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big_pipe.module

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    node.api.php 37.73 KiB
    <?php
    
    use Drupal\Core\Entity\EntityInterface;
    use Drupal\node\Entity\NodeInterface;
    use Drupal\Component\Utility\String;
    use Drupal\Component\Utility\Xss;
    
    /**
     * @file
     * Hooks provided by the Node module.
     */
    
    /**
     * @defgroup node_api_hooks Node API Hooks
     * @{
     * Functions to define and modify content types.
     *
     * Each content type is maintained by a primary module, which is either
     * node.module (for content types created in the user interface) or the module
     * that defines the content type by providing configuration file.
     *
     * During node operations (create, insert, update, view, delete, etc.), there
     * are several sets of hooks that get invoked to allow modules to modify the
     * base node operation:
     * - All-module hooks: This set of hooks is invoked on all implementing modules,
     *   to allow other modules to modify what the primary node module is doing. For
     *   example, hook_node_insert() is invoked on all modules when creating a forum
     *   node.
     * - Field hooks: Hooks related to the fields attached to the node. These are
     *   invoked from the field operations functions described below, and can be
     *   either field-type-specific or all-module hooks.
     * - Entity hooks: Generic hooks for "entity" operations. These are always
     *   invoked on all modules.
     *
     * Here is a list of the node and entity hooks that are invoked, field
     * operations, and other steps that take place during node operations:
     * - Instantiating a new node:
     *   - hook_node_create() (all)
     *   - hook_entity_create() (all)
     * - Creating a new node (calling $node->save() on a new node):
     *   - field_attach_presave()
     *   - hook_node_presave() (all)
     *   - hook_entity_presave() (all)
     *   - Node and revision records are written to the database
     *   - hook_node_insert() (all)
     *   - hook_entity_insert() (all)
     *   - hook_node_access_records() (all)
     *   - hook_node_access_records_alter() (all)
     * - Updating an existing node (calling $node->save() on an existing node):
     *   - field_attach_presave()
     *   - hook_node_presave() (all)
     *   - hook_entity_presave() (all)
     *   - Node and revision records are written to the database
     *   - hook_node_update() (all)
     *   - hook_entity_update() (all)
     *   - hook_node_access_records() (all)
     *   - hook_node_access_records_alter() (all)
     * - Loading a node (calling node_load(), node_load_multiple(), entity_load(),
     *   or entity_load_multiple() with $entity_type of 'node'):
     *   - Node and revision information is read from database.
     *   - hook_entity_load() (all)
     *   - hook_node_load() (all)
     * - Viewing a single node (calling node_view() - note that the input to
     *   node_view() is a loaded node, so the Loading steps above are already done):
     *   - field_attach_prepare_view()
     *   - hook_entity_prepare_view() (all)
     *   - field_attach_view()
     *   - hook_node_view() (all)
     *   - hook_entity_view() (all)
     *   - hook_node_view_alter() (all)
     *   - hook_entity_view_alter() (all)
     * - Viewing multiple nodes (calling node_view_multiple() - note that the input
     *   to node_view_multiple() is a set of loaded nodes, so the Loading steps
     *   above are already done):
     *   - field_attach_prepare_view()
     *   - hook_entity_prepare_view() (all)
     *   - field_attach_view()
     *   - hook_node_view() (all)
     *   - hook_entity_view() (all)
     *   - hook_node_view_alter() (all)
     *   - hook_entity_view_alter() (all)
     * - Deleting a node (calling $node->delete() or entity_delete_multiple()):
     *   - Node is loaded (see Loading section above)
     *   - hook_node_predelete() (all)
     *   - hook_entity_predelete() (all)
     *   - Node and revision information are deleted from database
     *   - hook_node_delete() (all)
     *   - hook_entity_delete() (all)
     * - Deleting a node revision (calling node_revision_delete()):
     *   - Node is loaded (see Loading section above)
     *   - Revision information is deleted from database
     *   - hook_node_revision_delete() (all)
     * - Preparing a node for editing (calling node_form() - note that if it is an
     *   existing node, it will already be loaded; see the Loading section above):
     *   - hook_node_prepare_form() (all)
     *   - hook_entity_prepare_form() (all)
     *   - field_attach_form()
     * - Validating a node during editing form submit (calling
     *   node_form_validate()):
     *   - hook_node_validate() (all)
     * - Searching (using the 'node_search' plugin):
     *   - hook_ranking() (all)
     *   - Query is executed to find matching nodes
     *   - Resulting node is loaded (see Loading section above)
     *   - Resulting node is prepared for viewing (see Viewing a single node above)
     *   - comment_node_update_index() is called (this adds "N comments" text)
     *   - hook_node_search_result() (all)
     * - Search indexing (calling updateIndex() on the 'node_search' plugin):
     *   - Node is loaded (see Loading section above)
     *   - Node is prepared for viewing (see Viewing a single node above)
     *   - hook_node_update_index() (all)
     * @}
     */
    
    /**
     * @addtogroup hooks
     * @{
     */
    
    /**
     * Inform the node access system what permissions the user has.
     *
     * This hook is for implementation by node access modules. In this hook,
     * the module grants a user different "grant IDs" within one or more
     * "realms". In hook_node_access_records(), the realms and grant IDs are
     * associated with permission to view, edit, and delete individual nodes.
     *
     * The realms and grant IDs can be arbitrarily defined by your node access
     * module; it is common to use role IDs as grant IDs, but that is not required.
     * Your module could instead maintain its own list of users, where each list has
     * an ID. In that case, the return value of this hook would be an array of the
     * list IDs that this user is a member of.
     *
     * A node access module may implement as many realms as necessary to properly
     * define the access privileges for the nodes. Note that the system makes no
     * distinction between published and unpublished nodes. It is the module's
     * responsibility to provide appropriate realms to limit access to unpublished
     * content.
     *
     * Node access records are stored in the {node_access} table and define which
     * grants are required to access a node. There is a special case for the view
     * operation -- a record with node ID 0 corresponds to a "view all" grant for
     * the realm and grant ID of that record. If there are no node access modules
     * enabled, the core node module adds a node ID 0 record for realm 'all'. Node
     * access modules can also grant "view all" permission on their custom realms;
     * for example, a module could create a record in {node_access} with:
     * @code
     * $record = array(
     *   'nid' => 0,
     *   'gid' => 888,
     *   'realm' => 'example_realm',
     *   'grant_view' => 1,
     *   'grant_update' => 0,
     *   'grant_delete' => 0,
     * );
     * drupal_write_record('node_access', $record);
     * @endcode
     * And then in its hook_node_grants() implementation, it would need to return:
     * @code
     * if ($op == 'view') {
     *   $grants['example_realm'] = array(888);
     * }
     * @endcode
     * If you decide to do this, be aware that the node_access_rebuild() function
     * will erase any node ID 0 entry when it is called, so you will need to make
     * sure to restore your {node_access} record after node_access_rebuild() is
     * called.
     *
     * @param $account
     *   The user object whose grants are requested.
     * @param $op
     *   The node operation to be performed, such as 'view', 'update', or 'delete'.
     *
     * @return
     *   An array whose keys are "realms" of grants, and whose values are arrays of
     *   the grant IDs within this realm that this user is being granted.
     *
     * For a detailed example, see node_access_example.module.
     *
     * @see node_access_view_all_nodes()
     * @see node_access_rebuild()
     * @ingroup node_access
     */
    function hook_node_grants($account, $op) {
      if (user_access('access private content', $account)) {
        $grants['example'] = array(1);
      }
      $grants['example_owner'] = array($account->id());
      return $grants;
    }
    
    /**
     * Set permissions for a node to be written to the database.
     *
     * When a node is saved, a module implementing hook_node_access_records() will
     * be asked if it is interested in the access permissions for a node. If it is
     * interested, it must respond with an array of permissions arrays for that
     * node.
     *
     * Node access grants apply regardless of the published or unpublished status
     * of the node. Implementations must make sure not to grant access to
     * unpublished nodes if they don't want to change the standard access control
     * behavior. Your module may need to create a separate access realm to handle
     * access to unpublished nodes.
     *
     * Note that the grant values in the return value from your hook must be
     * integers and not boolean TRUE and FALSE.
     *
     * Each permissions item in the array is an array with the following elements:
     * - 'realm': The name of a realm that the module has defined in
     *   hook_node_grants().
     * - 'gid': A 'grant ID' from hook_node_grants().
     * - 'grant_view': If set to 1 a user that has been identified as a member
     *   of this gid within this realm can view this node. This should usually be
     *   set to $node->isPublished(). Failure to do so may expose unpublished content
     *   to some users.
     * - 'grant_update': If set to 1 a user that has been identified as a member
     *   of this gid within this realm can edit this node.
     * - 'grant_delete': If set to 1 a user that has been identified as a member
     *   of this gid within this realm can delete this node.
     * - langcode: (optional) The language code of a specific translation of the
     *   node, if any. Modules may add this key to grant different access to
     *   different translations of a node, such that (e.g.) a particular group is
     *   granted access to edit the Catalan version of the node, but not the
     *   Hungarian version. If no value is provided, the langcode is set
     *   automatically from the $node parameter and the node's original language (if
     *   specified) is used as a fallback. Only specify multiple grant records with
     *   different languages for a node if the site has those languages configured.
     *
     * A "deny all" grant may be used to deny all access to a particular node or
     * node translation:
     * @code
     * $grants[] = array(
     *   'realm' => 'all',
     *   'gid' => 0,
     *   'grant_view' => 0,
     *   'grant_update' => 0,
     *   'grant_delete' => 0,
     *   'langcode' => 'ca',
     * );
     * @endcode
     * Note that another module node access module could override this by granting
     * access to one or more nodes, since grants are additive. To enforce that
     * access is denied in a particular case, use hook_node_access_records_alter().
     * Also note that a deny all is not written to the database; denies are
     * implicit.
     *
     * @param \Drupal\Core\Entity\EntityInterface $node
     *   The node that has just been saved.
     *
     * @return
     *   An array of grants as defined above.
     *
     * @see node_access_write_grants()
     * @see hook_node_access_records_alter()
     * @ingroup node_access
     */
    function hook_node_access_records(\Drupal\node\NodeInterface $node) {
      // We only care about the node if it has been marked private. If not, it is
      // treated just like any other node and we completely ignore it.
      if ($node->private->value) {
        $grants = array();
        // Only published Catalan translations of private nodes should be viewable
        // to all users. If we fail to check $node->isPublished(), all users would be able
        // to view an unpublished node.
        if ($node->isPublished()) {
          $grants[] = array(
            'realm' => 'example',
            'gid' => 1,
            'grant_view' => 1,
            'grant_update' => 0,
            'grant_delete' => 0,
            'langcode' => 'ca'
          );
        }
        // For the example_author array, the GID is equivalent to a UID, which
        // means there are many groups of just 1 user.
        // Note that an author can always view his or her nodes, even if they
        // have status unpublished.
        $grants[] = array(
          'realm' => 'example_author',
          'gid' => $node->getAuthorId(),
          'grant_view' => 1,
          'grant_update' => 1,
          'grant_delete' => 1,
          'langcode' => 'ca'
        );
    
        return $grants;
      }
    }
    
    /**
     * Alter permissions for a node before it is written to the database.
     *
     * Node access modules establish rules for user access to content. Node access
     * records are stored in the {node_access} table and define which permissions
     * are required to access a node. This hook is invoked after node access modules
     * returned their requirements via hook_node_access_records(); doing so allows
     * modules to modify the $grants array by reference before it is stored, so
     * custom or advanced business logic can be applied.
     *
     * Upon viewing, editing or deleting a node, hook_node_grants() builds a
     * permissions array that is compared against the stored access records. The
     * user must have one or more matching permissions in order to complete the
     * requested operation.
     *
     * A module may deny all access to a node by setting $grants to an empty array.
     *
     * @param $grants
     *   The $grants array returned by hook_node_access_records().
     * @param \Drupal\Core\Entity\EntityInterface $node
     *   The node for which the grants were acquired.
     *
     * The preferred use of this hook is in a module that bridges multiple node
     * access modules with a configurable behavior, as shown in the example with the
     * 'is_preview' field.
     *
     * @see hook_node_access_records()
     * @see hook_node_grants()
     * @see hook_node_grants_alter()
     * @ingroup node_access
     */
    function hook_node_access_records_alter(&$grants, Drupal\Core\Entity\EntityInterface $node) {
      // Our module allows editors to mark specific articles with the 'is_preview'
      // field. If the node being saved has a TRUE value for that field, then only
      // our grants are retained, and other grants are removed. Doing so ensures
      // that our rules are enforced no matter what priority other grants are given.
      if ($node->is_preview) {
        // Our module grants are set in $grants['example'].
        $temp = $grants['example'];
        // Now remove all module grants but our own.
        $grants = array('example' => $temp);
      }
    }
    
    /**
     * Alter user access rules when trying to view, edit or delete a node.
     *
     * Node access modules establish rules for user access to content.
     * hook_node_grants() defines permissions for a user to view, edit or delete
     * nodes by building a $grants array that indicates the permissions assigned to
     * the user by each node access module. This hook is called to allow modules to
     * modify the $grants array by reference, so the interaction of multiple node
     * access modules can be altered or advanced business logic can be applied.
     *
     * The resulting grants are then checked against the records stored in the
     * {node_access} table to determine if the operation may be completed.
     *
     * A module may deny all access to a user by setting $grants to an empty array.
     *
     * Developers may use this hook to either add additional grants to a user or to
     * remove existing grants. These rules are typically based on either the
     * permissions assigned to a user role, or specific attributes of a user
     * account.
     *
     * @param $grants
     *   The $grants array returned by hook_node_grants().
     * @param $account
     *   The user account requesting access to content.
     * @param $op
     *   The operation being performed, 'view', 'update' or 'delete'.
     *
     * @see hook_node_grants()
     * @see hook_node_access_records()
     * @see hook_node_access_records_alter()
     * @ingroup node_access
     */
    function hook_node_grants_alter(&$grants, $account, $op) {
      // Our sample module never allows certain roles to edit or delete
      // content. Since some other node access modules might allow this
      // permission, we expressly remove it by returning an empty $grants
      // array for roles specified in our variable setting.
    
      // Get our list of banned roles.
      $restricted = \Drupal::config('example.settings')->get('restricted_roles');
    
      if ($op != 'view' && !empty($restricted)) {
        // Now check the roles for this account against the restrictions.
        foreach ($account->getRoles() as $rid) {
          if (in_array($rid, $restricted)) {
            $grants = array();
          }
        }
      }
    }
    
    /**
     * Act before node deletion.
     *
     * This hook is invoked from entity_delete_multiple() before
     * hook_entity_predelete() is called and field values are deleted, and before
     * the node is removed from the node table in the database.
     *
     * @param \Drupal\Core\Entity\EntityInterface $node
     *   The node that is about to be deleted.
     *
     * @see hook_node_predelete()
     * @see entity_delete_multiple()
     * @ingroup node_api_hooks
     */
    function hook_node_predelete(\Drupal\Core\Entity\EntityInterface $node) {
      db_delete('mytable')
        ->condition('nid', $node->id())
        ->execute();
    }
    
    /**
     * Respond to node deletion.
     *
     * This hook is invoked from entity_delete_multiple() after field values are
     * deleted and after the node has been removed from the database.
     *
     * @param \Drupal\Core\Entity\EntityInterface $node
     *   The node that has been deleted.
     *
     * @see hook_node_predelete()
     * @see entity_delete_multiple()
     * @ingroup node_api_hooks
     */
    function hook_node_delete(\Drupal\Core\Entity\EntityInterface $node) {
      drupal_set_message(t('Node: @title has been deleted', array('@title' => $node->label())));
    }
    
    /**
     * Respond to deletion of a node revision.
     *
     * This hook is invoked from node_revision_delete() after the revision has been
     * removed from the node_revision table, and before field values are deleted.
     *
     * @param \Drupal\Core\Entity\EntityInterface $node
     *   The node revision (node object) that is being deleted.
     *
     * @ingroup node_api_hooks
     */
    function hook_node_revision_delete(\Drupal\Core\Entity\EntityInterface $node) {
      db_delete('mytable')
        ->condition('vid', $node->getRevisionId())
        ->execute();
    }
    
    /**
     * Respond to creation of a new node.
     *
     * This hook is invoked from $node->save() after the database query that will
     * insert the node into the node table is scheduled for execution, and after
     * field values are saved.
     *
     * Note that when this hook is invoked, the changes have not yet been written to
     * the database, because a database transaction is still in progress. The
     * transaction is not finalized until the save operation is entirely completed
     * and $node->save() goes out of scope. You should not rely on data in the
     * database at this time as it is not updated yet. You should also note that any
     * write/update database queries executed from this hook are also not committed
     * immediately. Check $node->save() and db_transaction() for more info.
     *
     * @param \Drupal\Core\Entity\EntityInterface $node
     *   The node that is being created.
     *
     * @ingroup node_api_hooks
     */
    function hook_node_insert(\Drupal\Core\Entity\EntityInterface $node) {
      db_insert('mytable')
        ->fields(array(
          'nid' => $node->id(),
          'extra' => $node->extra,
        ))
        ->execute();
    }
    
    /**
     * Act on a newly created node.
     *
     * This hook runs after a new node object has just been instantiated. It can be
     * used to set initial values, e.g. to provide defaults.
     *
     * @param \Drupal\Core\Entity\EntityInterface $node
     *   The node object.
     *
     * @ingroup node_api_hooks
     */
    function hook_node_create(\Drupal\Core\Entity\EntityInterface $node) {
      if (!isset($node->foo)) {
        $node->foo = 'some_initial_value';
      }
    }
    
    /**
     * Act on arbitrary nodes being loaded from the database.
     *
     * This hook should be used to add information that is not in the node or node
     * revisions table, not to replace information that is in these tables (which
     * could interfere with the entity cache). For performance reasons, information
     * for all available nodes should be loaded in a single query where possible.
     *
     * This hook is invoked during node loading, which is handled by entity_load(),
     * via classes Drupal\node\NodeStorageController and
     * Drupal\Core\Entity\DatabaseStorageController. After the node information and
     * field values are read from the database or the entity cache,
     * hook_entity_load() is invoked on all implementing modules, and finally
     * hook_node_load() is invoked on all implementing modules.
     *
     * @param $nodes
     *   An array of the nodes being loaded, keyed by nid.
     * @param $types
     *   An array containing the node types present in $nodes. Allows for an early
     *   return for modules that only support certain node types.
     *
     * For a detailed usage example, see nodeapi_example.module.
     *
     * @ingroup node_api_hooks
     */
    function hook_node_load($nodes, $types) {
      // Decide whether any of $types are relevant to our purposes.
      $types_we_want_to_process = \Drupal::config('my_types')->get('types');
      if (count(array_intersect($types_we_want_to_process, $types))) {
        // Gather our extra data for each of these nodes.
        $result = db_query('SELECT nid, foo FROM {mytable} WHERE nid IN(:nids)', array(':nids' => array_keys($nodes)));
        // Add our extra data to the node objects.
        foreach ($result as $record) {
          $nodes[$record->nid]->foo = $record->foo;
        }
      }
    }
    
    /**
     * Controls access to a node.
     *
     * Modules may implement this hook if they want to have a say in whether or not
     * a given user has access to perform a given operation on a node.
     *
     * The administrative account (user ID #1) always passes any access check, so
     * this hook is not called in that case. Users with the "bypass node access"
     * permission may always view and edit content through the administrative
     * interface.
     *
     * Note that not all modules will want to influence access on all node types. If
     * your module does not want to actively grant or block access, return
     * NODE_ACCESS_IGNORE or simply return nothing. Blindly returning FALSE will
     * break other node access modules.
     *
     * Also note that this function isn't called for node listings (e.g., RSS feeds,
     * the default home page at path 'node', a recent content block, etc.) See
     * @link node_access Node access rights @endlink for a full explanation.
     *
     * @param \Drupal\Core\Entity\EntityInterface|string $node
     *   Either a node entity or the machine name of the content type on which to
     *   perform the access check.
     * @param string $op
     *   The operation to be performed. Possible values:
     *   - "create"
     *   - "delete"
     *   - "update"
     *   - "view"
     * @param object $account
     *   The user object to perform the access check operation on.
     * @param object $langcode
     *   The language code to perform the access check operation on.
     *
     * @return string
     *   - NODE_ACCESS_ALLOW: if the operation is to be allowed.
     *   - NODE_ACCESS_DENY: if the operation is to be denied.
     *   - NODE_ACCESS_IGNORE: to not affect this operation at all.
     *
     * @ingroup node_access
     */
    function hook_node_access(\Drupal\node\NodeInterface $node, $op, $account, $langcode) {
      $type = is_string($node) ? $node : $node->getType();
    
      $configured_types = node_permissions_get_configured_types();
      if (isset($configured_types[$type])) {
        if ($op == 'create' && user_access('create ' . $type . ' content', $account)) {
          return NODE_ACCESS_ALLOW;
        }
    
        if ($op == 'update') {
          if (user_access('edit any ' . $type . ' content', $account) || (user_access('edit own ' . $type . ' content', $account) && ($account->id() == $node->getAuthorId()))) {
            return NODE_ACCESS_ALLOW;
          }
        }
    
        if ($op == 'delete') {
          if (user_access('delete any ' . $type . ' content', $account) || (user_access('delete own ' . $type . ' content', $account) && ($account->id() == $node->getAuthorId()))) {
            return NODE_ACCESS_ALLOW;
          }
        }
      }
    
      // Returning nothing from this function would have the same effect.
      return NODE_ACCESS_IGNORE;
    }
    
    
    /**
     * Act on a node object about to be shown on the add/edit form.
     *
     * This hook is invoked from NodeFormController::prepareEntity().
     *
     * @param \Drupal\node\NodeInterface $node
     *   The node that is about to be shown on the form.
     * @param $form_display
     *   The current form display.
     * @param $operation
     *   The current operation.
     * @param array $form_state
     *   An associative array containing the current state of the form.
     *
     * @ingroup node_api_hooks
     */
    function hook_node_prepare_form(\Drupal\node\NodeInterface $node, $form_display, $operation, array &$form_state) {
      if (!isset($node->my_rating)) {
        $node->my_rating = \Drupal::config("my_rating_{$node->bundle()}")->get('enabled');
      }
    }
    
    /**
     * Act on a node being displayed as a search result.
     *
     * This hook is invoked from the node search plugin during search execution,
     * after loading and rendering the node.
     *
     * @param \Drupal\Core\Entity\EntityInterface $node
     *   The node being displayed in a search result.
     * @param $langcode
     *   Language code of result being displayed.
     *
     * @return array
     *   Extra information to be displayed with search result. This information
     *   should be presented as an associative array. It will be concatenated with
     *   the post information (last updated, author) in the default search result
     *   theming.
     *
     * @see template_preprocess_search_result()
     * @see search-result.html.twig
     *
     * @ingroup node_api_hooks
     */
    function hook_node_search_result(\Drupal\Core\Entity\EntityInterface $node, $langcode) {
      $rating = db_query('SELECT SUM(points) FROM {my_rating} WHERE nid = :nid', array('nid' => $node->id()))->fetchField();
      return array('rating' => format_plural($rating, '1 point', '@count points'));
    }
    
    /**
     * Act on a node being inserted or updated.
     *
     * This hook is invoked from $node->save() before the node is saved to the
     * database.
     *
     * @param \Drupal\Core\Entity\EntityInterface $node
     *   The node that is being inserted or updated.
     *
     * @ingroup node_api_hooks
     */
    function hook_node_presave(\Drupal\Core\Entity\EntityInterface $node) {
      if ($node->id() && $node->moderate) {
        // Reset votes when node is updated:
        $node->score = 0;
        $node->users = '';
        $node->votes = 0;
      }
    }
    
    /**
     * Respond to updates to a node.
     *
     * This hook is invoked from $node->save() after the database query that will
     * update node in the node table is scheduled for execution, and after field
     * values are saved.
     *
     * Note that when this hook is invoked, the changes have not yet been written to
     * the database, because a database transaction is still in progress. The
     * transaction is not finalized until the save operation is entirely completed
     * and $node->save() goes out of scope. You should not rely on data in the
     * database at this time as it is not updated yet. You should also note that any
     * write/update database queries executed from this hook are also not committed
     * immediately. Check $node->save() and db_transaction() for more info.
     *
     * @param \Drupal\Core\Entity\EntityInterface $node
     *   The node that is being updated.
     *
     * @ingroup node_api_hooks
     */
    function hook_node_update(\Drupal\Core\Entity\EntityInterface $node) {
      db_update('mytable')
        ->fields(array('extra' => $node->extra))
        ->condition('nid', $node->id())
        ->execute();
    }
    
    /**
     * Act on a node being indexed for searching.
     *
     * This hook is invoked during search indexing, after loading, and after the
     * result of rendering is added as $node->rendered to the node object.
     *
     * @param \Drupal\Core\Entity\EntityInterface $node
     *   The node being indexed.
     * @param $langcode
     *   Language code of the variant of the node being indexed.
     *
     * @return string
     *   Additional node information to be indexed.
     *
     * @ingroup node_api_hooks
     */
    function hook_node_update_index(\Drupal\Core\Entity\EntityInterface $node, $langcode) {
      $text = '';
      $ratings = db_query('SELECT title, description FROM {my_ratings} WHERE nid = :nid', array(':nid' => $node->id()));
      foreach ($ratings as $rating) {
        $text .= '<h2>' . String::checkPlain($rating->title) . '</h2>' . Xss::filter($rating->description);
      }
      return $text;
    }
    
    /**
     * Perform node validation before a node is created or updated.
     *
     * This hook is invoked from NodeFormController::validate(), after a user has
     * finished editing the node and is previewing or submitting it. It is invoked
     * at the end of all the standard validation steps.
     *
     * To indicate a validation error, use form_set_error().
     *
     * Note: Changes made to the $node object within your hook implementation will
     * have no effect.  The preferred method to change a node's content is to use
     * hook_node_presave() instead. If it is really necessary to change the node at
     * the validate stage, you can use form_set_value().
     *
     * @param \Drupal\Core\Entity\EntityInterface $node
     *   The node being validated.
     * @param $form
     *   The form being used to edit the node.
     * @param $form_state
     *   The form state array.
     *
     * @ingroup node_api_hooks
     */
    function hook_node_validate(\Drupal\Core\Entity\EntityInterface $node, $form, &$form_state) {
      if (isset($node->end) && isset($node->start)) {
        if ($node->start > $node->end) {
          form_set_error('time', $form_state, t('An event may not end before it starts.'));
        }
      }
    }
    
    /**
     * Act on a node after validated form values have been copied to it.
     *
     * This hook is invoked when a node form is submitted with either the "Save" or
     * "Preview" button, after form values have been copied to the form state's node
     * object, but before the node is saved or previewed. It is a chance for modules
     * to adjust the node's properties from what they are simply after a copy from
     * $form_state['values']. This hook is intended for adjusting non-field-related
     * properties. See hook_field_attach_extract_form_values() for customizing
     * field-related properties.
     *
     * @param \Drupal\Core\Entity\EntityInterface $node
     *   The node entity being updated in response to a form submission.
     * @param $form
     *   The form being used to edit the node.
     * @param $form_state
     *   The form state array.
     *
     * @ingroup node_api_hooks
     */
    function hook_node_submit(\Drupal\Core\Entity\EntityInterface $node, $form, &$form_state) {
      // Decompose the selected menu parent option into 'menu_name' and 'plid', if
      // the form used the default parent selection widget.
      if (!empty($form_state['values']['menu']['parent'])) {
        list($node->menu['menu_name'], $node->menu['plid']) = explode(':', $form_state['values']['menu']['parent']);
      }
    }
    
    /**
     * Act on a node that is being assembled before rendering.
     *
     * The module may add elements to $node->content prior to rendering.
     * The structure of $node->content is a renderable array as expected by
     * drupal_render().
     *
     * When $view_mode is 'rss', modules can also add extra RSS elements and
     * namespaces to $node->rss_elements and $node->rss_namespaces respectively for
     * the RSS item generated for this node.
     * For details on how this is used, see node_feed().
     *
     * @param \Drupal\Core\Entity\EntityInterface $node
     *   The node that is being assembled for rendering.
     * @param \Drupal\entity\Entity\EntityDisplay $display
     *   The entity_display object holding the display options configured for the
     *   node components.
     * @param string $view_mode
     *   The $view_mode parameter from node_view().
     * @param string $langcode
     *   The language code used for rendering.
     *
     * @see forum_node_view()
     * @see hook_entity_view()
     *
     * @ingroup node_api_hooks
     */
    function hook_node_view(\Drupal\Core\Entity\EntityInterface $node, \Drupal\entity\Entity\EntityDisplay $display, $view_mode, $langcode) {
      // Only do the extra work if the component is configured to be displayed.
      // This assumes a 'mymodule_addition' extra field has been defined for the
      // node type in hook_field_extra_fields().
      if ($display->getComponent('mymodule_addition')) {
        $node->content['mymodule_addition'] = array(
          '#markup' => mymodule_addition($node),
          '#theme' => 'mymodule_my_additional_field',
        );
      }
    }
    
    /**
     * Alter the results of node_view().
     *
     * This hook is called after the content has been assembled in a structured
     * array and may be used for doing processing which requires that the complete
     * node content structure has been built.
     *
     * If the module wishes to act on the rendered HTML of the node rather than the
     * structured content array, it may use this hook to add a #post_render
     * callback.  Alternatively, it could also implement hook_preprocess_HOOK() for
     * node.html.twig. See drupal_render() and theme() documentation respectively
     * for details.
     *
     * @param $build
     *   A renderable array representing the node content.
     * @param \Drupal\Core\Entity\EntityInterface $node
     *   The node being rendered.
     * @param \Drupal\entity\Entity\EntityDisplay $display
     *   The entity_display object holding the display options configured for the
     *   node components.
     *
     * @see node_view()
     * @see hook_entity_view_alter()
     *
     * @ingroup node_api_hooks
     */
    function hook_node_view_alter(&$build, \Drupal\Core\Entity\EntityInterface $node, \Drupal\entity\Entity\EntityDisplay $display) {
      if ($build['#view_mode'] == 'full' && isset($build['an_additional_field'])) {
        // Change its weight.
        $build['an_additional_field']['#weight'] = -10;
      }
    
      // Add a #post_render callback to act on the rendered HTML of the node.
      $build['#post_render'][] = 'my_module_node_post_render';
    }
    
    /**
     * Provide additional methods of scoring for core search results for nodes.
     *
     * A node's search score is used to rank it among other nodes matched by the
     * search, with the highest-ranked nodes appearing first in the search listing.
     *
     * For example, a module allowing users to vote on content could expose an
     * option to allow search results' rankings to be influenced by the average
     * voting score of a node.
     *
     * All scoring mechanisms are provided as options to site administrators, and
     * may be tweaked based on individual sites or disabled altogether if they do
     * not make sense. Individual scoring mechanisms, if enabled, are assigned a
     * weight from 1 to 10. The weight represents the factor of magnification of
     * the ranking mechanism, with higher-weighted ranking mechanisms having more
     * influence. In order for the weight system to work, each scoring mechanism
     * must return a value between 0 and 1 for every node. That value is then
     * multiplied by the administrator-assigned weight for the ranking mechanism,
     * and then the weighted scores from all ranking mechanisms are added, which
     * brings about the same result as a weighted average.
     *
     * @return
     *   An associative array of ranking data. The keys should be strings,
     *   corresponding to the internal name of the ranking mechanism, such as
     *   'recent', or 'comments'. The values should be arrays themselves, with the
     *   following keys available:
     *   - title: (required) The human readable name of the ranking mechanism.
     *   - join: (optional) The part of a query string to join to any additional
     *     necessary table. This is not necessary if the table required is already
     *     joined to by the base query, such as for the {node} table. Other tables
     *     should use the full table name as an alias to avoid naming collisions.
     *   - score: (required) The part of a query string to calculate the score for
     *     the ranking mechanism based on values in the database. This does not need
     *     to be wrapped in parentheses, as it will be done automatically; it also
     *     does not need to take the weighted system into account, as it will be
     *     done automatically. It does, however, need to calculate a decimal between
     *     0 and 1; be careful not to cast the entire score to an integer by
     *     inadvertently introducing a variable argument.
     *   - arguments: (optional) If any arguments are required for the score, they
     *     can be specified in an array here.
     *
     * @ingroup node_api_hooks
     */
    function hook_ranking() {
      // If voting is disabled, we can avoid returning the array, no hard feelings.
      if (\Drupal::config('vote.settings')->get('node_enabled')) {
        return array(
          'vote_average' => array(
            'title' => t('Average vote'),
            // Note that we use i.sid, the search index's search item id, rather than
            // n.nid.
            'join' => 'LEFT JOIN {vote_node_data} vote_node_data ON vote_node_data.nid = i.sid',
            // The highest possible score should be 1, and the lowest possible score,
            // always 0, should be 0.
            'score' => 'vote_node_data.average / CAST(%f AS DECIMAL)',
            // Pass in the highest possible voting score as a decimal argument.
            'arguments' => array(\Drupal::config('vote.settings').get('score_max')),
          ),
        );
      }
    }
    
    /**
     * Respond to node type creation.
     *
     * @param \Drupal\node\NodeTypeInterface $type
     *   The node type entity that was created.
     */
    function hook_node_type_insert(\Drupal\node\NodeTypeInterface $type) {
      drupal_set_message(t('You have just created a content type with a machine name %type.', array('%type' => $type->id())));
    }
    
    /**
     * Respond to node type updates.
     *
     * @param \Drupal\node\NodeTypeInterface $type
     *   The node type entity that was updated.
     */
    function hook_node_type_update(\Drupal\node\NodeTypeInterface $type) {
      if ($type->original->id() != $type->id()) {
        drupal_set_message(t('You have just changed the machine name of a content type from %old_type to %type.', array('%old_type' => $type->original->id(), '%type' => $type->id())));
      }
    }
    
    /**
     * Respond to node type deletion.
     *
     * @param \Drupal\node\NodeTypeInterface $type
     *   The node type entity that was deleted.
     */
    function hook_node_type_delete(\Drupal\node\NodeTypeInterface $type) {
      drupal_set_message(t('You have just deleted a content type with the machine name %type.', array('%type' => $type->id())));
    }
    
    /**
     * Alter the links of a node.
     *
     * @param array &$links
     *   A renderable array representing the node links.
     * @param \Drupal\node\NodeInterface $entity
     *   The node being rendered.
     * @param array &$context
     *   Various aspects of the context in which the node links are going to be
     *   displayed, with the following keys:
     *   - 'view_mode': the view mode in which the comment is being viewed
     *   - 'langcode': the language in which the comment is being viewed
     *
     * @see \Drupal\node\NodeViewBuilder::renderLinks()
     * @see \Drupal\node\NodeViewBuilder::buildLinks()
     */
    function hook_node_links_alter(array &$links, NodeInterface $entity, array &$context) {
      $links['mymodule'] = array(
        '#theme' => 'links__node__mymodule',
        '#attributes' => array('class' => array('links', 'inline')),
        '#links' => array(
          'node-report' => array(
            'title' => t('Report'),
            'href' => "node/{$entity->id()}/report",
            'html' => TRUE,
            'query' => array('token' => \Drupal::getContainer()->get('csrf_token')->get("node/{$entity->id()}/report")),
          ),
        ),
      );
    }
    
    /**
     * @} End of "addtogroup hooks".
     */