l_url' );
	}

	/**
	 * @return bool
	 */
	private function is_permalink_filter_from_rel_canonical() {
		$back_trace_stack = $this->sitepress->get_wp_api()->get_backtrace( 20 );
		$keywords         = array( 'rel_canonical', 'canonical', 'generate_canonical' );

		$result = false;
		if ( $back_trace_stack ) {
			foreach ( $back_trace_stack as $key => $value ) {
				foreach ( $keywords as $keyword ) {
					if ( 'function' === $key && $keyword === $value ) {
						$result = true;
						break;
					}
				}
			}
		}

		return $result;
	}

	/**
	 * @param string $link
	 *
	 * @return bool|string
	 */
	private function get_url_in_default_language_if_rel_canonical( $link ) {
		if ( $this->is_permalink_filter_from_rel_canonical() ) {
			$default_language = $this->sitepress->get_default_language();
			$link             = (string) $this->sitepress->convert_url( $link, $default_language );
		}

		return $link;
	}

	/**
	 * @param WPML_Post_Element $post_element
	 *
	 * @return false|string
	 */
	private function get_canonical_of_duplicate( $post_element ) {
		$source_element = $post_element->get_source_element();
		if ( $source_element ) {
			$source_element_id    = $source_element->get_id();
			$source_language_code = $source_element->get_language_code();
			$current_language     = $this->sitepress->get_current_language();
			$this->sitepress->switch_lang( $source_language_code );
			$new_link = get_permalink( $source_element_id );
			$this->sitepress->switch_lang( $current_language );
		} else {
			$new_link = get_permalink( $post_element->get_id() );
		}

		return $new_link;
	}

	/**
	 * @return bool
	 */
	private function must_handle_a_canonical_url() {
		return ! $this->has_wp_get_canonical_url() && $this->sitepress->get_wp_api()->is_front_end();
	}

	private function init_wpml_translations() {
		if ( ! $this->wpml_translations ) {
			$this->wpml_translations = new WPML_Translations( $this->sitepress );
		}
	}
}