trait KeyValueWidgetTrait in Key value field 8

trait KeyValueWidgetTrait {

  /**
   * {@inheritdoc}
   */
  public static function defaultSettings() {
    return [
      'key_size' => 60,
      'key_label' => t('Key'),
      'key_placeholder' => '',
      'value_label' => t('Value'),
      'description_enabled' => TRUE,
      'description_label' => t('Description'),
      'description_rows' => 5,
      'description_placeholder' => '',
    ] + parent::defaultSettings();
  }

  /**
   * {@inheritdoc}
   */
  public function settingsForm(array $form, FormStateInterface $form_state) {

    // Get the default textfield form.
    $parent_form = parent::settingsForm($form, $form_state);

    // Change the title for the Rows field.
    $parent_form['rows']['#title'] = t('Value Rows');

    // Change the title for the Placeholder field.
    $parent_form['placeholder']['#title'] = t('Value Placeholder');

    // Get the field machine_id.
    $field_machine = $this->fieldDefinition
      ->getName();

    // Add an element for the label of the key field.
    $element['key_label'] = [
      '#type' => 'textfield',
      '#title' => t('Key Label'),
      '#default_value' => $this
        ->getSetting('key_label'),
      '#description' => t('Label for the "Key" field.'),
      '#weight' => -3,
    ];

    // Add an element for the size of the key field.
    $element['key_size'] = [
      '#type' => 'number',
      '#title' => t('Size of key textfield'),
      '#default_value' => $this
        ->getSetting('key_size'),
      '#required' => TRUE,
      '#weight' => -2,
      '#min' => 1,
    ];

    // Add a placeholder field for the key text field.
    $element['key_placeholder'] = [
      '#type' => 'textfield',
      '#title' => t('Key Placeholder'),
      '#default_value' => $this
        ->getSetting('key_placeholder'),
      '#description' => t('Text that will be shown inside the "Key" field until a value is entered. This hint is usually a sample value or a brief description of the expected format.'),
      '#weight' => -1,
    ];

    // Add an element for the label of the value field.
    $element['value_label'] = [
      '#type' => 'textfield',
      '#title' => t('Value Label'),
      '#default_value' => $this
        ->getSetting('value_label'),
      '#description' => t('Label for the "Value" field.'),
      '#weight' => 0,
    ];

    // Let the description field be hidden.
    $element['description_enabled'] = [
      '#type' => 'checkbox',
      '#title' => t('Enable Description'),
      '#default_value' => $this
        ->getSetting('description_enabled'),
      '#description' => t('Enable the description field (Generally used for administrative purposes).'),
      '#weight' => 2,
    ];

    // Add an element for the label of the value field.
    $element['description_label'] = [
      '#type' => 'textfield',
      '#title' => t('Description Label'),
      '#default_value' => $this
        ->getSetting('description_label'),
      '#description' => t('Label for the "Description" field.'),
      '#weight' => 3,
      '#states' => [
        'visible' => [
          ':input[name="fields[' . $field_machine . '][settings_edit_form][settings][description_enabled]"]' => [
            'checked' => TRUE,
          ],
        ],
      ],
    ];

    // Add a placeholder for teh description field.
    $element['description_placeholder'] = [
      '#type' => 'textfield',
      '#title' => t('Description Placeholder'),
      '#default_value' => $this
        ->getSetting('description_placeholder'),
      '#description' => t('Text that will be shown inside the "Description" field until a value is entered. This hint is usually a sample value or a brief description of the expected format.'),
      '#weight' => 4,
      '#states' => [
        'visible' => [
          ':input[name="fields[' . $field_machine . '][settings_edit_form][settings][description_enabled]"]' => [
            'checked' => TRUE,
          ],
        ],
      ],
    ];
    $element['description_rows'] = [
      '#type' => 'number',
      '#title' => t('Description Rows'),
      '#default_value' => $this
        ->getSetting('description_rows'),
      '#min' => 1,
      '#weight' => 5,
      '#states' => [
        'visible' => [
          ':input[name="fields[' . $field_machine . '][settings_edit_form][settings][description_enabled]"]' => [
            'checked' => TRUE,
          ],
        ],
      ],
    ];
    return $element + $parent_form;
  }

  /**
   * {@inheritdoc}
   */
  public function settingsSummary() {
    $summary = [];

    // Add a summary for the key field.
    $summary[] = t('Key label: @label', [
      '@label' => $this
        ->getSetting('key_label'),
    ]);
    $summary[] = t('Value label: @label', [
      '@label' => $this
        ->getSetting('value_label'),
    ]);
    $summary[] = t('Key textfield size: @size', [
      '@size' => $this
        ->getSetting('key_size'),
    ]);
    if (($placeholder = $this
      ->getSetting('key_placeholder')) && !empty($placeholder)) {
      $summary[] = t('Key Placeholder: "@placeholder"', [
        '@placeholder' => $placeholder,
      ]);
    }

    // Add a summary for the value placeholder.
    if (($placeholder = $this
      ->getSetting('placeholder')) && !empty($placeholder)) {
      $summary[] = t('Value Placeholder: "@placeholder"', [
        '@placeholder' => $placeholder,
      ]);
    }

    // Add a summary for the description if it is enabled.
    if ($this
      ->getSetting('description_enabled') && ($placeholder = $this
      ->getSetting('description_placeholder')) && !empty($placeholder)) {
      $summary[] = t('Description: Enabled', [
        '@placeholder' => $placeholder,
      ]);
      $summary[] = t('- Placeholder: @placeholder', [
        '@placeholder' => $placeholder,
      ]);
      $summary[] = t('- Label: @label', [
        '@label' => $this
          ->getSetting('description_label'),
      ]);
      $summary[] = t('- Rows: @rows', [
        '@rows' => $this
          ->getSetting('description_rows'),
      ]);
    }
    return $summary + parent::settingsSummary();
  }

  /**
   * {@inheritdoc}
   */
  public function formElement(FieldItemListInterface $items, $delta, array $element, array &$form, FormStateInterface $form_state) {

    // Get the textfield form element.
    $element = parent::formElement($items, $delta, $element, $form, $form_state);

    // Check for an empty format on formattable items.
    if (array_key_exists('#format', $element) && empty($element['#format'])) {

      // Get the default format.
      $default_format = $this
        ->getFieldSetting('default_format');

      // Get the formats available to the current user.
      $available_formats = filter_formats();

      // Set the format to the default if empty.
      if (!empty($default_format) && array_key_exists($default_format, $available_formats)) {
        $element['#format'] = $default_format;
      }
    }

    // Grab settings for all.
    $key_size = $this
      ->getSetting('key_size');
    $key_label = $this
      ->getSetting('key_label');
    $value_label = $this
      ->getSetting('value_label');
    $key_placeholder = $this
      ->getSetting('key_placeholder');
    $description_enabled = $this
      ->getSetting('description_enabled');
    $description_label = $this
      ->getSetting('description_label');
    $description_rows = $this
      ->getSetting('description_rows');
    $description_placeholder = $this
      ->getSetting('description_placeholder');

    // Display the title for key_value fields.
    if (isset($element['value']) && array_key_exists('#title_display', $element['value'])) {
      unset($element['value']['#title_display']);
      $element['value']['#title'] = !empty($value_label) ? $value_label : $this
        ->t('Value');
    }

    // Create a description field if it is enabled.
    $description = !$description_enabled ? [] : [
      '#title' => $description_label,
      '#type' => 'textarea',
      '#default_value' => isset($items[$delta]->value) ? $items[$delta]->description : NULL,
      '#placeholder' => $description_placeholder,
      '#maxlength' => 255,
      '#rows' => $description_rows,
      '#weight' => 2,
      '#attributes' => [
        'class' => [
          'js-text-full',
          'text-full',
          'key-value-widget-description',
        ],
      ],
    ];

    // Add the key field.
    $key_field = [
      'key' => [
        '#title' => $key_label,
        '#type' => 'textfield',
        '#default_value' => isset($items[$delta]->key) ? $items[$delta]->key : NULL,
        '#size' => $key_size,
        '#placeholder' => $key_placeholder,
        '#maxlength' => $this
          ->getFieldSetting('key_max_length'),
        '#attributes' => [
          'class' => [
            'js-text-full',
            'text-full',
            'key-value-widget-key',
          ],
        ],
        '#weight' => -1,
      ],
      // Add the description field.
      'description' => $description,
      // Add a class to the widget form.
      '#attributes' => [
        'class' => [
          'key-value-widget',
          'js-text-full',
          'text-full',
        ],
      ],
      '#title' => $value_label,
      '#title_display' => 'before',
      '#element_validate' => [
        [
          get_called_class(),
          'validateKeyElement',
        ],
      ],
    ];

    // Add the textarea form.
    $build = $key_field + $element;

    // Make the key dynamically required if value is not empty.
    // Only do this if both are initially empty. This avoids a confusing *
    // appearing on a field which is already filled in which makes some users
    // think that the whole field is required.
    if (empty($build['value']['#default_value']) && empty($build['key']['#default_value'])) {
      $build['key']['#states'] = [
        'required' => [
          ':input[name="' . $this->fieldDefinition
            ->getName() . '[' . $delta . '][value]"]' => [
            'empty' => FALSE,
          ],
        ],
      ];
    }
    return $build;
  }

  /**
   * Form element validation handler for the 'key' element.
   *
   * Conditionally requires the key if a value is filled in.
   */
  public static function validateKeyElement(&$element, FormStateInterface $form_state, $form) {
    if (!empty($element['value']['#value']) && empty($element['key']['#value'])) {
      $element['key']['#required'] = TRUE;
      $form_state
        ->setError($element['key'], t('@name field is required.', [
        '@name' => $element['key']['#title'],
      ]));
    }
  }

}