try to use dart as backend language

Signed-off-by: Peter Siegmund <developer@mars3142.org>

server/cinema/bin/server.dart

@@ -0,0 +1,71 @@
+import 'dart:async';
+import 'dart:io';
+
+import 'package:shelf/shelf.dart';
+import 'package:shelf/shelf_io.dart' as shelf_io;
+import 'package:shelf_router/shelf_router.dart';
+import 'package:shelf_web_socket/shelf_web_socket.dart';
+
+final List<dynamic> clients = [];
+
+// Configure routes.
+final _router = Router()
+  ..get('/', _rootHandler)
+  ..get('/echo/<message>', _echoHandler);
+
+Response _rootHandler(Request req) {
+  return Response.ok('Hello, World!\n');
+}
+
+Response _echoHandler(Request request) {
+  final message = request.params['message'];
+  return Response.ok('$message\n');
+}
+
+void main(List<String> args) async {
+  // Use any available host or container IP (usually `0.0.0.0`).
+  final ip = InternetAddress.anyIPv4;
+
+  // Configure a pipeline that logs requests.
+  final handler = Pipeline().addMiddleware(logRequests()).addHandler(_router.call);
+
+  var wsHandler = webSocketHandler((webSocket, _) {
+    clients.add(webSocket);
+    print('Client connected, total: ${clients.length}');
+
+    webSocket.stream.listen(
+      (message) {
+        webSocket.sink.add('echo $message');
+      },
+      onDone: () {
+        clients.remove(webSocket);
+        print('Client disconnected, total: ${clients.length}');
+      },
+      onError: (error) {
+        clients.remove(webSocket);
+        print('Client error: $error');
+      },
+      cancelOnError: true,
+    );
+  });
+
+  FutureOr<Response> combinedHandler(Request request) {
+    if (request.url.path == 'ws') {
+      return wsHandler(request);
+    }
+    return handler(request);
+  }
+
+  // For running in containers, we respect the PORT environment variable.
+  final port = int.parse(Platform.environment['PORT'] ?? '8080');
+  final server = await shelf_io.serve(combinedHandler, ip, port).then((server) {
+    print('Serving at http|ws://${server.address.host}:${server.port}');
+  });
+}
+
+// Broadcast to all clients
+void broadcast(String message) {
+  for (final client in clients) {
+    client.sink.add(message);
+  }
+}