// Tiny pure-Dart static file server for serving `flutter build web` output.
//
// Designed for local development as a replacement for `flutter run -d
// web-server`, which pins itself to a single browser session via DWDS and
// breaks when the browser is closed and reopened.
//
// Behavior:
//   * Serves files from a root directory passed on the command line.
//   * SPA fallback: requests with no file extension that don't match a real
//     file fall back to index.html so client-side routing works.
//   * No-cache headers on every response so a fresh `flutter build web`
//     always reaches the browser without a hard refresh.
//   * Rejects path traversal (`..` segments).
//
// Usage:
//   dart run scripts/web_static_server.dart <root-dir> <port>

import 'dart:async';
import 'dart:io';

Future<void> main(List<String> args) async {
  final String rootArg = args.isNotEmpty ? args[0] : 'build/web';
  final int port = args.length > 1 ? int.parse(args[1]) : 8080;

  final Directory rootDir = Directory(rootArg).absolute;
  if (!rootDir.existsSync()) {
    stderr.writeln('Static root not found: ${rootDir.path}');
    stderr.writeln(
      'Hint: run `flutter build web --debug` before starting this server.',
    );
    exit(1);
  }

  final HttpServer server = await HttpServer.bind('localhost', port);
  stdout.writeln('Static server listening on http://localhost:$port');
  stdout.writeln('Serving: ${rootDir.path}');

  await for (final HttpRequest req in server) {
    unawaited(_handle(req, rootDir));
  }
}

Future<void> _handle(HttpRequest req, Directory root) async {
  try {
    String requestPath = req.uri.path;
    if (requestPath.isEmpty || requestPath == '/') {
      requestPath = '/index.html';
    }
    if (requestPath.contains('..')) {
      req.response.statusCode = HttpStatus.forbidden;
      await req.response.close();
      return;
    }

    final String relPath = requestPath.startsWith('/')
        ? requestPath.substring(1)
        : requestPath;
    File target = File('${root.path}/$relPath');
    final bool hasExtension = relPath.contains('.');

    if (!target.existsSync()) {
      if (hasExtension) {
        req.response
          ..statusCode = HttpStatus.notFound
          ..write('Not Found');
        await req.response.close();
        return;
      }
      // SPA fallback: extensionless path → index.html.
      target = File('${root.path}/index.html');
      if (!target.existsSync()) {
        req.response
          ..statusCode = HttpStatus.notFound
          ..write('index.html not found');
        await req.response.close();
        return;
      }
    }

    req.response
      ..statusCode = HttpStatus.ok
      ..headers.contentType = ContentType.parse(_mimeFor(target.path))
      // Disable caching so dev rebuilds always reach the browser.
      ..headers.set(
        'Cache-Control',
        'no-store, no-cache, must-revalidate, max-age=0',
      )
      ..headers.set('Pragma', 'no-cache')
      ..headers.set('Expires', '0');

    await target.openRead().pipe(req.response);
  } catch (e, st) {
    stderr.writeln('static server error: $e\n$st');
    try {
      req.response.statusCode = HttpStatus.internalServerError;
      await req.response.close();
    } catch (_) {
      // Ignore: response may already be closed.
    }
  }
}

String _mimeFor(String filePath) {
  final int dot = filePath.lastIndexOf('.');
  final String ext = dot < 0 ? '' : filePath.substring(dot + 1).toLowerCase();
  switch (ext) {
    case 'html':
    case 'htm':
      return 'text/html; charset=utf-8';
    case 'js':
    case 'mjs':
      return 'application/javascript; charset=utf-8';
    case 'css':
      return 'text/css; charset=utf-8';
    case 'json':
    case 'map':
      return 'application/json; charset=utf-8';
    case 'wasm':
      return 'application/wasm';
    case 'svg':
      return 'image/svg+xml';
    case 'png':
      return 'image/png';
    case 'jpg':
    case 'jpeg':
      return 'image/jpeg';
    case 'gif':
      return 'image/gif';
    case 'webp':
      return 'image/webp';
    case 'ico':
      return 'image/x-icon';
    case 'woff':
      return 'font/woff';
    case 'woff2':
      return 'font/woff2';
    case 'ttf':
      return 'font/ttf';
    case 'otf':
      return 'font/otf';
    case 'txt':
      return 'text/plain; charset=utf-8';
    default:
      return 'application/octet-stream';
  }
}