Day 01

Mix.install([
  {:kino, "~> 0.11.0"},
  :nimble_parsec
])

Part 1

test = """
1abc2
pqr3stu8vwx
a1b2c3d4e5f
treb7uchet
"""

input =
  Kino.FS.file_path("input_01.txt")
  |> File.read!()

input
|> String.split("\n", trim: true)
|> Enum.map(fn line ->
  digits =
    line
    |> String.codepoints()
    |> Enum.filter(&Regex.match?(~r/\d/, &1))

  number = List.first(digits) <> List.last(digits)
  {number, ""} = Integer.parse(number)
  number
end)
|> Enum.sum()

Part 2

pattern = ~r/^(?:one|two|three|four|five|six|seven|eight|nine|[1-9])/

defmodule Matcher do
  def all(pattern, string, matches \\ [])

  def all(_pattern, "", matches) do
    Enum.reverse(matches)
  end

  def all(pattern, string, matches) do
    matches =
      case Regex.run(pattern, string) do
        nil ->
          matches

        [match] ->
          [match | matches]
      end

    all(pattern, String.slice(string, 1..-1), matches)
  end
end

defmodule Parser do
  def to_digit(number) do
    case number do
      "one" -> "1"
      "two" -> "2"
      "three" -> "3"
      "four" -> "4"
      "five" -> "5"
      "six" -> "6"
      "seven" -> "7"
      "eight" -> "8"
      "nine" -> "9"
      number -> number
    end
  end
end

test = """
two1nine
eightwothree
abcone2threexyz
xtwone3four
4nineeightseven2
zoneight234
7pqrstsixteen
"""

input
|> String.split("\n", trim: true)
|> Enum.map(fn line ->
  matches = Matcher.all(pattern, line)
  digits = Enum.map(matches, &Parser.to_digit/1)

  number = List.first(digits) <> List.last(digits)
  {number, ""} = Integer.parse(number)
  number
end)
|> Enum.sum()