* Output the rel next/prev tags on a paginated single post.
	 *
	 * @return void
	 */
	private function adjacent_rel_links_single() {
		$num_pages = 1;

		$queried_object = get_queried_object();
		if ( ! empty( $queried_object ) ) {
			$num_pages = substr_count( $queried_object->post_content, '<!--nextpage-->' ) + 1;
		}

		if ( 1 === $num_pages ) {
			return;
		}

		$page = max( 1, (int) get_query_var( 'page' ) );
		$url  = get_permalink( get_queried_object_id() );

		if ( $page > 1 ) {
			$this->adjacent_rel_link( 'prev', $url, $page - 1, 'page' );
		}

		if ( $page < $num_pages ) {
			$this->adjacent_rel_link( 'next', $url, $page + 1, 'page' );
		}
	}

	/**
	 * Output the rel next/prev tags on archives.
	 */
	private function adjacent_rel_links_archive() {
		$url = Paper::get()->get_canonical( true, true );
		if ( ! is_string( $url ) || '' === $url ) {
			return;
		}

		$paged = max( 1, (int) get_query_var( 'paged' ) );
		if ( 2 === $paged ) {
			$this->adjacent_rel_link( 'prev', $url, $paged - 1 );
		}

		if ( is_front_page() ) {
			$url = Router::get_base_url( '' );
		}

		if ( $paged > 2 ) {
			$this->adjacent_rel_link( 'prev', $url, $paged - 1 );
		}

		if ( $paged < $GLOBALS['wp_query']->max_num_pages ) {
			$this->adjacent_rel_link( 'next', $url, $paged + 1 );
		}
	}

	/**
	 * Build adjacent page link for archives.
	 *
	 * @param string $rel       Prev or next.
	 * @param string $url       The current archive URL without page parameter.
	 * @param string $page      The page number added to the $url in the link tag.
	 * @param string $query_arg The pagination query argument to use for the $url.
	 */
	private function adjacent_rel_link( $rel, $url, $page, $query_arg = 'paged' ) {
		global $wp_rewrite;

		if ( $page > 1 ) {
			$url = ! $wp_rewrite->using_permalinks() ? Security::add_query_arg_raw( $query_arg, $page, $url ) : user_trailingslashit( trailingslashit( $url ) . $this->get_pagination_base() . $page );
		}

		/**
		 * Change the link rel HTML output.
		 *
		 * @param string $link The `<link rel=""` tag.
		 */
		$link = $this->do_filter( "frontend/{$rel}_rel_link", '<link rel="' . esc_attr( $rel ) . '" href="' . esc_url( $url ) . "\" />\n" );
		if ( Str::is_non_empty( $link ) ) {
			$allowed_tags = [
				'link' => [
					'href' => [],
					'rel'  => [],
				],
			];
			echo wp_kses( $link, $allowed_tags );
		}
	}

	/**
	 * Get pagination base.
	 *
	 * @return string The pagination base.
	 */
	private function get_pagination_base() {
		global $wp_rewrite;

		return ( ! is_singular() || Post::is_home_static_page() ) ? trailingslashit( $wp_rewrite->pagination_base ) : '';
	}

	/**
	 * Credits.
	 *
	 * @param boolean $closing Is closing credits needed.
	 */
	private function credits( $closing = false ) {

		/**
		 * Disable credit in the HTML source.
		 *
		 * @param bool $remove
		 */
		if ( $this->do_filter( 'frontend/remove_credit_notice', false ) ) {
			return;
		}

		if ( false === $closing ) {
			if ( ! Helper::is_whitelabel() && ! defined( 'RANK_MATH_PRO_FILE' ) ) {
				echo "\n<!-- " . esc_html__( 'Search Engine Optimization by Rank Math - https://rankmath.com/', 'rank-math' ) . " -->\n";
			} elseif ( defined( 'RANK_MATH_PRO_FILE' ) ) {
				echo "\n<!-- " . esc_html__( 'Search Engine Optimization by Rank Math PRO - https://rankmath.com/', 'rank-math' ) . " -->\n";
			}
			return;
		}

		if ( ! Helper::is_whitelabel() ) {
			echo '<!-- /' . esc_html__( 'Rank Math WordPress SEO plugin', 'rank-math' ) . " -->\n\n";
		}
	}

	/**
	 * Start the Output Buffer.
	 *
	 * @since 1.0.29
	 */
	public function start_ob() {
		ob_start();
	}

	/**
	 * Use output buffering to force rewrite the title tag.
	 */
	public function rewrite_title() {
		global $wp_query;

		// Check if we're in the main query.
		$old_wp_query = null;
		if ( ! $wp_query->is_main_query() ) {
			$old_wp_query = $wp_query;
			wp_reset_query(); //phpcs:ignore -- This function is needed here to reset the query before running the head code.
		}

		$content = ob_get_clean();
		$title   = Paper::get()->get_title();
		if ( empty( $title ) ) {
			echo $content; // phpcs:ignore WordPress.Security.EscapeOutput.OutputNotEscaped -- This is the output buffer, escaping is unnecessary.
		}

		// Find all title tags, remove them, and add the new one.
		$content = preg_replace( '/<title.*?\/title>/i', '', $content );
		$content = str_replace( '<head>', '<head>' . "\n" . '<title>' . esc_html( $title ) . '</title>', $content );
		if ( ! empty( $old_wp_query ) ) {
			$GLOBALS['wp_query'] = $old_wp_query;
		}

		echo $content; // phpcs:ignore WordPress.Security.EscapeOutput.OutputNotEscaped -- This is the output buffer, escaping is unnecessary.
	}
}