rows.ex

{_, input} = File.read("input.txt")

rows = Enum.map(String.split(input, "\n"), fn(row) ->
  Enum.map(String.split(row), fn(n) ->
    {number, _} = String.to_integer(n)
    number
  end)
end)


defmodule MyList do
  def max_product([], previous), do: previous

  def max_product(list) do
    [_ | tail] = list
    max_product(tail, product(list))
  end

  def max_product(list, previous) do
    [_ | tail] = list
    max_product(tail, Enum.max([product(list), previous]))
  end

  def product(list) when length(list) > 4 do
    Enum.reduce(
      Enum.take(list, 4),
      1,
      fn(n, acc) -> n * acc end
    )
  end

  def product(_), do: 0
end

IO.puts Enum.max(
  Enum.map(rows, fn(row) -> MyList.max_product(row) end)
)