not-real.rb

// Counter browser program — compiler-known TEA shape.
// init/update return model only; `command` statements emit; handlers live in command block.

program Counter {
  model {
    count: Int,
    step: Int,
    is_resetting: Bool,
  }

  message {
    :clicked_increment,
    :clicked_decrement,
    :clicked_reset,
    :clicked_reset_after_delay,
    :changed_step(Int),
    :reset_completed,
  }

  command {
    :schedule_reset { after_ms: Int } => {
      use Browser
      Browser.set_timeout(~after_ms, fn() {
        send(:reset_completed);
      });
    }
  }

  fn init() {
    return { count: 0, step: 1, is_resetting: false };
  }

  fn scaled_total(model: Model): Int = model.count * model.step

  fn update(model: Model, message: Message) {
    return match message {
      | :clicked_increment -> { model with count: model.count + model.step }
      | :clicked_decrement -> { model with count: model.count - model.step }
      | :clicked_reset -> { model with count: 0, is_resetting: false }
      | :clicked_reset_after_delay -> {
        command :schedule_reset { after_ms: 1200 };
        { model with is_resetting: true };
      }
      | :changed_step(step) -> {
        if step < 1 {
          return model;
        }
        { model with step };
      }
      | :reset_completed -> { model with count: 0, is_resetting: false }
    };
  }

  fn view(model: Model): Html {
    let total = scaled_total(model);
    let reset_label = if model.is_resetting {
      "Resetting…"
    } else {
      "Reset after delay"
    };

    return html.main(
      ~class: "counter-app",
      [
        html.h1([], ["Browser counter"]),
        html.p(
          ~class: "counter-display",
          ~aria_live: "polite",
          [Int.to_string(model.count)],
        ),
        html.p(
          ~class: "counter-derived muted",
          ["Scaled total: " ++ Int.to_string(total)],
        ),
        html.div(
          ~class: "counter-controls",
          [
            html.button(
              ~type: "button",
              ~class: "btn",
              ~onclick: :clicked_decrement,
              ["−"],
            ),
            html.button(
              ~type: "button",
              ~class: "btn btn-primary",
              ~onclick: :clicked_increment,
              ["+"],
            ),
            html.button(
              ~type: "button",
              ~class: "btn",
              ~onclick: :clicked_reset,
              ["Reset now"],
            ),
          ],
        ),
        html.label(
          ~for: "step-input",
          ["Step"],
        ),
        html.input(
          ~id: "step-input",
          ~type: "number",
          ~min: "1",
          ~value: Int.to_string(model.step),
          ~oninput: fn(raw) {
            let step = Int.parse(raw) else 1;
            return :changed_step(step);
          },
        ),
        html.button(
          ~type: "button",
          ~class: "btn",
          ~disabled: model.is_resetting,
          ~onclick: :clicked_reset_after_delay,
          [reset_label],
        ),
      ],
    );
  }
}