Implementation
--------------

The goal of our plugin is simple - we need to extend the ``ProductVariant`` entity and provide a new flag, that could be set
on the product variant form. Following customizations are done just like in the **Sylius Customization Guide**,
take a look at :doc:`customizing models</customization/model>`, :doc:`form</customization/form>` and :doc:`template</customization/template>`.

.. attention::

    ``PluginSkeleton`` is focused on delivering the most friendly and testable environment. That's why in ``tests/Application`` directory,
    there is a **tiny Sylius application** placed, with your plugin already used. Thanks to that, you can test your plugin with Behat scenarios
    **within** Sylius application without installing it to any test app manually! There is, however, one important consequence of such an architecture.
    **Everything** that should be done by a plugin user (configuration import, templates copying etc.) should also be done in ``tests/Application``
    to simulate the real developer behavior - and therefore make your new features testable.

Model
*****

The only field we need to add is an additional ``$availableOnDemand`` boolean. To allow plugin's user to use multiple plugins extending
the same entity, it's recommended to provide a trait with new properties and methods, together with ORM mapping written in annotations
(if necessary). Providing an interface containing new methods is advisable.

.. code-block:: php

    <?php

    // src/Model/ProductVariantTrait.php

    declare(strict_types=1);

    namespace IronMan\SyliusProductOnDemandPlugin\Model;

    trait ProductVariantTrait
    {
        /**
         * @var bool
         *
         * @ORM\Column(type="boolean", name="available_on_demand")
         */
        private $availableOnDemand = false;

        public function setAvailableOnDemand(bool $availableOnDemand): void
        {
            $this->availableOnDemand = $availableOnDemand;
        }

        public function isAvailableOnDemand(): bool
        {
            return $this->availableOnDemand;
        }
    }

.. code-block:: php

    <?php

    // src/Model/ProductVariantInterface.php

    declare(strict_types=1);

    namespace IronMan\SyliusProductOnDemandPlugin\Entity;

    interface ProductVariantInterface
    {
        public function setAvailableOnDemand(bool $availableOnDemand): void;

        public function isAvailableOnDemand(): bool;
    }

.. warning::

    Remember that if you modify or add some mapping, you should either provide a migration for the plugin user (that could be
    copied to their migration folder) or mention the requirement of migration generation in the installation instructions.

Form
****

To make our new field available in Admin panel, a form extension is required:

.. code-block:: php

    <?php

    // src/Form/Extension/ProductVariantTypeExtension.php

    declare(strict_types=1);

    namespace IronMan\SyliusProductOnDemandPlugin\Form\Extension;

    use Symfony\Component\Form\AbstractTypeExtension;
    use Symfony\Component\Form\Extension\Core\Type\CheckboxType;
    use Sylius\Bundle\ProductBundle\Form\Type\ProductVariantType;
    use Symfony\Component\Form\FormBuilderInterface;

    final class ProductVariantTypeExtension extends AbstractTypeExtension
    {
        public function buildForm(FormBuilderInterface $builder, array $options): void
        {
            $builder->add('availableOnDemand', CheckboxType::class, [
                'label' => 'iron_man_sylius_product_on_demand_plugin.ui.available_on_demand',
            ]);
        }

        public function getExtendedType(): string
        {
            return ProductVariantType::class;
        }
    }

Translation keys placed in ``src/Resources/translations/messages.{locale}.yml`` will be resolved automatically.

.. code-block:: yaml

    # src/Resources/translations/messages.en.yml

    iron_man_sylius_product_on_demand_plugin:
        ui:
            available_on_demand: Available on demand

And in your ``services.yml`` file:

.. code-block:: yaml

    # src/Resources/config/services.yml

    services:
        iron_man_sylius_product_on_demand_plugin.form.extension.type.product_variant:
            class: IronMan\SyliusProductOnDemandPlugin\Form\Extension\ProductVariantTypeExtension
            tags:
                - { name: form.type_extension, extended_type: Sylius\Bundle\ProductBundle\Form\Type\ProductVariantType }

Again, you must remember about importing ``src/Resources/config/services.yml`` in ``tests/Application/config/services.yaml``.

Template
********

The last step is extending the template of a product variant form. It can be done in three ways:

* by overwriting template
* by using sonata block events
* by writing a theme

For the needs of this tutorial, we will go the first way. What's crucial, we need to determine which template should be overwritten.
Naming for twig files in Sylius, both in **ShopBundle** and **AdminBundle** are pretty clear and straightforward. In this specific case,
the template to override is ``src/Sylius/Bundle/AdminBundle/Resources/views/ProductVariant/Tab/_details.html.twig``. It should be copied
to ``src/Resources/views/SyliusAdminBundle/ProductVariant/Tab/`` directory, and additional field should be placed somewhere in the template.

.. code-block:: twig

    {# src/Resources/views/SyliusAdminBundle/ProductVariant/Tab/_details.html.twig #}

    {#...#}

    <div class="ui segment">
        <h4 class="ui dividing header">{{ 'sylius.ui.inventory'|trans }}</h4>
        {{ form_row(form.onHand) }}
        {{ form_row(form.tracked) }}
        {{ form_row(form.version) }}
        {{ form_row(form.availableOnDemand) }}
    </div>

    {#...#}

.. warning::

    Beware! Implementing a new template on the plugin level is **not** everything! You must remember that this template should be
    copied to ``templates/bundles/SyliusAdminBundle/`` directory (with whole catalogs structure, means ``/ProductVariant/Tab``
    in the application that uses your plugin - and therefore it should be mentioned in installation instruction.
    The same thing should be done for your test application (you should have ``tests/Application/templates/bundles/SyliusAdminBundle/`` catalog
    with this template copied).

    Take a look at :doc:`customizing the templates</customization/template>` section in the documentation,
    for a better understanding of this topic.