Create the stub files

How to implement a new voice application for Parula in Javascript

A voice app, or app, or "skill" allows you to teach Parula new voice commands and react to them. This document is intended for software developers that want to implement a new skill in JavaScript.

Motivation

So, you want to add new skills to Parula and write a voice app? That's great! We're very happy for your contributions to make Parula more versatile in situations and in tasks where you want her to help you. Once your app is working well and robust, please make a Pull Request to contribute it to Parula's skill set.

Requirements

We're going to assume you've done the basics:

1. Checked out the Parula source code with git clone

2. Have Parula running from that source

3. Know modern ES6 JavaScript with async/await

Create a stub

Your app will live in a subdirectory of app/. Find a nice, descriptive name for it.

Create the directory.

cd app/
mkdir myapp.js
cd myapp/
touch myapp.js README.md intents.en.json

Obviously, adapt myapp to your app name. Do the same in all other examples below.

The main entry file must have the same name as the directory name. Otherwise, your app will not load.

Now, let's add the app stub files.

App class stub

Open the file myappname.jsand adapt it to your app name:

import { JSONApp } from '../../baseapp/JSONApp.js';

export default class MyApp extends JSONApp {
  constructor() {
    super("myapp");
  }

  async load(lang) {
    await super.load(lang);
  }

  /**
   * Command
   * @param args {}
   * @param client {ClientAPI}
   */
  async personDetails(args, client)
  {
    throw this.error("not-implemented");
    return this.getResponse("person-details", { name, city });
  }
}

Please replace myapp with the directory name and MyApp with a class name.

The default export allows Parula to find your app class and load it.

README

Open README.mdand add a short and a long description of your application.

The first 1-2 lines should describe it in a very brief way. Then, make an empty line, and describe it in more detail. Include which uses cases and purposes you want your app to fulfill for the user, from an end user perspective. Also decribe on a very high level which technologies or third party applications or libraries it uses.

For example:

Plays local music stored on the local disk.

Uses MPD <https://www.musicpd.org> for the
music archive management, playlist, and playback.

MPD needs to be running.
The server name is configured in config under `mpd`.

Describe your app in a similar format.

This is a good moment for explicitly think about a feature list, and to write it down, before you start coding. This will guide you during your later development, and help you to focus on the original goal.

Use Markdown # headings and nested * lists to format it. Please clearly distinguish between working features and intended features.

However, there is no point in listing available user voice commands, because they will be spelled out in the intents JSON file.

Intents JSON

Open file intents.en.jsonand fill it out:

{
    "interactionModel": {
        "languageModel": {
            "invocationName": "myapp",
            "intents": [
                {
                    "name": "PersonDetails",
                    "samples": [
                      "Who is {Person}?",
                      "Do you know {Person}?",
                      "Tell me about {Person}"
                    ],
                    "slots": [
                        {
                            "name": "Person",
                            "type": "Person"
                        }
                    ]
                },
                {
                    "name": "AddAppointment",
                    "samples": [
                      "(Add|Make an appointment with {Person} on {Time}"
                    ],
                    "slots": [
                        {
                            "name": "Time",
                            "type": "Parula.DateTime"
                        },
                        {
                            "name": "Person",
                            "type": "Person"
                        }
                    ]
                }
            ],
            "types": [
                {
                    "name": "Person",
                    "basetype": "Parula.List"
                }
            ],
            "responses": {
              "person-details": "%name% lives in %city%",
              "not-implemented": [
                "I have not learned this yet",
                "Somebody please tell me?"
              ]
            }
        }
    }
}

You need to replace myapp with your app name. Leave the rest as examples for you for now. We will adapt it later.

Execution model

Before you start writing code, know that built-in apps are going to run in the same process as Parula, and are shipped with every instance of Parula. So, please make sure that your code is of good quality.

A crash in your app, or even just an uncaught exception from an async function, will lead to all of Parula crashing, and that's pretty bad. Also pay attention for leaks, as your app needs to run for months, without using more RAM. Likewise, do not waste computing resources, esp. unnecessary or large or slow network requests, nor CPU time. Remember that your app will run on a Raspberry Pi or an Android phone, not your desktop development machine.

Tip: Due to a bug in node.js import() loader, syntax errors in your JavaScript files will have no stack. For debugging, you can add this hardcoded import to baseapp/loader/BuiltinAppsLoader.js. But do not commit this change. Non-syntax errors get a proper stack.

`import MyApp from '../../app/myapp/myapp.js';`