Actions on Google

main.dart

/// This is pseudo-code which drafts possible way of using Google's `actions-on-google` Node.js package.
/// This code has not been tested, compiled or ran anywhere.
@JS()
library actionssdk;

import 'package:firebase_functions_interop/firebase_functions_interop.dart';
import 'package:js/js.dart';
import 'package:js/js_util.dart';
import 'package:node_interop/node_interop.dart';

void main() {
  final app = actionssdk(ActionsSDKAppOptions(debug: true));
  // Note that Dart functions cannot be passed to JS as-is and must be
  // wrapped with allowInterop or allowInteropCaptureThis
  app.intent('actions.intent.MAIN', allowInterop((ActionsSDKConversation conv,
      [String input, Argument argument, GoogleRpcStatus status]) {
    conv.ask('Your ssml goes here');
    // If above call fails when deployed we might need to use callMethod:
    callMethod(conv, 'ask', ['Your ssml goes here']);
    // As you can see in firebase_admin_interop and functions interop
    // I abstract away all these details from the user so that they only
    // need to deal with pure Dart.
  }));

  app.intent('actions.intent.MAIN', allowInterop((ActionsSDKConversation conv,
      [String input, Argument argument, GoogleRpcStatus status]) {
    if (input == 'bye') {
      // The `close` method is similar to `ask` method so might need the `callMethod`
      // approach
      conv.close('Goodbye!');
    }
    conv.ask('Your ssml goes here...');
  }));

  // This won't actually work currently as firebase_functions_interop expects a Dart function
  // in onRequest. This can be easily fixed by updating the package to support actionssdk
  // or expose native JS object to interact with directly.
  functions['sayNumber'] = functions.https.onRequest(app);
}

// This loads Node.js package
// Note that you need to have it in your package.json
final ActionsSDKExports _actionsOnGoogleExports = require('actions-on-google');
// This provides access to the actionssdk only
final ActionsSDKAppFactory actionssdk = _actionsOnGoogleExports.actionssdk;

/// Here we define interface of exports provided by Node.js package.
@JS()
@anonymous
abstract class ActionsSDKExports {
  // For this example we only declare the actionssdk binding, but can add more if needed.
  external ActionsSDKApp actionssdk(ActionsSDKAppOptions options);
}

typedef ActionsSDKAppFactory = ActionsSDKApp Function(
    ActionsSDKAppOptions options);

/// Here we define interface that's expected for the actionssdk.
@JS()
@anonymous
abstract class ActionsSDKApp {
  // Rough approximation of method signature from here:
  // https://actions-on-google.github.io/actions-on-google-nodejs/interfaces/actionssdk.actionssdkapp.html#intent
  // [intent] here can be either single value or an array, so had to declare
  // as dynamic
  external ActionsSDKApp intent(
      dynamic intent, ActionsSdkIntentHandler handler);
}

// This is how to declare basic JSON-like objects so that it's easy to use
// On the Dart side. Mostly useful for things like options (this case)
@JS()
@anonymous
abstract class ActionsSDKAppOptions {
  external bool get debug;
  // Must have external factory
  external factory ActionsSDKAppOptions({bool debug});
}

/// All the bindings continued...
/// You have to declare everything you're going to use.

/// This is rough approximation of signature from here:
/// https://actions-on-google.github.io/actions-on-google-nodejs/interfaces/actionssdk.actionssdkintenthandler.html
typedef ActionsSdkIntentHandler = dynamic Function(ActionsSDKConversation conv,
    [String input, Argument argument, GoogleRpcStatus status]);

@JS()
@anonymous
abstract class ActionsSDKConversation {
  // Type definition for ask seems like it could be a variadic function
  // in which case we won't be able to just call `conv.ask('something')` and
  // will have to invoke it using [callMethod].
  external ActionsSDKConversation ask(dynamic responses);
  // The same applies to this method.
  external ActionsSDKConversation close(dynamic responses);
  // ...
}

@JS()
@anonymous
abstract class Argument {
  // ...
}

@JS()
@anonymous
abstract class GoogleRpcStatus {
  // ...
}