manual)
 * @author   Monte Ohrt <monte at ohrt dot com>
 *
 * @param array                    $params   parameters
 * @param Smarty
 *
 * @return string|null
 */
function smarty_function_math($params, &$smarty)
{
    static $_allowed_funcs =
        array('int' => true, 'abs' => true, 'ceil' => true, 'cos' => true, 'exp' => true, 'floor' => true,
              'log' => true, 'log10' => true, 'max' => true, 'min' => true, 'pi' => true, 'pow' => true, 'rand' => true,
              'round' => true, 'sin' => true, 'sqrt' => true, 'srand' => true, 'tan' => true);
    // be sure equation parameter is present
    if (empty($params[ 'equation' ])) {
        trigger_error("math: missing equation parameter", E_USER_WARNING);

        return;
    }

    $equation = $params[ 'equation' ];

    // make sure parenthesis are balanced
    if (substr_count($equation, "(") != substr_count($equation, ")")) {
        trigger_error("math: unbalanced parenthesis", E_USER_WARNING);

        return;
    }

    // disallow backticks
    if (strpos($equation, '`') !== false) {
        trigger_error("math: backtick character not allowed in equation", E_USER_WARNING);

        return;
    }

    // also disallow dollar signs
    if (strpos($equation, '$') !== false) {
        trigger_error("math: dollar signs not allowed in equation", E_USER_WARNING);

        return;
    }

    foreach ($params as $key => $val) {
        if ($key != "equation" && $key != "format" && $key != "assign") {
            // make sure value is not empty
            if (strlen($val) == 0) {
                trigger_error("math: parameter '{$key}' is empty", E_USER_WARNING);

                return;
            }
            if (!is_numeric($val)) {
                trigger_error("math: parameter '{$key}' is not numeric", E_USER_WARNING);

                return;
            }
        }
    }

    // match all vars in equation, make sure all are passed
    preg_match_all('!(?:0x[a-fA-F0-9]+)|([a-zA-Z_\x7f-\xff][a-zA-Z0-9_\x7f-\xff]*)!', $equation, $match);

    foreach ($match[ 1 ] as $curr_var) {
        if ($curr_var && !isset($params[ $curr_var ]) && !isset($_allowed_funcs[ $curr_var ])) {
            trigger_error("math: function call '{$curr_var}' not allowed, or missing parameter '{$curr_var}'", E_USER_WARNING);

            return;
        }
    }

    foreach ($params as $key => $val) {
        if ($key != "equation" && $key != "format" && $key != "assign") {
            $equation = preg_replace("/\b$key\b/", " \$params['$key'] ", $equation);
        }
    }
    $smarty_math_result = null;
    eval("\$smarty_math_result = " . $equation . ";");

    if (empty($params[ 'format' ])) {
        if (empty($params[ 'assign' ])) {
            return $smarty_math_result;
        } else {
            $smarty->assign($params[ 'assign' ], $smarty_math_result);
        }
    } else {
        if (empty($params[ 'assign' ])) {
            printf($params[ 'format' ], $smarty_math_result);
        } else {
            $smarty->assign($params[ 'assign' ], sprintf($params[ 'format' ], $smarty_math_result));
        }
    }
}
