Technical test

Starting the server

If you have docker and docker-compose packages installed, you will only need to run this on the project root to start the server:

docker compose up -d

It will start a docker stack ready to serve requests.

If PHPStorm is configured to use these containers as interpreters, develop and debug tasks will be easier.

Brackets authentication

In order to implement custom authentication method without override the previous ones I've created a new middleware. It has been registered in the App\Http\Kernel $middlewareAliases property:

protected $middlewareAliases = [
    ...,
    'auth.brackets' => \App\Http\Middleware\BracketsAuthenticate::class,
]

Stack Automata

The best solution for the problem I thought is to create a stack automata.

It consists in to add the open brackets on a stack and to pop it if they match the closing bracket. If at the end of all iterations the stack is empty, the string will pass the test.

public function passes(string $token): bool
{
    $stack = [];

    if (strlen($token) % 2 != 0) return false;

    foreach (str_split($token) as $char)
    {
        $size = sizeof($stack);

        if ($size == 0) $stack[] = $char;
        else if (in_array($char, ['(', '{', '['])) $stack[] = $char;
        else {
            match ($char) {
                ')' => $match = $stack[$size - 1] == '(',
                '}' => $match = $stack[$size - 1] == '{',
                ']' => $match = $stack[$size - 1] == '[',
            };

            if ($match) array_pop($stack);
            else $stack[] = $char;
        }
    }

    return sizeof($stack) == 0;
}

Binding an interface to implementation

To bind an interface to a concrete implementation I've had to register it on register() method from AppServideProvider.

Once Laravel knows how to resolve which implementation has to inject we can forget about implementations and invert the dependency order. Now we only need to know the interface.

Class App\Http\Middleware\BracketsAuthenticate:

public function __construct(private readonly BracketsChecker $bracketsChecker)
{
}

Testing

Test Driven Development has been used in this project. You can find 4 simple tests in tests/ folder that checks that StackAutomataBracketsChecker and the API endpoint works as expected.

The HTTP requests to suggested endpoint are faked using the Http Laravel facade.

To run these tests you can use PHPStorm or exec this command:

docker exec -it tinyurl_api php artisan test

Once all tests passes, I've tested it though insomnia requests. The request export to curl is:

curl --request POST \
  --url http://localhost/api/v1/short-urls \
  --header 'Accept: application/json' \
  --header 'Authorization: Bearer {([])}' \
  --header 'Content-Type: application/json' \
  --data '{ "url": "https://youtu.be/dQw4w9WgXcQ" }'