defmodule ExDocAnki do
  @moduledoc """
  Generate Anki flashcards from Elixir project documentation using ExDoc.
  """

  @compile {:no_warn_undefined, ExDoc}

  @doc """
  Generate Anki CSV file for the given project.

  ## Options

    * `:project` - project name (required)
    * `:version` - project version (required)
    * `:source_beam` - path to compiled beam files (required, can be a list)
    * `:output` - output directory, defaults to "doc"
    * `:source_url` - URL to source code repository
    * `:formatters` - list of formatter modules, defaults to `[ExDocAnki.Formatter]`

  ## Example

      ExDocAnki.generate(
        project: "MyApp",
        version: "1.0.0",
        source_beam: "_build/dev/lib/my_app/ebin"
      )

  """
  @spec generate(keyword()) :: String.t()
  def generate(opts) do
    project = Keyword.fetch!(opts, :project)
    version = Keyword.fetch!(opts, :version)
    source_beam = Keyword.fetch!(opts, :source_beam)
    source_beams = if is_list(source_beam), do: source_beam, else: [source_beam]

    options =
      opts
      |> Keyword.put(:source_beam, source_beams)
      |> Keyword.put_new(:output, "doc")
      |> Keyword.put_new(:formatters, [ExDocAnki.Formatter])

    {:ok, _} = start_ex_doc_refs()
    [result | _] = ExDoc.generate(project, version, source_beams, options)
    result.entrypoint
  end

  defp start_ex_doc_refs do
    if :ets.whereis(ExDoc.Refs) == :undefined do
      GenServer.start_link(ExDoc.Refs, :ok, name: ExDoc.Refs)
    else
      {:ok, :already_started}
    end
  end
end