defmodule Tld do
  @moduledoc """
  Top-Level Domain module for BEAM.

  Lets you get the current list of TLDs, as well as find the TLD in a domain name.
  """

  alias Tld.DomainName
  alias Tld.ListServer

  @doc """
  Get list of all Top-Level Domains.

  ## Examples

      iex> list = Tld.get_list()
      iex> Enum.member?(list, "NET")
      true
      iex> Enum.member?(list, "TEST")
      false

  """
  def get_list() do
    ListServer.get_list()
  end

  @doc """
  If input string contains a domain name, get its TLD.

  Returns {:ok, "COM"} if found (COM being replaced with the actual TLD found),
  {:err, :not_found} if TLD was not found in string, and {:err, :invalid_input}
  if not given a string.

  ## Examples

      iex> Tld.get_tld_from_domain_name("contoso.com")
      {:ok, "COM"}

      iex> Tld.get_tld_from_domain_name("FACE.BORG.TEST")
      {:err, :not_found}

      iex> Tld.get_tld_from_domain_name("CORRUPT.GOV")
      {:ok, "GOV"}

      iex> Tld.get_tld_from_domain_name('NOTASTRING.NET')
      {:err, :invalid_input}

      iex> Tld.get_tld_from_domain_name(42)
      {:err, :invalid_input}

      iex> Tld.get_tld_from_domain_name(nil)
      {:err, :invalid_input}
  """
  def get_tld_from_domain_name(""), do: {:err, :not_found}

  def get_tld_from_domain_name(name) when is_binary(name) do
    match =
      name
      # Domain names are case-insensitive, but our matching logic is not, so
      # upcase the candidate string before matching.
      |> String.upcase()
      |> DomainName.match_tld(get_list())

    if is_binary(match) do
      {:ok, match}
    else
      {:err, :not_found}
    end
  end

  def get_tld_from_domain_name(_), do: {:err, :invalid_input}
end