<?php
/**
 * Server Class
 * 
 * Handles serving static HTML files as a PHP fallback when .htaccess rules don't work.
 */

// Prevent direct access
if (!defined('ABSPATH')) {
    exit;
}

class WP_To_HTML_Server {
    
    /**
     * Single instance
     */
    private static $instance = null;
    
    /**
     * Get singleton instance
     */
    public static function get_instance() {
        if (null === self::$instance) {
            self::$instance = new self();
        }
        return self::$instance;
    }
    
    /**
     * Constructor
     */
    private function __construct() {
        // Hook early to serve cached content before WordPress runs
        add_action('template_redirect', array($this, 'maybe_serve_cached'), 0);
    }
    
    /**
     * Check if we should serve a cached file and do so if appropriate
     */
    public function maybe_serve_cached() {
        // Check if generation is enabled
        $settings = WP_To_HTML::get_settings();
        if (!$settings['enabled']) {
            return;
        }
        
        // Don't serve cached content for logged-in users
        if (is_user_logged_in()) {
            return;
        }
        
        // Don't serve for POST requests
        if ($_SERVER['REQUEST_METHOD'] === 'POST') {
            return;
        }
        
        // Don't serve for requests with query strings
        if (!empty($_SERVER['QUERY_STRING'])) {
            return;
        }
        
        // Don't serve for admin pages
        if (is_admin()) {
            return;
        }
        
        // Don't serve for AJAX requests
        if (wp_doing_ajax()) {
            return;
        }
        
        // Don't serve for REST API requests
        if (defined('REST_REQUEST') && REST_REQUEST) {
            return;
        }
        
        // Get the current request URI
        $request_uri = $_SERVER['REQUEST_URI'];
        
        // Remove leading slash and get cache path
        $path = trim(parse_url($request_uri, PHP_URL_PATH), '/');
        
        if (empty($path)) {
            $cache_file = WP_TO_HTML_CACHE_DIR . 'index.html';
        } else {
            $cache_file = WP_TO_HTML_CACHE_DIR . $path . '/index.html';
        }
        
        // Check if cached file exists
        if (!file_exists($cache_file)) {
            return;
        }
        
        // Serve the cached file
        $this->serve_file($cache_file);
    }
    
    /**
     * Serve a cached HTML file
     * 
     * @param string $file_path Path to the cached file
     */
    private function serve_file($file_path) {
        // Set headers
        header('Content-Type: text/html; charset=utf-8');
        header('X-WP-To-HTML: served');
        header('Cache-Control: public, max-age=3600');
        
        // Get file modification time for caching headers
        $mtime = filemtime($file_path);
        header('Last-Modified: ' . gmdate('D, d M Y H:i:s', $mtime) . ' GMT');
        
        // Handle conditional requests
        if (isset($_SERVER['HTTP_IF_MODIFIED_SINCE'])) {
            $if_modified = strtotime($_SERVER['HTTP_IF_MODIFIED_SINCE']);
            if ($if_modified >= $mtime) {
                header('HTTP/1.1 304 Not Modified');
                exit;
            }
        }
        
        // Output the file
        readfile($file_path);
        exit;
    }
    
    /**
     * Check if current request is being served from cache
     * 
     * @return bool
     */
    public static function is_serving_from_cache() {
        return isset($_SERVER['HTTP_X_WP_TO_HTML']) || 
               (function_exists('apache_request_headers') && 
                isset(apache_request_headers()['X-WP-To-HTML']));
    }
}