<?php

namespace Friendica\Util\Logger;

use Friendica\Network\HTTPException\InternalServerErrorException;
use Psr\Log\InvalidArgumentException;
use Psr\Log\LoggerInterface;
use Psr\Log\LogLevel;

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

	/**
	 * Translates LogLevel log levels to syslog log priorities.
	 */
	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,
	];

	/**
	 * The standard ident of the syslog (added to each message)
	 * @var string
	 */
	private $channel;

	/**
	 * 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;

	/**
	 * The Introspector for the current call
	 * @var Introspection
	 */
	private $introspection;

	/**
	 * @param string $channel     The output channel
	 * @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    $logFacility Used to specify what type of program is logging the message
	 *
	 * @throws InternalServerErrorException if the loglevel isn't valid
	 */
	public function __construct($channel, Introspection $introspection, $level = LogLevel::NOTICE, $logOpts = LOG_PID, $logFacility = LOG_USER)
	{
		$this->channel = $channel;
		$this->logOpts = $logOpts;
		$this->logFacility = $logFacility;
		$this->logLevel = $this->mapLevelToPriority($level);
		$this->introspection = $introspection;
	}

	/**
	 * 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('LogLevel \'' . $level . '\' isn\'t valid.');
		}

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

	/**
	 * Writes a message to the syslog
	 *
	 * @param int    $priority The Priority ( @see http://php.net/manual/en/function.syslog.php#refsect1-function.syslog-parameters )
	 * @param string $message The message of the log
	 * @throws InternalServerErrorException if syslog cannot be used
	 */
	private function write($priority, $message)
	{
		if (!openlog(self::IDENT, $this->logOpts, $this->logFacility)) {
			throw new InternalServerErrorException('Can\'t open syslog for ident "' . $this->channel . '" and facility "' . $this->logFacility . '""');
		}

		syslog($priority, $message);
	}

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

	/**
	 * 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 = [])
	{
		$logMessage  = '';

		$logMessage .= $this->channel . ' ';
		$logMessage .= '[' . $level . ']: ';
		$logMessage .= $message . ' ';
		$logMessage .= json_encode($context) . ' - ';
		$logMessage .= json_encode($this->introspection->getRecord());

		return $logMessage;
	}

	private function addEntry($level, $message, $context = [])
	{
		if ($level >= $this->logLevel) {
			return;
		}

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

	/**
	 * {@inheritdoc}
	 */
	public function emergency($message, array $context = array())
	{
		$this->addEntry(LOG_EMERG, $message, $context);
	}

	/**
	 * {@inheritdoc}
	 */
	public function alert($message, array $context = array())
	{
		$this->addEntry(LOG_ALERT, $message, $context);
	}

	/**
	 * {@inheritdoc}
	 */
	public function critical($message, array $context = array())
	{
		$this->addEntry(LOG_CRIT, $message, $context);
	}

	/**
	 * {@inheritdoc}
	 */
	public function error($message, array $context = array())
	{
		$this->addEntry(LOG_ERR, $message, $context);
	}

	/**
	 * {@inheritdoc}
	 */
	public function warning($message, array $context = array())
	{
		$this->addEntry(LOG_WARNING, $message, $context);
	}

	/**
	 * {@inheritdoc}
	 */
	public function notice($message, array $context = array())
	{
		$this->addEntry(LOG_NOTICE, $message, $context);
	}

	/**
	 * {@inheritdoc}
	 */
	public function info($message, array $context = array())
	{
		$this->addEntry(LOG_INFO, $message, $context);
	}

	/**
	 * {@inheritdoc}
	 */
	public function debug($message, array $context = array())
	{
		$this->addEntry(LOG_DEBUG, $message, $context);
	}

	/**
	 * {@inheritdoc}
	 */
	public function log($level, $message, array $context = array())
	{
		$logLevel = $this->mapLevelToPriority($level);
		$this->addEntry($logLevel, $message, $context);
	}
}