<?php
/**
 * Plugin Name: Destination Section Nav
 * Description: Simple contextual navigation for parent pages/posts and their children (ideal for travel destination inner pages).
 * Version:     1.1.0
 * Author:      Syed Zeeshan Ali
 * Text Domain: destination-section-nav
 */

declare(strict_types=1);

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

final class DSN_Plugin {

	/**
	 * Meta key to store nav config.
	 */
	const META_KEY = '_dsn_nav_config';

	/**
	 * Bootstrap.
	 */
	public static function init() : void {
		// Meta box.
		add_action( 'add_meta_boxes', [ __CLASS__, 'register_meta_box' ] );
		add_action( 'save_post',      [ __CLASS__, 'save_meta_box' ], 10, 2 );

		// Shortcode.
		add_shortcode( 'destination_nav', [ __CLASS__, 'shortcode_nav' ] );

		// Frontend styles.
		add_action( 'wp_enqueue_scripts', [ __CLASS__, 'enqueue_styles' ] );

		// Admin assets for drag & drop in meta box.
		add_action( 'admin_enqueue_scripts', [ __CLASS__, 'admin_enqueue_scripts' ] );
	}

	/**
	 * Register meta box on pages and posts.
	 * Now in the main content area (under the editor), not in the sidebar.
	 */
	public static function register_meta_box() : void {
		$post_types = apply_filters( 'dsn_nav_post_types', [ 'page', 'post' ] );

		foreach ( $post_types as $post_type ) {
			add_meta_box(
				'dsn_nav_meta',
				__( 'Destination Section Navigation', 'destination-section-nav' ),
				[ __CLASS__, 'render_meta_box' ],
				$post_type,
				'normal',   // main column
				'default'   // after editor
			);
		}
	}

	/**
	 * Render meta box UI.
	 *
	 * @param \WP_Post $post Post object.
	 */
	public static function render_meta_box( \WP_Post $post ) : void {
		wp_nonce_field( 'dsn_nav_meta_save', 'dsn_nav_meta_nonce' );

		$config = get_post_meta( $post->ID, self::META_KEY, true );
		if ( ! is_array( $config ) ) {
			$config = [
				'mode'  => 'auto', // auto|manual|disabled
				'items' => [],
			];
		}

		$mode        = $config['mode'] ?? 'auto';
		$config_items = is_array( $config['items'] ?? null ) ? $config['items'] : [];

		// Get children of this post (direct children).
		$children = get_children( [
			'post_parent' => $post->ID,
			'post_type'   => $post->post_type,
			'post_status' => 'publish',
			'orderby'     => 'menu_order title',
			'order'       => 'ASC',
		] );

		$children = $children ? array_values( $children ) : [];
		$total    = count( $children );
		$per_page = 10;

		// Current page for pagination in the meta box.
		$current_page = isset( $_GET['dsn_child_page'] )
			? max( 1, intval( $_GET['dsn_child_page'] ) )
			: 1;

		$total_pages = max( 1, (int) ceil( $total / $per_page ) );
		if ( $current_page > $total_pages ) {
			$current_page = $total_pages;
		}

		$offset          = ( $current_page - 1 ) * $per_page;
		$children_paged  = array_slice( $children, $offset, $per_page );
		?>
		<p>
			<strong><?php esc_html_e( 'Navigation Mode', 'destination-section-nav' ); ?></strong>
		</p>

		<p>
			<label>
				<input type="radio" name="dsn_nav_mode" value="auto" <?php checked( $mode, 'auto' ); ?> />
				<?php esc_html_e( 'Automatic – show all direct children (custom labels/order still apply).', 'destination-section-nav' ); ?>
			</label><br/>
			<label>
				<input type="radio" name="dsn_nav_mode" value="manual" <?php checked( $mode, 'manual' ); ?> />
				<?php esc_html_e( 'Manual – choose specific child pages and order.', 'destination-section-nav' ); ?>
			</label><br/>
			<label>
				<input type="radio" name="dsn_nav_mode" value="disabled" <?php checked( $mode, 'disabled' ); ?> />
				<?php esc_html_e( 'Disabled – no navigation for this root.', 'destination-section-nav' ); ?>
			</label>
		</p>

		<hr/>

		<p>
			<strong><?php esc_html_e( 'Child pages navigation', 'destination-section-nav' ); ?></strong><br/>
			<small>
				<?php esc_html_e( 'You can set a custom display label and drag & drop to change the navigation order.', 'destination-section-nav' ); ?>
			</small>
		</p>

		<?php if ( ! empty( $children ) ) : ?>

			<table class="widefat striped dsn-nav-children-table" id="dsn-nav-children-table">
				<thead>
					<tr>
						<th style="width:24px;"></th>
						<th><?php esc_html_e( 'Child Page', 'destination-section-nav' ); ?></th>
						<th><?php esc_html_e( 'Display Label (optional)', 'destination-section-nav' ); ?></th>
					</tr>
				</thead>
				<tbody>
				<?php
				foreach ( $children_paged as $index => $child ) :
					$child_id     = $child->ID;
					$item_config  = $config_items[ $child_id ] ?? [];
					$enabled      = isset( $item_config['enabled'] ) ? (bool) $item_config['enabled'] : true;
					$label        = isset( $item_config['label'] ) ? (string) $item_config['label'] : '';
					$order        = isset( $item_config['order'] ) ? (int) $item_config['order'] : 0;
					if ( $order <= 0 ) {
						// Default order for new items (relative to their position).
						$order = $offset + $index + 1;
					}
					?>
					<tr class="dsn-nav-child-row" data-child-id="<?php echo esc_attr( (string) $child_id ); ?>">
						<td class="dsn-nav-sort-handle" style="cursor:move;">&#x2630;</td>
						<td>
							<label>
								<input type="checkbox"
									name="dsn_nav_items[<?php echo esc_attr( (string) $child_id ); ?>][enabled]"
									value="1"
									<?php checked( $enabled ); ?>
								/>
								<?php echo esc_html( get_the_title( $child ) ); ?>
							</label>
							<input type="hidden"
								name="dsn_nav_items[<?php echo esc_attr( (string) $child_id ); ?>][order]"
								class="dsn-nav-order-input"
								value="<?php echo esc_attr( (string) $order ); ?>"
							/>
						</td>
						<td>
							<input type="text"
								class="regular-text"
								name="dsn_nav_items[<?php echo esc_attr( (string) $child_id ); ?>][label]"
								value="<?php echo esc_attr( $label ); ?>"
								placeholder="<?php esc_attr_e( 'Leave empty to use page title', 'destination-section-nav' ); ?>"
							/>
						</td>
					</tr>
				<?php endforeach; ?>
				</tbody>
			</table>

			<?php if ( $total_pages > 1 ) : ?>
				<p class="dsn-nav-pagination">
					<?php
					$base_url = remove_query_arg( [ 'dsn_child_page' ] );
					for ( $i = 1; $i <= $total_pages; $i++ ) :
						if ( $i === $current_page ) :
							?>
							<span class="dsn-nav-page current"><?php echo esc_html( (string) $i ); ?></span>
							<?php
						else :
							$url = add_query_arg(
								[
									'dsn_child_page' => $i,
								],
								$base_url
							);
							?>
							<a class="dsn-nav-page" href="<?php echo esc_url( $url . '#dsn_nav_meta' ); ?>">
								<?php echo esc_html( (string) $i ); ?>
							</a>
							<?php
						endif;
					endfor;
					?>
				</p>
			<?php endif; ?>

		<?php else : ?>
			<p>
				<em><?php esc_html_e( 'This post currently has no child pages. Automatic and manual modes will have nothing to show.', 'destination-section-nav' ); ?></em>
			</p>
		<?php
		endif;
	}

	/**
	 * Save meta box.
	 *
	 * @param int      $post_id Post ID.
	 * @param \WP_Post $post    Post object.
	 */
	public static function save_meta_box( int $post_id, \WP_Post $post ) : void {
		// Check nonce.
		if ( ! isset( $_POST['dsn_nav_meta_nonce'] ) || ! wp_verify_nonce( sanitize_text_field( wp_unslash( $_POST['dsn_nav_meta_nonce'] ) ), 'dsn_nav_meta_save' ) ) {
			return;
		}

		// Autosave?
		if ( defined( 'DOING_AUTOSAVE' ) && DOING_AUTOSAVE ) {
			return;
		}

		// Proper capability check.
		if ( 'page' === $post->post_type ) {
			if ( ! current_user_can( 'edit_page', $post_id ) ) {
				return;
			}
		} else {
			if ( ! current_user_can( 'edit_post', $post_id ) ) {
				return;
			}
		}

		$mode = isset( $_POST['dsn_nav_mode'] ) ? sanitize_text_field( wp_unslash( $_POST['dsn_nav_mode'] ) ) : 'auto';
		if ( ! in_array( $mode, [ 'auto', 'manual', 'disabled' ], true ) ) {
			$mode = 'auto';
		}

		// Load existing config to merge, so pagination does not wipe previous pages.
		$existing = get_post_meta( $post_id, self::META_KEY, true );
		if ( ! is_array( $existing ) ) {
			$existing = [
				'mode'  => 'auto',
				'items' => [],
			];
		}
		$existing_items = is_array( $existing['items'] ?? null ) ? $existing['items'] : [];

		$items_raw = isset( $_POST['dsn_nav_items'] ) && is_array( $_POST['dsn_nav_items'] )
			? $_POST['dsn_nav_items']
			: [];

		foreach ( $items_raw as $child_id_str => $row ) {
			$child_id = absint( $child_id_str );
			if ( $child_id <= 0 ) {
				continue;
			}

			$row = is_array( $row ) ? $row : [];

			$enabled = ! empty( $row['enabled'] );
			$label   = isset( $row['label'] ) ? sanitize_text_field( wp_unslash( $row['label'] ) ) : '';
			$order   = isset( $row['order'] ) ? (int) $row['order'] : 0;

			$existing_items[ $child_id ] = [
				'enabled' => $enabled,
				'label'   => $label,
				'order'   => $order,
			];
		}

		$config = [
			'mode'  => $mode,
			'items' => $existing_items,
		];

		update_post_meta( $post_id, self::META_KEY, $config );
	}

	/**
	 * Shortcode callback: [destination_nav]
	 *
	 * @param array $atts Shortcode attributes (unused for now).
	 * @return string
	 */
	public static function shortcode_nav( array $atts ) : string {
		if ( ! is_singular() ) {
			return '';
		}

		global $post;

		if ( ! $post instanceof \WP_Post ) {
			return '';
		}

		$root_id = self::get_root_post_id( $post->ID );
		if ( ! $root_id ) {
			return '';
		}

		$config = get_post_meta( $root_id, self::META_KEY, true );
		if ( ! is_array( $config ) ) {
			$config = [
				'mode'  => 'auto',
				'items' => [],
			];
		}

		$mode         = $config['mode'] ?? 'auto';
		$config_items = is_array( $config['items'] ?? null ) ? $config['items'] : [];

		if ( 'disabled' === $mode ) {
			return '';
		}

		// All direct children of the root.
		$children = get_children( [
			'post_parent' => $root_id,
			'post_status' => 'publish',
			'orderby'     => 'menu_order title',
			'order'       => 'ASC',
		] );

		if ( empty( $children ) ) {
			return '';
		}

		$children = array_values( $children );
		$items    = [];

		foreach ( $children as $index => $child ) {
			$child_id    = $child->ID;
			$item_config = $config_items[ $child_id ] ?? [];

			$enabled = isset( $item_config['enabled'] ) ? (bool) $item_config['enabled'] : true;
			$label   = isset( $item_config['label'] ) ? (string) $item_config['label'] : '';
			$order   = isset( $item_config['order'] ) ? (int) $item_config['order'] : 0;

			if ( $order <= 0 ) {
				$order = $index + 1;
			}

			// In manual mode we respect the checkbox; in auto mode we include all.
			if ( 'manual' === $mode && ! $enabled ) {
				continue;
			}

			$items[] = [
				'post'  => $child,
				'label' => $label,
				'order' => $order,
			];
		}

		if ( empty( $items ) ) {
			return '';
		}

		// Sort by custom order.
		usort(
			$items,
			static function ( array $a, array $b ) : int {
				$ao = $a['order'];
				$bo = $b['order'];

				if ( $ao === $bo ) {
					return 0;
				}

				return ( $ao < $bo ) ? -1 : 1;
			}
		);

		$current_id = $post->ID;
		$root_title = get_the_title( $root_id );

		ob_start();
		?>
		<nav class="dsn-nav" aria-label="<?php echo esc_attr( $root_title ); ?>">
			<ul class="dsn-nav__list">
				<?php foreach ( $items as $item ) : ?>
					<?php
					$item_post   = $item['post'];
					$item_id     = $item_post->ID;
					$is_current  = ( $item_id === $current_id );
					$classes     = [ 'dsn-nav__item' ];
					if ( $is_current ) {
						$classes[] = 'dsn-nav__item--current';
					}
					$text = '' !== $item['label']
						? $item['label']
						: get_the_title( $item_post );
					?>
					<li class="<?php echo esc_attr( implode( ' ', $classes ) ); ?>">
						<a href="<?php echo esc_url( get_permalink( $item_post ) ); ?>" class="dsn-nav__link">
							<?php echo esc_html( $text ); ?>
						</a>
					</li>
				<?php endforeach; ?>
			</ul>
		</nav>
		<?php

		return (string) ob_get_clean();
	}

	/**
	 * Find the "root" post for a given post ID (top-most ancestor).
	 *
	 * @param int $post_id Post ID.
	 * @return int Root post ID.
	 */
	private static function get_root_post_id( int $post_id ) : int {
		$ancestors = get_post_ancestors( $post_id );
		if ( ! empty( $ancestors ) ) {
			// Ancestors are ordered from closest parent to furthest.
			return (int) end( $ancestors );
		}

		return $post_id;
	}

	/**
	 * Enqueue minimal CSS (frontend).
	 */
	public static function enqueue_styles() : void {
		$css = '
		.dsn-nav {
			margin: 0 0 1.5em;
		}
		.dsn-nav__list {
			list-style: none;
			margin: 0;
			padding: 0;
		}
		.dsn-nav__item {
			margin: 0;
		}
		.dsn-nav__link {
			display: block;
			padding: 0.4em 0.6em;
			text-decoration: none;
		}
		.dsn-nav__item--current > .dsn-nav__link {
			font-weight: 600;
			text-decoration: underline;
		}';

		wp_register_style( 'destination-section-nav', false );
		wp_enqueue_style( 'destination-section-nav' );
		wp_add_inline_style( 'destination-section-nav', $css );
	}

	/**
	 * Admin assets: enable drag & drop sorting for the child list.
	 */
	public static function admin_enqueue_scripts( string $hook_suffix ) : void {
		if ( 'post.php' !== $hook_suffix && 'post-new.php' !== $hook_suffix ) {
			return;
		}

		$screen = get_current_screen();
		if ( ! $screen ) {
			return;
		}

		$post_types = apply_filters( 'dsn_nav_post_types', [ 'page', 'post' ] );
		if ( ! in_array( $screen->post_type, $post_types, true ) ) {
			return;
		}

		// Drag & drop.
		wp_enqueue_script( 'jquery-ui-sortable' );

		$inline_js = '
		jQuery(function($){
			var $table = $("#dsn-nav-children-table");
			if (!$table.length) {
				return;
			}
			var $tbody = $table.find("tbody");
			$tbody.sortable({
				handle: ".dsn-nav-sort-handle",
				items: "> tr",
				update: function(){
					$tbody.find("tr").each(function(index){
						$(this).find(".dsn-nav-order-input").val(index + 1);
					});
				}
			});
		});
		';

		wp_add_inline_script( 'jquery-ui-sortable', $inline_js );

		$inline_css = '
		#dsn-nav-children-table .dsn-nav-sort-handle {
			text-align: center;
			width: 24px;
		}
		.dsn-nav-pagination {
			margin-top: 8px;
		}
		.dsn-nav-pagination .dsn-nav-page {
			display: inline-block;
			margin-right: 4px;
			padding: 2px 6px;
			text-decoration: none;
		}
		.dsn-nav-pagination .dsn-nav-page.current {
			font-weight: 600;
			text-decoration: underline;
		}
		';

		wp_register_style( 'dsn-nav-admin', false );
		wp_enqueue_style( 'dsn-nav-admin' );
		wp_add_inline_style( 'dsn-nav-admin', $inline_css );
	}
}

DSN_Plugin::init();