<?php

namespace App\EventSubscriber;

use App\Infrastructure\QueryCounter;
use Symfony\Component\EventDispatcher\EventSubscriberInterface;
use Symfony\Component\HttpKernel\Event\RequestEvent;
use Symfony\Component\HttpKernel\Event\ResponseEvent;
use Symfony\Component\HttpKernel\KernelEvents;

/**
 * Puts the number of database queries of a request into a header.
 *
 * Only outside production: it is an instrument for the browser checks and for looking at a page
 * while building it, not something a visitor should receive. The checks assert a ceiling with it,
 * so a page that starts asking the database ten times per section fails a test instead of only
 * getting slower.
 */
final class QueryHeaderSubscriber implements EventSubscriberInterface
{
    public function __construct(private QueryCounter $counter, private string $environment)
    {
    }

    public static function getSubscribedEvents(): array
    {
        return [
            KernelEvents::REQUEST => ['onRequest', 4096],
            KernelEvents::RESPONSE => ['onResponse', -512],
        ];
    }

    public function onRequest(RequestEvent $event): void
    {
        if ($event->isMainRequest()) {
            $this->counter->reset();
        }
    }

    public function onResponse(ResponseEvent $event): void
    {
        if ('prod' !== $this->environment && $event->isMainRequest()) {
            $event->getResponse()->headers->set('X-Kant-Queries', (string) $this->counter->count());
        }
    }
}