protected function _insert_post( $user, $content_struct ) {
		$defaults = array(
			'post_status'    => 'draft',
			'post_type'      => 'post',
			'post_author'    => null,
			'post_password'  => null,
			'post_excerpt'   => null,
			'post_content'   => null,
			'post_title'     => null,
			'post_date'      => null,
			'post_date_gmt'  => null,
			'post_format'    => null,
			'post_name'      => null,
			'post_thumbnail' => null,
			'post_parent'    => null,
			'ping_status'    => null,
			'comment_status' => null,
			'custom_fields'  => null,
			'terms_names'    => null,
			'terms'          => null,
			'sticky'         => null,
			'enclosure'      => null,
			'ID'             => null,
		);

		$post_data = wp_parse_args( array_intersect_key( $content_struct, $defaults ), $defaults );

		$post_type = get_post_type_object( $post_data['post_type'] );
		if ( ! $post_type ) {
			return new IXR_Error( 403, __( 'Invalid post type.' ) );
		}

		$update = ! empty( $post_data['ID'] );

		if ( $update ) {
			if ( ! get_post( $post_data['ID'] ) ) {
				return new IXR_Error( 401, __( 'Invalid post ID.' ) );
			}
			if ( ! current_user_can( 'edit_post', $post_data['ID'] ) ) {
				return new IXR_Error( 401, __( 'Sorry, you are not allowed to edit this post.' ) );
			}
			if ( $post_data['post_type'] != get_post_type( $post_data['ID'] ) ) {
				return new IXR_Error( 401, __( 'The post type may not be changed.' ) );
			}
		} else {
			if ( ! current_user_can( $post_type->cap->create_posts ) || ! current_user_can( $post_type->cap->edit_posts ) ) {
				return new IXR_Error( 401, __( 'Sorry, you are not allowed to post on this site.' ) );
			}
		}

		switch ( $post_data['post_status'] ) {
			case 'draft':
			case 'pending':
				break;
			case 'private':
				if ( ! current_user_can( $post_type->cap->publish_posts ) ) {
					return new IXR_Error( 401, __( 'Sorry, you are not allowed to create private posts in this post type.' ) );
				}
				break;
			case 'publish':
			case 'future':
				if ( ! current_user_can( $post_type->cap->publish_posts ) ) {
					return new IXR_Error( 401, __( 'Sorry, you are not allowed to publish posts in this post type.' ) );
				}
				break;
			default:
				if ( ! get_post_status_object( $post_data['post_status'] ) ) {
					$post_data['post_status'] = 'draft';
				}
				break;
		}

		if ( ! empty( $post_data['post_password'] ) && ! current_user_can( $post_type->cap->publish_posts ) ) {
			return new IXR_Error( 401, __( 'Sorry, you are not allowed to create password protected posts in this post type.' ) );
		}

		$post_data['post_author'] = absint( $post_data['post_author'] );
		if ( ! empty( $post_data['post_author'] ) && $post_data['post_author'] != $user->ID ) {
			if ( ! current_user_can( $post_type->cap->edit_others_posts ) ) {
				return new IXR_Error( 401, __( 'Sorry, you are not allowed to create posts as this user.' ) );
			}

			$author = get_userdata( $post_data['post_author'] );

			if ( ! $author ) {
				return new IXR_Error( 404, __( 'Invalid author ID.' ) );
			}
		} else {
			$post_data['post_author'] = $user->ID;
		}

		if ( isset( $post_data['comment_status'] ) && $post_data['comment_status'] != 'open' && $post_data['comment_status'] != 'closed' ) {
			unset( $post_data['comment_status'] );
		}

		if ( isset( $post_data['ping_status'] ) && $post_data['ping_status'] != 'open' && $post_data['ping_status'] != 'closed' ) {
			unset( $post_data['ping_status'] );
		}

		// Do some timestamp voodoo.
		if ( ! empty( $post_data['post_date_gmt'] ) ) {
			// We know this is supposed to be GMT, so we're going to slap that Z on there by force.
			$dateCreated = rtrim( $post_data['post_date_gmt']->getIso(), 'Z' ) . 'Z';
		} elseif ( ! empty( $post_data['post_date'] ) ) {
			$dateCreated = $post_data['post_date']->getIso();
		}

		// Default to not flagging the post date to be edited unless it's intentional.
		$post_data['edit_date'] = false;

		if ( ! empty( $dateCreated ) ) {
			$post_data['post_date']     = get_date_from_gmt( iso8601_to_datetime( $dateCreated ) );
			$post_data['post_date_gmt'] = iso8601_to_datetime( $dateCreated, 'GMT' );

			// Flag the post date to be edited.
			$post_data['edit_date'] = true;
		}

		if ( ! isset( $post_data['ID'] ) ) {
			$post_data['ID'] = get_default_post_to_edit( $post_data['post_type'], true )->ID;
		}
		$post_ID = $post_data['ID'];

		if ( $post_data['post_type'] == 'post' ) {
			$error = $this->_toggle_sticky( $post_data, $update );
			if ( $error ) {
				return $error;
			}
		}

		if ( isset( $post_data['post_thumbnail'] ) ) {
			// empty value deletes, non-empty value adds/updates.
			if ( ! $post_data['post_thumbnail'] ) {
				delete_post_thumbnail( $post_ID );
			} elseif ( ! get_post( absint( $post_data['post_thumbnail'] ) ) ) {
				return new IXR_Error( 404, __( 'Invalid attachment ID.' ) );
			}
			set_post_thumbnail( $post_ID, $post_data['post_thumbnail'] );
			unset( $content_struct['post_thumbnail'] );
		}

		if ( isset( $post_data['custom_fields'] ) ) {
			$this->set_custom_fields( $post_ID, $post_data['custom_fields'] );
		}

		if ( isset( $post_data['terms'] ) || isset( $post_data['terms_names'] ) ) {
			$post_type_taxonomies = get_object_taxonomies( $post_data['post_type'], 'objects' );

			// Accumulate term IDs from terms and terms_names.
			$terms = array();

			// First validate the terms specified by ID.
			if ( isset( $post_data['terms'] ) && is_array( $post_data['terms'] ) ) {
				$taxonomies = array_keys( $post_data['terms'] );

				// Validating term ids.
				foreach ( $taxonomies as $taxonomy ) {
					if ( ! array_key_exists( $taxonomy, $post_type_taxonomies ) ) {
						return new IXR_Error( 401, __( 'Sorry, one of the given taxonomies is not supported by the post type.' ) );
					}

					if ( ! current_user_can( $post_type_taxonomies[ $taxonomy ]->cap->assign_terms ) ) {
						return new IXR_Error( 401, __( 'Sorry, you are not allowed to assign a term to one of the given taxonomies.' ) );
					}

					$term_ids           = $post_data['terms'][ $taxonomy ];
					$terms[ $taxonomy ] = array();
					foreach ( $term_ids as $term_id ) {
						$term = get_term_by( 'id', $term_id, $taxonomy );

						if ( ! $term ) {
							return new IXR_Error( 403, __( 'Invalid term ID.' ) );
						}

						$terms[ $taxonomy ][] = (int) $term_id;
					}
				}
			}

			// Now validate terms specified by name.
			if ( isset( $post_data['terms_names'] ) && is_array( $post_data['terms_names'] ) ) {
				$taxonomies = array_keys( $post_data['terms_names'] );

				foreach ( $taxonomies as $taxonomy ) {
					if ( ! array_key_exists( $taxonomy, $post_type_taxonomies ) ) {
						return new IXR_Error( 401, __( 'Sorry, one of the given taxonomies is not supported by the post type.' ) );
					}

					if ( ! current_user_can( $post_type_taxonomies[ $taxonomy ]->cap->assign_terms ) ) {
						return new IXR_Error( 401, __( 'Sorry, you are not allowed to assign a term to one of the given taxonomies.' ) );
					}

					/*
					 * For hierarchical taxonomies, we can't assign a term when multiple terms
					 * in the hierarchy share the same name.
					 */
					$ambiguous_terms = array();
					if ( is_taxonomy_hierarchical( $taxonomy ) ) {
						$tax_term_names = get_terms(
							array(
								'taxonomy'   => $taxonomy,
								'fields'     => 'names',
								'hide_empty' => false,
							)
						);

						// Count the number of terms with the same name.
						$tax_term_names_count = array_count_values( $tax_term_names );

						// Filter out non-ambiguous term names.
						$ambiguous_tax_term_counts = array_filter( $tax_term_names_count, array( $this, '_is_greater_than_one' ) );

						$ambiguous_terms = array_keys( $ambiguous_tax_term_counts );
					}

					$term_names = $post_data['terms_names'][ $taxonomy ];
					foreach ( $term_names as $term_name ) {
						if ( in_array( $term_name, $ambiguous_terms ) ) {
							return new IXR_Error( 401, __( 'Ambiguous term name used in a hierarchical taxonomy. Please use term ID instead.' ) );
						}

						$term = get_term_by( 'name', $term_name, $taxonomy );

						if ( ! $term ) {
							// Term doesn't exist, so check that the user is allowed to create new terms.
							if ( ! current_user_can( $post_type_taxonomies[ $taxonomy ]->cap->edit_terms ) ) {
								return new IXR_Error( 401, __( 'Sorry, you are not allowed to add a term to one of the given taxonomies.' ) );
							}

							// Create the new term.
							$term_info = wp_insert_term( $term_name, $taxonomy );
							if ( is_wp_error( $term_info ) ) {
								return new IXR_Error( 500, $term_info->get_error_message() );
							}

							$terms[ $taxonomy ][] = (int) $term_info['term_id'];
						} else {
							$terms[ $taxonomy ][] = (int) $term->term_id;
						}
					}
				}
			}

			$post_data['tax_input'] = $terms;
			unset( $post_data['terms'], $post_data['terms_names'] );
		}

		if ( isset( $post_data['post_format'] ) ) {
			$format = set_post_format( $post_ID, $post_data['post_format'] );

			if ( is_wp_error( $format ) ) {
				return new IXR_Error( 500, $format->get_error_message() );
			}

			unset( $post_data['post_format'] );
		}

		// Handle enclosures.
		$enclosure = isset( $post_data['enclosure'] ) ? $post_data['enclosure'] : null;
		$this->add_enclosure_if_new( $post_ID, $enclosure );

		$this->attach_uploads( $post_ID, $post_data['post_content'] );

		/**
		 * Filters post data array to be inserted via XML-RPC.
		 *
		 * @since 3.4.0
		 *
		 * @param array $post_data      Parsed array of post data.
		 * @param array $content_struct Post data array.
		 */
		$post_data = apply_filters( 'xmlrpc_wp_insert_post_data', $post_data, $content_struct );

		$post_ID = $update ? wp_update_post( $post_data, true ) : wp_insert_post( $post_data, true );
		if ( is_wp_error( $post_ID ) ) {
			return new IXR_Error( 500, $post_ID->get_error_message() );
		}

		if ( ! $post_ID ) {
			return new IXR_Error( 401, __( 'Sorry, your entry could not be posted.' ) );
		}

		return strval( $post_ID );
	}