What is it?

app-compose is a library for module-based applications. It helps developers easily connect different parts of an application — features, entities, services, and so on — so they work together as a single system.

With app-compose, you can:

• Simplify the management of complex dependencies.
• Control the order in which modules run.
• Intuitively enable or disable parts of the application.
• Clearly visualize the parts of the application and their connections.

Instead of manually managing the chaos of modules, app-compose turns them into a well-organized and scalable application.

Cooking Up Your Application

An application is like a dish: a collection of features, entities, and services. But by themselves, they don’t make an application. To bring everything to life, you need to combine them properly: at the right time, in the right order, and without anything extra. One misstep, and instead of a pizza, you might end up with a cake.

If you’re unsure how to connect modules into a single system, app-compose can simplify the process for you.

Example

import { createContainer, compose } from '@grlt-hub/app-compose';

// Imagine we are cooking a dish in our restaurant kitchen.
// There are three steps:
// 1. hire the chef
// 2. order the ingredients,
// 3. and cook the pizza.

// First: prepare the "chef"
// it’s like hiring the chef to start cooking.
const chef = createContainer({
  // The name of our chef.
  id: 'John Doe',
  // This chef specializes in Italian cuisine.
  domain: 'italian-chef',
  start: async () => {
    // For example, we are hiring a chef.
    const hiredChef = await hireChef();

    // We return our chef.
    return { api: hiredChef };
  },
});

// Second: if the chef is hired,
// we need to order the ingredients.
const ingredients = createContainer({
  id: 'ingredients',
  domain: 'shop',
  // The ingredients ordering depends on the chef.
  dependencies: [chef],
  // If the chef is on break,
  // we can't proceed with the order.
  enable: (api) => api['John Doe'].hasBreak === false,
  start: async (api) => {
    // We order the ingredients.
    const orderedIngredients = await orderIngredients();

    // We return the ordered ingredients.
    return { api: { orderedIngredients } };
  },
});

// Third: we make the pizza.
const pizza = createContainer({
  id: 'pizza',
  domain: 'dish',
  dependencies: [chef, ingredients],
  start: (api) => {
    // The chef uses the ingredients
    // to make the pizza.
    const pepperoniPizza = api['John Doe'].makePizza({
      ingredients: api.ingredients.orderedIngredients,
    });

    // The pizza is ready!
    return { api: pepperoniPizza };
  },
});

// Now the stages: we split the process into steps.
// 1: "prepare" — hiring the chef and ordering the ingredients.
// 2: "cooking" — making the pizza.
const cmd = await compose({
  stages: [
    ['prepare', [chef, ingredients]],
    ['cooking', [pizza]],
  ],
  // We require everything to be ready.
  required: 'all',
});

// The cooking process has started!
await cmd.up();

Example Status Flow

Here’s how the statuses change during the cooking process:

1. Initial state:

• chef: 'idle', ingredients: 'idle' — Everything is waiting.
• chef: 'pending', ingredients: 'idle' — The chef is on the way to the kitchen.

2. If the chef is ready to work:

• chef: 'done', ingredients: 'pending' — Ordering the ingredients.
• chef: 'done', ingredients: 'done', pizza: 'idle' — All ingredients have been delivered.
• chef: 'done', ingredients: 'done', pizza: 'pending' — Starting to make the pizza.
• chef: 'done', ingredients: 'done', pizza: 'done' — The pizza is ready!

3. If the chef is here, but taking a break:

• chef: 'done', ingredients: 'off', pizza: 'off' — Cooking is canceled.

Strengths of the Library

• Automatically resolves dependencies, removing the need to manually specify all containers.
• Simplifies working with feature-toggles by eliminating excessive if/else logic for disabled functionality.
• Allows you to define which parts of the application to run and in what order, prioritizing more important and less important dependencies.
• Offers the ability to visualize the system composed of containers effectively (including transitive dependencies and their paths).
• Provides a simple and intuitive developer experience (DX).
• Ensures high performance, suitable for scalable applications.
• Includes debugging tools to facilitate the development process.
• Covered by 100% tests, including type tests.

What app-compose is NOT

• It does not tell you how to build a module. You choose how your modules work. app-compose only helps you put them together in one app.
• It does not manage data or state. If you need state (like Effector or Redux), you add it inside your modules. app-compose only starts them.

Documentation

Ready to get started? Check out the full documentation to dive deeper.

Community

Have questions or want to contribute? Join our community to connect with other developers.

• Discord
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