<?php
/**
 * TErrorHandler class file
 *
 * @author Qiang Xue <qiang.xue@gmail.com>
 * @link http://www.pradosoft.com/
 * @copyright Copyright &copy; 2005-2014 PradoSoft
 * @license http://www.pradosoft.com/license/
 * @package System.Exceptions
 */

/**
 * TErrorHandler class
 *
 * TErrorHandler handles all PHP user errors and exceptions generated during
 * servicing user requests. It displays these errors using different templates
 * and if possible, using languages preferred by the client user.
 * Note, PHP parsing errors cannot be caught and handled by TErrorHandler.
 *
 * The templates used to format the error output are stored under System.Exceptions.
 * You may choose to use your own templates, should you not like the templates
 * provided by Prado. Simply set {@link setErrorTemplatePath ErrorTemplatePath}
 * to the path (in namespace format) storing your own templates.
 *
 * There are two sets of templates, one for errors to be displayed to client users
 * (called external errors), one for errors to be displayed to system developers
 * (called internal errors). The template file name for the former is
 * <b>error[StatusCode][-LanguageCode].html</b>, and for the latter it is
 * <b>exception[-LanguageCode].html</b>, where StatusCode refers to response status
 * code (e.g. 404, 500) specified when {@link THttpException} is thrown,
 * and LanguageCode is the client user preferred language code (e.g. en, zh, de).
 * The templates <b>error.html</b> and <b>exception.html</b> are default ones
 * that are used if no other appropriate templates are available.
 * Note, these templates are not Prado control templates. They are simply
 * html files with keywords (e.g. %%ErrorMessage%%, %%Version%%)
 * to be replaced with the corresponding information.
 *
 * By default, TErrorHandler is registered with {@link TApplication} as the
 * error handler module. It can be accessed via {@link TApplication::getErrorHandler()}.
 * You seldom need to deal with the error handler directly. It is mainly used
 * by the application object to handle errors.
 *
 * TErrorHandler may be configured in application configuration file as follows
 * <module id="error" class="TErrorHandler" ErrorTemplatePath="System.Exceptions" />
 *
 * @author Qiang Xue <qiang.xue@gmail.com>
 * @package System.Exceptions
 * @since 3.0
 */
class TErrorHandler extends TModule
{
	/**
	 * error template file basename
	 */
	const ERROR_FILE_NAME='error';
	/**
	 * exception template file basename
	 */
	const EXCEPTION_FILE_NAME='exception';
	/**
	 * number of lines before and after the error line to be displayed in case of an exception
	 */
	const SOURCE_LINES=12;

	/**
	 * @var string error template directory
	 */
	private $_templatePath=null;

	/**
	 * Initializes the module.
	 * This method is required by IModule and is invoked by application.
	 * @param TXmlElement module configuration
	 */
	public function init($config)
	{
		$this->getApplication()->setErrorHandler($this);
	}

	/**
	 * @return string the directory containing error template files.
	 */
	public function getErrorTemplatePath()
	{
		if($this->_templatePath===null)
			$this->_templatePath=Prado::getFrameworkPath().'/Exceptions/templates';
		return $this->_templatePath;
	}

	/**
	 * Sets the path storing all error and exception template files.
	 * The path must be in namespace format, such as System.Exceptions (which is the default).
	 * @param string template path in namespace format
	 * @throws TConfigurationException if the template path is invalid
	 */
	public function setErrorTemplatePath($value)
	{
		if(($templatePath=Prado::getPathOfNamespace($value))!==null && is_dir($templatePath))
			$this->_templatePath=$templatePath;
		else
			throw new TConfigurationException('errorhandler_errortemplatepath_invalid',$value);
	}

	/**
	 * Handles PHP user errors and exceptions.
	 * This is the event handler responding to the <b>Error</b> event
	 * raised in {@link TApplication}.
	 * The method mainly uses appropriate template to display the error/exception.
	 * It terminates the application immediately after the error is displayed.
	 * @param mixed sender of the event
	 * @param mixed event parameter (if the event is raised by TApplication, it refers to the exception instance)
	 */
	public function handleError($sender,$param)
	{
		static $handling=false;
		// We need to restore error and exception handlers,
		// because within error and exception handlers, new errors and exceptions
		// cannot be handled properly by PHP
		restore_error_handler();
		restore_exception_handler();
		// ensure that we do not enter infinite loop of error handling
		if($handling)
			$this->handleRecursiveError($param);
		else
		{
			$handling=true;
			if(($response=$this->getResponse())!==null)
				$response->clear();
			if(!headers_sent())
				header('Content-Type: text/html; charset=UTF-8');
			if($param instanceof THttpException)
				$this->handleExternalError($param->getStatusCode(),$param);
			else if($this->getApplication()->getMode()===TApplicationMode::Debug)
				$this->displayException($param);
			else
				$this->handleExternalError(500,$param);
		}
	}


	/**
	 * @param string $value
	 * @param Exception|null$exception
	 * @return string
	 * @since 3.1.6
	 */
	protected static function hideSecurityRelated($value, $exception=null)
	{
		$aRpl = array();
		if($exception !== null && $exception instanceof Exception)
		{
			$aTrace = $exception->getTrace();
			foreach($aTrace as $item)
			{
				if(isset($item['file']))
					$aRpl[dirname($item['file']) . DIRECTORY_SEPARATOR] = '<hidden>' . DIRECTORY_SEPARATOR;
			}
		}
		$aRpl[$_SERVER['DOCUMENT_ROOT']] = '${DocumentRoot}';
		$aRpl[str_replace('/', DIRECTORY_SEPARATOR, $_SERVER['DOCUMENT_ROOT'])] = '${DocumentRoot}';
		$aRpl[PRADO_DIR . DIRECTORY_SEPARATOR] = '${PradoFramework}' . DIRECTORY_SEPARATOR;
		if(isset($aRpl[DIRECTORY_SEPARATOR])) unset($aRpl[DIRECTORY_SEPARATOR]);
		$aRpl = array_reverse($aRpl, true);

		return str_replace(array_keys($aRpl), $aRpl, $value);
	}

	/**
	 * Displays error to the client user.
	 * THttpException and errors happened when the application is in <b>Debug</b>
	 * mode will be displayed to the client user.
	 * @param integer response status code
	 * @param Exception exception instance
	 */
	protected function handleExternalError($statusCode,$exception)
	{
		if(!($exception instanceof THttpException))
			error_log($exception->__toString());

		$content=$this->getErrorTemplate($statusCode,$exception);

		$serverAdmin=isset($_SERVER['SERVER_ADMIN'])?$_SERVER['SERVER_ADMIN']:'';

		$isDebug = $this->getApplication()->getMode()===TApplicationMode::Debug;

		$errorMessage = $exception->getMessage();
		if($isDebug)
			$version=$_SERVER['SERVER_SOFTWARE'].' <a href="http://www.pradosoft.com/">PRADO</a>/'.Prado::getVersion();
		else
		{
			$version='';
			$errorMessage = self::hideSecurityRelated($errorMessage, $exception);
		}
		$tokens=array(
			'%%StatusCode%%' => "$statusCode",
			'%%ErrorMessage%%' => htmlspecialchars($errorMessage),
			'%%ServerAdmin%%' => $serverAdmin,
			'%%Version%%' => $version,
			'%%Time%%' => @strftime('%Y-%m-%d %H:%M',time())
		);

		$CGI=substr(php_sapi_name(), 0, 3) == 'cgi'; // FastCGI / IIS
		if($isDebug)
		{
			if ($CGI)
				header("Status: $statusCode ".$exception->getMessage(), true, TPropertyValue::ensureInteger($statusCode));
			else
				header("HTTP/1.0 $statusCode ".$exception->getMessage(), true, TPropertyValue::ensureInteger($statusCode));
		} else {
			if ($CGI)
				header("Status: $statusCode", true, TPropertyValue::ensureInteger($statusCode));
			else
				header("HTTP/1.0 $statusCode", true, TPropertyValue::ensureInteger($statusCode));
		}

		echo strtr($content,$tokens);
	}

	/**
	 * Handles error occurs during error handling (called recursive error).
	 * THttpException and errors happened when the application is in <b>Debug</b>
	 * mode will be displayed to the client user.
	 * Error is displayed without using existing template to prevent further errors.
	 * @param Exception exception instance
	 */
	protected function handleRecursiveError($exception)
	{
		if($this->getApplication()->getMode()===TApplicationMode::Debug)
		{
			echo "<html><head><title>Recursive Error</title></head>\n";
			echo "<body><h1>Recursive Error</h1>\n";
			echo "<pre>".$exception->__toString()."</pre>\n";
			echo "</body></html>";
		}
		else
		{
			error_log("Error happened while processing an existing error:\n".$exception->__toString());
			header('HTTP/1.0 500 Internal Error');
		}
	}

	/**
	 * Displays exception information.
	 * Exceptions are displayed with rich context information, including
	 * the call stack and the context source code.
	 * This method is only invoked when application is in <b>Debug</b> mode.
	 * @param Exception exception instance
	 */
	protected function displayException($exception)
	{
		if(php_sapi_name()==='cli')
		{
			echo $exception->getMessage()."\n";
			echo $exception->getTraceAsString();
			return;
		}

		if($exception instanceof TTemplateException)
		{
			$fileName=$exception->getTemplateFile();
			$lines=empty($fileName)?explode("\n",$exception->getTemplateSource()):@file($fileName);
			$source=$this->getSourceCode($lines,$exception->getLineNumber());
			if($fileName==='')
				$fileName='---embedded template---';
			$errorLine=$exception->getLineNumber();
		}
		else
		{
			if(($trace=$this->getExactTrace($exception))!==null)
			{
				$fileName=$trace['file'];
				$errorLine=$trace['line'];
			}
			else
			{
				$fileName=$exception->getFile();
				$errorLine=$exception->getLine();
			}
			$source=$this->getSourceCode(@file($fileName),$errorLine);
		}

		if($this->getApplication()->getMode()===TApplicationMode::Debug)
			$version=$_SERVER['SERVER_SOFTWARE'].' <a href="http://www.pradosoft.com/">PRADO</a>/'.Prado::getVersion();
		else
			$version='';

		$tokens=array(
			'%%ErrorType%%' => get_class($exception),
			'%%ErrorMessage%%' => $this->addLink(htmlspecialchars($exception->getMessage())),
			'%%SourceFile%%' => htmlspecialchars($fileName).' ('.$errorLine.')',
			'%%SourceCode%%' => $source,
			'%%StackTrace%%' => htmlspecialchars($exception->getTraceAsString()),
			'%%Version%%' => $version,
			'%%Time%%' => @strftime('%Y-%m-%d %H:%M',time())
		);

		$content=$this->getExceptionTemplate($exception);

		echo strtr($content,$tokens);
	}

	/**
	 * Retrieves the template used for displaying internal exceptions.
	 * Internal exceptions will be displayed with source code causing the exception.
	 * This occurs when the application is in debug mode.
	 * @param Exception the exception to be displayed
	 * @return string the template content
	 */
	protected function getExceptionTemplate($exception)
	{
		$lang=Prado::getPreferredLanguage();
		$exceptionFile=Prado::getFrameworkPath().'/Exceptions/templates/'.self::EXCEPTION_FILE_NAME.'-'.$lang.'.html';
		if(!is_file($exceptionFile))
			$exceptionFile=Prado::getFrameworkPath().'/Exceptions/templates/'.self::EXCEPTION_FILE_NAME.'.html';
		if(($content=@file_get_contents($exceptionFile))===false)
			die("Unable to open exception template file '$exceptionFile'.");
		return $content;
	}

	/**
	 * Retrieves the template used for displaying external exceptions.
	 * External exceptions are those displayed to end-users. They do not contain
	 * error source code. Therefore, you might want to override this method
	 * to provide your own error template for displaying certain external exceptions.
	 * The following tokens in the template will be replaced with corresponding content:
	 * %%StatusCode%% : the status code of the exception
	 * %%ErrorMessage%% : the error message (HTML encoded).
	 * %%ServerAdmin%% : the server admin information (retrieved from Web server configuration)
	 * %%Version%% : the version information of the Web server.
	 * %%Time%% : the time the exception occurs at
	 *
	 * @param integer status code (such as 404, 500, etc.)
	 * @param Exception the exception to be displayed
	 * @return string the template content
	 */
	protected function getErrorTemplate($statusCode,$exception)
	{
		$base=$this->getErrorTemplatePath().DIRECTORY_SEPARATOR.self::ERROR_FILE_NAME;
		$lang=Prado::getPreferredLanguage();
		if(is_file("$base$statusCode-$lang.html"))
			$errorFile="$base$statusCode-$lang.html";
		else if(is_file("$base$statusCode.html"))
			$errorFile="$base$statusCode.html";
		else if(is_file("$base-$lang.html"))
			$errorFile="$base-$lang.html";
		else
			$errorFile="$base.html";
		if(($content=@file_get_contents($errorFile))===false)
			die("Unable to open error template file '$errorFile'.");
		return $content;
	}

	private function getExactTrace($exception)
	{
		$trace=$exception->getTrace();
		$result=null;
		// if PHP exception, we want to show the 2nd stack level context
		// because the 1st stack level is of little use (it's in error handler)
		if($exception instanceof TPhpErrorException)
			$result=isset($trace[0]['file'])?$trace[0]:$trace[1];
		else if($exception instanceof TInvalidOperationException)
		{
			// in case of getter or setter error, find out the exact file and row
			if(($result=$this->getPropertyAccessTrace($trace,'__get'))===null)
				$result=$this->getPropertyAccessTrace($trace,'__set');
		}
		if($result!==null && strpos($result['file'],': eval()\'d code')!==false)
			return null;

		return $result;
	}

	private function getPropertyAccessTrace($trace,$pattern)
	{
		$result=null;
		foreach($trace as $t)
		{
			if(isset($t['function']) && $t['function']===$pattern)
				$result=$t;
			else
				break;
		}
		return $result;
	}

	private function getSourceCode($lines,$errorLine)
	{
		$beginLine=$errorLine-self::SOURCE_LINES>=0?$errorLine-self::SOURCE_LINES:0;
		$endLine=$errorLine+self::SOURCE_LINES<=count($lines)?$errorLine+self::SOURCE_LINES:count($lines);

		$source='';
		for($i=$beginLine;$i<$endLine;++$i)
		{
			if($i===$errorLine-1)
			{
				$line=htmlspecialchars(sprintf("%04d: %s",$i+1,str_replace("\t",'    ',$lines[$i])));
				$source.="<div class=\"error\">".$line."</div>";
			}
			else
				$source.=htmlspecialchars(sprintf("%04d: %s",$i+1,str_replace("\t",'    ',$lines[$i])));
		}
		return $source;
	}

	private function addLink($message)
	{
		$baseUrl='http://www.pradosoft.com/docs/classdoc';
		return preg_replace('/\b(T[A-Z]\w+)\b/',"<a href=\"$baseUrl/\${1}\" target=\"_blank\">\${1}</a>",$message);
	}
}