<?php
/**
 * 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 2 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, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 * http://www.gnu.org/copyleft/gpl.html
 *
 * @file
 */

namespace MediaWiki\Logger\Monolog;

use LogicException;
use MediaWiki\Logger\LegacyLogger;
use Monolog\Handler\AbstractProcessingHandler;
use Monolog\Logger;
use UnexpectedValueException;

/**
 * Log handler that replicates the behavior of MediaWiki's former wfErrorLog()
 * logging service. Log output can be directed to a local file, a PHP stream,
 * or a udp2log server.
 *
 * For udp2log output, the stream specification must have the form:
 * "udp://HOST:PORT[/PREFIX]"
 * where:
 * - HOST: IPv4, IPv6 or hostname
 * - PORT: server port
 * - PREFIX: optional (but recommended) prefix telling udp2log how to route
 * the log event. The special prefix "{channel}" will use the log event's
 * channel as the prefix value.
 *
 * When not targeting a udp2log stream this class will act as a drop-in
 * replacement for \Monolog\Handler\StreamHandler.
 *
 * @since 1.25
 * @copyright © 2013 Wikimedia Foundation and contributors
 */
class LegacyHandler extends AbstractProcessingHandler {

	/**
	 * Log sink descriptor
	 * @var string
	 */
	protected $uri;

	/**
	 * Filter log events using legacy rules
	 * @var bool
	 */
	protected $useLegacyFilter;

	/**
	 * Log sink
	 * @var resource
	 */
	protected $sink;

	/**
	 * @var string
	 */
	protected $error;

	/**
	 * @var string
	 */
	protected $host;

	/**
	 * @var int
	 */
	protected $port;

	/**
	 * @var string
	 */
	protected $prefix;

	/**
	 * @param string $stream Stream URI
	 * @param bool $useLegacyFilter Filter log events using legacy rules
	 * @param int $level Minimum logging level that will trigger handler
	 * @param bool $bubble Can handled meesages bubble up the handler stack?
	 */
	public function __construct(
		$stream,
		$useLegacyFilter = false,
		$level = Logger::DEBUG,
		$bubble = true
	) {
		parent::__construct( $level, $bubble );
		$this->uri = $stream;
		$this->useLegacyFilter = $useLegacyFilter;
	}

	/**
	 * Open the log sink described by our stream URI.
	 */
	protected function openSink() {
		if ( !$this->uri ) {
			throw new LogicException(
				'Missing stream uri, the stream can not be opened.' );
		}
		$this->error = null;
		set_error_handler( [ $this, 'errorTrap' ] );

		if ( substr( $this->uri, 0, 4 ) == 'udp:' ) {
			$parsed = parse_url( $this->uri );
			if ( !isset( $parsed['host'] ) ) {
				throw new UnexpectedValueException( sprintf(
					'Udp transport "%s" must specify a host', $this->uri
				) );
			}
			if ( !isset( $parsed['port'] ) ) {
				throw new UnexpectedValueException( sprintf(
					'Udp transport "%s" must specify a port', $this->uri
				) );
			}

			$this->host = $parsed['host'];
			$this->port = $parsed['port'];
			$this->prefix = '';

			if ( isset( $parsed['path'] ) ) {
				$this->prefix = ltrim( $parsed['path'], '/' );
			}

			if ( filter_var( $this->host, FILTER_VALIDATE_IP, FILTER_FLAG_IPV6 ) ) {
				$domain = AF_INET6;

			} else {
				$domain = AF_INET;
			}

			$this->sink = socket_create( $domain, SOCK_DGRAM, SOL_UDP );

		} else {
			$this->sink = fopen( $this->uri, 'a' );
		}
		restore_error_handler();

		if ( !$this->sink ) {
			$this->sink = null;
			throw new UnexpectedValueException( sprintf(
				'The stream or file "%s" could not be opened: %s',
				$this->uri, $this->error
			) );
		}
	}

	/**
	 * Custom error handler.
	 * @param int $code Error number
	 * @param string $msg Error message
	 */
	protected function errorTrap( $code, $msg ) {
		$this->error = $msg;
	}

	/**
	 * Should we use UDP to send messages to the sink?
	 * @return bool
	 */
	protected function useUdp() {
		return $this->host !== null;
	}

	protected function write( array $record ): void {
		if ( $this->useLegacyFilter &&
			!LegacyLogger::shouldEmit(
				$record['channel'], $record['message'],
				$record['level'], $record
		) ) {
			// Do not write record if we are enforcing legacy rules and they
			// do not pass this message. This used to be done in isHandling(),
			// but Monolog 1.12.0 made a breaking change that removed access
			// to the needed channel and context information.
			return;
		}

		if ( $this->sink === null ) {
			$this->openSink();
		}

		$text = (string)$record['formatted'];
		if ( $this->useUdp() ) {
			// Clean it up for the multiplexer
			if ( $this->prefix !== '' ) {
				$leader = ( $this->prefix === '{channel}' ) ?
					$record['channel'] : $this->prefix;
				$text = preg_replace( '/^/m', "{$leader} ", $text );

				// Limit to 64 KiB
				if ( strlen( $text ) > 65506 ) {
					$text = substr( $text, 0, 65506 );
				}

				if ( substr( $text, -1 ) != "\n" ) {
					$text .= "\n";
				}

			} elseif ( strlen( $text ) > 65507 ) {
				$text = substr( $text, 0, 65507 );
			}

			socket_sendto(
				$this->sink, $text, strlen( $text ), 0, $this->host, $this->port
			);

		} else {
			fwrite( $this->sink, $text );
		}
	}

	public function close(): void {
		if ( $this->sink ) {
			if ( $this->useUdp() ) {
				socket_close( $this->sink );

			} else {
				fclose( $this->sink );
			}
		}
		$this->sink = null;
	}
}
