defmodule Domainatrex do
  require Logger
  @moduledoc """
  Documentation for Domainatrex.
  """
  @fallback_local_copy Application.get_env(:domainatrex, :fallback_local_copy, "lib/public_suffix_list.dat")
  @fetch_latest Application.get_env(:domainatrex, :fetch_latest, true)
  @public_suffix_list nil

  :inets.start
  :ssl.start

  with true <- @fetch_latest,
       public_suffix_list_url <- Application.get_env(:domainatrex, :public_suffix_list_url, 'https://raw.githubusercontent.com/publicsuffix/list/master/public_suffix_list.dat'),
       {:ok, {_, _, string}} <- :httpc.request(:get, {public_suffix_list_url, []}, [], []) do
    @public_suffix_list to_string(string)
  else
    _ ->
      case File.read @fallback_local_copy do
        {:ok, string} ->
          if @fetch_latest do
            Logger.error "[Domainatrex] Could not read the public suffix list from the internet, trying to read from the backup at #{@fallback_local_copy}"
          end

          @public_suffix_list string
        _ ->
          Logger.error "[Domainatrex] Could not read the public suffix list, please make sure that you either have an internet connection or #{@fallback_local_copy} exists"
          @public_suffix_list nil
      end
  end

  custom_suffixes = Application.get_env(:domainatrex, :custom_suffixes, [])
  string = if Application.get_env(:domainatrex, :include_private, false) do
    @public_suffix_list
  else
    @public_suffix_list
    |> String.split("// ===END ICANN DOMAINS===")
    |> List.first
  end
  suffixes =
    string
    |> String.split("\n")
    |> Enum.reject(&(&1 == ""))
    |> Enum.reject(&(String.contains?(&1, "//")))
    |> Enum.concat(custom_suffixes)
    |> Enum.map(&(String.split(&1, ".")))
    |> Enum.map(&Enum.reverse/1)
    |> Enum.sort_by(&length/1)
    |> Enum.reverse

  Enum.each(suffixes, fn(suffix) ->
    if List.last(suffix) == "*" do
      case length(suffix) do
        2 ->
          defp match([unquote(Enum.at(suffix,0)), a]) do
            format_response([unquote(Enum.at(suffix,0))], [a])
          end
          defp match([unquote(Enum.at(suffix,0)), a, b]) do
            format_response([unquote(Enum.at(suffix,0))], [a,b])
          end
          defp match([unquote(Enum.at(suffix,0)) | _] = args) do
            format_response(Enum.slice(args, 0,2), Enum.slice(args, 2, 10))
          end
        3 ->
          defp match([unquote(Enum.at(suffix,0)), unquote(Enum.at(suffix,1)), a]) do
            format_response([unquote(Enum.at(suffix,0)),unquote(Enum.at(suffix,1))], [a])
          end
          defp match([unquote(Enum.at(suffix,0)), unquote(Enum.at(suffix,1)), a, b]) do
            format_response([unquote(Enum.at(suffix,0)),unquote(Enum.at(suffix,1))], [a, b])
          end
          defp match([unquote(Enum.at(suffix,0)), unquote(Enum.at(suffix,1)) | _] = args) do
            format_response(Enum.slice(args, 0,3), Enum.slice(args, 3, 10))
          end
      end
    else
      case length(suffix) do
        1 ->
          defp match([unquote(Enum.at(suffix,0)) | tail] = args) do
            format_response([Enum.at(args, 0)], tail)
          end
        2 ->
          defp match([unquote(Enum.at(suffix,0)), unquote(Enum.at(suffix,1)) | tail] = args) do
            format_response([Enum.at(args, 0), Enum.at(args, 1)], tail)
          end
        3 ->
          defp match([unquote(Enum.at(suffix,0)), unquote(Enum.at(suffix,1)), unquote(Enum.at(suffix,2)) | tail] = args) do
            format_response([Enum.at(args, 0), Enum.at(args, 1), Enum.at(args, 2)], tail)
          end
        4 ->
          defp match([unquote(Enum.at(suffix,0)), unquote(Enum.at(suffix,1)), unquote(Enum.at(suffix,2)), unquote(Enum.at(suffix,3)) | tail] = args) do
            format_response([Enum.at(args, 0), Enum.at(args, 1), Enum.at(args, 2), Enum.at(args, 3)], tail)
          end
        5 ->
          defp match([unquote(Enum.at(suffix,0)), unquote(Enum.at(suffix,1)), unquote(Enum.at(suffix,2)), unquote(Enum.at(suffix,3)), unquote(Enum.at(suffix,4)) | tail] = args) do
            format_response([Enum.at(args, 0), Enum.at(args, 1), Enum.at(args, 2), Enum.at(args, 3), Enum.at(args, 4)], tail)
          end
        _ ->
          {:error, "There exists a domain in the list which contains more than 5 dots: #{suffix}"}
      end
    end
  end)

  defp format_response(tld, domain) do
    with [domain |subdomains] <- domain do
      tld = tld |> Enum.reverse |> Enum.join(".")
      subdomains = subdomains |> Enum.reverse |> Enum.join(".")
      {:ok, %{domain: domain, subdomain: subdomains, tld: tld}}
    else
      _ -> {:error, "Cannot parse: invalid domain"}
    end
  end

  @doc """
  ## Examples
      iex> Domainatrex.parse("someone.com")
      {:ok, %{domain: "someone", subdomain: "", tld: "com"}}

      iex> Domainatrex.parse("blog.someone.id.au")
      {:ok, %{domain: "someone", subdomain: "blog", tld: "id.au"}}

      iex> Domainatrex.parse("zen.s3.amazonaws.com")
      {:ok, %{domain: "amazonaws", subdomain: "zen.s3", tld: "com"}}
  """
  def parse(url) do
    case String.length(url) > 1 && String.contains?(url, ".") do
      true ->
        adjusted_url = url |> String.split(".") |> Enum.reverse
        match(adjusted_url)
      _ ->
        {:error, "Cannot parse: invalid domain"}
    end
  end

  defp match(_it) do
    {:error, "Cannot match: invalid domain"}
  end
end