Mocking in Amphp, 2

amp_io.php

<?php

require __DIR__ . '/../vendor/autoload.php';

use Amp\Http\Client\HttpClientBuilder;
use Amp\Http\Client\Request;
use Amp\Http\Client\HttpClient;
use Amp\Loop;
use Amp\ByteStream\ClosedException;
use Amp\File\File;
use Amp\LazyPromise;

interface IO extends Amp\Promise
{
    public function equals(IO $io): bool;
    public function __toString(): string;
}

class WriteIO implements IO
{
    /** @var string */
    private $message;

    /** @var LazyPromise */
    private $promise;

    public function __construct(File $handle = null, string $message)
    {
        $this->message = $message;
        $this->promise = new LazyPromise(
            function() use ($handle, $message) { 
                if (is_null($handle)) {
                    throw new Exception('File handle is null');
                }
                return $handle->write($this->message);
            }
        );
    }

    public function onResolve(callable $onResolved)
    {
        $this->promise->onResolve($onResolved);
    }

    public function equals(IO $io): bool
    {
        return (string) $io === (string) $this;
    }

    public function __toString(): string
    {
        return $this->message;
    }
}

class HttpIO implements IO
{
    /** @var Request */
    private $request;

    /** @var LazyPromise */
    private $promise;
    
    public function __construct(HttpClient $httpClient = null, Request $request)
    {
        $this->request = $request;
        $this->promise = new LazyPromise(
            function() use ($httpClient, $request) {
                if (is_null($httpClient)) {
                    throw new Exception('HttpClient is null');
                }
                return $httpClient->request($request);
            }
        );
    }

    public function equals(IO $io): bool
    {
        return $io === $this->request;
    }

    public function onResolve(callable $onResolved)
    {
        $this->promise->onResolve($onResolved);
    }

    public function __toString(): string
    {
        //return (string) $request;
        return '';
    }
}

class FileSaver
{
    /** @var File */
    private $logger;

    /** @var HttpClient */
    private $httpClient;

    public function __construct(File $logger, HttpClient $httpClient)
    {
        $this->logger = $logger;
        $this->httpClient = $httpClient;
    }

    /**
     * @return Generator<WriteIO|HttpIO>
     */
    public function saveFile(string $path, int $file): generator
    {
        $logger = $this->logger;
        //yield new Amp\LazyPromise(static function() use ($path, $logger) { $logger->write('Saving file ' . $path); });
        yield new WriteIO($logger, 'Saving file ' . $path);
        //$request = new Request('https://cloudfiles.fooservice.com/', 'POST');
        $request = new Request('https://google.com', 'POST');
        $request->setBody($file);
        //$response = yield $this->httpClient->request($request);
        $response = yield new HttpIO($this->httpClient, $request);
        if ($response->getStatus() === 200) {
            yield new WriteIO($logger, 'Successfully saved file ' . $path);
        } else {
            $msg = 'Failed to save file ' . $path;
            yield new WriteIO($logger, $msg);
            throw new Exception($msg);
        }
    }
}

Loop::run(function() {
    $httpClient = HttpClientBuilder::buildDefault();
    $logger = yield Amp\File\open('log.txt', "c+");
    $fileSaver = new FileSaver($logger, $httpClient);
    yield from $fileSaver->saveFile('moo', 0);
    return;

    $effects = [
        [
            'yield' => new WriteIO(null, 'Saving file moo'),
            'send' => null
        ],
        [
            'yield' => null,
            'send' => new class { public function getStatus(): int { return 200; } }
        ]
    ];
    $gen = $fileSaver->saveFile('moo', 0);
    testGenerator($gen, $effects);
});

function testGenerator(generator $gen, array $effects): void
{
    foreach ($gen as $i => $promise) {
        if ($effects[$i]['yield']) {
            if (!$promise->equals($effects[$i]['yield'])) {
                //var_dump($promise);
                throw new Exception('Failed test');
            }
        }
        if ($effects[$i]['send']) {
            $gen->send($effects[$i]['send']);
        }
    }
}