feat: show tip of the day

lib/nerves_motd.ex

@@ -14,6 +14,7 @@ defmodule NervesMOTD do
   \e[38;5;24m███▌    \e[38;5;74m▀▀████\e[0m
   """
 
+  alias NervesMOTD.Tips
   alias NervesMOTD.Utils
 
   @excluded_ifnames [~c"lo", ~c"lo0"]
@@ -47,6 +48,7 @@ defmodule NervesMOTD do
     an empty logo (`""`) to remove it completely.
   * `:extra_rows` - a list of custom rows or a callback for returning rows.
     The callback can be a 0-arity function reference or MFArgs tuple.
+  * `:show tip` - a boolean flag to show the tip of the day.
   """
   @spec print([option()]) :: :ok
   def print(opts \\ []) do
@@ -63,7 +65,8 @@ defmodule NervesMOTD do
         "\n",
         """
         Nerves CLI help: https://hexdocs.pm/nerves/iex-with-nerves.html
-        """
+        """,
+        tips(opts)
       ]
       |> IO.ANSI.format()
       |> IO.puts()
@@ -81,6 +84,23 @@ defmodule NervesMOTD do
     Keyword.get(opts, :logo, @logo)
   end
 
+  @spec tips([option()]) :: IO.ANSI.ansidata()
+  defp tips(opts) do
+    if opts[:show_tip] do
+      {title, content} = Tips.random()
+
+      """
+      ==========================================================================
+      [Tip of the day] #{title}
+      --------------------------------------------------------------------------
+      #{String.strip(content)}
+      ==========================================================================
+      """
+    else
+      []
+    end
+  end
+
   @spec rows(map(), list()) :: [[cell()]]
   defp rows(apps, opts) do
     [

lib/nerves_motd/tips.ex

@@ -0,0 +1,210 @@
+defmodule NervesMOTD.Tips do
+  @moduledoc false
+
+  @tips [
+    {
+      "Toolshed",
+      """
+      Want more traditional shell tools in your Nerves IEx?
+
+      Use Toolshed!
+
+      Its included by default and has may familiar functions, such as `cat`,
+      `ls`, or even `weather` 🌤️
+
+      https://hexdocs.pm/toolshed
+      """
+    },
+    {
+      "Kernek log message",
+      """
+      Need more than Elixir logs? Run `dmesg` to see log messages from device
+      drivers and the Linux kernel. Nerves also routes kernel log messages to
+      the Elixir logger.
+      """
+    },
+    {
+      "erlinit",
+      """
+      Erlinit is a small program that starts the Erlang VM on boot. It has many
+      options - especially for debugging startup issues.
+
+      https://hexdocs.pm/nerves/advanced-configuration.html#overriding-erlinit-config-from-mix-config
+      """
+    },
+    {
+      "Disable automatic reboot",
+      """
+      Nerves automatically reboots devices when the Erlang VM exits. This can
+      make some debugging harder, but you can easily disable it to let those
+      sessions hang for debugging
+      """
+    },
+    {
+      "Whats in a firmware?",
+      """
+      Use `mix firmware.unpack` to decompress a local copy of your firmware on
+      host and inspect the files within before installing on device
+      """
+    },
+    {
+      "Elixir Circuits libraries",
+      """
+      See if someone has already implemented support for a sensor or other
+      hardware device that you have by checking
+      https://elixir-circuits.github.io/.
+      """
+    },
+    {
+      "Read-only filesystems",
+      """
+      Nerves stores all BEAM files, the Erlang runtime and various support
+      libraries/apps in a compressed and read-only SquashFS filesystem.
+
+      Need to write to disk? Use the application partition mounted R/W at
+      `/data`
+      """
+    },
+    {
+      "SASL log messages",
+      """
+      Configuring the Elixir Logger to show SASL reports can help debug
+      unexpected GenServer restarts.
+
+      https://hexdocs.pm/logger/Logger.html#module-erlang-otp-integration
+      """
+    },
+    {
+      "Viewing the file system",
+      """
+      Sometimes, you just need to see whats on your Nerves device's disk.
+      Luckily, there are a few ways to do that. You can even use VSCode!
+
+      https://embedded-elixir.com/post/2021-05-08-nerves-file-peeking/#sshfs
+      """
+    },
+    {
+      "NervesPack",
+      """
+      Get all of the default packages for starting a new Nerves project by
+      depending on `:nerves_pack`
+
+      https://github.com/nerves-project/nerves_pack
+      """
+    },
+    {
+      "Hardware watchdogs",
+      """
+      Nerves enables hardware watchdogs and connects them to Erlang's heart
+      feature to detect and recover from the Erlang VM hanging.
+
+      See https://embedded-elixir.com/post/2018-12-10-heart/ to learn more
+      about this.
+      """
+    },
+    {
+      "Copy and paste",
+      """
+      Make small code changes to your running application by copy/pasting
+      Elixir source files at the IEx prompt.
+      """
+    },
+    {
+      "Read-only filesystems",
+      """
+      Nerves stores all BEAM files, the Erlang runtime and various support
+      libraries and apps in a compressed and read-only SquashFS filesystem.
+
+      The writable application partition is mounted at `/data`
+      """
+    },
+    {
+      "Device serial numbers",
+      """
+      Identify your Nerves devices using a unique ID that's already programmed
+      into the hardware using the boardid command. Details at
+      https://github.com/nerves-project/boardid/ and the boardid.config file.
+      """
+    },
+    {
+      "Need an example?",
+      """
+      Nerves maintains a set of examples for common use-cases with devices.
+      Things like running a phoenix app, using SQLite, controlling GPIO, using
+      Zig lang, and more!
+
+      https://github.com/nerves-project/nerves_examples
+      """
+    },
+    {
+      "Logs",
+      """
+      Use `RingLogger.next` to dump the current log buffer to screen.
+
+      Use `log_attach` from `Toolshed` to attach the current session to the
+      Elixir logger for live logs.
+
+      https://hexdocs.pm/toolshed/Toolshed.Log.html#log_attach/1
+      """
+    },
+    {
+      "Eye from the Sky",
+      """
+      Get some insights to Nerves internals with this high level overview of
+      the Nerves architecture and choice to use the BEAM VM
+
+      https://youtu.be/VzOaSvTcvU4
+      """
+    },
+    {
+      "Revert to the previously loaded firmware",
+      """
+      Run `Nerves.Runtime.revert` to go back to the previously loaded firmware.
+      """
+    },
+    {
+      "Compiling systems",
+      """
+      Compiling systems on linux or via `mix nerves.system.shell`?
+
+      Don't forgot about `make help` and other tips from the Buildroot manual
+      (thanks @ericr3r)
+
+      https://buildroot.org/downloads/manual/manual.html#make-tips
+      """
+    },
+    {
+      "Order matters",
+      """
+      Sometimes when compiling Nerves systems, order matters!
+
+      Use `make show-build-order` while in `mix nerves.system.shell` to see the
+      compilation order and make sure all your 🦆🦆 are in a row (thanks
+      @ericr3r!)
+      """
+    },
+    {
+      "RamoopsLogger",
+      """
+      Use the `RamoopsLogger` backend to store log messages in DRAM that can
+      survive unexpected reboots.
+
+      https://github.com/smartrent/ramoops_logger
+      """
+    }
+  ]
+
+  @type tip :: {title :: String.t(), content :: String.t()}
+
+  @doc """
+  List all Nerves tips
+  """
+  @spec all() :: [tip]
+  def all(), do: @tips
+
+  @doc """
+  Pick one Nerves tip randomly
+  """
+  @spec random() :: tip
+  def random(), do: Enum.random(@tips)
+end

test/nerves_motd/tips_test.exs

@@ -0,0 +1,13 @@
+defmodule NervesMOTD.TipsTest do
+  use ExUnit.Case
+  alias NervesMOTD.Tips
+  doctest NervesMOTD.Tips
+
+  test "all" do
+    assert [{_title, _content} | _] = Tips.all()
+  end
+
+  test "random" do
+    assert {_title, _content} = Tips.random()
+  end
+end

test/nerves_motd_test.exs

@@ -347,4 +347,23 @@ defmodule NervesMOTDTest do
 
     assert capture_motd() == ""
   end
+
+  describe "tip of the day" do
+    setup _context do
+      NervesMOTD.MockRuntime
+      |> Mox.expect(:applications, 1, default_applications_code())
+      |> Mox.expect(:active_partition, 1, fn -> "A" end)
+      |> Mox.expect(:firmware_validity, 1, fn -> :valid end)
+
+      :ok
+    end
+
+    test "does nothing by default" do
+      refute capture_motd() =~ ~r/Tip of the day/
+    end
+
+    test "shows tip when enabled" do
+      assert capture_motd(show_tip: true) =~ ~r/Tip of the day/
+    end
+  end
 end