class OverviewTerms

class OverviewTerms extends FormBase {
    
    /**
     * The module handler service.
     *
     * @var \Drupal\Core\Extension\ModuleHandlerInterface
     */
    protected $moduleHandler;
    
    /**
     * The entity type manager.
     *
     * @var \Drupal\Core\Entity\EntityTypeManagerInterface
     */
    protected $entityTypeManager;
    
    /**
     * The term storage handler.
     *
     * @var \Drupal\taxonomy\TermStorageInterface
     */
    protected $storageController;
    
    /**
     * The term list builder.
     *
     * @var \Drupal\Core\Entity\EntityListBuilderInterface
     */
    protected $termListBuilder;
    
    /**
     * The renderer service.
     *
     * @var \Drupal\Core\Render\RendererInterface
     */
    protected $renderer;
    
    /**
     * The entity repository.
     *
     * @var \Drupal\Core\Entity\EntityRepositoryInterface
     */
    protected $entityRepository;
    
    /**
     * The pager manager.
     *
     * @var \Drupal\Core\Pager\PagerManagerInterface
     */
    protected $pagerManager;
    
    /**
     * Constructs an OverviewTerms object.
     *
     * @param \Drupal\Core\Extension\ModuleHandlerInterface $module_handler
     *   The module handler service.
     * @param \Drupal\Core\Entity\EntityTypeManagerInterface $entity_type_manager
     *   The entity type manager service.
     * @param \Drupal\Core\Render\RendererInterface $renderer
     *   The renderer service.
     * @param \Drupal\Core\Entity\EntityRepositoryInterface $entity_repository
     *   The entity repository.
     * @param \Drupal\Core\Pager\PagerManagerInterface $pager_manager
     *   The pager manager.
     */
    public function __construct(ModuleHandlerInterface $module_handler, EntityTypeManagerInterface $entity_type_manager, RendererInterface $renderer, EntityRepositoryInterface $entity_repository, PagerManagerInterface $pager_manager) {
        $this->moduleHandler = $module_handler;
        $this->entityTypeManager = $entity_type_manager;
        $this->storageController = $entity_type_manager->getStorage('taxonomy_term');
        $this->termListBuilder = $entity_type_manager->getListBuilder('taxonomy_term');
        $this->renderer = $renderer;
        $this->entityRepository = $entity_repository;
        $this->pagerManager = $pager_manager;
    }
    
    /**
     * {@inheritdoc}
     */
    public static function create(ContainerInterface $container) {
        return new static($container->get('module_handler'), $container->get('entity_type.manager'), $container->get('renderer'), $container->get('entity.repository'), $container->get('pager.manager'));
    }
    
    /**
     * {@inheritdoc}
     */
    public function getFormId() {
        return 'taxonomy_overview_terms';
    }
    
    /**
     * Form constructor.
     *
     * Display a tree of all the terms in a vocabulary, with options to edit
     * each one. The form is made drag and drop by the theme function.
     *
     * @param array $form
     *   An associative array containing the structure of the form.
     * @param \Drupal\Core\Form\FormStateInterface $form_state
     *   The current state of the form.
     * @param \Drupal\taxonomy\VocabularyInterface $taxonomy_vocabulary
     *   The vocabulary to display the overview form for.
     *
     * @return array
     *   The form structure.
     */
    public function buildForm(array $form, FormStateInterface $form_state, VocabularyInterface $taxonomy_vocabulary = NULL) {
        $form_state->set([
            'taxonomy',
            'vocabulary',
        ], $taxonomy_vocabulary);
        $vocabulary_hierarchy = $this->storageController
            ->getVocabularyHierarchyType($taxonomy_vocabulary->id());
        $parent_fields = FALSE;
        $page = $this->pagerManager
            ->findPage();
        // Number of terms per page.
        $page_increment = $this->config('taxonomy.settings')
            ->get('terms_per_page_admin');
        // Elements shown on this page.
        $page_entries = 0;
        // Elements at the root level before this page.
        $before_entries = 0;
        // Elements at the root level after this page.
        $after_entries = 0;
        // Elements at the root level on this page.
        $root_entries = 0;
        // Terms from previous and next pages are shown if the term tree would have
        // been cut in the middle. Keep track of how many extra terms we show on
        // each page of terms.
        $back_step = NULL;
        $forward_step = 0;
        // An array of the terms to be displayed on this page.
        $current_page = [];
        $delta = 0;
        $term_deltas = [];
        $tree = $this->storageController
            ->loadTree($taxonomy_vocabulary->id(), 0, NULL, TRUE);
        $tree_index = 0;
        $complete_tree = NULL;
        do {
            // In case this tree is completely empty.
            if (empty($tree[$tree_index])) {
                break;
            }
            $delta++;
            // Count entries before the current page.
            if ($page && $page * $page_increment > $before_entries && !isset($back_step)) {
                $before_entries++;
                continue;
            }
            elseif ($page_entries > $page_increment && isset($complete_tree)) {
                $after_entries++;
                continue;
            }
            // Do not let a term start the page that is not at the root.
            $term = $tree[$tree_index];
            if (isset($term->depth) && $term->depth > 0 && !isset($back_step)) {
                $back_step = 0;
                while ($pterm = $tree[--$tree_index]) {
                    $before_entries--;
                    $back_step++;
                    if ($pterm->depth == 0) {
                        $tree_index--;
                        // Jump back to the start of the root level parent.
                        continue 2;
                    }
                }
            }
            $back_step = $back_step ?? 0;
            // Continue rendering the tree until we reach the a new root item.
            if ($page_entries >= $page_increment + $back_step + 1 && $term->depth == 0 && $root_entries > 1) {
                $complete_tree = TRUE;
                // This new item at the root level is the first item on the next page.
                $after_entries++;
                continue;
            }
            if ($page_entries >= $page_increment + $back_step) {
                $forward_step++;
            }
            // Finally, if we've gotten down this far, we're rendering a term on this
            // page.
            $page_entries++;
            $term_deltas[$term->id()] = isset($term_deltas[$term->id()]) ? $term_deltas[$term->id()] + 1 : 0;
            $key = 'tid:' . $term->id() . ':' . $term_deltas[$term->id()];
            // Keep track of the first term displayed on this page.
            if ($page_entries == 1) {
                $form['#first_tid'] = $term->id();
            }
            // Keep a variable to make sure at least 2 root elements are displayed.
            if ($term->parents[0] == 0) {
                $root_entries++;
            }
            $current_page[$key] = $term;
        } while (isset($tree[++$tree_index]));
        // Because we didn't use a pager query, set the necessary pager variables.
        $total_entries = $before_entries + $page_entries + $after_entries;
        $this->pagerManager
            ->createPager($total_entries, $page_increment);
        // If this form was already submitted once, it's probably hit a validation
        // error. Ensure the form is rebuilt in the same order as the user
        // submitted.
        $user_input = $form_state->getUserInput();
        if (!empty($user_input['terms'])) {
            // Get the POST order.
            $order = array_flip(array_keys($user_input['terms']));
            // Update our form with the new order.
            $current_page = array_merge($order, $current_page);
            foreach ($current_page as $key => $term) {
                // Verify this is a term for the current page and set at the current
                // depth.
                if (is_array($user_input['terms'][$key]) && is_numeric($user_input['terms'][$key]['term']['tid'])) {
                    $current_page[$key]->depth = $user_input['terms'][$key]['term']['depth'];
                }
                else {
                    unset($current_page[$key]);
                }
            }
        }
        $args = [
            '%capital_name' => Unicode::ucfirst($taxonomy_vocabulary->label()),
            '%name' => $taxonomy_vocabulary->label(),
        ];
        if ($this->currentUser()
            ->hasPermission('administer taxonomy') || $this->currentUser()
            ->hasPermission('edit terms in ' . $taxonomy_vocabulary->id())) {
            switch ($vocabulary_hierarchy) {
                case VocabularyInterface::HIERARCHY_DISABLED:
                    $help_message = $this->t('You can reorganize the terms in %capital_name using their drag-and-drop handles, and group terms under a parent term by sliding them under and to the right of the parent.', $args);
                    break;
                case VocabularyInterface::HIERARCHY_SINGLE:
                    $help_message = $this->t('%capital_name contains terms grouped under parent terms. You can reorganize the terms in %capital_name using their drag-and-drop handles.', $args);
                    break;
                case VocabularyInterface::HIERARCHY_MULTIPLE:
                    $help_message = $this->t('%capital_name contains terms with multiple parents. Drag and drop of terms with multiple parents is not supported, but you can re-enable drag-and-drop support by editing each term to include only a single parent.', $args);
                    break;
            }
        }
        else {
            switch ($vocabulary_hierarchy) {
                case VocabularyInterface::HIERARCHY_DISABLED:
                    $help_message = $this->t('%capital_name contains the following terms.', $args);
                    break;
                case VocabularyInterface::HIERARCHY_SINGLE:
                    $help_message = $this->t('%capital_name contains terms grouped under parent terms', $args);
                    break;
                case VocabularyInterface::HIERARCHY_MULTIPLE:
                    $help_message = $this->t('%capital_name contains terms with multiple parents.', $args);
                    break;
            }
        }
        // Get the IDs of the terms edited on the current page which have pending
        // revisions.
        $edited_term_ids = array_map(function ($item) {
            return $item->id();
        }, $current_page);
        $pending_term_ids = array_intersect($this->storageController
            ->getTermIdsWithPendingRevisions(), $edited_term_ids);
        if ($pending_term_ids) {
            $help_message = $this->formatPlural(count($pending_term_ids), '%capital_name contains 1 term with pending revisions. Drag and drop of terms with pending revisions is not supported, but you can re-enable drag-and-drop support by getting each term to a published state.', '%capital_name contains @count terms with pending revisions. Drag and drop of terms with pending revisions is not supported, but you can re-enable drag-and-drop support by getting each term to a published state.', $args);
        }
        // Only allow access to change parents and reorder the tree if there are no
        // pending revisions and there are no terms with multiple parents.
        $update_tree_access = AccessResult::allowedIf(empty($pending_term_ids) && $vocabulary_hierarchy !== VocabularyInterface::HIERARCHY_MULTIPLE);
        $form['help'] = [
            '#type' => 'container',
            'message' => [
                '#markup' => $help_message,
            ],
        ];
        if (!$update_tree_access->isAllowed()) {
            $form['help']['#attributes']['class'] = [
                'messages',
                'messages--warning',
            ];
        }
        $errors = $form_state->getErrors();
        $row_position = 0;
        // Build the actual form.
        $access_control_handler = $this->entityTypeManager
            ->getAccessControlHandler('taxonomy_term');
        $create_access = $access_control_handler->createAccess($taxonomy_vocabulary->id(), NULL, [], TRUE);
        if ($create_access->isAllowed()) {
            $empty = $this->t('No terms available. <a href=":link">Add term</a>.', [
                ':link' => Url::fromRoute('entity.taxonomy_term.add_form', [
                    'taxonomy_vocabulary' => $taxonomy_vocabulary->id(),
                ])
                    ->toString(),
            ]);
        }
        else {
            $empty = $this->t('No terms available.');
        }
        $form['terms'] = [
            '#type' => 'table',
            '#empty' => $empty,
            '#header' => [
                'term' => $this->t('Name'),
                'operations' => $this->t('Operations'),
                'weight' => $update_tree_access->isAllowed() ? $this->t('Weight') : NULL,
            ],
            '#attributes' => [
                'id' => 'taxonomy',
            ],
        ];
        $this->renderer
            ->addCacheableDependency($form['terms'], $create_access);
        foreach ($current_page as $key => $term) {
            $form['terms'][$key] = [
                'term' => [],
                'operations' => [],
                'weight' => $update_tree_access->isAllowed() ? [] : NULL,
            ];
            
            /** @var \Drupal\Core\Entity\EntityInterface $term */
            $term = $this->entityRepository
                ->getTranslationFromContext($term);
            $form['terms'][$key]['#term'] = $term;
            $indentation = [];
            if (isset($term->depth) && $term->depth > 0) {
                $indentation = [
                    '#theme' => 'indentation',
                    '#size' => $term->depth,
                ];
            }
            $form['terms'][$key]['term'] = [
                '#prefix' => !empty($indentation) ? $this->renderer
                    ->render($indentation) : '',
                '#type' => 'link',
                '#title' => $term->getName(),
                '#url' => $term->toUrl(),
            ];
            // Add a special class for terms with pending revision so we can highlight
            // them in the form.
            $form['terms'][$key]['#attributes']['class'] = [];
            if (in_array($term->id(), $pending_term_ids)) {
                $form['terms'][$key]['#attributes']['class'][] = 'color-warning';
                $form['terms'][$key]['#attributes']['class'][] = 'taxonomy-term--pending-revision';
            }
            if ($update_tree_access->isAllowed() && count($tree) > 1) {
                $parent_fields = TRUE;
                $form['terms'][$key]['term']['tid'] = [
                    '#type' => 'hidden',
                    '#value' => $term->id(),
                    '#attributes' => [
                        'class' => [
                            'term-id',
                        ],
                    ],
                ];
                $form['terms'][$key]['term']['parent'] = [
                    '#type' => 'hidden',
                    // Yes, default_value on a hidden. It needs to be changeable by the
                    // javascript.
'#default_value' => $term->parents[0],
                    '#attributes' => [
                        'class' => [
                            'term-parent',
                        ],
                    ],
                ];
                $form['terms'][$key]['term']['depth'] = [
                    '#type' => 'hidden',
                    // Same as above, the depth is modified by javascript, so it's a
                    // default_value.
'#default_value' => $term->depth,
                    '#attributes' => [
                        'class' => [
                            'term-depth',
                        ],
                    ],
                ];
            }
            $update_access = $term->access('update', NULL, TRUE);
            $update_tree_access = $update_tree_access->andIf($update_access);
            if ($update_tree_access->isAllowed()) {
                $form['terms'][$key]['weight'] = [
                    '#type' => 'weight',
                    '#delta' => $delta,
                    '#title' => $this->t('Weight for added term'),
                    '#title_display' => 'invisible',
                    '#default_value' => $term->getWeight(),
                    '#attributes' => [
                        'class' => [
                            'term-weight',
                        ],
                    ],
                ];
            }
            if ($operations = $this->termListBuilder
                ->getOperations($term)) {
                $form['terms'][$key]['operations'] = [
                    '#type' => 'operations',
                    '#links' => $operations,
                ];
            }
            if ($parent_fields) {
                $form['terms'][$key]['#attributes']['class'][] = 'draggable';
            }
            // Add classes that mark which terms belong to previous and next pages.
            if ($row_position < $back_step || $row_position >= $page_entries - $forward_step) {
                $form['terms'][$key]['#attributes']['class'][] = 'taxonomy-term-preview';
            }
            if ($row_position !== 0 && $row_position !== count($tree) - 1) {
                if ($row_position == $back_step - 1 || $row_position == $page_entries - $forward_step - 1) {
                    $form['terms'][$key]['#attributes']['class'][] = 'taxonomy-term-divider-top';
                }
                elseif ($row_position == $back_step || $row_position == $page_entries - $forward_step) {
                    $form['terms'][$key]['#attributes']['class'][] = 'taxonomy-term-divider-bottom';
                }
            }
            // Add an error class if this row contains a form error.
            foreach ($errors as $error_key => $error) {
                if (strpos($error_key, $key) === 0) {
                    $form['terms'][$key]['#attributes']['class'][] = 'error';
                }
            }
            $row_position++;
        }
        $this->renderer
            ->addCacheableDependency($form['terms'], $update_tree_access);
        if ($update_tree_access->isAllowed()) {
            if ($parent_fields) {
                $form['terms']['#tabledrag'][] = [
                    'action' => 'match',
                    'relationship' => 'parent',
                    'group' => 'term-parent',
                    'subgroup' => 'term-parent',
                    'source' => 'term-id',
                    'hidden' => FALSE,
                ];
                $form['terms']['#tabledrag'][] = [
                    'action' => 'depth',
                    'relationship' => 'group',
                    'group' => 'term-depth',
                    'hidden' => FALSE,
                ];
                $form['terms']['#attached']['library'][] = 'taxonomy/drupal.taxonomy';
                $form['terms']['#attached']['drupalSettings']['taxonomy'] = [
                    'backStep' => $back_step,
                    'forwardStep' => $forward_step,
                ];
            }
            $form['terms']['#tabledrag'][] = [
                'action' => 'order',
                'relationship' => 'sibling',
                'group' => 'term-weight',
            ];
        }
        if ($update_tree_access->isAllowed() && count($tree) > 1) {
            $form['actions'] = [
                '#type' => 'actions',
                '#tree' => FALSE,
            ];
            $form['actions']['submit'] = [
                '#type' => 'submit',
                '#value' => $this->t('Save'),
                '#button_type' => 'primary',
            ];
            $form['actions']['reset_alphabetical'] = [
                '#type' => 'submit',
                '#submit' => [
                    '::submitReset',
                ],
                '#value' => $this->t('Reset to alphabetical'),
            ];
        }
        $form['pager_pager'] = [
            '#type' => 'pager',
        ];
        return $form;
    }
    
    /**
     * Form submission handler.
     *
     * Rather than using a textfield or weight field, this form depends entirely
     * upon the order of form elements on the page to determine new weights.
     *
     * Because there might be hundreds or thousands of taxonomy terms that need to
     * be ordered, terms are weighted from 0 to the number of terms in the
     * vocabulary, rather than the standard -10 to 10 scale. Numbers are sorted
     * lowest to highest, but are not necessarily sequential. Numbers may be
     * skipped when a term has children so that reordering is minimal when a child
     * is added or removed from a term.
     *
     * @param array $form
     *   An associative array containing the structure of the form.
     * @param \Drupal\Core\Form\FormStateInterface $form_state
     *   The current state of the form.
     */
    public function submitForm(array &$form, FormStateInterface $form_state) {
        // Sort term order based on weight.
        uasort($form_state->getValue('terms'), [
            'Drupal\\Component\\Utility\\SortArray',
            'sortByWeightElement',
        ]);
        $vocabulary = $form_state->get([
            'taxonomy',
            'vocabulary',
        ]);
        $changed_terms = [];
        $tree = $this->storageController
            ->loadTree($vocabulary->id(), 0, NULL, TRUE);
        if (empty($tree)) {
            return;
        }
        // Build a list of all terms that need to be updated on previous pages.
        $weight = 0;
        $term = $tree[0];
        while ($term->id() != $form['#first_tid']) {
            if ($term->parents[0] == 0 && $term->getWeight() != $weight) {
                $term->setWeight($weight);
                $changed_terms[$term->id()] = $term;
            }
            $weight++;
            $term = $tree[$weight];
        }
        // Renumber the current page weights and assign any new parents.
        $level_weights = [];
        foreach ($form_state->getValue('terms') as $tid => $values) {
            if (isset($form['terms'][$tid]['#term'])) {
                $term = $form['terms'][$tid]['#term'];
                // Give terms at the root level a weight in sequence with terms on previous pages.
                if ($values['term']['parent'] == 0 && $term->getWeight() != $weight) {
                    $term->setWeight($weight);
                    $changed_terms[$term->id()] = $term;
                }
                elseif ($values['term']['parent'] > 0) {
                    $level_weights[$values['term']['parent']] = isset($level_weights[$values['term']['parent']]) ? $level_weights[$values['term']['parent']] + 1 : 0;
                    if ($level_weights[$values['term']['parent']] != $term->getWeight()) {
                        $term->setWeight($level_weights[$values['term']['parent']]);
                        $changed_terms[$term->id()] = $term;
                    }
                }
                // Update any changed parents.
                if ($values['term']['parent'] != $term->parents[0]) {
                    $term->parent->target_id = $values['term']['parent'];
                    $changed_terms[$term->id()] = $term;
                }
                $weight++;
            }
        }
        // Build a list of all terms that need to be updated on following pages.
        for ($weight; $weight < count($tree); $weight++) {
            $term = $tree[$weight];
            if ($term->parents[0] == 0 && $term->getWeight() != $weight) {
                $term->parent->target_id = $term->parents[0];
                $term->setWeight($weight);
                $changed_terms[$term->id()] = $term;
            }
        }
        if (!empty($changed_terms)) {
            $pending_term_ids = $this->storageController
                ->getTermIdsWithPendingRevisions();
            // Force a form rebuild if any of the changed terms has a pending
            // revision.
            if (array_intersect_key(array_flip($pending_term_ids), $changed_terms)) {
                $this->messenger()
                    ->addError($this->t('The terms with updated parents have been modified by another user, the changes could not be saved.'));
                $form_state->setRebuild();
                return;
            }
            // Save all updated terms.
            foreach ($changed_terms as $term) {
                $term->save();
            }
            $this->messenger()
                ->addStatus($this->t('The configuration options have been saved.'));
        }
    }
    
    /**
     * Redirects to confirmation form for the reset action.
     */
    public function submitReset(array &$form, FormStateInterface $form_state) {
        
        /** @var \Drupal\taxonomy\VocabularyInterface $vocabulary */
        $vocabulary = $form_state->get([
            'taxonomy',
            'vocabulary',
        ]);
        $form_state->setRedirectUrl($vocabulary->toUrl('reset-form'));
    }

}