defmodule WineCellar do
  @colors [
    white: "Fermented without skin contact.",
    red: "Fermented with skin contact using dark-colored grapes.",
    rose: "Fermented with some skin contact, but not enough to qualify as a red wine."
  ]

  # @cellar [
  #   white: {"Chardonnay", 2015, "Italy"},
  #   white: {"Pinot grigio", 2017, "Germany"},
  #   red: {"Pinot noir", 2016, "France"},
  #   rose: {"Dornfelder", 2018, "Germany"}
  # ]

  def explain_colors(), do: @colors

  def filter(cellar, color, opts \\ []) do
    cellar
    |> Keyword.get_values(color)
    |> filter_by_year(opts[:year])
    |> filter_by_country(opts[:country])
  end

  # The functions below do not need to be modified.

  defp filter_by_year(wines, year)
  defp filter_by_year(wines, nil), do: wines
  defp filter_by_year([], _year), do: []

  defp filter_by_year([{_, year, _} = wine | tail], year) do
    [wine | filter_by_year(tail, year)]
  end

  defp filter_by_year([{_, _, _} | tail], year) do
    filter_by_year(tail, year)
  end

  defp filter_by_country(wines, country)
  defp filter_by_country(wines, nil), do: wines
  defp filter_by_country([], _country), do: []

  defp filter_by_country([{_, _, country} = wine | tail], country) do
    [wine | filter_by_country(tail, country)]
  end

  defp filter_by_country([{_, _, _} | tail], country) do
    filter_by_country(tail, country)
  end
end