WordPress/wp-includes/rest-api/endpoints/class-wp-rest-terms-controller.php

<?php

/**
 * Access terms associated with a taxonomy.
 */
class WP_REST_Terms_Controller extends WP_REST_Controller {

	/**
	 * Taxonomy key.
	 *
	 * @access protected
	 * @var string
	 */
	protected $taxonomy;

	/**
	 * Instance of a term meta fields object.
	 *
	 * @access protected
	 * @var WP_REST_Term_Meta_Fields
	 */
	protected $meta;

	/**
	 * Column to have the terms be sorted by.
	 *
	 * @access protected
	 * @var string
	 */
	protected $sort_column;

	/**
	 * Number of terms that were found.
	 *
	 * @access protected
	 * @var int
	 */
	protected $total_terms;

	/**
	 * Constructor.
	 *
	 * @param string $taxonomy Taxonomy key.
	 */
	public function __construct( $taxonomy ) {
		$this->taxonomy = $taxonomy;
		$this->namespace = 'wp/v2';
		$tax_obj = get_taxonomy( $taxonomy );
		$this->rest_base = ! empty( $tax_obj->rest_base ) ? $tax_obj->rest_base : $tax_obj->name;

		$this->meta = new WP_REST_Term_Meta_Fields( $taxonomy );
	}

	/**
	 * Registers the routes for the objects of the controller.
	 */
	public function register_routes() {

		register_rest_route( $this->namespace, '/' . $this->rest_base, array(
			array(
				'methods'             => WP_REST_Server::READABLE,
				'callback'            => array( $this, 'get_items' ),
				'permission_callback' => array( $this, 'get_items_permissions_check' ),
				'args'                => $this->get_collection_params(),
			),
			array(
				'methods'             => WP_REST_Server::CREATABLE,
				'callback'            => array( $this, 'create_item' ),
				'permission_callback' => array( $this, 'create_item_permissions_check' ),
				'args'                => $this->get_endpoint_args_for_item_schema( WP_REST_Server::CREATABLE ),
			),
			'schema' => array( $this, 'get_public_item_schema' ),
		) );
		register_rest_route( $this->namespace, '/' . $this->rest_base . '/(?P<id>[\d]+)', array(
			array(
				'methods'             => WP_REST_Server::READABLE,
				'callback'            => array( $this, 'get_item' ),
				'permission_callback' => array( $this, 'get_item_permissions_check' ),
				'args'                => array(
					'context' => $this->get_context_param( array( 'default' => 'view' ) ),
				),
			),
			array(
				'methods'             => WP_REST_Server::EDITABLE,
				'callback'            => array( $this, 'update_item' ),
				'permission_callback' => array( $this, 'update_item_permissions_check' ),
				'args'                 => $this->get_endpoint_args_for_item_schema( WP_REST_Server::EDITABLE ),
			),
			array(
				'methods'             => WP_REST_Server::DELETABLE,
				'callback'            => array( $this, 'delete_item' ),
				'permission_callback' => array( $this, 'delete_item_permissions_check' ),
				'args'                => array(
					'force' => array(
						'default'     => false,
						'description' => __( 'Required to be true, as resource does not support trashing.' ),
					),
				),
			),
			'schema' => array( $this, 'get_public_item_schema' ),
		) );
	}

	/**
	 * Checks if a request has access to read terms in the specified taxonomy.
	 *
	 * @param  WP_REST_Request $request Full details about the request.
	 * @return WP_Error|boolean
	 */
	public function get_items_permissions_check( $request ) {
		$tax_obj = get_taxonomy( $this->taxonomy );
		if ( ! $tax_obj || ! $this->check_is_taxonomy_allowed( $this->taxonomy ) ) {
			return false;
		}
		if ( 'edit' === $request['context'] && ! current_user_can( $tax_obj->cap->edit_terms ) ) {
			return new WP_Error( 'rest_forbidden_context', __( 'Sorry, you cannot view this resource with edit context.' ), array( 'status' => rest_authorization_required_code() ) );
		}
		return true;
	}

	/**
	 * Gets terms associated with a taxonomy.
	 *
	 * @param WP_REST_Request $request Full details about the request.
	 * @return WP_REST_Response|WP_Error
	 */
	public function get_items( $request ) {

		// Retrieve the list of registered collection query parameters.
		$registered = $this->get_collection_params();

		// This array defines mappings between public API query parameters whose
		// values are accepted as-passed, and their internal WP_Query parameter
		// name equivalents (some are the same). Only values which are also
		// present in $registered will be set.
		$parameter_mappings = array(
			'exclude'    => 'exclude',
			'include'    => 'include',
			'order'      => 'order',
			'orderby'    => 'orderby',
			'post'       => 'post',
			'hide_empty' => 'hide_empty',
			'per_page'   => 'number',
			'search'     => 'search',
			'slug'       => 'slug',
		);

		$prepared_args = array();

		// For each known parameter which is both registered and present in the request,
		// set the parameter's value on the query $prepared_args.
		foreach ( $parameter_mappings as $api_param => $wp_param ) {
			if ( isset( $registered[ $api_param ], $request[ $api_param ] ) ) {
				$prepared_args[ $wp_param ] = $request[ $api_param ];
			}
		}

		if ( isset( $registered['offset'] ) && ! empty( $request['offset'] ) ) {
			$prepared_args['offset'] = $request['offset'];
		} else {
			$prepared_args['offset'] = ( $request['page'] - 1 ) * $prepared_args['number'];
		}

		$taxonomy_obj = get_taxonomy( $this->taxonomy );

		if ( $taxonomy_obj->hierarchical && isset( $registered['parent'], $request['parent'] ) ) {
			if ( 0 === $request['parent'] ) {
				// Only query top-level terms.
				$prepared_args['parent'] = 0;
			} else {
				if ( $request['parent'] ) {
					$prepared_args['parent'] = $request['parent'];
				}
			}
		}

		/**
		 * Filters the query arguments before passing them to get_terms().
		 *
		 * Enables adding extra arguments or setting defaults for a terms
		 * collection request.
		 *
		 * @see https://developer.wordpress.org/reference/functions/get_terms/
		 *
		 * @param array           $prepared_args Array of arguments to be
		 *                                       passed to get_terms().
		 * @param WP_REST_Request $request       The current request.
		 */
		$prepared_args = apply_filters( "rest_{$this->taxonomy}_query", $prepared_args, $request );

		if ( ! empty( $prepared_args['post'] )  ) {
			$query_result = $this->get_terms_for_post( $prepared_args );
			$total_terms = $this->total_terms;
		} else {
			$query_result = get_terms( $this->taxonomy, $prepared_args );

			$count_args = $prepared_args;
			unset( $count_args['number'], $count_args['offset'] );
			$total_terms = wp_count_terms( $this->taxonomy, $count_args );

			// wp_count_terms can return a falsy value when the term has no children
			if ( ! $total_terms ) {
				$total_terms = 0;
			}
		}
		$response = array();
		foreach ( $query_result as $term ) {
			$data = $this->prepare_item_for_response( $term, $request );
			$response[] = $this->prepare_response_for_collection( $data );
		}

		$response = rest_ensure_response( $response );

		// Store pagination values for headers.
		$per_page = (int) $prepared_args['number'];
		$page = ceil( ( ( (int) $prepared_args['offset'] ) / $per_page ) + 1 );

		$response->header( 'X-WP-Total', (int) $total_terms );
		$max_pages = ceil( $total_terms / $per_page );
		$response->header( 'X-WP-TotalPages', (int) $max_pages );

		$base = add_query_arg( $request->get_query_params(), rest_url( $this->namespace . '/' . $this->rest_base ) );
		if ( $page > 1 ) {
			$prev_page = $page - 1;
			if ( $prev_page > $max_pages ) {
				$prev_page = $max_pages;
			}
			$prev_link = add_query_arg( 'page', $prev_page, $base );
			$response->link_header( 'prev', $prev_link );
		}
		if ( $max_pages > $page ) {
			$next_page = $page + 1;
			$next_link = add_query_arg( 'page', $next_page, $base );
			$response->link_header( 'next', $next_link );
		}

		return $response;
	}

	/**
	 * Gets the terms attached to a post.
	 *
	 * This is an alternative to get_terms() that uses get_the_terms()
	 * instead, which hits the object cache. There are a few things not
	 * supported, notably `include`, `exclude`. In `self::get_items()` these
	 * are instead treated as a full query.
	 *
	 * @param array $prepared_args Arguments for get_terms().
	 * @return array List of term objects. (Total count in `$this->total_terms`)
	 */
	protected function get_terms_for_post( $prepared_args ) {
		$query_result = get_the_terms( $prepared_args['post'], $this->taxonomy );
		if ( empty( $query_result ) ) {
			$this->total_terms = 0;
			return array();
		}

		/*
		 * get_items() verifies that we don't have `include` set, and default
		 * ordering is by `name`.
		 */
		if ( ! in_array( $prepared_args['orderby'], array( 'name', 'none', 'include' ), true ) ) {
			switch ( $prepared_args['orderby'] ) {
				case 'id':
					$this->sort_column = 'term_id';
					break;

				case 'slug':
				case 'term_group':
				case 'description':
				case 'count':
					$this->sort_column = $prepared_args['orderby'];
					break;
			}
			usort( $query_result, array( $this, 'compare_terms' ) );
		}
		if ( strtolower( $prepared_args['order'] ) !== 'asc' ) {
			$query_result = array_reverse( $query_result );
		}

		// Pagination.
		$this->total_terms = count( $query_result );
		$query_result = array_slice( $query_result, $prepared_args['offset'], $prepared_args['number'] );

		return $query_result;
	}

	/**
	 * Comparison function for sorting terms by a column.
	 *
	 * Uses `$this->sort_column` to determine field to sort by.
	 *
	 * @access protected
	 *
	 * @param stdClass $left Term object.
	 * @param stdClass $right Term object.
	 * @return int <0 if left is higher "priority" than right, 0 if equal, >0 if right is higher "priority" than left.
	 */
	protected function compare_terms( $left, $right ) {
		$col = $this->sort_column;
		$left_val = $left->$col;
		$right_val = $right->$col;

		if ( is_int( $left_val ) && is_int( $right_val ) ) {
			return $left_val - $right_val;
		}

		return strcmp( $left_val, $right_val );
	}

	/**
	 * Checks if a request has access to read the specified term.
	 *
	 * @param  WP_REST_Request $request Full details about the request.
	 * @return WP_Error|boolean
	 */
	public function get_item_permissions_check( $request ) {
		$tax_obj = get_taxonomy( $this->taxonomy );
		if ( ! $tax_obj || ! $this->check_is_taxonomy_allowed( $this->taxonomy ) ) {
			return false;
		}
		if ( 'edit' === $request['context'] && ! current_user_can( $tax_obj->cap->edit_terms ) ) {
			return new WP_Error( 'rest_forbidden_context', __( 'Sorry, you cannot view this resource with edit context.' ), array( 'status' => rest_authorization_required_code() ) );
		}
		return true;
	}

	/**
	 * Gets a single term from a taxonomy.
	 *
	 * @param WP_REST_Request $request Full details about the request
	 * @return WP_REST_Request|WP_Error
	 */
	public function get_item( $request ) {

		$term = get_term( (int) $request['id'], $this->taxonomy );
		if ( ! $term || $term->taxonomy !== $this->taxonomy ) {
			return new WP_Error( 'rest_term_invalid', __( "Resource doesn't exist." ), array( 'status' => 404 ) );
		}
		if ( is_wp_error( $term ) ) {
			return $term;
		}

		$response = $this->prepare_item_for_response( $term, $request );

		return rest_ensure_response( $response );
	}

	/**
	 * Checks if a request has access to create a term.
	 *
	 * @param  WP_REST_Request $request Full details about the request.
	 * @return WP_Error|boolean
	 */
	public function create_item_permissions_check( $request ) {

		if ( ! $this->check_is_taxonomy_allowed( $this->taxonomy ) ) {
			return false;
		}

		$taxonomy_obj = get_taxonomy( $this->taxonomy );
		if ( ! current_user_can( $taxonomy_obj->cap->manage_terms ) ) {
			return new WP_Error( 'rest_cannot_create', __( 'Sorry, you cannot create new resource.' ), array( 'status' => rest_authorization_required_code() ) );
		}

		return true;
	}

	/**
	 * Creates a single term in a taxonomy.
	 *
	 * @param WP_REST_Request $request Full details about the request
	 * @return WP_REST_Request|WP_Error
	 */
	public function create_item( $request ) {
		if ( isset( $request['parent'] ) ) {
			if ( ! is_taxonomy_hierarchical( $this->taxonomy ) ) {
				return new WP_Error( 'rest_taxonomy_not_hierarchical', __( 'Can not set resource parent, taxonomy is not hierarchical.' ), array( 'status' => 400 ) );
			}

			$parent = get_term( (int) $request['parent'], $this->taxonomy );

			if ( ! $parent ) {
				return new WP_Error( 'rest_term_invalid', __( "Parent resource doesn't exist." ), array( 'status' => 400 ) );
			}
		}

		$prepared_term = $this->prepare_item_for_database( $request );

		$term = wp_insert_term( $prepared_term->name, $this->taxonomy, $prepared_term );
		if ( is_wp_error( $term ) ) {

			/*
			 * If we're going to inform the client that the term already exists,
			 * give them the identifier for future use.
			 */
			if ( $term_id = $term->get_error_data( 'term_exists' ) ) {
				$existing_term = get_term( $term_id, $this->taxonomy );
				$term->add_data( $existing_term->term_id, 'term_exists' );
			}

			return $term;
		}

		$term = get_term( $term['term_id'], $this->taxonomy );

		/**
		 * Fires after a single term is created or updated via the REST API.
		 *
		 * @param WP_Term         $term     Inserted Term object.
		 * @param WP_REST_Request $request  Request object.
		 * @param boolean         $creating True when creating term, false when updating.
		 */
		do_action( "rest_insert_{$this->taxonomy}", $term, $request, true );

		$schema = $this->get_item_schema();
		if ( ! empty( $schema['properties']['meta'] ) && isset( $request['meta'] ) ) {
			$meta_update = $this->meta->update_value( $request['meta'], (int) $request['id'] );
			if ( is_wp_error( $meta_update ) ) {
				return $meta_update;
			}
		}

		$fields_update = $this->update_additional_fields_for_object( $term, $request );
		if ( is_wp_error( $fields_update ) ) {
			return $fields_update;
		}

		$request->set_param( 'context', 'view' );
		$response = $this->prepare_item_for_response( $term, $request );
		$response = rest_ensure_response( $response );
		$response->set_status( 201 );
		$response->header( 'Location', rest_url( $this->namespace . '/' . $this->rest_base . '/' . $term->term_id ) );
		return $response;
	}

	/**
	 * Checks if a request has access to update the specified term.
	 *
	 * @param  WP_REST_Request $request Full details about the request.
	 * @return WP_Error|boolean
	 */
	public function update_item_permissions_check( $request ) {

		if ( ! $this->check_is_taxonomy_allowed( $this->taxonomy ) ) {
			return false;
		}

		$term = get_term( (int) $request['id'], $this->taxonomy );
		if ( ! $term ) {
			return new WP_Error( 'rest_term_invalid', __( "Resource doesn't exist." ), array( 'status' => 404 ) );
		}

		$taxonomy_obj = get_taxonomy( $this->taxonomy );
		if ( ! current_user_can( $taxonomy_obj->cap->edit_terms ) ) {
			return new WP_Error( 'rest_cannot_update', __( 'Sorry, you cannot update resource.' ), array( 'status' => rest_authorization_required_code() ) );
		}

		return true;
	}

	/**
	 * Updates a single term from a taxonomy.
	 *
	 * @param WP_REST_Request $request Full details about the request
	 * @return WP_REST_Request|WP_Error
	 */
	public function update_item( $request ) {
		if ( isset( $request['parent'] ) ) {
			if ( ! is_taxonomy_hierarchical( $this->taxonomy ) ) {
				return new WP_Error( 'rest_taxonomy_not_hierarchical', __( 'Can not set resource parent, taxonomy is not hierarchical.' ), array( 'status' => 400 ) );
			}

			$parent = get_term( (int) $request['parent'], $this->taxonomy );

			if ( ! $parent ) {
				return new WP_Error( 'rest_term_invalid', __( "Parent resource doesn't exist." ), array( 'status' => 400 ) );
			}
		}

		$prepared_term = $this->prepare_item_for_database( $request );

		$term = get_term( (int) $request['id'], $this->taxonomy );

		// Only update the term if we haz something to update.
		if ( ! empty( $prepared_term ) ) {
			$update = wp_update_term( $term->term_id, $term->taxonomy, (array) $prepared_term );
			if ( is_wp_error( $update ) ) {
				return $update;
			}
		}

		$term = get_term( (int) $request['id'], $this->taxonomy );

		/* This action is documented in lib/endpoints/class-wp-rest-terms-controller.php */
		do_action( "rest_insert_{$this->taxonomy}", $term, $request, false );

		$schema = $this->get_item_schema();
		if ( ! empty( $schema['properties']['meta'] ) && isset( $request['meta'] ) ) {
			$meta_update = $this->meta->update_value( $request['meta'], (int) $request['id'] );
			if ( is_wp_error( $meta_update ) ) {
				return $meta_update;
			}
		}

		$fields_update = $this->update_additional_fields_for_object( $term, $request );
		if ( is_wp_error( $fields_update ) ) {
			return $fields_update;
		}

		$request->set_param( 'context', 'view' );
		$response = $this->prepare_item_for_response( $term, $request );
		return rest_ensure_response( $response );
	}

	/**
	 * Checks if a request has access to delete the specified term.
	 *
	 * @param  WP_REST_Request $request Full details about the request.
	 * @return WP_Error|boolean
	 */
	public function delete_item_permissions_check( $request ) {
		if ( ! $this->check_is_taxonomy_allowed( $this->taxonomy ) ) {
			return false;
		}
		$term = get_term( (int) $request['id'], $this->taxonomy );
		if ( ! $term ) {
			return new WP_Error( 'rest_term_invalid', __( "Resource doesn't exist." ), array( 'status' => 404 ) );
		}
		$taxonomy_obj = get_taxonomy( $this->taxonomy );
		if ( ! current_user_can( $taxonomy_obj->cap->delete_terms ) ) {
			return new WP_Error( 'rest_cannot_delete', __( 'Sorry, you cannot delete resource.' ), array( 'status' => rest_authorization_required_code() ) );
		}
		return true;
	}

	/**
	 * Deletes a single term from a taxonomy.
	 *
	 * @param WP_REST_Request $request Full details about the request
	 * @return WP_REST_Response|WP_Error
	 */
	public function delete_item( $request ) {

		$force = isset( $request['force'] ) ? (bool) $request['force'] : false;

		// We don't support trashing for this resource type.
		if ( ! $force ) {
			return new WP_Error( 'rest_trash_not_supported', __( 'Resource does not support trashing.' ), array( 'status' => 501 ) );
		}

		$term = get_term( (int) $request['id'], $this->taxonomy );
		$request->set_param( 'context', 'view' );
		$response = $this->prepare_item_for_response( $term, $request );

		$retval = wp_delete_term( $term->term_id, $term->taxonomy );
		if ( ! $retval ) {
			return new WP_Error( 'rest_cannot_delete', __( 'The resource cannot be deleted.' ), array( 'status' => 500 ) );
		}

		/**
		 * Fires after a single term is deleted via the REST API.
		 *
		 * @param WP_Term          $term     The deleted term.
		 * @param WP_REST_Response $response The response data.
		 * @param WP_REST_Request  $request  The request sent to the API.
		 */
		do_action( "rest_delete_{$this->taxonomy}", $term, $response, $request );

		return $response;
	}

	/**
	 * Prepares a single term for create or update.
	 *
	 * @param WP_REST_Request $request Request object.
	 * @return object $prepared_term Term object.
	 */
	public function prepare_item_for_database( $request ) {
		$prepared_term = new stdClass;

		$schema = $this->get_item_schema();
		if ( isset( $request['name'] ) && ! empty( $schema['properties']['name'] ) ) {
			$prepared_term->name = $request['name'];
		}

		if ( isset( $request['slug'] ) && ! empty( $schema['properties']['slug'] ) ) {
			$prepared_term->slug = $request['slug'];
		}

		if ( isset( $request['taxonomy'] ) && ! empty( $schema['properties']['taxonomy'] ) ) {
			$prepared_term->taxonomy = $request['taxonomy'];
		}

		if ( isset( $request['description'] ) && ! empty( $schema['properties']['description'] ) ) {
			$prepared_term->description = $request['description'];
		}

		if ( isset( $request['parent'] ) && ! empty( $schema['properties']['parent'] ) ) {
			$parent_term_id = 0;
			$parent_term = get_term( (int) $request['parent'], $this->taxonomy );

			if ( $parent_term ) {
				$parent_term_id = $parent_term->term_id;
			}

			$prepared_term->parent = $parent_term_id;
		}

		/**
		 * Filters term data before inserting term via the REST API.
		 *
		 * @param object          $prepared_term Term object.
		 * @param WP_REST_Request $request       Request object.
		 */
		return apply_filters( "rest_pre_insert_{$this->taxonomy}", $prepared_term, $request );
	}

	/**
	 * Prepares a single term output for response.
	 *
	 * @param obj             $item    Term object.
	 * @param WP_REST_Request $request Request object.
	 * @return WP_REST_Response $response
	 */
	public function prepare_item_for_response( $item, $request ) {

		$schema = $this->get_item_schema();
		$data = array();
		if ( ! empty( $schema['properties']['id'] ) ) {
			$data['id'] = (int) $item->term_id;
		}
		if ( ! empty( $schema['properties']['count'] ) ) {
			$data['count'] = (int) $item->count;
		}
		if ( ! empty( $schema['properties']['description'] ) ) {
			$data['description'] = $item->description;
		}
		if ( ! empty( $schema['properties']['link'] ) ) {
			$data['link'] = get_term_link( $item );
		}
		if ( ! empty( $schema['properties']['name'] ) ) {
			$data['name'] = $item->name;
		}
		if ( ! empty( $schema['properties']['slug'] ) ) {
			$data['slug'] = $item->slug;
		}
		if ( ! empty( $schema['properties']['taxonomy'] ) ) {
			$data['taxonomy'] = $item->taxonomy;
		}
		if ( ! empty( $schema['properties']['parent'] ) ) {
			$data['parent'] = (int) $item->parent;
		}
		if ( ! empty( $schema['properties']['meta'] ) ) {
			$data['meta'] = $this->meta->get_value( $item->term_id, $request );
		}

		$context = ! empty( $request['context'] ) ? $request['context'] : 'view';
		$data = $this->add_additional_fields_to_object( $data, $request );
		$data = $this->filter_response_by_context( $data, $context );

		$response = rest_ensure_response( $data );

		$response->add_links( $this->prepare_links( $item ) );

		/**
		 * Filters a term item returned from the API.
		 *
		 * Allows modification of the term data right before it is returned.
		 *
		 * @param WP_REST_Response  $response  The response object.
		 * @param object            $item      The original term object.
		 * @param WP_REST_Request   $request   Request used to generate the response.
		 */
		return apply_filters( "rest_prepare_{$this->taxonomy}", $response, $item, $request );
	}

	/**
	 * Prepares links for the request.
	 *
	 * @param object $term Term object.
	 * @return array Links for the given term.
	 */
	protected function prepare_links( $term ) {
		$base = $this->namespace . '/' . $this->rest_base;
		$links = array(
			'self'       => array(
				'href' => rest_url( trailingslashit( $base ) . $term->term_id ),
			),
			'collection' => array(
				'href' => rest_url( $base ),
			),
			'about'      => array(
				'href' => rest_url( sprintf( 'wp/v2/taxonomies/%s', $this->taxonomy ) ),
			),
		);

		if ( $term->parent ) {
			$parent_term = get_term( (int) $term->parent, $term->taxonomy );
			if ( $parent_term ) {
				$links['up'] = array(
					'href'       => rest_url( trailingslashit( $base ) . $parent_term->term_id ),
					'embeddable' => true,
				);
			}
		}

		$taxonomy_obj = get_taxonomy( $term->taxonomy );
		if ( empty( $taxonomy_obj->object_type ) ) {
			return $links;
		}

		$post_type_links = array();
		foreach ( $taxonomy_obj->object_type as $type ) {
			$post_type_object = get_post_type_object( $type );
			if ( empty( $post_type_object->show_in_rest ) ) {
				continue;
			}
			$rest_base = ! empty( $post_type_object->rest_base ) ? $post_type_object->rest_base : $post_type_object->name;
			$post_type_links[] = array(
				'href' => add_query_arg( $this->rest_base, $term->term_id, rest_url( sprintf( 'wp/v2/%s', $rest_base ) ) ),
			);
		}
		if ( ! empty( $post_type_links ) ) {
			$links['https://api.w.org/post_type'] = $post_type_links;
		}

		return $links;
	}

	/**
	 * Gets the term's schema, conforming to JSON Schema.
	 *
	 * @return array
	 */
	public function get_item_schema() {
		$schema = array(
			'$schema'    => 'http://json-schema.org/draft-04/schema#',
			'title'      => 'post_tag' === $this->taxonomy ? 'tag' : $this->taxonomy,
			'type'       => 'object',
			'properties' => array(
				'id'          => array(
					'description'  => __( 'Unique identifier for the resource.' ),
					'type'         => 'integer',
					'context'      => array( 'view', 'embed', 'edit' ),
					'readonly'     => true,
				),
				'count'       => array(
					'description'  => __( 'Number of published posts for the resource.' ),
					'type'         => 'integer',
					'context'      => array( 'view', 'edit' ),
					'readonly'     => true,
				),
				'description' => array(
					'description'  => __( 'HTML description of the resource.' ),
					'type'         => 'string',
					'context'      => array( 'view', 'edit' ),
					'arg_options'  => array(
						'sanitize_callback' => 'wp_filter_post_kses',
					),
				),
				'link'        => array(
					'description'  => __( 'URL to the resource.' ),
					'type'         => 'string',
					'format'       => 'uri',
					'context'      => array( 'view', 'embed', 'edit' ),
					'readonly'     => true,
				),
				'name'        => array(
					'description'  => __( 'HTML title for the resource.' ),
					'type'         => 'string',
					'context'      => array( 'view', 'embed', 'edit' ),
					'arg_options'  => array(
						'sanitize_callback' => 'sanitize_text_field',
					),
					'required'     => true,
				),
				'slug'        => array(
					'description'  => __( 'An alphanumeric identifier for the resource unique to its type.' ),
					'type'         => 'string',
					'context'      => array( 'view', 'embed', 'edit' ),
					'arg_options'  => array(
						'sanitize_callback' => array( $this, 'sanitize_slug' ),
					),
				),
				'taxonomy'    => array(
					'description'  => __( 'Type attribution for the resource.' ),
					'type'         => 'string',
					'enum'         => array_keys( get_taxonomies() ),
					'context'      => array( 'view', 'embed', 'edit' ),
					'readonly'     => true,
				),
			),
		);
		$taxonomy = get_taxonomy( $this->taxonomy );
		if ( $taxonomy->hierarchical ) {
			$schema['properties']['parent'] = array(
				'description'  => __( 'The id for the parent of the resource.' ),
				'type'         => 'integer',
				'context'      => array( 'view', 'edit' ),
			);
		}

		$schema['properties']['meta'] = $this->meta->get_field_schema();
		return $this->add_additional_fields_schema( $schema );
	}

	/**
	 * Gets the query params for collections.
	 *
	 * @return array
	 */
	public function get_collection_params() {
		$query_params = parent::get_collection_params();
		$taxonomy = get_taxonomy( $this->taxonomy );

		$query_params['context']['default'] = 'view';

		$query_params['exclude'] = array(
			'description'       => __( 'Ensure result set excludes specific ids.' ),
			'type'              => 'array',
			'default'           => array(),
			'sanitize_callback' => 'wp_parse_id_list',
		);
		$query_params['include'] = array(
			'description'       => __( 'Limit result set to specific ids.' ),
			'type'              => 'array',
			'default'           => array(),
			'sanitize_callback' => 'wp_parse_id_list',
		);
		if ( ! $taxonomy->hierarchical ) {
			$query_params['offset'] = array(
				'description'       => __( 'Offset the result set by a specific number of items.' ),
				'type'              => 'integer',
				'sanitize_callback' => 'absint',
				'validate_callback' => 'rest_validate_request_arg',
			);
		}
		$query_params['order'] = array(
			'description'       => __( 'Order sort attribute ascending or descending.' ),
			'type'              => 'string',
			'sanitize_callback' => 'sanitize_key',
			'default'           => 'asc',
			'enum'              => array(
				'asc',
				'desc',
			),
			'validate_callback' => 'rest_validate_request_arg',
		);
		$query_params['orderby'] = array(
			'description'       => __( 'Sort collection by resource attribute.' ),
			'type'              => 'string',
			'sanitize_callback' => 'sanitize_key',
			'default'           => 'name',
			'enum'              => array(
				'id',
				'include',
				'name',
				'slug',
				'term_group',
				'description',
				'count',
			),
			'validate_callback' => 'rest_validate_request_arg',
		);
		$query_params['hide_empty'] = array(
			'description'       => __( 'Whether to hide resources not assigned to any posts.' ),
			'type'              => 'boolean',
			'default'           => false,
			'sanitize_callback' => 'rest_sanitize_request_arg',
			'validate_callback' => 'rest_validate_request_arg',
		);
		if ( $taxonomy->hierarchical ) {
			$query_params['parent'] = array(
				'description'       => __( 'Limit result set to resources assigned to a specific parent.' ),
				'type'              => 'integer',
				'sanitize_callback' => 'absint',
				'validate_callback' => 'rest_validate_request_arg',
			);
		}
		$query_params['post'] = array(
			'description'       => __( 'Limit result set to resources assigned to a specific post.' ),
			'type'              => 'integer',
			'default'           => null,
			'validate_callback' => 'rest_validate_request_arg',
		);
		$query_params['slug'] = array(
			'description'       => __( 'Limit result set to resources with a specific slug.' ),
			'type'              => 'string',
			'validate_callback' => 'rest_validate_request_arg',
		);
		return $query_params;
	}

	/**
	 * Checks that the taxonomy is valid.
	 *
	 * @param string $taxonomy Taxonomy to check.
	 * @return WP_Error|boolean
	 */
	protected function check_is_taxonomy_allowed( $taxonomy ) {
		$taxonomy_obj = get_taxonomy( $taxonomy );
		if ( $taxonomy_obj && ! empty( $taxonomy_obj->show_in_rest ) ) {
			return true;
		}
		return false;
	}
}