defmodule ReadDoc do
  use ReadDoc.Types

  import ReadDoc.StateMachine, only: [run!: 3]
  alias ReadDoc.Options

  @moduledoc """
  Implements reading a file and replacing indicated portions (as defined by `%Options{}` and the
  strings `"begin @doc " docname` and
          `"end @doc " docname` and
  """

  @spec rewrite_files(pair(Options.t(), list(String.t()))) :: :ok
  def rewrite_files({options, files}) do
    options_prime = Options.finalize(options)
    files |> Enum.each(fn file -> rewrite_file(file, options_prime) end)
  end

  @spec rewrite_file(String.t(), Options.t()) :: :ok
  defp rewrite_file(file, options) do
    case File.read(file) do
      {:ok, content} -> rewrite_existing_file(file, content, options)
      {:error, reason} -> Options.croak(options, "#{file}: #{:file.format_error(reason)}")
    end
  end

  @spec rewrite_existing_file(String.t(), String.t(), Options.t()) :: :ok
  defp rewrite_existing_file(file, content, options) do
    content
    |> String.split("\n")
    |> run!(options, file)
    |> Enum.join("\n")
    |> write_back(file)
    |> file_written_message(file, options)
  end

  @spec write_back(String.t(), String.t()) :: :ok | {:error, File.posix()}
  defp write_back(text, file), do: File.write(file, text)

  @spec file_written_message(:ok | {:error, File.posix()}, String.t(), Options.t()) :: :ok
  defp file_written_message(:ok, file, options), do: Options.croak(options, "#{file} updated")

  defp file_written_message({:error, reason}, file, options),
    do: Options.croak(options, "#{file}: #{:file.format_error(reason)}")
end