<?php

namespace Friendica\Util\Logger;

use Friendica\Network\HTTPException\InternalServerErrorException;
use Friendica\Util\Introspection;
use Psr\Log\LogLevel;

/**
 * A Logger instance for syslogging (fast, but simple)
 * @see http://php.net/manual/en/function.syslog.php
 */
class SyslogLogger extends AbstractLogger
{
	const IDENT = 'Friendica';

	/**
	 * Translates LogLevel log levels to syslog log priorities.
	 * @var array
	 */
	private $logLevels = [
		LogLevel::DEBUG     => LOG_DEBUG,
		LogLevel::INFO      => LOG_INFO,
		LogLevel::NOTICE    => LOG_NOTICE,
		LogLevel::WARNING   => LOG_WARNING,
		LogLevel::ERROR     => LOG_ERR,
		LogLevel::CRITICAL  => LOG_CRIT,
		LogLevel::ALERT     => LOG_ALERT,
		LogLevel::EMERGENCY => LOG_EMERG,
	];

	/**
	 * Translates log priorities to string outputs
	 * @var array
	 */
	private $logToString = [
		LOG_DEBUG   => 'DEBUG',
		LOG_INFO    => 'INFO',
		LOG_NOTICE  => 'NOTICE',
		LOG_WARNING => 'WARNING',
		LOG_ERR     => 'ERROR',
		LOG_CRIT    => 'CRITICAL',
		LOG_ALERT   => 'ALERT',
		LOG_EMERG   => 'EMERGENCY'
	];

	/**
	 * Indicates what logging options will be used when generating a log message
	 * @see http://php.net/manual/en/function.openlog.php#refsect1-function.openlog-parameters
	 *
	 * @var int
	 */
	private $logOpts;

	/**
	 * Used to specify what type of program is logging the message
	 * @see http://php.net/manual/en/function.openlog.php#refsect1-function.openlog-parameters
	 *
	 * @var int
	 */
	private $logFacility;

	/**
	 * The minimum loglevel at which this logger will be triggered
	 * @var int
	 */
	private $logLevel;

	/**
	 * A error message of the current operation
	 * @var string
	 */
	private $errorMessage;

	/**
	 * {@inheritdoc}
	 * @param string $level       The minimum loglevel at which this logger will be triggered
	 * @param int    $logOpts     Indicates what logging options will be used when generating a log message
	 * @param int    $logFacility Used to specify what type of program is logging the message
	 *
	 * @throws \Exception
	 */
	public function __construct($channel, Introspection $introspection, $level = LogLevel::NOTICE, $logOpts = LOG_PID, $logFacility = LOG_USER)
	{
		parent::__construct($channel, $introspection);
		$this->logOpts = $logOpts;
		$this->logFacility = $logFacility;
		$this->logLevel = $this->mapLevelToPriority($level);
		$this->introspection->addClasses(array(self::class));
	}

	/**
	 * Adds a new entry to the syslog
	 *
	 * @param int    $level
	 * @param string $message
	 * @param array  $context
	 *
	 * @throws InternalServerErrorException if the syslog isn't available
	 */
	protected function addEntry($level, $message, $context = [])
	{
		$logLevel = $this->mapLevelToPriority($level);

		if ($logLevel > $this->logLevel) {
			return;
		}

		$formattedLog = $this->formatLog($logLevel, $message, $context);
		$this->write($logLevel, $formattedLog);
	}

	/**
	 * Maps the LogLevel (@see LogLevel) to a SysLog priority (@see http://php.net/manual/en/function.syslog.php#refsect1-function.syslog-parameters)
	 *
	 * @param string $level A LogLevel
	 *
	 * @return int The SysLog priority
	 *
	 * @throws \Psr\Log\InvalidArgumentException If the loglevel isn't valid
	 */
	public function mapLevelToPriority($level)
	{
		if (!array_key_exists($level, $this->logLevels)) {
			throw new \InvalidArgumentException(sprintf('The level "%s" is not valid.', $level));
		}

		return $this->logLevels[$level];
	}

	/**
	 * Closes the Syslog
	 */
	public function close()
	{
		closelog();
	}

	/**
	 * Writes a message to the syslog
	 * @see http://php.net/manual/en/function.syslog.php#refsect1-function.syslog-parameters
	 *
	 * @param int    $priority The Priority
	 * @param string $message  The message of the log
	 *
	 * @throws InternalServerErrorException if syslog cannot be used
	 */
	private function write($priority, $message)
	{
		set_error_handler([$this, 'customErrorHandler']);
		$opened = openlog(self::IDENT, $this->logOpts, $this->logFacility);
		restore_error_handler();

		if (!$opened) {
			throw new \UnexpectedValueException(sprintf('Can\'t open syslog for ident "%s" and facility "%s": ' . $this->errorMessage, $this->channel, $this->logFacility));
		}

		$this->syslogWrapper($priority, $message);
	}

	/**
	 * Formats a log record for the syslog output
	 *
	 * @param int    $level   The loglevel/priority
	 * @param string $message The message
	 * @param array  $context The context of this call
	 *
	 * @return string the formatted syslog output
	 */
	private function formatLog($level, $message, $context = [])
	{
		$record = $this->introspection->getRecord();
		$record = array_merge($record, ['uid' => $this->logUid]);
		$logMessage = '';

		$logMessage .= $this->channel . ' ';
		$logMessage .= '[' . $this->logToString[$level] . ']: ';
		$logMessage .= $this->psrInterpolate($message, $context) . ' ';
		$logMessage .= @json_encode($context) . ' - ';
		$logMessage .= @json_encode($record);

		return $logMessage;
	}

	private function customErrorHandler($code, $msg)
	{
		$this->errorMessage = preg_replace('{^(fopen|mkdir)\(.*?\): }', '', $msg);
	}

	/**
	 * A syslog wrapper to make syslog functionality testable
	 *
	 * @param int    $level The syslog priority
	 * @param string $entry The message to send to the syslog function
	 */
	protected function syslogWrapper($level, $entry)
	{
		set_error_handler([$this, 'customErrorHandler']);
		$written = syslog($level, $entry);
		restore_error_handler();

		if (!$written) {
			throw new \UnexpectedValueException(sprintf('Can\'t write into syslog for ident "%s" and facility "%s": ' . $this->errorMessage, $this->channel, $this->logFacility));
		}
	}
}