<?php
declare(strict_types=1);

/*
 * Security baseline, loaded first by every web entry point (via helpers.php):
 * error handling, request-method guard, security headers, HTTPS detection,
 * and hardened session settings.
 */

require_once __DIR__ . '/db.php';

function security_config(): array
{
    return (app_config()['security'] ?? []) + [
        'force_https'     => false,
        'trusted_proxies' => [],
        'setup_key'       => '',
    ];
}

/** True when the client reached us over HTTPS (directly or via a trusted reverse proxy). */
function is_https(): bool
{
    if (!empty($_SERVER['HTTPS']) && strtolower((string)$_SERVER['HTTPS']) !== 'off') {
        return true;
    }
    if ((int)($_SERVER['SERVER_PORT'] ?? 0) === 443) {
        return true;
    }
    $proxies = security_config()['trusted_proxies'];
    if ($proxies && in_array($_SERVER['REMOTE_ADDR'] ?? '', $proxies, true)) {
        return strtolower((string)($_SERVER['HTTP_X_FORWARDED_PROTO'] ?? '')) === 'https';
    }
    return false;
}

/** Client IP; X-Forwarded-For is honoured only when the request came from a trusted proxy. */
function client_ip(): string
{
    $remote = (string)($_SERVER['REMOTE_ADDR'] ?? '0.0.0.0');
    $proxies = security_config()['trusted_proxies'];
    if ($proxies && in_array($remote, $proxies, true) && !empty($_SERVER['HTTP_X_FORWARDED_FOR'])) {
        $chain = array_map('trim', explode(',', (string)$_SERVER['HTTP_X_FORWARDED_FOR']));
        // right-most address that is not one of our proxies
        foreach (array_reverse($chain) as $ip) {
            if (filter_var($ip, FILTER_VALIDATE_IP) && !in_array($ip, $proxies, true)) {
                return substr($ip, 0, 45);
            }
        }
    }
    return substr($remote, 0, 45);
}

/** Per-request nonce for the few inline scripts (Content-Security-Policy). */
function csp_nonce(): string
{
    static $nonce = null;
    if ($nonce === null) {
        $nonce = rtrim(strtr(base64_encode(random_bytes(18)), '+/', '-_'), '=');
    }
    return $nonce;
}

function send_security_headers(bool $sensitive = false): void
{
    if (headers_sent()) {
        return;
    }
    header_remove('X-Powered-By');
    $csp = [
        "default-src 'none'",
        "script-src 'self' 'nonce-" . csp_nonce() . "'",
        "style-src 'self'",
        "img-src 'self'",
        "font-src 'self'",
        "connect-src 'self'",
        "manifest-src 'self'",
        "form-action 'self'",
        "frame-ancestors 'none'",
        "base-uri 'none'",
        "object-src 'none'",
    ];
    if (is_https()) {
        $csp[] = 'upgrade-insecure-requests';
        header('Strict-Transport-Security: max-age=31536000; includeSubDomains');
    }
    header('Content-Security-Policy: ' . implode('; ', $csp));
    header('X-Frame-Options: DENY');
    header('X-Content-Type-Options: nosniff');
    header('Referrer-Policy: same-origin');
    header('Permissions-Policy: camera=(), microphone=(), geolocation=(), payment=(), usb=(), interest-cohort=()');
    header('Cross-Origin-Opener-Policy: same-origin');
    header('Cross-Origin-Resource-Policy: same-origin');
    header('X-Permitted-Cross-Domain-Policies: none');
    // Pages always revalidate so they reference the newest versioned assets;
    // admin pages are never stored at all.
    header($sensitive ? 'Cache-Control: no-store, max-age=0' : 'Cache-Control: no-cache, must-revalidate');
    if ($sensitive) {
        header('Pragma: no-cache');
    }
}

function security_bootstrap(): void
{
    static $done = false;
    if ($done || PHP_SAPI === 'cli') {
        return;
    }
    $done = true;

    // Never leak errors or stack traces to the client.
    ini_set('display_errors', '0');
    ini_set('display_startup_errors', '0');
    ini_set('log_errors', '1');
    ini_set('expose_php', '0');
    error_reporting(E_ALL);
    set_exception_handler(function (Throwable $e): void {
        error_log('[serubi] ' . get_class($e) . ': ' . $e->getMessage() . ' in ' . $e->getFile() . ':' . $e->getLine());
        if (!headers_sent()) {
            http_response_code(500);
            header('Content-Type: text/html; charset=utf-8');
            header('Cache-Control: no-store');
        }
        echo '<!doctype html><meta charset="utf-8"><title>Terjadi kesalahan</title><p>Terjadi kesalahan pada server. Silakan coba lagi beberapa saat lagi.</p>';
    });

    // Hardened session settings (before any session_start()).
    ini_set('session.use_strict_mode', '1');
    ini_set('session.use_only_cookies', '1');
    ini_set('session.use_trans_sid', '0');
    ini_set('session.cookie_httponly', '1');
    ini_set('session.sid_length', '48');
    ini_set('session.sid_bits_per_character', '5');
    ini_set('session.gc_maxlifetime', '28800');

    // Only GET, HEAD and POST are meaningful here (blocks TRACE/PUT/DELETE/OPTIONS...).
    $method = strtoupper((string)($_SERVER['REQUEST_METHOD'] ?? 'GET'));
    if (!in_array($method, ['GET', 'HEAD', 'POST'], true)) {
        header('Allow: GET, HEAD, POST');
        http_response_code(405);
        exit;
    }

    // Optional HTTP -> HTTPS redirect for production.
    if (security_config()['force_https'] && !is_https()) {
        $host = preg_replace('/[^A-Za-z0-9.\-:\[\]]/', '', (string)($_SERVER['HTTP_HOST'] ?? ''));
        $uri = (string)($_SERVER['REQUEST_URI'] ?? '/');
        if ($host !== '' && $uri !== '' && $uri[0] === '/') {
            header('Location: https://' . $host . $uri, true, 301);
            exit;
        }
    }
}