teashop

Teashop is a terminal application framework for Gleam based on The Elm Architecture heavily inspired by Bubble Tea and Mint Tea. Teashop currently supports the Javascript target for Gleam.

Tutorial

Getting Started

For this tutorial, let's build a tea shop.

We'll start with creating a new Gleam project:

gleam new shop_tutorial

Then we add teashop to our project by adding it as a path dependency in our gleam.toml:

[dependencies]
teashop = { path = "../teashop" }

Now we can open up src/shop_tutorial.gleam and import the modules we'll need:

// Teashop modules
import teashop
import teashop/event
import teashop/command
import teashop/key

// Gleam standard library modules
import gleam/list
import gleam/string

Teashop programs are composed of 3 parts:

init, that specifies an initial model and any commands to be run right after startup
update, that handles incoming events and updates the model accordingly
view, that turns your model into a string to be rendered

The Model

First we create a type and constructor for our model. This model will be responsible for holding all of the state we use throughout the app.

pub type Status {
  Selected
  Unselected
}

pub type Model {
  Model(choices: List(#(String, Status)), cursor: Int)
}

Initialization

We need to define our init function. It returns the initial model, and a command to perform any initial input or output.

Here, I've specified the initial model as a constant:

const initial_model = Model(
  cursor: 0,
  choices: [
    #("Kitten cuddles 🐈", Unselected),
    #("Strawberry shortcake 🍰", Unselected),
    #("Blueberry muffins 🫐", Unselected),
  ],
)

Which we can use in the actual init function here. Here, we use a command to set the window title to something appropriate for our app:

pub fn init(_) {
  #(initial_model, command.set_window_title("teashop"))
}

Update

pub fn update(model: Model, event) {
  case event {
    event.Key(key.Char("q")) | event.Key(key.Esc) -> #(model, command.quit())

    event.Key(key.Char("k")) | event.Key(key.Up) -> {
      let choices_len = list.length(model.choices)
      let cursor = case model.cursor == 0 {
        True -> choices_len - 1
        False -> model.cursor - 1
      }
      #(Model(..model, cursor: cursor), command.none())
    }

    event.Key(key.Char("j")) | event.Key(key.Down) -> {
      let choices_len = list.length(model.choices)
      let cursor = case model.cursor == { choices_len - 1 } {
        True -> 0
        False -> model.cursor + 1
      }
      #(Model(..model, cursor: cursor), command.none())
    }

    event.Key(key.Enter) | event.Key(key.Space) -> {
      let toggle = fn(status) {
        case status {
          Selected -> Unselected
          Unselected -> Selected
        }
      }
      let choices =
        list.index_map(model.choices, fn(element, index) {
          let #(name, status) = element
          let status = case index == model.cursor {
            True -> toggle(status)
            False -> status
          }
          #(name, status)
        })
      #(Model(..model, choices: choices), command.none())
    }
    _otherwise -> #(model, command.none())
  }
}

View

pub fn view(model: Model) {
  let options =
    model.choices
    |> list.index_map(fn(element, index) {
      let #(name, status) = element
      let cursor = case model.cursor == index {
        True -> ">"
        False -> " "
      }
      let checked = case status {
        Selected -> "x"
        _ -> " "
      }
      cursor <> " [" <> checked <> "] " <> name
    })
    |> string.join("\n")

  let header = "What should we get at the tea shop?"
  let footer = "Press q to quit."

  [header, options, footer]
  |> string.join("\n\n")
}

All Together Now

pub fn main() {
  let app = teashop.app(init, update, view)
  teashop.start(app, Nil)
}

Running our teashop:

gleam run -m shop_tutorial --target js

Acknowledgments

Teashop is based on The Elm Architecture by Evan Czaplicki et alia. It is heavily inspired by Bubble Tea and Mint Tea. Teashop builds on work from deno_tui and borrows heavily from Lustre.

erikareads/teashop