include 'vendor/autoload.php';

$schema = [
    'root' => [ // Schema must begins with 'root'
        'title' => [
            '_type' => 'required_string'
        ],
        'price' => [
            '_type' => 'number'
        ],
        'author' => [
            '_type' => 'string'
        ],
        'instock' => [
            '_type' => 'required_boolean'
        ],
        'info' =>  [
            '_type' => 'array',
            'isbn' => [
                '_type' => 'string'
            ],
            'pages' => [
                '_type' => 'number'
            ]
        ],
        'comments' => [
            '_type' => 'nested_array',
            'user_id' => [
                '_type' => 'required_number'
            ],
            'comment' => [
                '_type' => 'required_string'
            ]
        ]
    ]
];

$book = [
    'title' => 'The Idiot', // Cannot be omitted
    'instock' => true, // Cannot be omitted and has to be bool type
    'info' => ['isbn' => '978-0451531520'],
    //  'price' can be omitted but if present has to be numeric type 
    'comments' => [ // Nested array check nested elements
        [
            'user_id' => 1,
            'comment' => 'Good book',
            // 'extra_field' => 'bad field' 
            // By default if key not present in schema validation stops and returns false 
        ],
        [
            'user_id' => 2,
            'comment' => 'I like it'
        ]
    ]
];

$validator = new \Volan\Volan($schema);
$result = $validator->validate($book);

// if $result->isValid() === false you can get full information about invalid node
var_dump($result->getErrorInfo());

namespace Volan\Validator;
class MongoidValidator extends AbstractValidator
{
    public function isValid($nodeData)
    {
        return ($nodeData instanceof \MongoId);
    }
}

namespace Volan\Validator;
use Respect\Validation\Validator as v;

class IntBetween10And20Validator extends AbstractValidator
{
    public function isValid($nodeData)
    {
        return v::int()->between(10, 20)->validate($nodeData);
        
    }
}

$validator = new \Volan\Volan($schema, $strictMode = false);

$validator = new \Volan\Volan($schema);
$validator->setRequiredMode(false);
$result = $validator->validate($book);

$validator = new \Volan\Volan($schema);

$result = $validator->validate($book);
$result->getLog();

namespace Volan\Validator;

class MongoidValidator extends AbstractValidator
{
    public function isValid($nodeData)
    {
        return ($nodeData instanceof \MongoId);
    }
}

...
'categories' => [new \MongoId('111111111111111111111111'),new \MongoId('111111111111111111111112')]
...

class ArrayOfMongoids extends AbstractValidator
{
    public function isValid($nodeData)
    {
        foreach($nodeData as $id) {
            if($id !instanceof \MongoId) || !$this->presentInCategoryCollection($id))
                return false;
            }
        }
        
        return true;
    }
    
    public function presentInCategoryCollection($id)
    {
        // Getting connection and so on

        $collection = $db->selectCollection('categories');
        return (bool)$collection->findOne(['_id' => $id]);
    }
    
}

...
'categories' => ['_type' => 'array_of_mongoids']
...