Sprocket

A library for building live views and real-time server components in Gleam ✨

Demo Documentation

Heavily inspired by Phoenix LiveView, React and Elm. The name “sprocket” is loosely derived from the metaphor of a bicycle’s sprocket, cassette and chain.

Sprocket combines the best of LiveView server-side productivity and scalability, React components and Elm functional state management patterns implemented in Gleam, a type-safe language built on the venerable BEAM (Erlang Virtual Machine).

An initial static view is rendered as HTML on the “first paint” which then establishes a connection to the server over a WebSocket to facilitate sending browser events and receiving view update diffs. These updates are patched into a client-side in-memory representation of the DOM and rendered to the browser using morphdom. Declarative views are built using functional components that accept props and re-render each time those props change and reducers are used for state management using strongly-typed models and message structs.

Under the hood, a reducer is a lightweight Gleam Actor OTP process (i.e. gen_server) and changes to the state (via dispatch) result in a re-render of the view.

Component interfaces snap together and are used to create higher-level views. Data flow is “uni-directional” in that State always flows down into components as props while Events flow up out of components through event handlers (which are also passed in as props, e.g. on_some_event("Something happened")).

This library is currently in a proof of concept state and should be considered highly unstable. There is still a lot of work to be done, including adding support for more event types, introducing additional hooks, improving unit test coverage, providing extensive documentation of modules and API, and optimizing performance.

Key Features

• Real-time, scalable server-side component library
• Renders initial HTML and efficiently patches update diffs using a persistent WebSocket connection
• Declarative and composable functional components that re-render when props change
• Strongly-typed language means less runtime bugs and better peace of mind
• Lightweight OTP processes used for composable & scalable state management

Example

Clock Component

type Model {
  Model(time: Int, timezone: String)
}

type Msg {
  NoOp
  UpdateTime(Int)
}

fn update(model: Model, msg: Msg) -> Model {
  case msg {
    NoOp -> model
    UpdateTime(time) -> {
      Model(..model, time: time)
    }
  }
}

fn initial() -> Model {
  Model(time: erlang.system_time(erlang.Second), timezone: "UTC")
}

pub type ClockProps {
  ClockProps(label: Option(String))
}

pub fn clock(ctx: Context, props) {
  let ClockProps(label) = props

  // Define a reducer to handle events and update the state
  use ctx, State(Model(time: time, ..), dispatch) <- reducer(
    ctx,
    initial(),
    update,
  )

  // Example effect that runs whenever the `time` variable changes and has a cleanup function
  use ctx <- effect(
    ctx,
    fn() {
      let cancel =
        interval(
          1000,
          fn() { dispatch(UpdateTime(erlang.system_time(erlang.Second))) },
        )

      Some(fn() { cancel() })
    },
    WithDeps([dep(time)]),
  )

  let current_time = int.to_string(time)

  render(
    ctx,
    case label {
      Some(label) -> [span([], [text(label)]), span([], [text(current_time)])]
      None -> [text(current_time)]
    },
  )
}

Parent view

pub type ExampleViewProps {
  ExampleViewProps
}

pub fn example_view(ctx: Context, _props: ExampleViewProps) {
  render(
    ctx,
    [
      html(
        [lang("en")],
        [
          head([], [link([rel("stylesheet"), href("/app.css")])]),
          body(
            [class("bg-white dark:bg-gray-900 dark:text-white p-4")],
            [
              component(
                clock,
                ClockProps(label: Some("The current time is: ")),
              ),
            ],
          ),
        ],
      ),
    ],
  )
}

Getting Started

To get started with Sprocket, follow the instructions below:

1. Clone the Sprocket repository:

git clone https://github.com/eliknebel/sprocket.git

2. Install the required dependencies:

gleam deps download
yarn

3. Start the development server:

yarn run watch

4. Open your web browser and visit http://localhost:3000 to see the docs sample app.

Installation

This package can be added to your Gleam project:

gleam add sprocket

and its documentation can be found at https://hexdocs.pm/sprocket.

Documentation

Documentation for Sprocket can be found at the docs sample app. It provides detailed information on how to use Sprocket, including module descriptions, API references, and examples.

Roadmap

Sprocket is still in its early stages and has a roadmap for future development. Here are some of the planned improvements:

• Build out full set of base HTML functions for components
• Explore other http and websocket server options
• Add support for additional event types to handle various user interactions
• Expand the available hooks to enable more flexible component behavior
• Convert client TypeScript to gleam
• Improve unit test coverage to ensure code quality and reliability
• Provide extensive documentation of modules and API for easier adoption
• Optimize performance to enhance responsiveness and scalability
• Investigate extending to support more than just web views, such as native desktop, iOS, and Android applications.

Contributing

Contributions to Sprocket are welcome and encouraged! If you would like to contribute, please follow the guidelines outlined in the CONTRIBUTING.md file.

License

Sprocket is released under the MIT License.