<?php

/**
* The Mega Error Handling.
*
* Copyright (C) 2007 Toby Inkster
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 3 of the License, or
* (at your option) any later version.
*
* This program 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
* General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
* @package demiblog
* @subpackage Core
* @author Toby Inkster <demiblog@tobyinkster.co.uk>
* @copyright Copyright (C) 2007 Toby Inkster
* @license http://www.gnu.org/licenses/gpl-3.0.html GNU General Public Licence
*/

/* This is used in PHP<5.2 */
if (!function_exists('json_encode'))
    require_once 'Services/JSON.php';

/**
* Damn Nice Error Handling
*
* This class is able to output errors in a variety of styles, such as
* HTML, e-mail and syslog. However, it's raison d'etre is to be able
* to output errors as specially-formatted HTML comments, which can be
* collected and manipulated by a nifty piece of Javascript and displayed
* as an interactive console.
*/
class MegaErrorHandler
{
    const DEBUG_SILENT =   1;
    const DEBUG_HTML   =   2;
    const DEBUG_HTMLX  =   4;
    const DEBUG_JSON   =  32;
    const DEBUG_MAIL   =  64;
    const DEBUG_SYSLOG = 256;

    private static $instance = NULL;
    private $current_mime_type = NULL;
    private $json_encoder = NULL;
    private $queue = array();
    private static $debug_mode = 1;
    
    private function __construct ()
    {
    }
    
    public function __clone ()
    {
        throw new Exception('MegaErrorHandler must not be cloned.');
    }
    
    public function __destruct ()
    {
        $this->handle_queue();
    }
    
    /**
     * Get instance of MegaErrorHandler.
     *
     * MegaErrorHandler is a singleton, so should not be constructed
     * directly. Call this method to get an instance.
     */
    public function singleton ()
    {
        if (!isset(self::$instance))
            self::$instance = new MegaErrorHandler;
        return self::$instance;
    }
    
    /**
     * Get/set the debugging mode of the handler.
     *
     * Use the defined class constants to set your preferred output mode. They
     * may be combined additively. May be called without any parameters to
     * avoid changing the mode at all.
     *
     * @param int $mode Preferred mode. Optional.
     * @return int Old mode.
     */
    public static function set_debug_mode ($mode=NULL)
    {
        $retval = self::$debug_mode;
        if (isset($mode))
            self::$debug_mode = $mode;
        return $retval;
    }

    /**
     * Call this function to start using this error handler.
     *
     * May be passed a debugging mode so that you don't need to call
     * set_debug_mode seperately.
     *
     * @param int $mode Preferred mode. Optional.
     * @return void
     */
    public static function set_error_handler ($mode=NULL)
    {
        set_error_handler(MegaErrorHandler__error_handler);
        if (isset($mode))
            self::set_debug_mode($mode);
    }
    
    /**
     * Print out an error message if certain conditions are met.
     *
     * Will not print out the message if error_reporting doesn't match it.
     * Will delay the printing of errors until after headers have been sent.
     *
     * @param int $errno Error severity number
     * @param string $errstr Error message
     * @param string $errfile File in which error occurred
     * @param int $errline Line number of file which caused error
     * @param array $errcontext Context information
     * @return boolean Should error be considered handled?
     */
    public function handle_error_conditional ($errno, $errstr, $errfile, $errline, $errcontext, $bt)
    {
        if (!($errno & error_reporting()))
            return TRUE;
        if (!$this->sent_headers())
            return $this->enqueue($errno, $errstr, $errfile, $errline, $errcontext, $bt);
        $this->handle_queue();
        return $this->handle_error($errno, $errstr, $errfile, $errline, $errcontext, $bt);
    }
    
    /**
     * Check if PHP has sent HTTP header block yet.
     *
     * @return boolean Has it?
     */
    private function sent_headers ()
    {
        return headers_sent();
    }
    
    /**
     * Queue up an error message to be printed later.
     *
     * @param int $errno Error severity number
     * @param string $errstr Error message
     * @param string $errfile File in which error occurred
     * @param int $errline Line number of file which caused error
     * @param array $errcontext Context information
     * @return boolean Successfully queued?
     */
    private function enqueue ($errno, $errstr, $errfile, $errline, $errcontext, $bt)
    {
        $this->queue[] = array($errno, $errstr, $errfile, $errline, $errcontext, $bt);
        return TRUE;
    }
    
    /**
     * Empty out queue of messages.
     *
     * Prints out any messages in the queue and removes them from it.
     *
     * @return bool Did anything actually need to be done?
     */
    private function handle_queue ()
    {
        if (!count($this->queue) || !$this->sent_headers())
            return FALSE;
        
        while ($E = array_shift($this->queue))
        {
            list ($errno, $errstr, $errfile, $errline, $errcontext, $bt) = $E;
            $this->handle_error($errno, $errstr, $errfile, $errline, $errcontext, $bt);
        }
        return TRUE;
    }
    
    /**
     * Print out an error message unconditionally.
     *
     * This should never be called directly. Use the conditional function
     * instead.
     *
     * @param int $errno Error severity number
     * @param string $errstr Error message
     * @param string $errfile File in which error occurred
     * @param int $errline Line number of file which caused error
     * @param array $errcontext Context information
     * @return boolean Should error be considered handled?
     */
    private function handle_error ($errno, $errstr, $errfile, $errline, $errcontext, $bt)
    {
        for ($i=0; $i<1; $i++)
            array_shift($bt);

        $errorType = array (
            E_ERROR              => 'ERROR',
            E_WARNING            => 'WARNING',
            E_PARSE              => 'PARSING ERROR',
            E_NOTICE             => 'NOTICE',
            E_CORE_ERROR         => 'CORE ERROR',
            E_CORE_WARNING       => 'CORE WARNING',
            E_COMPILE_ERROR      => 'COMPILE ERROR',
            E_COMPILE_WARNING    => 'COMPILE WARNING',
            E_USER_ERROR         => 'USER ERROR',
            E_USER_WARNING       => 'USER WARNING',
            E_USER_NOTICE        => 'USER NOTICE',
            E_STRICT             => 'STRICT NOTICE',
            4096                 => 'RECOVERABLE ERROR'
            );
                  
        $E = array(
            'E_NUMBER'  => $errno,
            'E_TYPE'    => ucfirst(strtolower($errorType[$errno])),
            'E_STRING'  => $errstr,
            'E_FILE'    => $errfile,
            'E_BASENAME'=> basename($errfile),
            'E_LINE'    => $errline,
            'E_CONTEXT' => print_r($errcontext, TRUE),
            '_SERVER'   => print_r($_SERVER, TRUE),
            '_GET'      => print_r($_GET, TRUE),
            '_POST'     => print_r($_POST, TRUE),
            '_COOKIE'   => print_r($_COOKIE, TRUE),
            '_ENV'      => print_r($_ENV, TRUE),
            'GLOBALS'   => print_r($GLOBALS, TRUE),
            'classes'   => print_r(get_declared_classes(), TRUE),
            'interfaces'=> print_r(get_declared_interfaces(), TRUE),
            'constants' => print_r(get_defined_constants(), TRUE),
            'includes'  => print_r(get_included_files(), TRUE),
            'ini'       => print_r(ini_get_all(), TRUE),
            'extensions'=> print_r(get_loaded_extensions(), TRUE),
            'backtrace' => print_r($bt, TRUE),
            'source'    => highlight_file($errfile, TRUE)
            );

        if (strlen(session_id()))
            $E['_SESSION'] = print_r($_SESSION, TRUE);

        if ((self::DEBUG_JSON & self::$debug_mode) && $this->is_html())
        {
            print '<!--ERROR ' .
                str_replace('--','=-', $this->json_encode($E)) .
                " RORRE-->\n";
        }

        if ((self::DEBUG_HTMLX & self::$debug_mode) && $this->is_html())
        {
            printf("<p><b>Error (%d)</b> at <tt>%s</tt><small>:%s</small><br>%s.</p>\n",
                $errno, $errfile, $errline, $errstr);
            print "<pre>\n";
            print htmlentities(print_r($E, TRUE));
            print "</pre>\n";            
        }
        elseif ((self::DEBUG_HTML & self::$debug_mode) && $this->is_html())
        {
            printf("<p><b>Error (%d)</b> at <tt>%s</tt><small>:%s</small><br>%s.</p>\n",
                $errno, $errfile, $errline, $errstr);
        }

        return TRUE;
    }
    
    /**
     * Detects whether the currently output page is in HTML.
     *
     * Or rather, doesn't at the moment. Needs working on.
     *
     * @return bool TRUE.
     */
    private function is_html()
    {
        return TRUE;
    }

    /**
     * Detects whether the currently output page is in HTML.
     *
     * Or rather, doesn't at the moment. Needs working on.
     *
     * @return bool TRUE.
     */
    private function json_encode ($struct)
    {
        /* PHP 5.2 includes JSON abilities natively. If available
         * then use them, because they're really fast.
         */
        if (function_exists('json_encode'))
            return json_encode($struct);
    
        /* We need to support earlier versions of PHP 5.x though, so try
         * using PEAR library too.
         */
        if (isset($this->json_encoder) && ($this->json_encoder instanceof Services_JSON))
            return $this->json_encoder->encode($struct);
        
        $this->json_encoder = new Services_JSON;
        return $this->json_encoder->encode($struct);
    }    
}

/**
* This function should be MegaErrorHandler::error_handler().
*
* Seems to be a bug in PHP 5.0.x (and possibly other versions of PHP) in dealing
* with error handlers which are static class methods. It doesn't always seem to
* cause a problem, but does so enough for it to *be* a problem.
*
* Anyway, this is the function which should be made the error_handler. You shouldn't
* use set_error_handler directly. Call MegaErrorHandler::set_error_handler()
* instead.
*
* @param int $errno Error severity number
* @param string $errstr Error message
* @param string $errfile File in which error occurred
* @param int $errline Line number of file which caused error
* @param array $errcontext Context information
* @return boolean Should error be considered handled?
*/
function MegaErrorHandler__error_handler ($errno, $errstr, $errfile, $errline, $errcontext)
{
    if (!isset($errfile))
        $errfile = '';
    if (!isset($errline))
        $errline = 0;
    if (!isset($errcontext))
        $errcontext = array();

    $eh = MegaErrorHandler::singleton();
    return $eh->handle_error_conditional(    $errno,
                        $errstr,
                        $errfile,
                        $errline,
                        $errcontext,
                        debug_backtrace()
                        );
}

/**
* Quick debugging function.
*/
function barf ($param)
{
    if (is_array($param))
        $param = print_r($param, TRUE);
    if (class_exists('DemiblogException'))
        throw new DemiblogException($param);
    throw new Exception($param);
}

?>