Nette Schema
************

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Introduction
============

A practical library for validation and normalization of data structures against a given schema with a smart & easy-to-understand API.

Documentation can be found on the [website](https://doc.nette.org/schema).

Installation:

```shell
composer require nette/schema
```

It requires PHP version 8.1 and supports PHP up to 8.3.


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Basic Usage
-----------

In variable `$schema` we have a validation schema (what exactly this means and how to create it we will say later) and in variable `$data` we have a data structure that we want to validate and normalize. This can be, for example, data sent by the user through an API, configuration file, etc.

The task is handled by the [Nette\Schema\Processor](https://api.nette.org/schema/master/Nette/Schema/Processor.html) class, which processes the input and either returns normalized data or throws an [Nette\Schema\ValidationException](https://api.nette.org/schema/master/Nette/Schema/ValidationException.html) exception on error.

```php
$processor = new Nette\Schema\Processor;

try {
    $normalized = $processor->process($schema, $data);
} catch (Nette\Schema\ValidationException $e) {
    echo 'Data is invalid: ' . $e->getMessage();
}
```

Method `$e->getMessages()` returns array of all message strings and `$e->getMessageObjects()` return all messages as [Nette\Schema\Message](https://api.nette.org/schema/master/Nette/Schema/Message.html) objects.


Defining Schema
---------------

And now let's create a schema. The class [Nette\Schema\Expect](https://api.nette.org/schema/master/Nette/Schema/Expect.html) is used to define it, we actually define expectations of what the data should look like. Let's say that the input data must be a structure (e.g. an array) containing elements `processRefund` of type bool and `refundAmount` of type int.

```php
use Nette\Schema\Expect;

$schema = Expect::structure([
    'processRefund' => Expect::bool(),
    'refundAmount' => Expect::int(),
]);
```

We believe that the schema definition looks clear, even if you see it for the very first time.

Lets send the following data for validation:

```php
$data = [
    'processRefund' => true,
    'refundAmount' => 17,
];

$normalized = $processor->process($schema, $data); // OK, it passes
```

The output, i.e. the value `$normalized`, is the object `stdClass`. If we want the output to be an array, we add a cast to schema `Expect::structure([...])->castTo('array')`.

All elements of the structure are optional and have a default value `null`. Example:

```php
$data = [
    'refundAmount' => 17,
];

$normalized = $processor->process($schema, $data); // OK, it passes
// $normalized = {'processRefund' => null, 'refundAmount' => 17}
```

The fact that the default value is `null` does not mean that it would be accepted in the input data `'processRefund' => null`. No, the input must be boolean, i.e. only `true` or `false`. We would have to explicitly allow `null` via `Expect::bool()->nullable()`.

An item can be made mandatory using `Expect::bool()->required()`. We change the default value to `false` using `Expect::bool()->default(false)` or shortly using `Expect::bool(false)`.

And what if we wanted to accept `1` and `0` besides booleans? Then we list the allowed values, which we will also normalize to boolean:

```php
$schema = Expect::structure([
    'processRefund' => Expect::anyOf(true, false, 1, 0)->castTo('bool'),
    'refundAmount' => Expect::int(),
]);

$normalized = $processor->process($schema, $data);
is_bool($normalized->processRefund); // true
```

Now you know the basics of how the schema is defined and how the individual elements of the structure behave. We will now show what all the other elements can be used in defining a schema.


Data Types: type()
------------------

All standard PHP data types can be listed in the schema:

```php
Expect::string($default = null)
Expect::int($default = null)
Expect::float($default = null)
Expect::bool($default = null)
Expect::null()
Expect::array($default = [])
```

And then all types [supported by the Validators](https://doc.nette.org/validators#toc-validation-rules) via `Expect::type('scalar')` or abbreviated `Expect::scalar()`. Also class or interface names are accepted, e.g. `Expect::type('AddressEntity')`.

You can also use union notation:

```php
Expect::type('bool|string|array')
```

The default value is always `null` except for `array` and `list`, where it is an empty array. (A list is an array indexed in ascending order of numeric keys from zero, that is, a non-associative array).


Array of Values: arrayOf() listOf()
-----------------------------------

The array is too general structure, it is more useful to specify exactly what elements it can contain. For example, an array whose elements can only be strings:

```php
$schema = Expect::arrayOf('string');

$processor->process($schema, ['hello', 'world']); // OK
$processor->process($schema, ['a' => 'hello', 'b' => 'world']); // OK
$processor->process($schema, ['key' => 123]); // ERROR: 123 is not a string
```

The second parameter can be used to specify keys (since version 1.2):

```php
$schema = Expect::arrayOf('string', 'int');

$processor->process($schema, ['hello', 'world']); // OK
$processor->process($schema, ['a' => 'hello']); // ERROR: 'a' is not int
```

The list is an indexed array:

```php
$schema = Expect::listOf('string');

$processor->process($schema, ['a', 'b']); // OK
$processor->process($schema, ['a', 123]); // ERROR: 123 is not a string
$processor->process($schema, ['key' => 'a']); // ERROR: is not a list
$processor->process($schema, [1 => 'a', 0 => 'b']); // ERROR: is not a list
```

The parameter can also be a schema, so we can write:

```php
Expect::arrayOf(Expect::bool())
```

The default value is an empty array. If you specify a default value, it will be merged with the passed data. This can be disabled using `mergeDefaults(false)`.


Enumeration: anyOf()
--------------------

`anyOf()` is a set of values or schemas that a value can be. Here's how to write an array of elements that can be either `'a'`, `true`, or `null`:

```php
$schema = Expect::listOf(
    Expect::anyOf('a', true, null),
);

$processor->process($schema, ['a', true, null, 'a']); // OK
$processor->process($schema, ['a', false]); // ERROR: false does not belong there
```

The enumeration elements can also be schemas:

```php
$schema = Expect::listOf(
    Expect::anyOf(Expect::string(), true, null),
);

$processor->process($schema, ['foo', true, null, 'bar']); // OK
$processor->process($schema, [123]); // ERROR
```

The `anyOf()` method accepts variants as individual parameters, not as array. To pass it an array of values, use the unpacking operator `anyOf(...$variants)`.

The default value is `null`. Use the `firstIsDefault()` method to make the first element the default:

```php
// default is 'hello'
Expect::anyOf(Expect::string('hello'), true, null)->firstIsDefault();
```


Structures
----------

Structures are objects with defined keys. Each of these key => value pairs is referred to as a "property":

Structures accept arrays and objects and return objects `stdClass` (unless you change it with `castTo('array')`, etc.).

By default, all properties are optional and have a default value of `null`. You can define mandatory properties using `required()`:

```php
$schema = Expect::structure([
    'required' => Expect::string()->required(),
    'optional' => Expect::string(), // the default value is null
]);

$processor->process($schema, ['optional' => '']);
// ERROR: option 'required' is missing

$processor->process($schema, ['required' => 'foo']);
// OK, returns {'required' => 'foo', 'optional' => null}
```

If you do not want to output properties with only a default value, use `skipDefaults()`:

```php
$schema = Expect::structure([
    'required' => Expect::string()->required(),
    'optional' => Expect::string(),
])->skipDefaults();

$processor->process($schema, ['required' => 'foo']);
// OK, returns {'required' => 'foo'}
```

Although `null` is the default value of the `optional` property, it is not allowed in the input data (the value must be a string). Properties accepting `null` are defined using `nullable()`:

```php
$schema = Expect::structure([
    'optional' => Expect::string(),
    'nullable' => Expect::string()->nullable(),
]);

$processor->process($schema, ['optional' => null]);
// ERROR: 'optional' expects to be string, null given.

$processor->process($schema, ['nullable' => null]);
// OK, returns {'optional' => null, 'nullable' => null}
```

By default, there can be no extra items in the input data:

```php
$schema = Expect::structure([
    'key' => Expect::string(),
]);

$processor->process($schema, ['additional' => 1]);
// ERROR: Unexpected item 'additional'
```

Which we can change with `otherItems()`. As a parameter, we will specify the schema for each extra element:

```php
$schema = Expect::structure([
    'key' => Expect::string(),
])->otherItems(Expect::int());

$processor->process($schema, ['additional' => 1]); // OK
$processor->process($schema, ['additional' => true]); // ERROR
```


Deprecations
------------

You can deprecate property using the `deprecated([string $message])` method. Deprecation notices are returned by `$processor->getWarnings()`:

```php
$schema = Expect::structure([
    'old' => Expect::int()->deprecated('The item %path% is deprecated'),
]);

$processor->process($schema, ['old' => 1]); // OK
$processor->getWarnings(); // ["The item 'old' is deprecated"]
```


Ranges: min() max()
-------------------

Use `min()` and `max()` to limit the number of elements for arrays:

```php
// array, at least 10 items, maximum 20 items
Expect::array()->min(10)->max(20);
```

For strings, limit their length:

```php
// string, at least 10 characters long, maximum 20 characters
Expect::string()->min(10)->max(20);
```

For numbers, limit their value:

```php
// integer, between 10 and 20 inclusive
Expect::int()->min(10)->max(20);
```

Of course, it is possible to mention only `min()`, or only `max()`:

```php
// string, maximum 20 characters
Expect::string()->max(20);
```


Regular Expressions: pattern()
------------------------------

Using `pattern()`, you can specify a regular expression which the **whole** input string must match (i.e. as if it were wrapped in characters `^` a `$`):

```php
// just 9 digits
Expect::string()->pattern('\d{9}');
```


Custom Assertions: assert()
---------------------------

You can add any other restrictions using `assert(callable $fn)`.

```php
$countIsEven = fn($v) => count($v) % 2 === 0;

$schema = Expect::arrayOf('string')
    ->assert($countIsEven); // the count must be even

$processor->process($schema, ['a', 'b']); // OK
$processor->process($schema, ['a', 'b', 'c']); // ERROR: 3 is not even
```

Or

```php
Expect::string()->assert('is_file'); // the file must exist
```

You can add your own description for each assertion. It will be part of the error message.

```php
$schema = Expect::arrayOf('string')
    ->assert($countIsEven, 'Even items in array');

$processor->process($schema, ['a', 'b', 'c']);
// Failed assertion "Even items in array" for item with value array.
```

The method can be called repeatedly to add multiple constraints. It can be intermixed with calls to `transform()` and `castTo()`.


Transformation: transform()
---------------------------

Successfully validated data can be modified using a custom function:

```php
// conversion to uppercase:
Expect::string()->transform(fn(string $s) => strtoupper($s));
```

The method can be called repeatedly to add multiple transformations. It can be intermixed with calls to `assert()` and `castTo()`. The operations will be executed in the order in which they are declared:

```php
Expect::type('string|int')
    ->castTo('string')
    ->assert('ctype_lower', 'All characters must be lowercased')
    ->transform(fn(string $s) => strtoupper($s)); // conversion to uppercase
```

The `transform()` method can both transform and validate the value simultaneously. This is often simpler and less redundant than chaining `transform()` and `assert()`. For this purpose, the function receives a [Nette\Schema\Context](https://api.nette.org/schema/master/Nette/Schema/Context.html) object with an `addError()` method, which can be used to add information about validation issues:

```php
Expect::string()
    ->transform(function (string $s, Nette\Schema\Context $context) {
        if (!ctype_lower($s)) {
            $context->addError('All characters must be lowercased', 'my.case.error');
            return null;
        }

        return strtoupper($s);
    });
```


Casting: castTo()
-----------------

Successfully validated data can be cast:

```php
Expect::scalar()->castTo('string');
```

In addition to native PHP types, you can also cast to classes. It distinguishes whether it is a simple class without a constructor or a class with a constructor. If the class has no constructor, an instance of it is created and all elements of the structure are written to its properties:

```php
class Info
{
    public bool $processRefund;
    public int $refundAmount;
}

Expect::structure([
    'processRefund' => Expect::bool(),
    'refundAmount' => Expect::int(),
])->castTo(Info::class);

// creates '$obj = new Info' and writes to $obj->processRefund and $obj->refundAmount
```

If the class has a constructor, the elements of the structure are passed as named parameters to the constructor:

```php
class Info
{
    public function __construct(
        public bool $processRefund,
        public int $refundAmount,
    ) {
    }
}

// creates $obj = new Info(processRefund: ..., refundAmount: ...)
```

Casting combined with a scalar parameter creates an object and passes the value as the sole parameter to the constructor:

```php
Expect::string()->castTo(DateTime::class);
// creates new DateTime(...)
```


Normalization: before()
-----------------------

Prior to the validation itself, the data can be normalized using the method `before()`. As an example, let's have an element that must be an array of strings (eg `['a', 'b', 'c']`), but receives input in the form of a string `a b c`:

```php
$explode = fn($v) => explode(' ', $v);

$schema = Expect::arrayOf('string')
    ->before($explode);

$normalized = $processor->process($schema, 'a b c');
// OK, returns ['a', 'b', 'c']
```


Mapping to Objects: from()
--------------------------

You can generate structure schema from the class. Example:

```php
class Config
{
    /** @var string */
    public $name;
    /** @var string|null */
    public $password;
    /** @var bool */
    public $admin = false;
}

$schema = Expect::from(new Config);

$data = [
    'name' => 'jeff',
];

$normalized = $processor->process($schema, $data);
// $normalized instanceof Config
// $normalized = {'name' => 'jeff', 'password' => null, 'admin' => false}
```

If you are using PHP 7.4 or higher, you can use native types:

```php
class Config
{
    public string $name;
    public ?string $password;
    public bool $admin = false;
}

$schema = Expect::from(new Config);
```

Anonymous classes are also supported:

```php
$schema = Expect::from(new class {
    public string $name;
    public ?string $password;
    public bool $admin = false;
});
```

Because the information obtained from the class definition may not be sufficient, you can add a custom schema for the elements with the second parameter:

```php
$schema = Expect::from(new Config, [
    'name' => Expect::string()->pattern('\w:.*'),
]);
```

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