<?php
/**
 * Copyright 2018 OpenCensus Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

namespace App\EventSubscriber;

use Symfony\Component\EventDispatcher\EventSubscriberInterface;
use Symfony\Component\HttpKernel\Event\GetResponseEvent;
use Symfony\Component\HttpKernel\KernelEvents;
use OpenCensus\Trace\Exporter\FileExporter;
use OpenCensus\Trace\Tracer;
use OpenCensus\Trace\Integrations\Symfony;

class OpenCensusSubscriber implements EventSubscriberInterface
{
    public static function getSubscribedEvents()
    {
        // return the subscribed events, their methods and priorities
        return array(
           KernelEvents::REQUEST => ['startTrace', 10]
        );
    }

    public function startTrace(GetResponseEvent $event)
    {
        Symfony::load();

        $file = sys_get_temp_dir() . '/spans.json';
        Tracer::start(new FileExporter($file));
    }
}