<?php
/**
 * AKSRT Docs Presenter
 *
 * Builds document tree structures, breadcrumb chains,
 * and chapter navigation for the docs mode.
 *
 * @package AKSRT
 */

defined('ABSPATH') || exit;

class AKSRT_Docs_Presenter {

    private static $instance = null;

    private function __construct() {}

    public static function get_instance(): self {
        if (null === self::$instance) {
            self::$instance = new self();
        }
        return self::$instance;
    }

    /**
     * Get the document root page ID for a given page.
     *
     * @param int $page_id Current page ID.
     * @return int Root page ID (self if top-level, parent otherwise).
     */
    public function get_root_id(int $page_id): int {
        $parent_id = wp_get_post_parent_id($page_id);
        return $parent_id ?: $page_id;
    }

    /**
     * Build a flat ordered list of all pages under a document root.
     *
     * @param int $root_id Root page ID.
     * @param int $max_depth Maximum depth (default 4).
     * @return array Array of page objects with added '_depth' property.
     */
    public function get_flat_tree(int $root_id, int $max_depth = 4): array {
        $result = [];
        $this->collect_children($root_id, $result, 0, $max_depth);
        return $result;
    }

    /**
     * Recursive helper to collect pages in order.
     */
    private function collect_children(int $parent_id, array &$result, int $depth, int $max_depth): void {
        if ($depth >= $max_depth) {
            return;
        }

        $children = get_pages([
            'parent'      => $parent_id,
            'sort_column' => 'menu_order, post_title',
            'sort_order'  => 'ASC',
            'post_status' => 'publish',
        ]);

        foreach ($children as $child) {
            $child->_depth = $depth;
            $result[] = $child;
            $this->collect_children($child->ID, $result, $depth + 1, $max_depth);
        }
    }

    /**
     * Get sibling pages for chapter navigation (prev/next).
     *
     * @param int $page_id Current page ID.
     * @return array{prev: object|null, next: object|null}
     */
    public function get_chapter_nav(int $page_id): array {
        $parent_id = wp_get_post_parent_id($page_id);

        $siblings = get_pages([
            'parent'      => $parent_id ?: 0,
            'sort_column' => 'menu_order, post_title',
            'sort_order'  => 'ASC',
            'post_status' => 'publish',
        ]);

        $current_index = -1;
        foreach ($siblings as $i => $sibling) {
            if ((int) $sibling->ID === $page_id) {
                $current_index = $i;
                break;
            }
        }

        $prev = $current_index > 0 ? $siblings[$current_index - 1] : null;
        $next = ($current_index >= 0 && $current_index < count($siblings) - 1)
            ? $siblings[$current_index + 1]
            : null;

        return ['prev' => $prev, 'next' => $next];
    }

    /**
     * Get root-level document pages for the document navigation index.
     *
     * @param string $order Sort order: 'menu_order', 'date', 'title'.
     * @return array
     */
    public function get_root_pages(string $order = 'menu_order'): array {
        $sort_column = 'menu_order, post_title';
        if ($order === 'title') {
            $sort_column = 'post_title';
        } elseif ($order === 'date') {
            $sort_column = 'post_date';
        }

        return get_pages([
            'sort_column'  => $sort_column,
            'sort_order'   => 'ASC',
            'parent'       => 0,
            'hierarchical' => 0,
            'post_status'  => 'publish',
        ]);
    }

    /**
     * Get recently modified pages for the sidebar.
     *
     * @param int $count Number of pages to return.
     * @return array
     */
    public function get_recent_pages(int $count = 8): array {
        return get_pages([
            'sort_column' => 'post_modified',
            'sort_order'  => 'DESC',
            'number'      => $count,
            'post_status' => 'publish',
        ]);
    }

    /**
     * Build breadcrumb trail for a document page.
     *
     * @param int $page_id Current page ID.
     * @return array Array of {id, title, url} objects.
     */
    public function get_breadcrumbs(int $page_id): array {
        $trail = [];
        $current = get_post($page_id);

        while ($current) {
            array_unshift($trail, [
                'id'    => $current->ID,
                'title' => $current->post_title,
                'url'   => get_permalink($current->ID),
            ]);
            $parent_id = wp_get_post_parent_id($current->ID);
            $current = $parent_id ? get_post($parent_id) : null;
        }

        return $trail;
    }

    /**
     * Search document pages by keyword.
     *
     * @param string $keyword Search keyword.
     * @param int    $root_id Optional root page ID to scope search.
     * @param int    $limit   Max results.
     * @return array Array of page objects with 'url' and 'excerpt' added.
     */
    public function search_pages(string $keyword, int $root_id = 0, int $limit = 20): array {
        $args = [
            'post_type'      => 'page',
            'post_status'    => 'publish',
            's'              => $keyword,
            'posts_per_page' => $limit,
            'orderby'        => 'relevance',
        ];

        if ($root_id > 0) {
            $tree_ids = [$root_id];
            $this->collect_children($root_id, $tree_ids, 0, 4);
            $ids = array_map(static function ($item) {
                return is_object($item) ? $item->ID : (int) $item;
            }, $tree_ids);
            $ids[] = $root_id;
            $args['post__in'] = array_unique($ids);
        }

        $query = new WP_Query($args);
        $results = [];

        foreach ($query->posts as $post) {
            $results[] = [
                'id'       => $post->ID,
                'title'    => $post->post_title,
                'url'      => get_permalink($post->ID),
                'excerpt'  => wp_trim_words(wp_strip_all_tags($post->post_content), 30),
                'modified' => $post->post_modified,
                'parent'   => (int) $post->post_parent,
            ];
        }

        wp_reset_postdata();
        return $results;
    }

    /**
     * Check whether a given page belongs to the docs mode.
     *
     * @param int $page_id Page ID.
     * @return bool
     */
    public function is_docs_page(int $page_id): bool {
        if (!class_exists('AKSRT_Settings')) {
            return false;
        }

        $settings = AKSRT_Settings::get_docs_mode_settings();
        if (empty($settings['enabled'])) {
            return false;
        }

        $template = get_page_template_slug($page_id);
        return in_array($template, [
            'templates/pages/page-documentnav.php',
            'templates/pages/page-special.php',
        ], true);
    }
}