Chapter 1: Stub Definition

Welcome to the break-cache project!

In this first chapter, we are going to explore the foundation of our plugin: the Stub Definition. Before we add complex logic or fancy features, we need to make sure our code sits safely inside the main application without breaking anything.

Why do we need a Stub?

Imagine you are building a new store in a shopping mall. You've rented the space, and the mall directory needs to list your shop. However, you aren't ready to sell products yet.

Do you leave a gaping hole in the wall? No. You put up a nice "Coming Soon" sign.

In software, a Stub acts like that sign. It is a "dummy" object that fits into the system. It tells the main application, "I am here, I follow the rules, but I'm not doing any active work right now."

The Use Case

Let's say our main application loads a list of plugins. The application expects every plugin to answer three specific questions:

1. What is your name?
2. Are you turned on?
3. Should I show you in the menu?

If a plugin fails to answer these questions, the application might crash (throw an error). Our goal is to create a safe, default object that answers these questions politely so the app keeps running smoothly.

Creating the Stub

Let's look at how we define this stub in code. We are going to create a simple Javascript object that satisfies the application's requirements without actually doing any heavy lifting.

The Code

Here is the code for our index.js file. This is the entry point of our package.

// File: index.js
export default { 
  isEnabled: () => false, 
  isHidden: true, 
  name: 'stub' 
};

What just happened?

1. export default: We are exporting a single object that the main app can import.
2. name: 'stub': We identify ourselves. This acts like an ID card.
3. isEnabled: ... and isHidden: ...: These are the default answers we give to the application.

Understanding the Input and Output

Even though this is a static object, let's imagine how the Main Application interacts with it.

Example Scenario: The Main Application loops through all plugins and checks them.

// Imagine this is the Main App code checking our stub
import myPlugin from './index.js';

// Question 1: What is your name?
console.log(myPlugin.name); 
// Output: 'stub'

What happened: The app successfully read our name. It knows who we are.

// Question 2: Are you enabled?
const active = myPlugin.isEnabled();

console.log(active);
// Output: false

What happened: We told the app, "No, I am not active." This is the safe default state. We aren't running any logic yet.

Internal Implementation: Under the Hood

To understand how this stub fits into the bigger picture, let's visualize the conversation between the Main App and our Stub.

The Flow of Control

When the system starts, it "plugs in" our code. It performs a safety check.

Deep Dive: Properties

Let's break down the implementation details of the object properties defined in index.js.

1. The Identity

name: 'stub'

This is a simple string. It prevents the system from labeling our plugin as undefined. It identifies the nature of this object—it is explicitly a stub.

2. The Behavior Flag

isEnabled: () => false

This is a function that returns a boolean. We use a function here (instead of just false) because in the future, we might want to calculate this based on settings. For now, we hard-code it to false to ensure the plugin starts in a safe, "off" mode.

We will expand on how to make this dynamic in Chapter 2: Feature State Control.

3. The Visibility Flag

isHidden: true

This is a simple boolean property. It tells the User Interface (UI) not to render any buttons or menus for this plugin. Since it is a stub, there is nothing for the user to interact with.

We will learn how to configure this in Chapter 3: Visibility Configuration.

Conclusion

In this chapter, we learned that a Stub Definition is crucial for system stability. It acts like a "dummy plug" or a "Coming Soon" sign—it occupies the space and follows the rules (the interface) so the main application doesn't crash, but it doesn't perform any logic yet.

Now that we have a safe placeholder, we need to learn how to control when our plugin actually turns on.

Next Chapter: Feature State Control

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