Add bidirectional host bridge

test/runtime/scripting/lua_dardo_script_engine_test.dart

@@ -3,6 +3,7 @@ import 'dart:io';
 import 'package:flame_lua_runtime/runtime/diagnostics/runtime_diagnostics.dart';
 import 'package:flame_lua_runtime/runtime/packages/game_package.dart';
 import 'package:flame_lua_runtime/runtime/packages/game_package_manifest.dart';
+import 'package:flame_lua_runtime/runtime/host/runtime_host_bridge.dart';
 import 'package:flame_lua_runtime/runtime/models/runtime_event.dart';
 import 'package:flame_lua_runtime/runtime/network/runtime_network_manager.dart';
 import 'package:flame_lua_runtime/runtime/protocol/runtime_protocol.dart';
@@ -1021,6 +1022,57 @@ function on_event(event) return {} end
       expect(network.closedWebSockets, ['chat']);
     });
 
+    test('exposes host bridge runtime API to Lua', () async {
+      final package = await _createPackage(
+        mainScript: '''
+function smoke_test(ctx) return true end
+function init(ctx)
+  local id = runtime.host_call({
+    id = "profile",
+    method = "user.profile",
+    data = { userId = 9 },
+  })
+  local notified = runtime.host_notify({
+    method = "analytics",
+    data = { event = "open" },
+  })
+  return {
+    commands = {
+      { type = "toast", text = id .. ":" .. tostring(notified) },
+    },
+  }
+end
+function on_event(event)
+  if event.type == "host_call" then
+    runtime.host_respond({ id = event.data.id, result = { handled = event.data.method } })
+  end
+  return {}
+end
+''',
+      );
+      final hostBridge = _RecordingHostBridgeManager();
+      final engine = LuaDardoScriptEngine();
+
+      await engine.loadPackage(
+        package,
+        services: RuntimeScriptServices(hostBridge: hostBridge),
+      );
+      final diff = engine.init({'runtimeApiVersion': 1});
+
+      expect(diff.commands.single.payload['text'], 'profile:true');
+      expect(hostBridge.calls.single.method, 'user.profile');
+      expect(hostBridge.calls.single.data, {'userId': 9});
+      expect(hostBridge.notifications.single.method, 'analytics');
+      expect(hostBridge.notifications.single.data, {'event': 'open'});
+
+      final callFuture = hostBridge.callLua('flutter.request', data: {'id': 2});
+      final event = _RecordingHostBridgeManager.events.singleWhere(
+        (item) => item.type == RuntimeHostEventType.call,
+      );
+      engine.dispatchEvent(event);
+      expect(await callFuture, {'handled': 'flutter.request'});
+    });
+
     test('rejects undeclared module imports', () async {
       final package = await _createPackage(
         mainScript: '''
@@ -1052,6 +1104,26 @@ function on_event(event) return {} end
   });
 }
 
+class _RecordingHostBridgeManager extends RuntimeHostBridgeManager {
+  _RecordingHostBridgeManager()
+    : super(bridge: const RuntimeHostBridge(), eventSink: events.add);
+
+  static final events = <RuntimeEvent>[];
+  final calls = <RuntimeHostCall>[];
+  final notifications = <RuntimeHostNotification>[];
+
+  @override
+  Future<void> callHost(RuntimeHostCall call) async {
+    calls.add(call);
+  }
+
+  @override
+  bool notifyHost(RuntimeHostNotification notification) {
+    notifications.add(notification);
+    return true;
+  }
+}
+
 class _RecordingNetworkManager extends RuntimeNetworkManager {
   _RecordingNetworkManager()
     : super(