Conditional middleware

Sometimes you may need to add some condition, so a middleware is only effective to part of the whole traffic.

There's a interface RequestPredictionInterface for this.

RequestPredictionInterface::isTrue(ServerRequestInterface $request): bool;

For example, a naiive prediction about whether the request is googlebot may look like this

$isGooglebot = new class implements RequestPredictionInterface {
    public function isTrue(ServerRequestInterface $request): bool
    {
        return strpos($request->getHeaderLine('User-Agent'), 'Googlebot') !== false;
    }
};

Then you can wrap you middleware so

$prerenderContentForGooglebotMiddleware = $prerenderMiddleware->when($isGooglebot);

$excludeGoogleBotLoggerMiddleware = $loggerMiddleware->unless($isGooglebot); 

This is powered by MiddlewareTrait::when, MiddlewareTrait::unless, Without the trait, you can wrap your middleware by hand

new PredictionWrapperMiddleware($prerenderMiddleware, $isGooglebot);

new PredictionWrapperMiddleware($loggerMiddleware, $isGooglebot, true); // use 3rd parameter to reverse the prediction