BP_REST_Group_Membership_Endpoint::create_item_permissions_check( WP_REST_Request $request )

	public function create_item_permissions_check( $request ) {
		$retval = true;

		if ( ! is_user_logged_in() ) {
			$retval = new WP_Error(
				'bp_rest_authorization_required',
				__( 'Sorry, you need to be logged in to join a group.', 'buddyboss' ),
				array(
					'status' => rest_authorization_required_code(),
				)
			);
		}

		$user = bp_rest_get_user( $request['user_id'] );

		if ( true === $retval && ! $user instanceof WP_User ) {
			$retval = new WP_Error(
				'bp_rest_group_member_invalid_id',
				__( 'Invalid group member ID.', 'buddyboss' ),
				array(
					'status' => 404,
				)
			);
		}

		$group = $this->groups_endpoint->get_group_object( $request['group_id'] );
		if ( true === $retval && ! $group instanceof BP_Groups_Group ) {
			$retval = new WP_Error(
				'bp_rest_group_invalid_id',
				__( 'Invalid group ID.', 'buddyboss' ),
				array(
					'status' => 404,
				)
			);
		}

		// Site administrators can do anything.
		if ( true === $retval && bp_current_user_can( 'bp_moderate' ) ) {
			$retval = true;
		} else {

			$loggedin_user_id = bp_loggedin_user_id();

			// Users may only freely join public groups.
			if ( true === $retval && (
					! bp_current_user_can( 'groups_join_group', array( 'group_id' => $group->id ) )
					|| groups_is_user_member( $loggedin_user_id, $group->id ) // As soon as they are not already members.
					|| groups_is_user_banned( $loggedin_user_id, $group->id ) // And as soon as they are not banned from it.
					|| $loggedin_user_id !== $user->ID // You can only add yourself to a group.
				) ) {
				$retval = new WP_Error(
					'bp_rest_group_member_failed_to_join',
					__( 'Could not join the group.', 'buddyboss' ),
					array(
						'status' => 500,
					)
				);
			}
		}

		/**
		 * Filter the group members `create_item` permissions check.
		 *
		 * @param bool|WP_Error $retval Returned value.
		 * @param WP_REST_Request $request The request sent to the API.
		 *
		 * @since 0.1.0
		 */
		return apply_filters( 'bp_rest_group_members_create_item_permissions_check', $retval, $request );
	}