@unional/gizmo

@unional/gizmo is a library to create gizmos.

A gizmo is really just an object with some behaviors or states.

There is not much difference between a gizmo and a simple object or an instance of a class.

The difference is that a gizmo can be defined, composed, and created asynchronously.

Motivation

@just-web is a framework that provides a simple way to build web applications using plugins.

It needs a mechanism to define and compose plugins, where each plugin can perform some async work when the application starts.

@unional/gizmo generalizes this pattern so that any object can be created and initialized asynchronously.

Installation

# npm
npm install @unional/gizmo

# yarn
yarn add @unional/gizmo

# pnpm
pnpm install @unional/gizmo

#rush
rush add -p @unional/gizmo

This library is also available in async-fp as gizmo or under async-fp/gizmo.

What is a gizmo

When we talk about gizmo, for simplicity, we use the term gizmo to refer to multiple things.

The concept is pretty simple, so it is not hard to differentiate what we are talking about at a given context.

But for the sake of clarity, here are the precise terms and the one we use loosely in parenthesis:

• gizmo definition (gizmo): a definition of a gizmo created using define().
  It is similar to a trait or abstract class.
• gizmo definition creator/function (gizmo function): a function that returns a gizmo definition created using define().
  It is really just a higher-order gizmo definition.
• gizmo incubator (incubator): a incubator created using incubate().
  It is similar to a class or factory function.
• gizmo instance (gizmo): an instance of a gizmo definition created using incubate()....create().
  It is similar to an instance of a class or an object.

We will use the loose team most of the time, and use the precise term when it is necessary.

One thing to note is that a gizmo instance will always be an object in the form of Record<string | symbol, unknown>.

Meaning the first level properties are used as identifiers or namespaces.

While technically you can create a gizmo like this (you will learn how to define a gizmo in the next section):

const gizmo = define({
  async create() {
    return { value: 123 }
  }
})

It is much better to create a gizmo with a better namedspace:

const gizmo = define({
  async create() {
    return { counter: { value: 123 } }
  }
})

There are exceptions such as the IDGizmo in @just-web, but normally gizmos should follow this rule.

Defining a gizmo

You define a gizmo using the define() function.

In its simplest form, you only need to provide an async create function.

import { define } from '@unional/gizmo'

const gizmo = define({
  async create(ctx) {
    return {
      miku: {
        sing() { /* ..snap.. */ }
      }
    }
  }
})

---

A gizmo can have static or dynamic dependencies. You define the dependencies with the static and dynamic properties.

NOTE: dynamic dependencies are not fully testing and may be removed in the future for simplicity. We may add them back in the future when the use case is clear.

import { define } from '@unional/gizmo'

const gizmo = define({
  static: define.require<MicGizmo>().optional<DressGizmo>(),
  dynamic: {
    'wand': define.require<WandGizmo>(),
    'piano': define.optional<StairGizmo>()
  },
  async create(ctx) {
    const mic = ctx.microphone // from MicGizmo
    const dress = ctx.dress // from DressGizmo
    const wand = await ctx.load('wand') // from WandGizmo
    const piano = await ctx.load('piano') // from StairGizmo
    return {
      miku: {
        sing() { /* ..snap.. */ }
      }
    }
  }
})

---

You can also define a start function to perform some work when the gizmo is created.

The start function can be either synchronous or asynchronous.

import { define } from '@unional/gizmo'

const gizmo = define({
  async create(ctx) {
    return [
      { miku: { sing() { /* ..snap.. */ } } },
      async start() {
        // websocket will connect on start
        ws = new WebSocket('ws://lyric.com')
        // ...
      }
    ]
  }
})

---

Your gizmo can also return nothing, meaning it only provide some side effects.

import { define } from '@unional/gizmo'

const gizmo = define({
  async create(ctx) {
    /* do something */
  }
})

However, typically you should not do any work inside the create function except loading the dynamic dependencies.

So a better approach is to do the work inside the start function.

import { define } from '@unional/gizmo'

const gizmo = define({
  async create(ctx) {
    return [undefined, () => { /* do something */ }]
  }
})

---

You can also create a gizmo function using define().

A gizmo function allows you to customize the gizmo when it is composed.

One common use case is to provide external dependencies to your gizmo.

(external dependencies means things that are outside the boundary of your application. e.g. UI, database, service, etc. Check out Clean Architecture to learn more.)

import { define, incubate } from '@unional/gizmo'

const gizmoFn = define((options) => {
  async create() { /* ..snap.. */ }
})

const gizmo = await incubate().with(gizmoFn({ /* options */ })).create()

Note: due to a bug in TypeScript 4.8.4 to 5.0.0, if your gizmo function uses optional parameter, the function type is not inferred correctly.

While this is fixed in TypeScript 5.1.0, if your code need to support those versions, you will need to define the gizmo function type explicitly:

const gizmoFn: (options?: MyOptions) => GizmoBase<void> =
  define((options?: MyOptions) => {
    async create() { /* ..snap.. */ }
  })

You can get do this by getting the type using typeof gizmoFn, and then adjust the param.

---

After you have defined your gizmo, you can infer its resulting type using define.Infer<T>:

import { define } from '@unional/gizmo'

const yourGizmo = define({
  async create() { return { ... } }
})

type YourGizmo = define.Infer<typeof yourGizmo>

The define.Infer<T> will infer the correct type for your gizmo, regardless of how do you return the value from the create function.

It works with gizmo function as well.

Composing gizmos

As seen above, you can define dependencies for your gizmo. That is one way to compose gizmos.

You can also compose gizmos by including them directly.

There are two ways to do this.

The first way is to use the with function.

The with function expects a gizmo definition:

import { define } from '@unional/gizmo'

const gizmo = define({
  async create(ctx) {
    const { mic } = await ctx.with(micGizmo).create()
    return {
      mic,
      miku: { sing() { /* ... */ } }
    }
  }
})

The second way is to merge them during incubation, which will be covered in the next section.

Incubating gizmos

After you have defined your gizmo, you can use the incubate function to compose them and create an incubator.

Here, one good way to think of this is to think of gizmo definition as a recipe, trait, or interface.

Each gizmo provides some specific behaviors. and the incubate function combines them to handle specific use cases.

import { incubate } from '@unional/gizmo'

const incubator = incubate()
  .with(gizmoA)
  .with(gizmoB)
  .with(gizmoCFn())

const app = await incubator.create()

---

When creating an incubator, the type system will ensure that all dependencies are loaded.

If there are some missing dependencies, the type will become a MissingDependency, which you cannot call create on.

import { incubate } from '@unional/gizmo'

// MissingDependency<'mic'>
const incubator = incubate().with(mikuGizmo)

---

Besides using the with function to compose gizmo definitions together, you can also use the merge function to merge gizmo instances together.

import { define } from '@unional/gizmo'

export async function activate({ mic }) {
  const miku = await incubate().merge(mic).with(mikuGizmo).create()
}

Creating gizmos

To create a gizmo (gizmo instance, or really just the resulting object), you call the create function on the incubator.

import { incubate } from '@unional/gizmo'

const incubator = incubate().with(gizmoA).with(gizmoB)

const app = await incubator.create()

Of course, you can skip the incubator variable and chain the create function:

import { incubate } from '@unional/gizmo'

const app = await incubate().with(gizmoA).with(gizmoB).create()

---

When creating the gizmo, you can specify a start function to perform some initialization.

const gizmo = await incubate().with(...).with(...).create(gizmo => {
    // do something
})

The start function can also provide a cleanup function. Which will be called when you call incubator.cleanup(gizmo):

const gizmo = await incubate().with(...).with(...).create(gizmo => () => {
  // clean up
})

incubator.cleanup(gizmo)

The same cleanup function can also be provided in the init() function, or the start function of each gizmo.

---

You can also use the init function to perform some initialization.

The init function is useful when you are exporting your gizmo incubator, and you want to perform some initialization before the gizmo is created.

// gizmo.ts
export const yourGizmoIncubator = incubate().with(...).with(...).init(gizmo => {
    // do something
})

// consumer.ts
import { yourGizmoIncubator } from './gizmo'

const gizmo = await yourGizmoIncubator.create()

// the consumer can also perform some initialization
const gizmo = await yourGizmoIncubator.create(gizmo => { /* do something */ })

Performance

gizmo creation is asynchronous. It allows the dependencies to be loaded asynchronously.

As it is asynchronous, it is not as fast as creating a plain object synchronously.

Here is a comparison between plain object creation, using Object.assign() to do mixins, and gizmo to create 100,000 objects:

plain object	Object.assign()	gizmo
21-26 ms	57-90 ms	170-219 ms

The test is done on a Ryzen 7 5800X, Windows 11, Node 18.15.0

While you can say that gizmo is up to 8x slower than plain object creation, in practice this hardly matters.

Gizmo is specifically designed to compose objects asynchronously. It is used to compose objects that are used throughout the application, and you typically only need to create one such object.