
# Schema

This library can parse a [TypeSchema](https://typeschema.org/) specification either from a JSON file or from PHP
classes using reflection and attributes. Based on this schema it can generate source code and transform raw JSON data
into DTO objects. Through this you can work with fully typed objects in your API for incoming and outgoing data. It
provides basically the following features:

* Transform raw JSON data into DTO objects
* Generate source code based on a schema (i.e. PHP, Typescript)
* Validate data according to the provided schema

## Usage

At first, we need to describe our data format with a [TypeSchema](https://typeschema.org/) specification. Then we can
generate based on this specification the fitting PHP classes.

```json
{
  "definitions": {
    "Person": {
      "type": "object",
      "properties": {
        "firstName": {
          "type": "string"
        },
        "lastName": {
          "type": "string"
        },
        "age": {
          "description": "Age in years",
          "type": "integer",
          "minimum": 0
        }
      },
      "required": [
        "firstName",
        "lastName"
      ]
    }
  },
  "$ref": "Person"
}
```

To generate the PHP classes we use the following command:

```
vendor/bin/schema schema:parse --format=php schema.json
```

Note you can also skip this step and directly write the PHP class by your self. The advantage of starting with a JSON
representation is that you have defined your models in a neutral format so that you can generate the models for
different environments i.e. also for the frontend using the TypeScript generator. The command generates the following
source code:

```php
<?php

declare(strict_types = 1);

#[Required(["firstName", "lastName"])]
class Person implements \JsonSerializable
{
    protected ?string $firstName = null;
    protected ?string $lastName = null;
    #[Description("Age in years")]
    #[Minimum(0)]
    protected ?int $age = null;
    public function setFirstName(?string $firstName) : void
    {
        $this->firstName = $firstName;
    }
    public function getFirstName() : ?string
    {
        return $this->firstName;
    }
    public function setLastName(?string $lastName) : void
    {
        $this->lastName = $lastName;
    }
    public function getLastName() : ?string
    {
        return $this->lastName;
    }
    public function setAge(?int $age) : void
    {
        $this->age = $age;
    }
    public function getAge() : ?int
    {
        return $this->age;
    }
    public function jsonSerialize()
    {
        return (object) array_filter(array('firstName' => $this->firstName, 'lastName' => $this->lastName, 'age' => $this->age), static function ($value) : bool {
            return $value !== null;
        });
    }
}
```

Now we can parse raw JSON data and fill this in to our object model:

```php
// the data which we want to import
$data = json_decode('{"firstName": "foo", "lastName": "bar"}');

$schemaManager = new SchemaManager();

// we read the schema from the class
$schema = $schemaManager->getSchema(Person::class);

try {
    $person = (new SchemaTraverser())->traverse($data, $schema, new TypeVisitor());
    
    // $example contains now an instance of the Person class containing 
    // the firstName and lastName property
    echo $person->getFirstName();

} catch (\PSX\Schema\Exception\ValidationException $e) {
    // the validation failed
    echo $e->getMessage();
}

```

Every generated PHP class implements also the `JsonSerializable` interface so you can simply encode an object to json.

```php
$schema = new Person();
$schema->setFirstName('foo');
$schema->setLastName('bar');
$schema->setAge(12);

echo json_encode($schema);

// would result in
// {"firstName": "foo", "lastName": "bar", "age": 12}

```

## Generator

Beside PHP classes this library can generate the following types:

* CSharp
* Go
* HTML
* Java
* JsonSchema
* Markdown
* PHP
* Protobuf
* Python
* Swift
* TypeSchema
* TypeScript

## Attributes

The following attributes are available:

| Attribute            | Target         | Example                          |
|----------------------|----------------|----------------------------------|
| Deprecated           | Property       | #[Deprecated(true)]              |
| Description          | Class/Property | #[Description("content")]        |
| Discriminator        | Property       | #[Discriminator("type")]         |
| Enum                 | Property       | #[Enum({"foo", "bar"})]          |
| Exclude              | Property       | #[Exclude]                       |
| ExclusiveMaximum     | Property       | #[ExclusiveMaximum(true)]        |
| ExclusiveMinimum     | Property       | #[ExclusiveMinimum(true)]        |
| Format               | Property       | #[Format("uri")]                 |
| Key                  | Property       | #[Key("$ref")]                   |
| Maximum              | Property       | #[Maximum(16)]                   |
| MaxItems             | Property       | #[MaxItems(16)]                  |
| MaxLength            | Property       | #[MaxLength(16)]                 |
| MaxProperties        | Class          | #[MaxProperties(16)]             |
| Minimum              | Property       | #[Minimum(4)]                    |
| MinItems             | Property       | #[MinItems(4)]                   |
| MinLength            | Property       | #[MinLength(4)]                  |
| MinProperties        | Property       | #[MinProperties(4)]              |
| MultipleOf           | Property       | #[MultipleOf(2)]                 |
| Nullable             | Property       | #[Nullable(true)]                |
| Pattern              | Property       | #[Pattern("A-z+")]               |
| Required             | Class          | #[Required(["name", "title"])]   |
| Title                | Class          | #[Title("foo")]                  |
| UniqueItems          | Property       | #[UniqueItems(true)]             |

