<?php

namespace Drupal\views\Form;

use Drupal\Component\Utility\UrlHelper;
use Drupal\Core\DependencyInjection\ClassResolverInterface;
use Drupal\Core\DependencyInjection\ContainerInjectionInterface;
use Drupal\Core\DependencyInjection\DependencySerializationTrait;
use Drupal\Core\Form\FormInterface;
use Drupal\Core\Form\FormStateInterface;
use Drupal\Core\Routing\UrlGeneratorInterface;
use Drupal\Core\Url;
use Drupal\views\ViewExecutable;
use Symfony\Component\DependencyInjection\ContainerInterface;
use Symfony\Component\HttpFoundation\RequestStack;

/**
 * Provides a base class for single- or multistep view forms.
 *
 * This class only dispatches logic to the form for the current step. The form
 * is always assumed to be multistep, even if it has only one step (which by
 * default is \Drupal\views\Form\ViewsFormMainForm). That way it is actually
 * possible for modules to have a multistep form if they need to.
 */
class ViewsForm implements FormInterface, ContainerInjectionInterface {
  use DependencySerializationTrait;

  /**
   * The class resolver to get the subform form objects.
   *
   * @var \Drupal\Core\DependencyInjection\ClassResolverInterface
   */
  protected $classResolver;

  /**
   * The request stack.
   *
   * @var \Symfony\Component\HttpFoundation\RequestStack
   */
  protected $requestStack;

  /**
   * The url generator to generate the form action.
   *
   * @var \Drupal\Core\Routing\UrlGeneratorInterface
   */
  protected $urlGenerator;

  /**
   * The ID of the view.
   *
   * @var string
   */
  protected $viewId;

  /**
   * The ID of the active view's display.
   *
   * @var string
   */
  protected $viewDisplayId;

  /**
   * The arguments passed to the active view.
   *
   * @var string[]
   */
  protected $viewArguments;

  /**
   * Constructs a ViewsForm object.
   *
   * @param \Drupal\Core\DependencyInjection\ClassResolverInterface $class_resolver
   *   The class resolver to get the subform form objects.
   * @param \Drupal\Core\Routing\UrlGeneratorInterface $url_generator
   *   The url generator to generate the form action.
   * @param \Symfony\Component\HttpFoundation\RequestStack $requestStack
   *   The request stack.
   * @param string $view_id
   *   The ID of the view.
   * @param string $view_display_id
   *   The ID of the active view's display.
   * @param string[] $view_args
   *   The arguments passed to the active view.
   */
  public function __construct(ClassResolverInterface $class_resolver, UrlGeneratorInterface $url_generator, RequestStack $requestStack, $view_id, $view_display_id, array $view_args) {
    $this->classResolver = $class_resolver;
    $this->urlGenerator = $url_generator;
    $this->requestStack = $requestStack;
    $this->viewId = $view_id;
    $this->viewDisplayId = $view_display_id;
    $this->viewArguments = $view_args;
  }

  /**
   * {@inheritdoc}
   */
  public static function create(ContainerInterface $container, $view_id = NULL, $view_display_id = NULL, array $view_args = NULL) {
    return new static(
      $container->get('class_resolver'),
      $container->get('url_generator'),
      $container->get('request_stack'),
      $view_id,
      $view_display_id,
      $view_args
    );
  }

  /**
   * Returns a string for the form's base ID.
   *
   * @return string
   *   The string identifying the form's base ID.
   */
  public function getBaseFormId() {
    $parts = [
      'views_form',
      $this->viewId,
      $this->viewDisplayId,
    ];

    return implode('_', $parts);
  }

  /**
   * {@inheritdoc}
   */
  public function getFormId() {
    $parts = [
      $this->getBaseFormId(),
    ];

    if (!empty($this->viewArguments)) {
      // Append the passed arguments to ensure form uniqueness.
      $parts = array_merge($parts, $this->viewArguments);
    }

    return implode('_', $parts);
  }

  /**
   * {@inheritdoc}
   */
  public function buildForm(array $form, FormStateInterface $form_state, ViewExecutable $view = NULL, $output = []) {
    if (!$step = $form_state->get('step')) {
      $step = 'views_form_views_form';
      $form_state->set('step', $step);
    }
    $form_state->set(['step_controller', 'views_form_views_form'], 'Drupal\views\Form\ViewsFormMainForm');

    // Add the base form ID.
    $form_state->addBuildInfo('base_form_id', $this->getBaseFormId());

    $form = [];

    $query = $this->requestStack->getCurrentRequest()->query->all();
    $query = UrlHelper::filterQueryParameters($query, [], '');

    $options = ['query' => $query];
    $form['#action'] = $view->hasUrl() ? $view->getUrl()->setOptions($options)->toString() : Url::fromRoute('<current>')->setOptions($options)->toString();
    // Tell the preprocessor whether it should hide the header, footer, pager,
    // etc.
    $form['show_view_elements'] = [
      '#type' => 'value',
      '#value' => ($step == 'views_form_views_form') ? TRUE : FALSE,
    ];

    $form_object = $this->getFormObject($form_state);
    $form += $form_object->buildForm($form, $form_state, $view, $output);

    return $form;
  }

  /**
   * {@inheritdoc}
   */
  public function validateForm(array &$form, FormStateInterface $form_state) {
    $form_object = $this->getFormObject($form_state);
    $form_object->validateForm($form, $form_state);
  }

  /**
   * {@inheritdoc}
   */
  public function submitForm(array &$form, FormStateInterface $form_state) {
    $form_object = $this->getFormObject($form_state);
    $form_object->submitForm($form, $form_state);
  }

  /**
   * Returns the object used to build the step form.
   *
   * @param \Drupal\Core\Form\FormStateInterface $form_state
   *   The form_state of the current form.
   *
   * @return \Drupal\Core\Form\FormInterface
   *   The form object to use.
   */
  protected function getFormObject(FormStateInterface $form_state) {
    // If this is a class, instantiate it.
    $form_step_class = $form_state->get(['step_controller', $form_state->get('step')]) ?: 'Drupal\views\Form\ViewsFormMainForm';
    return $this->classResolver->getInstanceFromDefinition($form_step_class);
  }

}