<?php
if ( ! defined( 'ABSPATH' ) ) {
	exit;
}

/**
 * Class Awp_Table_Of_Contents
 *
 * Provides shared heading-parsing/anchor-injection logic used by both the
 * Table of Contents widget and its matching block, plus the the_content
 * filter that gives each heading a stable id= to link to.
 */
class Awp_Table_Of_Contents extends WP_Widget {
	protected $defaults;

	function __construct() {
		$this->defaults = array(
			'title'    => __( 'Table of Contents', 'advance-widget-pack' ),
			'min'      => '2',
			'max'      => '3',
		);
		$widget_ops = array(
			'classname'   => 'awp_toc awp_widget',
			'description' => __( 'Widget to display a table of contents for the current post.', 'advance-widget-pack' ),
		);
		$control_ops = array(
			'id_base' => 'awp_toc',
			'width'   => 200,
			'height'  => 250,
		);
		parent::__construct( 'awp_toc', __( 'AWP Table of Contents', 'advance-widget-pack' ), $widget_ops, $control_ops );
	}

	public function widget( $args, $instance ) {
		$instance = wp_parse_args( (array) $instance, $this->defaults );
		$title    = apply_filters( 'widget_title', $instance['title'] );

		$post_id = get_the_ID();
		if ( ! $post_id ) {
			return;
		}

		$headings = self::get_headings( $post_id, absint( $instance['min'] ), absint( $instance['max'] ) );

		if ( ! $headings ) {
			return;
		}

		echo $args['before_widget']; // phpcs:ignore WordPress.Security.EscapeOutput.OutputNotEscaped -- sidebar-provided wrapper markup, trusted per WP core convention.
		if ( ! empty( $title ) ) {
			echo $args['before_title'] . esc_html( $title ) . $args['after_title']; // phpcs:ignore WordPress.Security.EscapeOutput.OutputNotEscaped -- title text is esc_html()'d; before/after_title are sidebar-provided wrapper markup.
		}
		self::render_list( $headings );
		echo $args['after_widget']; // phpcs:ignore WordPress.Security.EscapeOutput.OutputNotEscaped -- sidebar-provided wrapper markup, trusted per WP core convention.
	}

	/**
	 * Extracts headings (with pre-assigned anchor ids) from a post's content,
	 * within the given heading-level range (2-6).
	 *
	 * Cached two ways: a request-scoped static cache (so rendering both the
	 * widget and the block for the same post in one request only parses
	 * once), and a transient (keyed by awp_cache_generation() like every
	 * other AWP query) so repeat page views skip the do_blocks()/do_shortcode()
	 * + regex work entirely, which is otherwise the most expensive per-request
	 * operation in the plugin on posts with substantial content.
	 *
	 * @param int $post_id Post to extract headings from.
	 * @param int $min     Minimum heading level (e.g. 2 for H2).
	 * @param int $max     Maximum heading level (e.g. 3 for H3).
	 * @return array[] List of array( 'level' => int, 'text' => string, 'anchor' => string ).
	 */
	public static function get_headings( $post_id, $min = 2, $max = 3 ) {
		$min = max( 2, min( 6, absint( $min ) ?: 2 ) );
		$max = max( $min, min( 6, absint( $max ) ?: 3 ) );

		static $request_cache = array();
		// Includes the generation so an in-request post edit (which bumps the
		// generation) can't serve a stale result from before the edit — the
		// static cache must invalidate exactly when the transient would.
		$request_key = awp_cache_generation() . '_' . $post_id . '_' . $min . '_' . $max;

		if ( isset( $request_cache[ $request_key ] ) ) {
			return $request_cache[ $request_key ];
		}

		// Re-entrancy guard: do_blocks() below re-renders the post's full
		// block tree, including this TOC block itself if it's placed inside
		// the same post it's summarizing. That second render_block() call
		// reaches this same method again before the first call has finished
		// (and therefore before $request_cache above is populated), which
		// without this guard recurses until PHP's memory limit is exhausted.
		// Returning an empty list on the nested call is safe: it only
		// affects what do_blocks() renders internally for its own throwaway
		// copy of the content, not the actual headings list returned to the
		// original caller once do_blocks() finishes below.
		static $in_progress = array();
		if ( ! empty( $in_progress[ $post_id ] ) ) {
			return array();
		}

		$cache_key = 'awp_toc_' . $request_key;
		$headings  = get_transient( $cache_key );

		if ( false === $headings ) {
			$post = get_post( $post_id );
			if ( ! $post ) {
				return array();
			}

			$in_progress[ $post_id ] = true;

			// try/finally so a throwing block render_callback or shortcode
			// handler still clears the flag — otherwise it would stay stuck
			// "true" for the rest of the request, silently making every
			// later TOC render for this post_id return an empty list.
			try {
				// Run blocks/shortcodes through do_blocks()+do_shortcode() to
				// get real rendered heading markup, then always (re)assign
				// anchor ids ourselves — the_content's own
				// awp_toc_filter_the_content is gated to the main singular
				// loop and won't have run for this call.
				$content = do_blocks( $post->post_content );
				$content = do_shortcode( $content );
				$content = awp_toc_add_heading_ids( $content );
			} finally {
				unset( $in_progress[ $post_id ] );
			}

			$pattern = '#<h([' . $min . '-' . $max . '])[^>]*\bid=["\']([^"\']+)["\'][^>]*>(.*?)</h\1>#is';

			$headings = array();
			if ( preg_match_all( $pattern, $content, $matches, PREG_SET_ORDER ) ) {
				foreach ( $matches as $match ) {
					$headings[] = array(
						'level'  => (int) $match[1],
						'anchor' => $match[2],
						'text'   => wp_strip_all_tags( $match[3] ),
					);
				}
			}

			set_transient( $cache_key, $headings, 15 * MINUTE_IN_SECONDS );
		}

		$request_cache[ $request_key ] = $headings;

		return $headings;
	}

	/**
	 * Renders a nested <ul> of heading links. Shared by the widget and the
	 * Table of Contents block's render.php.
	 *
	 * @param array[] $headings From get_headings().
	 */
	public static function render_list( $headings ) {
		if ( ! $headings ) {
			return;
		}

		$base_level = $headings[0]['level'];
		?>
		<ul class="awp-toc-list">
			<?php foreach ( $headings as $heading ) : ?>
				<li class="awp-toc-item awp-toc-level-<?php echo esc_attr( $heading['level'] ); ?>">
					<a href="#<?php echo esc_attr( $heading['anchor'] ); ?>"><?php echo esc_html( $heading['text'] ); ?></a>
				</li>
			<?php endforeach; ?>
		</ul>
		<?php
	}

	public function form( $instance ) {
		$instance = wp_parse_args( (array) $instance, $this->defaults );
		?>
		<p>
			<label for="<?php echo esc_attr( $this->get_field_id( 'title' ) ); ?>"><?php esc_html_e( 'Title', 'advance-widget-pack' ); ?></label>
			<input class="widefat" id="<?php echo esc_attr( $this->get_field_id( 'title' ) ); ?>" name="<?php echo esc_attr( $this->get_field_name( 'title' ) ); ?>" type="text" value="<?php echo esc_attr( $instance['title'] ); ?>" />
		</p>
		<p>
			<label for="<?php echo esc_attr( $this->get_field_id( 'min' ) ); ?>"><?php esc_html_e( 'Minimum heading level', 'advance-widget-pack' ); ?></label>
			<select id="<?php echo esc_attr( $this->get_field_id( 'min' ) ); ?>" name="<?php echo esc_attr( $this->get_field_name( 'min' ) ); ?>">
				<?php for ( $i = 2; $i <= 6; $i++ ) : ?>
					<option value="<?php echo esc_attr( $i ); ?>" <?php selected( $instance['min'], $i ); ?>>H<?php echo esc_html( $i ); ?></option>
				<?php endfor; ?>
			</select>
		</p>
		<p>
			<label for="<?php echo esc_attr( $this->get_field_id( 'max' ) ); ?>"><?php esc_html_e( 'Maximum heading level', 'advance-widget-pack' ); ?></label>
			<select id="<?php echo esc_attr( $this->get_field_id( 'max' ) ); ?>" name="<?php echo esc_attr( $this->get_field_name( 'max' ) ); ?>">
				<?php for ( $i = 2; $i <= 6; $i++ ) : ?>
					<option value="<?php echo esc_attr( $i ); ?>" <?php selected( $instance['max'], $i ); ?>>H<?php echo esc_html( $i ); ?></option>
				<?php endfor; ?>
			</select>
		</p>
		<?php
	}

	public function update( $new_instance, $old_instance ) {
		$instance          = $old_instance;
		$instance['title'] = sanitize_text_field( $new_instance['title'] );
		$instance['min']   = max( 2, min( 6, absint( $new_instance['min'] ) ) );
		$instance['max']   = max( $instance['min'], min( 6, absint( $new_instance['max'] ) ) );
		return $instance;
	}
}

/**
 * Injects a stable id="" attribute into every heading in the given HTML,
 * so the Table of Contents widget/block (and any external deep link) has a
 * real anchor to point at. Anchor uniqueness is tracked per-call (not
 * globally), matching how it's used: once for the real page render via the
 * the_content filter below, and once whenever get_headings() re-derives the
 * same content for the widget/block itself.
 *
 * @param string $content HTML content containing headings.
 * @return string
 */
function awp_toc_add_heading_ids( $content ) {
	$used_anchors = array();

	return preg_replace_callback(
		'#<h([2-6])([^>]*)>(.*?)</h\1>#is',
		function ( $match ) use ( &$used_anchors ) {
			// Leave existing ids alone (theme/other plugin may have already set one).
			if ( preg_match( '#\bid=["\'][^"\']+["\']#i', $match[2] ) ) {
				return $match[0];
			}

			$text   = wp_strip_all_tags( $match[3] );
			$anchor = sanitize_title( $text );

			if ( '' === $anchor ) {
				$anchor = 'section';
			}

			$base = $anchor;
			$i    = 2;
			while ( isset( $used_anchors[ $anchor ] ) ) {
				$anchor = $base . '-' . $i;
				++$i;
			}
			$used_anchors[ $anchor ] = true;

			return '<h' . $match[1] . $match[2] . ' id="' . esc_attr( $anchor ) . '">' . $match[3] . '</h' . $match[1] . '>';
		},
		$content
	);
}

/**
 * Applies awp_toc_add_heading_ids() to real post content on singular views,
 * so headings rendered on the page actually have the anchors the Table of
 * Contents widget/block links to.
 *
 * @param string $content Post content.
 * @return string
 */
function awp_toc_filter_the_content( $content ) {
	if ( ! is_singular() || ! in_the_loop() || ! is_main_query() ) {
		return $content;
	}

	return awp_toc_add_heading_ids( $content );
}
add_filter( 'the_content', 'awp_toc_filter_the_content', 20 );