<?php
/**
 * Extracts label/href pairs (with nested dropdowns) from a <nav> fragment.
 * Pure DOM/string parsing, no WordPress calls.
 *
 * @package Esipher
 */

namespace Esipher;

if ( ! defined( 'ABSPATH' ) ) {
	exit;
}

/**
 * Maps a raw <nav>...</nav> HTML fragment into an ordered list of
 * ['label' => string, 'href' => string, 'children' => array] items.
 */
class Nav_Mapper {

	/**
	 * Map a <nav> fragment to a nested link list.
	 *
	 * @param string $nav_html Raw outerHTML of a single <nav> element, as
	 *                         produced by Html_Parser::parse()->nav_html.
	 *
	 * @return array[]
	 */
	public function map( $nav_html ) {
		$dom = new \DOMDocument();

		$previous_setting = libxml_use_internal_errors( true );
		$dom->loadHTML(
			'<?xml encoding="utf-8" ?>' . $nav_html,
			LIBXML_NOWARNING | LIBXML_NOERROR
		);
		libxml_clear_errors();
		libxml_use_internal_errors( $previous_setting );

		$xpath     = new \DOMXPath( $dom );
		$nav_nodes = $xpath->query( '//nav' );

		if ( ! $nav_nodes || 0 === $nav_nodes->length ) {
			return array();
		}

		$nav = $nav_nodes->item( 0 );
		$ul  = $xpath->query( './ul', $nav );

		if ( $ul && $ul->length ) {
			return $this->map_list( $xpath, $ul->item( 0 ) );
		}

		// No wrapping <ul> — fall back to any <a> tags directly under <nav>.
		return $this->map_links( $xpath, $nav );
	}

	/**
	 * Map every direct <li> child of a <ul> into a link item, recursing
	 * into nested <ul>s for dropdown children.
	 *
	 * @param \DOMXPath   $xpath Query interface.
	 * @param \DOMElement $ul    The <ul> element.
	 *
	 * @return array[]
	 */
	private function map_list( \DOMXPath $xpath, \DOMElement $ul ) {
		$items = array();

		foreach ( $xpath->query( './li', $ul ) as $li ) {
			$items[] = $this->map_item( $xpath, $li );
		}

		return $items;
	}

	/**
	 * Map a single <li>: its own link plus any nested dropdown.
	 *
	 * @param \DOMXPath   $xpath Query interface.
	 * @param \DOMElement $li    The <li> element.
	 *
	 * @return array{label: string, href: string, children: array[]}
	 */
	private function map_item( \DOMXPath $xpath, \DOMElement $li ) {
		$label = '';
		$href  = '';

		$anchor_nodes = $xpath->query( './a', $li );

		if ( $anchor_nodes && $anchor_nodes->length ) {
			$anchor = $anchor_nodes->item( 0 );
			$label  = trim( $anchor->textContent );
			$href   = $anchor->getAttribute( 'href' );
		}

		$children = array();
		$child_ul = $xpath->query( './ul', $li );

		if ( $child_ul && $child_ul->length ) {
			$children = $this->map_list( $xpath, $child_ul->item( 0 ) );
		}

		return array(
			'label'    => $label,
			'href'     => $href,
			'children' => $children,
		);
	}

	/**
	 * Map <a> tags that are direct children of <nav> (no <ul> wrapper).
	 *
	 * @param \DOMXPath   $xpath Query interface.
	 * @param \DOMElement $nav   The <nav> element.
	 *
	 * @return array[]
	 */
	private function map_links( \DOMXPath $xpath, \DOMElement $nav ) {
		$items = array();

		foreach ( $xpath->query( './a', $nav ) as $anchor ) {
			$items[] = array(
				'label'    => trim( $anchor->textContent ),
				'href'     => $anchor->getAttribute( 'href' ),
				'children' => array(),
			);
		}

		return $items;
	}
}