defmodule AdventOfCodeHelper.FileCache do
  @moduledoc """
  Contains all the logic for reading/writing files on disk
  """

  @doc """
  Saves puzzle input to file for later usage
  ## Parameters
    - Year: Int year of puzzle
    - Day: Int day of puzzle
    - Content: Puzzle input
  """
  @spec save_file(integer(), integer(), String.t()) :: :ok
  def save_file(year, day, content) do
    cache_dir = Application.get_env(:advent_of_code_helper, :cache_dir)

    unless cache_dir |> File.exists?() do
      File.mkdir(cache_dir)
    end

    write_out("input_#{year}_#{day}", content)
    :ok
  end

  defp write_out(file, content) do
    Path.join(Application.get_env(:advent_of_code_helper, :cache_dir), file)
    |> File.write(content, [])
  end

  @doc """
  Gets file from cache, should we have it stored
  ## Parameters
    - Year: year of puzzle
    - Day: day of puzzle
  """
  @spec get_file(integer(), integer()) :: {:ok, String.t()}
  def get_file(year, day) do
    case get_filename(year, day) |> File.read() do
      {:ok, contents} -> {:ok, contents}
      {:error, _msg} -> {:fail, "No file found"}
    end
  end

  @doc """
  Checks to see if we have a puzzle input cached
  ## Parameters
    - year: year of puzzle
    - day: day of puzzle
  """
  @spec in_cache?(integer(), integer()) :: boolean()
  def in_cache?(year, day) do
    get_filename(year, day)
    |> File.exists?()
  end

  defp get_filename(year, day) do
    Application.get_env(:advent_of_code_helper, :cache_dir)
    |> Path.join("input_#{year}_#{day}")
  end
end