<?php
declare(strict_types=1);

namespace WPMultiCity;

final class Router
{
    public static function register(): void
    {
        \add_action('wp', [self::class, 'route'], 9999);
        \add_filter('query_vars', [self::class, 'add_town_query_var']);
    }

    public static function add_town_query_var(array $vars): array
    {
        $vars[] = 'town';
        return $vars;
    }

    public static function route(): void
    {
        if (\is_admin()) {
            return;
        }
        if (\defined('DOING_AJAX') && \DOING_AJAX) {
            return;
        }
        $town_slug = Helpers::current_town();
        if ($town_slug === null) {
            return;
        }
        $main = Helpers::main_town_slug();
        if ($main !== null && $town_slug === $main) {
            return;
        }
        $request_uri = $_SERVER['REQUEST_URI'] ?? '/';
        if (!Helpers::is_routable_path($request_uri)) {
            return;
        }

        $url_original = self::strip_town_prefix($request_uri, $town_slug);

        if (self::is_root($url_original)) {
            $term = Helpers::get_term_by_slug($town_slug);
            if ($term === null) {
                return;
            }
            $page_id = 0;
            if (\function_exists('get_field')) {
                $page_id = (int) (\get_field('main_page_alt', 'town_' . $term->term_id) ?? 0);
            }
            if (!$page_id) {
                $fallback = Helpers::index_town_alt_page_id();
                if ($fallback === null) {
                    return;
                }
                $page_id = $fallback;
            }
            self::install_query($page_id, $town_slug, true);
            return;
        }

        // Internal page handling lands in Task 13.
    }

    private static function strip_town_prefix(string $uri, string $town_slug): string
    {
        $path = strtok($uri, '?');
        $query = (strpos($uri, '?') !== false) ? substr($uri, strpos($uri, '?')) : '';
        $new_path = preg_replace('#^/' . preg_quote($town_slug, '#') . '(/|$)#', '/', (string) $path);
        return ($new_path ?? '/') . $query;
    }

    private static function is_root(string $url): bool
    {
        $path = strtok($url, '?');
        return $path === '/' || $path === false || $path === '';
    }

    private static function install_query(int $page_id, string $town_slug, bool $is_front_page): void
    {
        global $wp_query, $wp_the_query, $post;
        $post = \get_post($page_id);
        $wp_query = new \WP_Query(['page_id' => $page_id, 'town' => $town_slug]);
        $wp_query->is_page = true;
        if ($is_front_page) {
            $wp_query->is_front_page = true;
        }
        $wp_the_query = $wp_query;
        \status_header(200);
    }
}