Add talk timer

.formatter.exs

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+# Used by "mix format"
+[
+  inputs: ["{mix,.formatter}.exs", "{config,lib,test}/**/*.{ex,exs}"]
+]

.gitignore

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+# The directory Mix will write compiled artifacts to.
+/_build/
+
+# If you run "mix test --cover", coverage assets end up here.
+/cover/
+
+# The directory Mix downloads your dependencies sources to.
+/deps/
+
+# Where third-party dependencies like ExDoc output generated docs.
+/doc/
+
+# Ignore .fetch files in case you like to edit your project deps locally.
+/.fetch
+
+# If the VM crashes, it generates a dump, let's ignore it too.
+erl_crash.dump
+
+# Also ignore archive artifacts (built via "mix archive.build").
+*.ez
+
+# Ignore package tarball (built via "mix hex.build").
+ranch_talk-*.tar
+
+# Temporary files, for example, from tests.
+/tmp/

README.md

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+# RanchTalk
+
+**TODO: Add description**
+
+## Installation
+
+If [available in Hex](https://hex.pm/docs/publish), the package can be installed
+by adding `ranch_talk` to your list of dependencies in `mix.exs`:
+
+```elixir
+def deps do
+  [
+    {:ranch_talk, "~> 0.1.0"}
+  ]
+end
+```
+
+Documentation can be generated with [ExDoc](https://github.com/elixir-lang/ex_doc)
+and published on [HexDocs](https://hexdocs.pm). Once published, the docs can
+be found at <https://hexdocs.pm/ranch_talk>.
+

lib/ranch_talk.ex

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+defmodule RanchTalk do
+  @moduledoc """
+  Documentation for `RanchTalk`.
+  """
+
+  @doc """
+  Hello world.
+
+  ## Examples
+
+      iex> RanchTalk.hello()
+      :world
+
+  """
+  def hello do
+    :world
+  end
+end

lib/ranch_talk/talk_timer.ex

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+defmodule RanchTalk.TalkTimer do
+  use Kino.JS
+  use Kino.JS.Live
+
+  require Logger
+
+  defmodule Opts do
+    @ten_minutes_in_seconds 60 * 10
+
+    defstruct done_message: "Timer finished!",
+              seconds_to_count: @ten_minutes_in_seconds
+  end
+
+  @default_opts %{
+    done_message: "Timer finished!",
+    seconds_to_count: 600
+  }
+
+  @spec new(opts :: Opts.t()) :: Kino.JS.Live.t()
+  def new(opts) do
+    state =
+      @default_opts
+      |> Map.merge(opts)
+      |> update_state_html()
+
+    Kino.JS.Live.new(__MODULE__, state)
+  end
+
+  def set_html(widget, html) do
+    Kino.JS.Live.cast(widget, {:set_html, html})
+  end
+
+  def get_state(widget) do
+    Kino.JS.Live.call(widget, :get_state)
+  end
+
+  @impl true
+  def init(state, ctx) do
+    {:ok, assign(ctx, state)}
+  end
+
+  def tick(widget) do
+    state = get_state(widget)
+    tick(widget, state)
+  end
+
+  def tick(widget, %{seconds_to_count: seconds_to_count, done_message: done_message} = state) do
+    if seconds_to_count < 1 do
+      set_html(widget, done_message)
+      Kino.JS.Live.cast(widget, :timer_finished)
+    else
+      new_state =
+        state
+        |> Map.put(:seconds_to_count, seconds_to_count - 1)
+        |> update_state_html()
+
+      set_html(widget, state.html)
+      Process.sleep(1000)
+      tick(widget, new_state)
+    end
+  end
+
+  @impl true
+  def handle_connect(ctx) do
+    {:ok, ctx.assigns, ctx}
+  end
+
+  @impl true
+  def handle_cast({:set_html, html}, ctx) do
+    broadcast_event(ctx, "set_html", html)
+    {:noreply, assign(ctx, html: html)}
+  end
+
+  @impl true
+  def handle_cast(:timer_finished, ctx) do
+    broadcast_event(ctx, "timer_finished", ctx.assigns.done_message)
+    {:noreply, ctx}
+  end
+
+  @impl true
+  def handle_call(:get_state, _from, ctx) do
+    {:reply, ctx.assigns, ctx}
+  end
+
+  def start(widget) do
+    spawn(fn -> tick(widget) end)
+    widget
+  end
+
+  defp update_state_html(%{seconds_to_count: seconds} = state) do
+    minutes = seconds |> div(60) |> to_string()
+    seconds = seconds |> rem(60) |> to_string() |> String.pad_leading(2, "0")
+    Map.put(state, :html, Enum.join([minutes, ":", seconds]))
+  end
+
+  asset "main.js" do
+    """
+    export function init(ctx, state) {
+      ctx.root.innerHTML = state.html;
+      ctx.handleEvent("set_html", html => ctx.root.innerHTML = html)
+      ctx.handleEvent("timer_finished", message => alert(message))
+    }
+    """
+  end
+end

mix.exs

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+defmodule RanchTalk.MixProject do
+  use Mix.Project
+
+  def project do
+    [
+      app: :ranch_talk,
+      version: "0.1.0",
+      elixir: "~> 1.13",
+      start_permanent: Mix.env() == :prod,
+      deps: deps()
+    ]
+  end
+
+  def application do
+    [
+      extra_applications: [:logger]
+    ]
+  end
+
+  defp deps do
+    [
+      {:kino, "~> 0.5.2"}
+    ]
+  end
+end

mix.lock

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+%{
+  "kino": {:hex, :kino, "0.5.2", "42716edc9e41f17325f81a30985f81366cc673dfa5c559f58b8d7f8560b62212", [:mix], [{:ecto, "~> 3.0", [hex: :ecto, repo: "hexpm", optional: true]}, {:vega_lite, "~> 0.1.0", [hex: :vega_lite, repo: "hexpm", optional: true]}], "hexpm", "0911fb49ea6a26b4ac2ee10a075d9a08f5c8e5b5b9bbd385b7fb06f811c9949b"},
+}

ranch-talk.livemd

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+# About Ranch
+
+## Talk Timer
+
+This talk is supposed to be 5-15 minutes long, so let's make sure we keep it that way with a timer and a super annoying alert!
+
+```elixir
+alias RanchTalk.TalkTimer
+
+%{
+  # 10 minutes
+  seconds_to_count: 3,
+  done_message: "Time's up! Shut up and get back to work!"
+}
+|> TalkTimer.new()
+|> TalkTimer.start()
+```
+
+## Ranch Overview
+
+```elixir
+:observer.start()
+```

readme.md

@@ -1 +1,30 @@
 # ranch-talk
+
+I was asked to give a 5-15 minute talk on [Ranch][ranch], a TCP socket acceptor
+pool, to show how OTP constructs are used in the real world and expose some of
+[Phoenix's][phoenix] underpinnings. This [Livebook][livebook] contains my code
+and notes for that talk.
+
+Thanks to [Divvy][divvy] for inviting me to give this talk.
+
+# Usage
+
+Install and run a local Livebook in `attached` mode and automatically grab my
+code:
+
+```bash
+mix escript.install github livebook-dev/livebook
+git clone https://git.lyte.dev/lytedev/ranch-talk.git
+mix deps.get
+env LIVEBOOK_PORT=5588 LIVEBOOK_IFRAME_PORT=5589 \
+  livebook server --name ranch_is_neat@localhost --cookie yes-please \
+  --default-runtime attached:ranch_is_neat@localhost:yes-please \
+  "$(pwd)/ranch-talk.livemd"
+```
+
+Enjoy!
+
+[ranch]: https://github.com/ninenines/ranch
+[phoenix]: https://www.phoenixframework.org/
+[livebook]: https://github.com/livebook-dev/livebook
+[divvy]: https://getdivvy.com/