defmodule Aoc2023.Day1 do
  use Aoc2023

  def parse(input) do
    fn (replacement) ->
      input
      |> String.split("\n")
      |> Enum.map(replacement)
      |> Enum.map(fn (line) -> 
        line
        |> String.to_charlist()
        |> Enum.filter(&(?0 <= &1 && &1 <= ?9))
        |> Enum.map(&(&1 - ?0))
      end)
      |> Enum.map(&[List.first(&1), List.last(&1)])
      |> Enum.filter(fn (l) -> Enum.all?(l, &(&1 != nil)) end)
      |> Enum.map(&Integer.undigits/1)
      |> Enum.sum
    end
  end

  def part1(input) do
    input.(fn line -> line end)
  end

  @numbers [
    "one",
    "two",
    "three",
    "four",
    "five",
    "six",
    "seven",
    "eight",
    "nine",
  ]

  defp replacements(line) do
    line
    |> String.replace(@numbers, fn (n) -> Integer.to_string(Enum.find_index(@numbers, &(&1 == n)) + 1) <> String.slice(n, 1..String.length(n)) end)
  end

  defp replacements_rec(line) do
    if replacements(line) == line, do: line, else: replacements_rec(replacements(line))
  end
  def part2(input) do
    input.(&replacements_rec/1)
 end
end