Advent Of Code

This is a small framework to help with Advent of Code by managing inputs, tests and boilerplate code while you focus on problem solving in a TDD fashion.

Installation

Install the library

This framework is distributed as a library as it consists mostly of mix tasks. You may add the dependency to your project, or add it to a new project created with mix new my_app.

defp deps do
  [
    {:aoc, "~> 0.11"},
  ]
end

Configuration

If it does not exist, create a configuration file in your application:

mkdir -p config
touch config/config.exs

Then add the following configuration:

import Config

# The prefix is used when creating solutions and test modules with
# `mix aoc.create`.
config :aoc, prefix: MyApp

Install your cookie

Retrieve your cookie from the AoC website (with you browser developer tools) and write the session ID in $HOME/.adventofcode.session. It should be a long hex number like 53616c7465645f5f1d5792d97e3370392425dea84ca4653bd9a083f164ecd92278bef5b6bd50...

Use the commands

The following commands use the default year and day based on current date. It is possible to override the defaults with the mix aoc.set command, or provide the --year and --day options.

• mix aoc.create – Create the solution file, the test file and the input file for the current day. The input is downloaded from the AoC website and requires the session cookie. But you can create any of those files manually and the command will not overwrite them.
• mix aoc.fetch – Download the input. This will not overwrite an existing file. Inputs are stored in the priv directory.
• mix aoc.open – Open the problem page on AoC website.
• mix aoc.url – Prints the URL of the problem. Note that due to Elixir compilation prints you may need to grep for the URL. For instance xdg-open $(mix aoc.url | grep 'https').
• mix aoc.test – Run the tests. This relies on the mix test command and will call it with the default test filename that would be generated byt mix aoc.create. Supports the --trace, --failed, --stale, --seed and --max-failures options.
• mix aoc.run – Run the solution. There are more options available
  • -p, --part to run only one part
  • -b, --benchmark to run the solution multiple times and print statistics thanks to Benchee.

Defaults management commands

The mix aoc.set command allows to set the default year and day. Those values are used by default when other commands are not called with --year or --day options.

This is useful when working on a problem from a previous year, or when you finish the last days after December 25th, so your CLI history or bash scripts can just call mix aoc.test or mix aoc.run without options.

• mix aoc.set --year 2022 – Set the default year to 2022
• mix aoc.set --day 12 – Set the default day
• mix aoc.set --year 2022 --day 12 – Set both defaults
• mix aoc.set – Delete the default values

Writing solutions

The mix aoc.create command will generate modules with the boilerplate code to be called by mix aoc.run and the generated tests.

defmodule MyApp.Y23.Day1 do
  alias AoC.Input

  def read_file(file, _part) do
    # Return each line
    Input.stream!(file, trim: true)
    # Or return the whole file
    # Input.read!(file)
  end

  def parse_input(input, _part) do
    input
  end

  def part_one(problem) do
    problem
  end

  def part_two(problem) do
    problem
  end
end

To call your code manually, you may use the following code:

solution_for_p1 =
  "path/to/input/file"
  |> MyApp.Y23.Day1.read_file(:part_one)
  |> MyApp.Y23.Day1.parse_input(:part_one)
  |> MyApp.Y23.Day1.part_one()

The generated tests will also call those functions one by one, so you can debug and assert each part separately.

The different callbacks are:

• read_file/2 and parse_input/2 – The first one accepts an input file path, or a AoC.Input.FakeFile struct from the tests. Call Input.read! or Input.stream! to return the whole contents or a stream of lines.

  The return value will be passed to parse_input/2. This allows to separate the parsing logic from the raw file manipulation. Most logic is generally contained in one of those two functions, and the other one is a oneliner.

  Note that the second argument to each callback, :part_one or :part_two can help to apply different logic for each problem part.

• part_one/1 and part_two/1 – The first argument is the result of parse_input/2. The return should be the solution to the problem that will be printed by mix aoc.run.

  The return value is also checked in the generated tests.

  Some problems may require to print a drawing to the console, or produce other side effects, so you may return a dummy value those callbacks.