<?php
/**
* @version	$Id: logger.php 16797 2024-08-16 08:27:01Z alex $
* @package	In-Portal
* @copyright	Copyright (C) 1997 - 2012 Intechnic. All rights reserved.
* @license      GNU/GPL
* In-Portal is Open Source software.
* This means that this software may have been modified pursuant
* the GNU General Public License, and as distributed it includes
* or is derivative of works licensed under the GNU General Public License
* or other free or open source software licenses.
* See http://www.in-portal.org/license for copyright notices and details.
*/

defined('FULL_PATH') or die('restricted access!');

/**
 * Class for logging system activity
 */
class kLogger extends kBase {

	/**
	 * Prefix of all database related errors
	 */
	const DB_ERROR_PREFIX = 'SQL Error:';

	/**
	 * Logger state: logging of errors and user-defined messages
	 */
	const STATE_ENABLED = 1;

	/**
	 * Logger state: logging of user-defined messages only
	 */
	const STATE_USER_ONLY = 2;

	/**
	 * Logger state: don't log anything
	 */
	const STATE_DISABLED = 0;

	/**
	 * Log store: automatically determine where log should be written
	 */
	const LS_AUTOMATIC = 1;

	/**
	 * Log store: always write log to database
	 */
	const LS_DATABASE = 2;

	/**
	 * Log store: always write log to disk
	 */
	const LS_DISK = 3;

	/**
	 * Log level: system is unusable
	 */
	const LL_EMERGENCY = 0;

	/**
	 * Log level: action must be taken immediately
	 */
	const LL_ALERT = 1;

	/**
	 * Log level: the system is in a critical condition
	 */
	const LL_CRITICAL = 2;

	/**
	 * Log level: there is an error condition
	 */
	const LL_ERROR = 3;

	/**
	 * Log level: there is a warning condition
	 */
	const LL_WARNING = 4;

	/**
	 * Log level: a normal but significant condition
	 */
	const LL_NOTICE = 5;

	/**
	 * Log level: a purely informational message
	 */
	const LL_INFO = 6;

	/**
	 * Log level: messages generated to debug the application
	 */
	const LL_DEBUG = 7;

	/**
	 * Log type: PHP related activity
	 */
	const LT_PHP = 1;

	/**
	 * Log type: database related activity
	 */
	const LT_DATABASE = 2;

	/**
	 * Log type: custom activity
	 */
	const LT_OTHER = 3;

	/**
	 * Log interface: Front
	 */
	const LI_FRONT = 1;

	/**
	 * Log interface: Admin
	 */
	const LI_ADMIN = 2;

	/**
	 * Log interface: Cron (Front)
	 */
	const LI_CRON_FRONT = 3;

	/**
	 * Log interface: Cron (Admin)
	 */
	const LI_CRON_ADMIN = 4;

	/**
	 * Log interface: API
	 */
	const LI_API = 5;

	/**
	 * Log notification status: disabled
	 */
	const LNS_DISABLED = 0;

	/**
	 * Log notification status: pending
	 */
	const LNS_PENDING = 1;

	/**
	 * Log notification status: sent
	 */
	const LNS_SENT = 2;

	/**
	 * Database connection used for logging.
	 *
	 * @var kDBConnection
	 */
	protected $dbStorage;

	/**
	 * List of error/exception handlers
	 *
	 * @var Array
	 * @access protected
	 */
	protected $_handlers = Array ();

	/**
	 * Long messages are saved here, because "trigger_error" doesn't support error messages over 1KB in size
	 *
	 * @var Array
	 * @access protected
	 */
	protected static $_longMessages = Array ();

	/**
	 * Log record being worked on
	 *
	 * @var Array
	 * @access protected
	 */
	protected $_logRecord = Array ();

	/**
	 * Maximal level of a message, that can be logged
	 *
	 * @var int
	 * @access protected
	 */
	protected $_maxLogLevel = self::LL_NOTICE;

	/**
	 * State of the logger
	 *
	 * @var int
	 * @access protected
	 */
	protected $_state = self::STATE_DISABLED;

	/**
	 * Caches state of debug mode
	 *
	 * @var bool
	 * @access protected
	 */
	protected $_debugMode = false;

	/**
	 * Ignores backtrace record where following classes/files are mentioned
	 *
	 * @var array
	 */
	protected $_ignoreInTrace = array(
		'kLogger' => 'logger.php',
		'kErrorHandlerStack' => 'logger.php',
		'kExceptionHandlerStack' => 'logger.php',
		'kDBConnection' => 'db_connection.php',
		'kDBConnectionDebug' => 'db_connection.php',
		'kDBLoadBalancer' => 'db_load_balancer.php',
	);

	/**
	 * Create event log
	 *
	 * @param Array $methods_to_call List of invokable kLogger class method with their parameters (if any)
	 * @access public
	 */
	public function __construct($methods_to_call = Array ())
	{
		parent::__construct();

		$this->dbStorage = $this->getDBStorage();

		$system_config = kUtil::getSystemConfig();

		$this->_debugMode = $this->Application->isDebugMode();
		$this->setState($system_config->get('EnableSystemLog', self::STATE_DISABLED));
		$this->_maxLogLevel = $system_config->get('SystemLogMaxLevel', self::LL_NOTICE);

		foreach ($methods_to_call as $method_to_call) {
			call_user_func_array(Array ($this, $method_to_call[0]), $method_to_call[1]);
		}

		if ( !kUtil::constOn('DBG_ZEND_PRESENT') && !$this->Application->isDebugMode() ) {
			// don't report error on screen if debug mode is turned off
			error_reporting(0);
			ini_set('display_errors', 0);
		}

		register_shutdown_function(Array ($this, 'catchLastError'));
	}

	/**
	 * Create separate connection for logging purposes.
	 *
	 * @return kDBConnection
	 */
	protected function getDBStorage()
	{
		$system_config = new kSystemConfig(true);
		$vars = $system_config->getData();
		$db_class = $this->Application->isDebugMode() ? 'kDBConnectionDebug' : 'kDBConnection';

		// Can't use "kApplication::makeClass", because class factory isn't initialized at this point.
		$db = new $db_class(SQL_TYPE, array($this, 'handleSQLError'), 'logger');
		$db->setup($vars);

		return $db;
	}

	/**
	 * Sets state of the logged (enabled/user-only/disabled)
	 *
	 * @param $new_state
	 * @return void
	 * @access public
	 */
	public function setState($new_state = null)
	{
		if ( isset($new_state) ) {
			$this->_state = (int)$new_state;
		}

		if ( $this->_state === self::STATE_ENABLED ) {
			$this->_enableErrorHandling();
		}
		elseif ( $this->_state === self::STATE_DISABLED ) {
			$this->_disableErrorHandling();
		}
	}

	/**
	 * Enable error/exception handling capabilities
	 *
	 * @return void
	 * @access protected
	 */
	protected function _enableErrorHandling()
	{
		$this->_disableErrorHandling();

		$this->_handlers[self::LL_ERROR] = new kErrorHandlerStack($this);
		$this->_handlers[self::LL_CRITICAL] = new kExceptionHandlerStack($this);
	}

	/**
	 * Disables error/exception handling capabilities
	 *
	 * @return void
	 * @access protected
	 */
	protected function _disableErrorHandling()
	{
		foreach ($this->_handlers as $index => $handler) {
			$this->_handlers[$index]->__destruct();
			unset($this->_handlers[$index]);
		}
	}

	/**
	 * Initializes new log record. Use "kLogger::write" to save to db/disk
	 *
	 * @param string $message
	 * @param int $code
	 * @return kLogger
	 * @access public
	 */
	public function prepare($message = '', $code = null)
	{
		$this->_logRecord = Array (
			'LogUniqueId' => kUtil::generateId(),
			'LogMessage' => $message,
			'LogLevel' => self::LL_INFO,
			'LogCode' => $code,
			'LogType' => self::LT_OTHER,
			'LogHostname' => $_SERVER['HTTP_HOST'],
			'LogRequestSource' => php_sapi_name() == 'cli' ? 2 : 1,
			'LogRequestURI' => php_sapi_name() == 'cli' ? implode(' ', $GLOBALS['argv']) : $_SERVER['REQUEST_URI'],
			'LogUserId' => USER_GUEST,
			'IpAddress' => isset($_SERVER['REMOTE_ADDR']) ? $_SERVER['REMOTE_ADDR'] : '',
			'LogSessionKey' => '',
			'LogProcessId' => getmypid(),
			'LogUserData' => '',
			'LogNotificationStatus' => self::LNS_DISABLED,
		);

		if ( $this->Application->isAdmin ) {
			$this->_logRecord['LogInterface'] = defined('CRON') && CRON ? self::LI_CRON_ADMIN : self::LI_ADMIN;
		}
		else {
			$this->_logRecord['LogInterface'] = defined('CRON') && CRON ? self::LI_CRON_FRONT : self::LI_FRONT;
		}

		if ( $this->Application->InitDone ) {
			$this->_logRecord['LogUserId'] = $this->Application->RecallVar('user_id');
			$this->_logRecord['LogSessionKey'] = $this->Application->GetSID(Session::PURPOSE_STORAGE);
			$this->_logRecord['IpAddress'] = $this->Application->getClientIp();
		}

		return $this;
	}

	/**
	 * Sets one or more fields of log record
	 *
	 * @param string|Array $field_name
	 * @param string|null $field_value
	 * @return kLogger
	 * @access public
	 * @throws UnexpectedValueException
	 */
	public function setLogField($field_name, $field_value = null)
	{
		if ( isset($field_value) ) {
			$this->_logRecord[$field_name] = $field_value;
		}
		elseif ( is_array($field_name) ) {
			$this->_logRecord = array_merge($this->_logRecord, $field_name);
		}
		else {
			throw new UnexpectedValueException('Invalid arguments');
		}

		return $this;
	}

	/**
	 * Sets user data
	 *
	 * @param string $data
	 * @param bool $as_array
	 * @return kLogger
	 * @access public
	 */
	public function setUserData($data, $as_array = false)
	{
		if ( $as_array ) {
			$data = serialize((array)$data);
		}

		return $this->setLogField('LogUserData', $data);
	}

	/**
	 * Add user data
	 *
	 * @param string $data
	 * @param bool $as_array
	 * @return kLogger
	 * @access public
	 */
	public function addUserData($data, $as_array = false)
	{
		$new_data = $this->_logRecord['LogUserData'];

		if ( $as_array ) {
			$new_data = $new_data ? unserialize($new_data) : Array ();
			$new_data[] = $data;
			$new_data = serialize($new_data);
		}
		else {
			$new_data .= ($new_data ? PHP_EOL : '') . $data;
		}

		return $this->setLogField('LogUserData', $new_data);
	}

	/**
	 * Adds event to log record
	 *
	 * @param kEvent $event
	 * @return kLogger
	 * @access public
	 */
	public function addEvent(kEvent $event)
	{
		$this->_logRecord['LogEventName'] = (string)$event;

		return $this;
	}

	/**
	 * Adds log source file & file to log record
	 *
	 * @param string|Array $file_or_trace file path
	 * @param int $line file line
	 * @return kLogger
	 * @access public
	 */
	public function addSource($file_or_trace = '', $line = 0)
	{
		if ( is_array($file_or_trace) ) {
			$trace_info = $file_or_trace[0];
			$this->_logRecord['LogSourceFilename'] = $trace_info['file'];
			$this->_logRecord['LogSourceFileLine'] = $trace_info['line'];
		}
		else {
			$this->_logRecord['LogSourceFilename'] = $file_or_trace;
			$this->_logRecord['LogSourceFileLine'] = $line;
		}

		$code_fragment = $this->getCodeFragment(
			$this->_logRecord['LogSourceFilename'],
			$this->_logRecord['LogSourceFileLine']
		);

		if ( $code_fragment !== null ) {
			$this->_logRecord['LogCodeFragment'] = $code_fragment;
		}

		return $this;
	}

	/**
	 * Adds session contents to log record
	 *
	 * @param bool $include_optional Include optional session variables
	 * @return kLogger
	 * @access public
	 */
	public function addSessionData($include_optional = false)
	{
		if ( $this->Application->InitDone ) {
			$this->_logRecord['LogSessionData'] = serialize($this->Application->Session->getSessionData($include_optional));
		}

		return $this;
	}

	/**
	 * Adds user request information to log record
	 *
	 * @return kLogger
	 * @access public
	 */
	public function addRequestData()
	{
		$request_data = array(
			'Headers' => $this->Application->HttpQuery->getHeaders(),
		);

		$request_variables = Array('_GET' => $_GET, '_POST' => $_POST, '_COOKIE' => $_COOKIE);

		foreach ( $request_variables as $title => $data ) {
			if ( !$data ) {
				continue;
			}

			$request_data[$title] = $data;
		}

		$this->_logRecord['LogRequestData'] = serialize($request_data);

		return $this;
	}

	/**
	 * Adds trace to log record
	 *
	 * @param Array $trace
	 * @param int $skip_levels
	 * @param Array $skip_files
	 * @return kLogger
	 * @access public
	 */
	public function addTrace($trace = null, $skip_levels = 1, $skip_files = null)
	{
		$trace = $this->createTrace($trace, $skip_levels, $skip_files);

		foreach ($trace as $trace_index => $trace_info) {
			if ( isset($trace_info['args']) ) {
				$trace[$trace_index]['args'] = $this->_implodeObjects($trace_info['args']);
			}

			if ( isset($trace_info['file'], $trace_info['line']) ) {
				$code_fragment = $this->getCodeFragment($trace_info['file'], $trace_info['line']);

				if ( $code_fragment !== null ) {
					$trace[$trace_index]['code_fragment'] = $code_fragment;
				}
			}
		}

		$this->_logRecord['LogBacktrace'] = serialize($this->_removeObjectsFromTrace($trace));

		return $this;
	}

	/**
	 * Returns a code fragment.
	 *
	 * @param string  $file Filename.
	 * @param integer $line Line.
	 *
	 * @return string|null
	 */
	protected function getCodeFragment($file, $line)
	{
		static $path_filter_regexp;

		// Lazy detect path filter regexp, because it's not available at construction time.
		if ( $path_filter_regexp === null ) {
			$application =& kApplication::Instance();
			$path_filter_regexp = $application->ConfigValue('SystemLogCodeFragmentPathFilterRegExp');
		}

		if ( strpos($file, 'eval()\'d code') !== false
			|| ($path_filter_regexp && !preg_match($path_filter_regexp, $file))
		) {
			return null;
		}

		$from_line = max(1, $line - 10);
		$to_line = $line + 10;

		// Prefix example: ">>> 5. " or "    5. ".
		$prefix_length = 4 + strlen($to_line) + 2;

		$cmd_parts = array(
			'sed',
			'-n',
			escapeshellarg($from_line . ',' . $to_line . 'p'),
			escapeshellarg($file),
		);
		$command = implode(' ', $cmd_parts);

		$ret = array();
		$code_fragment = preg_replace('/(\r\n|\n|\r)$/', '', shell_exec($command), 1);

		foreach ( explode("\n", $code_fragment) as $line_offset => $code_fragment_part ) {
			$line_number = $from_line + $line_offset;
			$line_indicator = $line_number == $line ? '>>> ' : '    ';

			$ret[] = str_pad($line_indicator . $line_number . '.', $prefix_length) . $code_fragment_part;
		}

		return implode("\n", $ret);
	}

	/**
	 * Remove objects from trace, since before PHP 5.2.5 there wasn't possible to remove them initially
	 *
	 * @param Array $trace
	 * @return Array
	 * @access protected
	 */
	protected function _removeObjectsFromTrace($trace)
	{
		if ( version_compare(PHP_VERSION, '5.3', '>=') ) {
			return $trace;
		}

		$trace_indexes = array_keys($trace);

		foreach ($trace_indexes as $trace_index) {
			unset($trace[$trace_index]['object']);
		}

		return $trace;
	}

	/**
	 * Implodes object to prevent memory leaks
	 *
	 * @param Array $array
	 * @return Array
	 * @access protected
	 */
	protected function _implodeObjects($array)
	{
		$ret = Array ();

		foreach ($array as $key => $value) {
			if ( is_array($value) ) {
				$ret[$key] = $this->_implodeObjects($value);
			}
			elseif ( is_object($value) ) {
				if ( $value instanceof kEvent ) {
					$ret[$key] = 'Event: ' . (string)$value;
				}
				elseif ( $value instanceof kBase ) {
					$ret[$key] = (string)$value;
				}
				else {
					$ret[$key] = 'Class: ' . get_class($value);
				}
			}
			elseif ( is_resource($value) ) {
				$ret[$key] = (string)$value;
			}
			elseif ( strlen($value) > 200 ) {
				$ret[$key] = substr($value, 0, 50) . ' ...';
			}
			else {
				$ret[$key] = $value;
			}
		}

		return $ret;
	}

	/**
	 * Removes first N levels from trace
	 *
	 * @param Array $trace
	 * @param int $levels
	 * @param Array $files
	 * @return Array
	 * @access public
	 */
	public function createTrace($trace = null, $levels = null, $files = null)
	{
		if ( !isset($trace) ) {
			$trace = debug_backtrace(false);
		}

		if ( !$trace ) {
			// no trace information
			return $trace;
		}

		if ( isset($levels) && is_numeric($levels) ) {
			for ($i = 0; $i < $levels; $i++) {
				array_shift($trace);
			}
		}

		if ( isset($files) && is_array($files) ) {
			$classes = array_keys($files);

			while ( true ) {
				$trace_info = $trace[0];
				$file = isset($trace_info['file']) ? basename($trace_info['file']) : '';
				$class = isset($trace_info['class']) ? $trace_info['class'] : '';

				if ( ($file && !in_array($file, $files)) || ($class && !in_array($class, $classes)) ) {
					break;
				}

				array_shift($trace);
			}
		}

		return $trace;
	}

	/**
	 * Adds PHP error to log record
	 *
	 * @param int $errno
	 * @param string $errstr
	 * @param string $errfile
	 * @param int $errline
	 * @return kLogger
	 * @access public
	 */
	public function addError($errno, $errstr, $errfile = null, $errline = null)
	{
		$errstr = self::expandMessage($errstr, !$this->_debugMode);
		$this->_logRecord['LogLevel'] = $this->_getLogLevelByErrorNo($errno);

		if ( $this->isLogType(self::LT_DATABASE, $errstr) ) {
			list ($errno, $errstr, $sql) = self::parseDatabaseError($errstr);

			$this->_logRecord['LogType'] = self::LT_DATABASE;
			$this->_logRecord['LogUserData'] = $sql;

			$trace = $this->createTrace(null, 4, $this->_ignoreInTrace);
			$this->addSource($trace);
			$this->addTrace($trace, 0);
		}
		else {
			$this->_logRecord['LogType'] = self::LT_PHP;

			$this->addSource((string)$errfile, $errline);
			$this->addTrace(null, 4);
		}

		$this->_logRecord['LogCode'] = $errno;
		$this->_logRecord['LogMessage'] = $errstr;

		return $this;
	}

	/**
	 * Adds PHP exception to log record
	 *
	 * @param Exception $exception
	 * @return kLogger
	 * @access public
	 */
	public function addException($exception)
	{
		$errstr = self::expandMessage($exception->getMessage(), !$this->_debugMode);
		$this->_logRecord['LogLevel'] = self::LL_CRITICAL;

		$exception_trace = $exception->getTrace();

		array_unshift($exception_trace, array(
			'function' => '',
			'file' => $exception->getFile() !== null ? $exception->getFile() : 'n/a',
			'line' => $exception->getLine() !== null ? $exception->getLine() : 'n/a',
			'args' => array(),
		));

		if ( $this->isLogType(self::LT_DATABASE, $errstr) ) {
			list ($errno, $errstr, $sql) = self::parseDatabaseError($errstr);

			$this->_logRecord['LogType'] = self::LT_DATABASE;
			$this->_logRecord['LogUserData'] = $sql;

			$trace = $this->createTrace($exception_trace, null, $this->_ignoreInTrace);
			$this->addSource($trace);
			$this->addTrace($trace, 0);
		}
		else {
			$this->_logRecord['LogType'] = self::LT_PHP;
			$errno = $exception->getCode();

			$this->addSource((string)$exception->getFile(), $exception->getLine());
			$this->addTrace($exception_trace, 0);
		}

		$this->_logRecord['LogCode'] = $errno;
		$this->_logRecord['LogMessage'] = $errstr;

		return $this;
	}

	/**
	 * Allows to map PHP error numbers to syslog log level
	 *
	 * @param int $errno
	 * @return int
	 * @access protected
	 */
	protected function _getLogLevelByErrorNo($errno)
	{
		$error_number_mapping = Array (
			self::LL_ERROR 		=>	Array (E_RECOVERABLE_ERROR, E_USER_ERROR, E_ERROR, E_CORE_ERROR, E_COMPILE_ERROR, E_PARSE),
			self::LL_WARNING	=>	Array (E_WARNING, E_USER_WARNING, E_CORE_WARNING, E_COMPILE_WARNING),
			self::LL_NOTICE		=>	Array (E_NOTICE, E_USER_NOTICE, E_STRICT),
		);

		if ( version_compare(PHP_VERSION, '5.3.0', '>=') ) {
			$error_number_mapping[self::LL_NOTICE][] = E_DEPRECATED;
			$error_number_mapping[self::LL_NOTICE][] = E_USER_DEPRECATED;
		}

		foreach ($error_number_mapping as $log_level => $error_numbers) {
			if ( in_array($errno, $error_numbers) ) {
				return $log_level;
			}
		}

		return self::LL_ERROR;
	}

	/**
	 * Changes log level of a log record
	 *
	 * @param int $log_level
	 * @return kLogger
	 * @access public
	 */
	public function setLogLevel($log_level)
	{
		$this->_logRecord['LogLevel'] = $log_level;

		return $this;
	}

	/**
	 * Writes prepared log to database or disk, when database isn't available
	 *
	 * @param integer $storage_medium Storage medium.
	 * @param boolean $check_origin   Check error origin.
	 *
	 * @return integer|boolean
	 * @throws InvalidArgumentException When unknown storage medium is given.
	 */
	public function write($storage_medium = self::LS_AUTOMATIC, $check_origin = false)
	{
		if ( $check_origin && isset($this->_logRecord['LogSourceFilename']) ) {
			$origin_allowed = self::isErrorOriginAllowed($this->_logRecord['LogSourceFilename']);
		}
		else {
			$origin_allowed = true;
		}

		if ( !$this->_logRecord
			|| $this->_logRecord['LogLevel'] > $this->_maxLogLevel
			|| !$origin_allowed
			|| $this->_state == self::STATE_DISABLED
		) {
			// Nothing to save OR less detailed logging requested OR origin not allowed OR disabled.
			$this->_logRecord = array();

			return false;
		}

		$this->_logRecord['LogMemoryUsed'] = memory_get_usage();
		$this->_logRecord['LogTimestamp'] = adodb_mktime();
		$this->_logRecord['LogDate'] = adodb_date('Y-m-d H:i:s');

		if ( $storage_medium == self::LS_AUTOMATIC ) {
			$storage_medium = $this->dbStorage->connectionOpened() ? self::LS_DATABASE : self::LS_DISK;
		}

		if ( $storage_medium == self::LS_DATABASE ) {
			$result = $this->dbStorage->doInsert($this->_logRecord, TABLE_PREFIX . 'SystemLog');
		}
		elseif ( $storage_medium == self::LS_DISK ) {
			$result = $this->_saveToFile(RESTRICTED . '/system.log');
		}
		else {
			throw new InvalidArgumentException('Unknown storage medium "' . $storage_medium . '"');
		}

		$unique_id = $this->_logRecord['LogUniqueId'];

		if ( $this->_logRecord['LogNotificationStatus'] == self::LNS_SENT ) {
			$this->_sendNotification($unique_id);
		}

		$this->_logRecord = Array ();

		return $result ? $unique_id : false;
	}

	/**
	 * Catches last error happened before script ended
	 *
	 * @return void
	 * @access public
	 */
	public function catchLastError()
	{
		$this->write();
		$last_error = error_get_last();

		if ( !is_null($last_error) && isset($this->_handlers[self::LL_ERROR]) ) {
			/** @var kErrorHandlerStack $handler */
			$handler = $this->_handlers[self::LL_ERROR];

			$handler->handle($last_error['type'], $last_error['message'], $last_error['file'], $last_error['line']);
		}
	}

	/**
	 * Deletes log with given id from database or disk, when database isn't available
	 *
	 * @param int $unique_id
	 * @param int $storage_medium
	 * @return void
	 * @access public
	 * @throws InvalidArgumentException
	 */
	public function delete($unique_id, $storage_medium = self::LS_AUTOMATIC)
	{
		if ( $storage_medium == self::LS_AUTOMATIC ) {
			$storage_medium = $this->dbStorage->connectionOpened() ? self::LS_DATABASE : self::LS_DISK;
		}

		if ( $storage_medium == self::LS_DATABASE ) {
			$sql = 'DELETE FROM ' . TABLE_PREFIX . 'SystemLog
					WHERE LogUniqueId = ' . $unique_id;
			$this->dbStorage->Query($sql);
		}
		elseif ( $storage_medium == self::LS_DISK ) {
			// TODO: no way to delete a line from a file
		}
		else {
			throw new InvalidArgumentException('Unknown storage medium "' . $storage_medium . '"');
		}
	}

	/**
	 * Send notification (delayed or instant) about log record to e-mail from configuration
	 *
	 * @param bool $instant
	 * @return kLogger
	 * @access public
	 */
	public function notify($instant = false)
	{
		$this->_logRecord['LogNotificationStatus'] = $instant ? self::LNS_SENT : self::LNS_PENDING;

		return $this;
	}

	/**
	 * Sends notification e-mail about message with given $unique_id
	 *
	 * @param int $unique_id
	 * @return void
	 * @access protected
	 */
	protected function _sendNotification($unique_id)
	{
		$notification_email = $this->Application->ConfigValue('SystemLogNotificationEmail');

		if ( !$notification_email ) {
			trigger_error('System Log notification E-mail not specified', E_USER_NOTICE);

			return;
		}

		$send_params = Array (
			'to_name' => $notification_email,
			'to_email' => $notification_email,
		);

		// initialize list outside of e-mail event with right settings
		$this->Application->recallObject('system-log.email', 'system-log_List', Array ('unique_id' => $unique_id));

		$this->Application->emailAdmin('SYSTEM.LOG.NOTIFY', null, $send_params);
		$this->Application->removeObject('system-log.email');
	}

	/**
	 * Adds error/exception handler
	 *
	 * @param string|Array $handler
	 * @param bool $is_exception
	 * @return void
	 * @access public
	 */
	public function addErrorHandler($handler, $is_exception = false)
	{
		$this->_handlers[$is_exception ? self::LL_CRITICAL : self::LL_ERROR]->add($handler);
	}

	/**
	 * SQL Error Handler
	 *
	 * When not debug mode, then fatal database query won't break anything.
	 *
	 * @param int $code
	 * @param string $msg
	 * @param string $sql
	 * @return bool
	 * @access public
	 * @throws RuntimeException
	 */
	public function handleSQLError($code, $msg, $sql)
	{
		$error_msg = self::shortenMessage(self::DB_ERROR_PREFIX . ' #' . $code . ' - ' . $msg . '. SQL: ' . trim($sql));

		if ( isset($this->Application->Debugger) ) {
			if ( kUtil::constOn('DBG_SQL_FAILURE') && !defined('IS_INSTALL') ) {
				throw new RuntimeException($error_msg);
			}
			else {
				$this->Application->Debugger->appendTrace();
			}
		}

		if ( PHP_SAPI === 'cli' ) {
			throw new RuntimeException($error_msg);
		}

		// Next line also trigger attached error handlers.
		trigger_error($error_msg, E_USER_WARNING);

		return true;
	}

	/**
	 * Packs information about error into a single line
	 *
	 * @param string $errno
	 * @param bool $strip_tags
	 * @return string
	 * @access public
	 */
	public function toString($errno = null, $strip_tags = false)
	{
		if ( PHP_SAPI !== 'cli' && !$this->Application->isDebugMode() ) {
			$date = date('Y-m-d H:i:s');
			$reference = $this->_logRecord['LogUniqueId'] . '-' . time();

			$message = <<<HTML
<h1 style="margin-top: 0;">Oops, something went wrong</h1>
This is page is currently not available. 
We are working on the problem, and appreciate your patience.<br/>
<br/>
Date: {$date}<br/>
Reference: {$reference}<br/>
HTML;

			return $message;
		}

		if ( !isset($errno) ) {
			$errno = $this->_logRecord['LogCode'];
		}

		$errstr = $this->_logRecord['LogMessage'];
		$errfile = $this->convertPathToRelative($this->_logRecord['LogSourceFilename']);
		$errline = $this->_logRecord['LogSourceFileLine'];

		if ( PHP_SAPI === 'cli' ) {
			$result = sprintf('  [%s]  ' . PHP_EOL . '  %s', $errno, $errstr);

			if ( $this->_logRecord['LogBacktrace'] ) {
				$result .= $this->printBacktrace(unserialize($this->_logRecord['LogBacktrace']));
			}
		}
		else {
			$result = '<strong>' . $errno . ': </strong>' . "{$errstr} in {$errfile} on line {$errline}";
		}

		return $strip_tags ? strip_tags($result) : $result;
	}

	/**
	 * Prints backtrace result
	 *
	 * @param array $trace Trace.
	 *
	 * @return string
	 */
	protected function printBacktrace(array $trace)
	{
		if ( !$trace ) {
			return '';
		}

		$ret = PHP_EOL . PHP_EOL . PHP_EOL . 'Exception trace:' . PHP_EOL;

		foreach ( $trace as $trace_info ) {
			$class = isset($trace_info['class']) ? $trace_info['class'] : '';
			$type = isset($trace_info['type']) ? $trace_info['type'] : '';
			$function = $trace_info['function'];
			$args = isset($trace_info['args']) && $trace_info['args'] ? '...' : '';
			$file = isset($trace_info['file']) ? $this->convertPathToRelative($trace_info['file']) : 'n/a';
			$line = isset($trace_info['line']) ? $trace_info['line'] : 'n/a';

			$ret .= sprintf(' %s%s%s(%s) at %s:%s' . PHP_EOL, $class, $type, $function, $args, $file, $line);
		}

		return $ret;
	}

	/**
	 * Short description.
	 *
	 * @param string $absolute_path Absolute path.
	 *
	 * @return string
	 */
	protected function convertPathToRelative($absolute_path)
	{
		return preg_replace('/^' . preg_quote(FULL_PATH, '/') . '/', '...', $absolute_path, 1);
	}

	/**
	 * Saves log to file (e.g. when not possible to save into database)
	 *
	 * @param $filename
	 * @return bool
	 * @access protected
	 */
	protected function _saveToFile($filename)
	{
		$time = adodb_date('Y-m-d H:i:s');
		$log_file = new SplFileObject($filename, 'a');

		return $log_file->fwrite('[' . $time . '] #' . $this->toString(null, true) . PHP_EOL) > 0;
	}

	/**
	 * Checks if log type of current log record matches given one
	 *
	 * @param int $log_type
	 * @param string $log_message
	 * @return bool
	 * @access public
	 */
	public function isLogType($log_type, $log_message = null)
	{
		if ( $this->_logRecord['LogType'] == $log_type ) {
			return true;
		}

		if ( $log_type == self::LT_DATABASE ) {
			if ( !isset($log_message) ) {
				$log_message = $this->_logRecord['LogMessage'];
			}

			return strpos($log_message, self::DB_ERROR_PREFIX) !== false;
		}

		return false;
	}

	/**
	 * Shortens message
	 *
	 * @param string $message
	 * @return string
	 * @access public
	 */
	public static function shortenMessage($message)
	{
		$max_len = ini_get('log_errors_max_len');

		if ( strlen($message) > $max_len ) {
			$long_key = kUtil::generateId();
			self::$_longMessages[$long_key] = $message;

			return mb_substr($message, 0, $max_len - strlen($long_key) - 2) . ' #' . $long_key;
		}

		return $message;
	}

	/**
	 * Expands shortened message
	 *
	 * @param string $message
	 * @param bool $clear_cache Allow debugger to expand message after it's been expanded by kLogger
	 * @return string
	 * @access public
	 */
	public static function expandMessage($message, $clear_cache = true)
	{
		if ( preg_match('/(.*)#([\d]+)$/', $message, $regs) ) {
			$long_key = $regs[2];

			if ( isset(self::$_longMessages[$long_key]) ) {
				$message = self::$_longMessages[$long_key];

				if ( $clear_cache ) {
					unset(self::$_longMessages[$long_key]);
				}
			}
		}

		return $message;
	}

	/**
	 * Determines if error should be logged based on it's origin.
	 *
	 * @param string $file File.
	 *
	 * @return boolean
	 */
	public static function isErrorOriginAllowed($file)
	{
		static $error_origin_regexp;

		// Lazy detect error origins, because they're not available at construction time.
		if ( !$error_origin_regexp ) {
			$error_origins = array();
			$application = kApplication::Instance();

			foreach ( $application->ModuleInfo as $module_info ) {
				$error_origins[] = preg_quote(rtrim($module_info['Path'], '/'), '/');
			}

			$error_origins = array_unique($error_origins);
			$error_origin_regexp = '/^' . preg_quote(FULL_PATH, '/') . '\/(' . implode('|', $error_origins) . ')\//';
		}

		// Allow dynamically generated code.
		if ( strpos($file, 'eval()\'d code') !== false ) {
			return true;
		}

		// Allow known modules.
		if ( preg_match('/^' . preg_quote(MODULES_PATH, '/') . '\//', $file) ) {
			return preg_match($error_origin_regexp, $file) == 1;
		}

		// Don't allow Vendors.
		if ( preg_match('/^' . preg_quote(FULL_PATH, '/') . '\/vendor\//', $file) ) {
			return false;
		}

		// Allow everything else within main folder.
		return preg_match('/^' . preg_quote(FULL_PATH, '/') . '\//', $file) == 1;
	}

	/**
	 * Parses database error message into error number, error message and sql that caused that error
	 *
	 * @static
	 * @param string $message
	 * @return Array
	 * @access public
	 */
	public static function parseDatabaseError($message)
	{
		$regexp = '/' . preg_quote(self::DB_ERROR_PREFIX) . ' #(.*?) - (.*?)\. SQL: (.*?)$/s';

		if ( preg_match($regexp, $message, $regs) ) {
			// errno, errstr, sql
			return Array ($regs[1], $regs[2], $regs[3]);
		}

		return Array (0, $message, '');
	}
}


/**
 * Base class for error or exception handling
 */
abstract class kHandlerStack extends kBase {

	/**
	 * List of added handlers
	 *
	 * @var Array
	 * @access protected
	 */
	protected $_handlers = Array ();

	/**
	 * Reference to event log, which created this object
	 *
	 * @var kLogger
	 * @access protected
	 */
	protected $_logger;

	/**
	 * Remembers if handler is activated
	 *
	 * @var bool
	 * @access protected
	 */
	protected $_enabled = false;

	public function __construct(kLogger $logger)
	{
		parent::__construct();

		$this->_logger = $logger;

		if ( !kUtil::constOn('DBG_ZEND_PRESENT') ) {
			$this->attach();
			$this->_enabled = true;
		}
	}

	/**
	 * Detaches from error handling routines on class destruction
	 *
	 * @return void
	 * @access public
	 */
	public function __destruct()
	{
		if ( !$this->_enabled ) {
			return;
		}

		$this->detach();
		$this->_enabled = false;
	}

	/**
	 * Attach to error handling routines
	 *
	 * @abstract
	 * @return void
	 * @access protected
	 */
	abstract protected function attach();

	/**
	 * Detach from error handling routines
	 *
	 * @abstract
	 * @return void
	 * @access protected
	 */
	abstract protected function detach();

	/**
	 * Adds new handler to the stack
	 *
	 * @param callable $handler
	 * @return void
	 * @access public
	 */
	public function add($handler)
	{
		$this->_handlers[] = $handler;
	}

	/**
	 * Returns `true`, when no other error handlers should process this error.
	 *
	 * @param integer $errno Error code.
	 *
	 * @return boolean
	 */
	protected function _handleFatalError($errno)
	{
		$debug_mode = defined('DEBUG_MODE') && DEBUG_MODE;
		$skip_reporting = defined('DBG_SKIP_REPORTING') && DBG_SKIP_REPORTING;

		if ( !$this->_handlers || ($debug_mode && $skip_reporting) ) {
			// when debugger absent OR it's present, but we actually can't see it's error report (e.g. during ajax request)

			if ( $this->_isFatalError($errno) ) {
				$this->_displayFatalError($errno);
			}

			if ( !$this->_handlers ) {
				return true;
			}
		}

		return false;
	}

	/**
	 * Determines if given error is a fatal
	 *
	 * @abstract
	 * @param Exception|int $errno
	 * @return bool
	 */
	abstract protected function _isFatalError($errno);

	/**
	 * Displays div with given error message
	 *
	 * @param string $errno
	 * @return void
	 * @access protected
	 */
	protected function _displayFatalError($errno)
	{
		$errno = $this->_getFatalErrorTitle($errno);

		$margin = $this->Application->isAdmin ? '8px' : 'auto';
		$error_msg = $this->_logger->toString($errno, PHP_SAPI === 'cli');

		if ( PHP_SAPI === 'cli' ) {
			echo $error_msg;
			exit(1);
		}

		echo '<div style="background-color: #F5F5F5; margin: ' . $margin . '; padding: 10px; border: 2px solid #0067b8; color: #0067b8;">' . $error_msg . '</div>';
		exit;
	}

	/**
	 * Returns title to show for a fatal
	 *
	 * @abstract
	 * @param Exception|int $errno
	 * @return string
	 */
	abstract protected function _getFatalErrorTitle($errno);
}


/**
 * Class, that handles errors
 */
class kErrorHandlerStack extends kHandlerStack {

	/**
	 * Attach to error handling routines
	 *
	 * @return void
	 * @access protected
	 */
	protected function attach()
	{
		// set as error handler
		$error_handler = set_error_handler(Array ($this, 'handle'));

		if ( $error_handler ) {
			// wrap around previous error handler, if any was set
			$this->_handlers[] = $error_handler;
		}
	}

	/**
	 * Detach from error handling routines
	 *
	 * @return void
	 * @access protected
	 */
	protected function detach()
	{
		restore_error_handler();
	}

	/**
	 * Determines if given error is a fatal
	 *
	 * @param int $errno
	 * @return bool
	 * @access protected
	 */
	protected function _isFatalError($errno)
	{
		$fatal_errors = Array (E_USER_ERROR, E_RECOVERABLE_ERROR, E_ERROR, E_CORE_ERROR, E_COMPILE_ERROR, E_PARSE);

		return in_array($errno, $fatal_errors);
	}

	/**
	 * Returns title to show for a fatal
	 *
	 * @param int $errno
	 * @return string
	 * @access protected
	 */
	protected function _getFatalErrorTitle($errno)
	{
		return 'Fatal Error';
	}

	/**
	 * Default error handler
	 *
	 * @param int $errno
	 * @param string $errstr
	 * @param string $errfile
	 * @param int $errline
	 * @param Array $errcontext
	 * @return bool
	 * @access public
	 */
	public function handle($errno, $errstr, $errfile = null, $errline = null, $errcontext = Array ())
	{
		$log = $this->_logger->prepare()->addError($errno, $errstr, $errfile, $errline);

		if ( $this->_handleFatalError($errno) ) {
			$log->write(kLogger::LS_AUTOMATIC, !$this->_isFatalError($errno));

			return true;
		}

		$log->write(kLogger::LS_AUTOMATIC, !$this->_isFatalError($errno));

		$res = false;

		foreach ($this->_handlers as $handler) {
			$res = call_user_func($handler, $errno, $errstr, $errfile, $errline, $errcontext);
		}

		return $res;
	}
}


/**
 * Class, that handles exceptions
 */
class kExceptionHandlerStack extends kHandlerStack {

	/**
	 * Attach to error handling routines
	 *
	 * @return void
	 * @access protected
	 */
	protected function attach()
	{
		// set as exception handler
		$exception_handler = set_exception_handler(Array ($this, 'handle'));

		if ( $exception_handler ) {
			// wrap around previous exception handler, if any was set
			$this->_handlers[] = $exception_handler;
		}
	}

	/**
	 * Detach from error handling routines
	 *
	 * @return void
	 * @access protected
	 */
	protected function detach()
	{
		restore_exception_handler();
	}

	/**
	 * Determines if given error is a fatal
	 *
	 * @param Exception $errno
	 * @return bool
	 */
	protected function _isFatalError($errno)
	{
		return true;
	}

	/**
	 * Returns title to show for a fatal
	 *
	 * @param Exception $errno
	 * @return string
	 */
	protected function _getFatalErrorTitle($errno)
	{
		return get_class($errno);
	}

	/**
	 * Handles exception
	 *
	 * @param Exception $exception
	 * @return bool
	 * @access public
	 */
	public function handle($exception)
	{
		$log = $this->_logger->prepare()->addException($exception);

		if ( $exception instanceof kRedirectException ) {
			/** @var kRedirectException $exception */

			$exception->run();
		}

		if ( $this->_handleFatalError($exception) ) {
			$log->write();

			return true;
		}

		$log->write();

		$res = false;

		foreach ($this->_handlers as $handler) {
			$res = call_user_func($handler, $exception);
		}

		return $res;
	}
}