defmodule Localizator.Translitor.BE do
  @moduledoc """
  Translit module for Belorussian language.
  """
  @locale "be"
  @table %{
    "А" => "A",
    "Б" => "B",
    "В" => "V",
    "Г" => "G",
    "Д" => "D",
    "Ж" => "Zh",
    "З" => "Z",
    "И" => "I",
    "І" => "I",
    "Й" => "J",
    "К" => "K",
    "Л" => "L",
    "М" => "M",
    "Н" => "N",
    "О" => "O",
    "П" => "P",
    "Р" => "R",
    "С" => "S",
    "Т" => "T",
    "У" => "U",
    "Ф" => "F",
    "Х" => "Kh",
    "Ц" => "Ts",
    "Ч" => "Ch",
    "Ш" => "Sh",
    "Щ" => "Shch",
    "Ы" => "Y",
    "Э" => "E",
    "Ь" => "",
    "Ъ" => "",
    "Ў" => "W",
    "а" => "a",
    "б" => "b",
    "в" => "v",
    "г" => "g",
    "д" => "d",
    "ж" => "zh",
    "з" => "z",
    "и" => "i",
    "і" => "i",
    "й" => "j",
    "к" => "k",
    "л" => "l",
    "м" => "m",
    "н" => "n",
    "о" => "o",
    "п" => "p",
    "р" => "r",
    "с" => "s",
    "т" => "t",
    "у" => "u",
    "ф" => "f",
    "х" => "kh",
    "ц" => "ts",
    "ч" => "ch",
    "ш" => "sh",
    "щ" => "shch",
    "ы" => "y",
    "э" => "e",
    "ў" => "w",
    "ь" => "",
    "ъ" => "",
    "'" => "",
    "’" => ""
  }

  @typedoc """
  Plain Text
  """
  @type text :: String.t()

  @typedoc """
  Locale
  """
  @type locale :: String.t()

  @behaviour Localizator.Translitor.Base

  @impl true
  @spec locale() :: {:ok, locale}
  def locale(), do: @locale

  @doc """
  A belorussian to english transliteration
  ## Example
  ``elixir
    iex> Localizator.Translitor.BE.convert("Ева Салаўёва")
    "Jeva Salawjova"
  ``
  """
  @impl true
  @spec convert(text) :: text
  def convert(text) when is_bitstring(text) do
    text
    |> String.graphemes()
    |> Enum.reduce([], &convert_letter/2)
    |> Enum.join()
  end

  # special case for "<consonant>е", that should be mapped as "<translited consonant>ie"
  defp convert_letter(letter, acc)
       when letter in ~w(Е е Ё ё Ю ю Я я) do
    cond do
      List.last(acc) in ~w(B V G D Zh Z K L M N P R S T F Kh Ts Ch Sh Shch b v g d zh z k l m n p r s t f kh ts ch sh shch) ->
        acc ++ [convert_i(letter)]

      List.last(acc) in (~w(A I J O U Y E W a i j o u y e w) ++ ["", " ", nil]) ->
        acc ++ [convert_j(letter)]
    end
  end

  defp convert_letter(letter, acc) do
    acc ++ [convert_letter(letter)]
  end

  defp convert_letter(letter) do
    case Map.get(@table, letter) do
      nil -> letter
      latin -> latin
    end
  end

  defp convert_i("Е"), do: "Ie"
  defp convert_i("е"), do: "ie"
  defp convert_i("Ё"), do: "Io"
  defp convert_i("ё"), do: "io"
  defp convert_i("Ю"), do: "Iu"
  defp convert_i("ю"), do: "iu"
  defp convert_i("Я"), do: "Ia"
  defp convert_i("я"), do: "ia"

  defp convert_j("Е"), do: "Je"
  defp convert_j("е"), do: "je"
  defp convert_j("Ё"), do: "Jo"
  defp convert_j("ё"), do: "jo"
  defp convert_j("Ю"), do: "Ju"
  defp convert_j("ю"), do: "ju"
  defp convert_j("Я"), do: "Ja"
  defp convert_j("я"), do: "ja"
end