quine.ex

defmodule Quine do
  @header "defmodule Quine do\n  @header \""

  @indent """
    def indent(str) do
      str
      |> String.split(\"\\n\")
      |> Enum.map(&(\"  \" <> &1))
      |> Enum.join(\"\\n\")
    end
  """

  @escape """
    def escape(str) do
      str
      |> String.replace(\"\\\\\", \"\\\\\\\\\")
      |> String.replace(\"\\\"\", \"\\\\\\\"\")
    end
  """

  @terminate """
    def terminate(str) do
      String.replace(str, ~r/$/, \"\\\"\\\"\\\"\\n\")
    end
  """

  @process """
    def process(str) do
      str
      |> indent()
      |> escape()
      |> terminate()
    end
  """

  @run """
    def run() do
      IO.puts(@header <> \"defmodule Quine do\\\\n @header \\\\\\\"\\\"\")
      IO.puts(\"\")
      IO.puts(\"  @indent \\\"\\\"\\\"\")
      IO.puts(process(@indent))
      IO.puts(\"  @escape \\\"\\\"\\\"\")
      IO.puts(process(@escape))
      IO.puts(\"  @terminate \\\"\\\"\\\"\")
      IO.puts(process(@terminate))
      IO.puts(\"  @process \\\"\\\"\\\"\")
      IO.puts(process(@process))
      IO.puts(\"  @run \\\"\\\"\\\"\")
      IO.puts(process(@run))
      IO.puts(\"  @footer \\\"end\\\"\")
      IO.puts(\"\")
      IO.puts(@indent)
      IO.puts(@escape)
      IO.puts(@terminate)
      IO.puts(@process)
      IO.puts(@run)
      IO.puts(@footer)
    end
  """

  @footer "end"

  def indent(str) do
    str
    |> String.split("\n")
    |> Enum.map(&("  " <> &1))
    |> Enum.join("\n")
  end

  def escape(str) do
    str
    |> String.replace("\\", "\\\\")
    |> String.replace("\"", "\\\"")
  end

  def terminate(str) do
    String.replace(str, ~r/$/, "\"\"\"\n")
  end

  def process(str) do
    str
    |> indent()
    |> escape()
    |> terminate()
  end
  
  def run() do    
    IO.puts(@header <> "defmodule Quine do\\n  @header \\\"\"")
    IO.puts("")
    IO.puts("  @indent \"\"\"")
    IO.puts(process(@indent))
    IO.puts("  @escape \"\"\"")
    IO.puts(process(@escape))
    IO.puts("  @terminate \"\"\"")
    IO.puts(process(@terminate))
    IO.puts("  @process \"\"\"")
    IO.puts(process(@process))
    IO.puts("  @run \"\"\"")
    IO.puts(process(@run))
    IO.puts("  @footer \"end\"")
    IO.puts("")
    IO.puts(@indent)
    IO.puts(@escape)
    IO.puts(@terminate)
    IO.puts(@process)
    IO.puts(@run)
    IO.puts(@footer)
  end

end