root/trunk/Phergie/Plugin/Math.php @ 60

<?php

/**
* @see Phergie_Event_Handler
*/
require_once 'Phergie/Event/Handler.php';

/**
* Checks incoming requests for simple mathematical expressions, computes the
* result of such expressions, and responds with a message containing the
* result.
*/
class Phergie_Plugin_Math extends Phergie_Event_Handler
{
    /**
    * Holds the allowed function, characters, operators and constants
    *
    * @var array
    */
    protected $allowed = array
    (
        '0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
        '+', '-', '/', '*', '.', ' ', '<<', '>>', '%', '&', '^', '|', '~',
        'abs(', 'ceil(', 'floor(', 'exp(',
        'log10(',
        'cos(', 'sin(', 'sqrt(', 'tan(',
        'M_PI', 'INF', 'M_E',
    );

    /**
    * Holds the functions that can accept multiple arguments.
    *
    * @return void
    */
    protected $funcs = array
    (
        'round(', 'log(', 'pow(',
        'max(', 'min(', 'rand(',
    );

    /**
    * Parses a simple arithmetic expression, evaluates it, and returns the
    * result to the sender.
    *
    * @return void
    */
    public function onPrivmsg()
    {
        $source = $this->event->getSource();
        $message = $this->event->getArgument(1);
        if (preg_match('/^(?:math|calc) /', $message)) {
            // Get equation
            $equation = substr($message, 5);
            // Replace constants
            $equation = str_ireplace(
                array('pi', 'M_PI()', 'chucknorris', 'inf', ' e '),
                array('M_PI', 'M_PI', 1e10000, 'INF', ' M_E '),
                $equation
            );
            $equationSrc = $equation;

            // Parse equation
            $out = '';
            $ptr = 1;
            $allowcomma = 0;
            while (strlen($equation) > 0) {
                $substr = substr($equation, 0, $ptr);
                // Allowed string
                if (array_search($substr, $this->allowed) !== false) {
                    $out .= $substr;
                    $equation = substr($equation, $ptr);
                    $ptr = 0;
                // Allowed func
                } elseif (array_search($substr, $this->funcs) !== false) {
                    $out .= $substr;
                    $equation = substr($equation, $ptr);
                    $ptr = 0;
                    $allowcomma++;
                    if ($allowcomma === 1) {
                        $this->allowed[] = ',';
                    }
                // Opening parenthesis
                } elseif ($substr === '(') {
                    if ($allowcomma > 0) {
                        $allowcomma++;
                    }
                    $out .= $substr;
                    $equation = substr($equation, $ptr);
                    $ptr = 0;
                // Closing parenthesis
                } elseif ($substr === ')') {
                    if ($allowcomma > 0) {
                        $allowcomma--;
                        if($allowcomma === 0) {
                            array_pop($this->allowed);
                        }
                    }

                    $out .= $substr;
                    $equation = substr($equation, $ptr);
                    $ptr = 0;
                // Parse error if we've consumed the entire equation without finding anything valid
                } elseif ($ptr >= strlen($equation)) {
                    $this->doPrivmsg($source, 'Syntax error at "' . $substr . '" in equation "' . $equationSrc . '"');
                    return;
                } else {
                    $ptr++;
                }
            }
            $res = @eval('return ' . $out . ';');
            if($res === false) {
                $this->doPrivmsg($source, 'Computation error, division by zero?');
            } else {
                $this->doPrivmsg($source, $res);
            }
        }
    }
}