defmodule Mbcs do
  @moduledoc """
  Wrapper for erlang-mbcs.
  This module provides functions for character encoding conversion.
  See `https://code.google.com/p/erlang-mbcs/` for detail.

  ## Usage
  
      # Start mbcs server
      iex> Mbcs.start
      :ok

      # Convert UTF-8 to Shift_JIS
      iex> Mbcs.encode!("九条カレン", :cp932)
      <<139, 227, 143, 240, 131, 74, 131, 140, 131, 147>>

      # Convert Shift_JIS to UTF-8, and return as a list
      iex> Mbcs.decode!([139, 227, 143, 240, 131, 74, 131, 140, 131, 147], :cp932, return: :list)
      [20061, 26465, 12459, 12524, 12531]
 
  ## Support encodings

  * `:cp037`
  * `:cp437`
  * `:cp500`
  * `:cp737`, `:cp775`
  * `:cp850`, `:cp852`, `:cp855`, `:cp857`, `:cp860`, `:cp861`, `:cp862`, `:cp863`, `:cp864`, `:cp865`, `:cp866`, `:cp869`, `:cp874`, `:cp875`
  * `:cp932`, `:cp936`, `:gbk`, `:cp949`, `:cp950`, `:big5`
  * `:cp1026`, `:cp1250`, `:cp1251`, `:cp1252`, `:cp1253`, `:cp1254`, `:cp1255`, `:cp1256`, `:cp1257`, `:cp1258`
  * `:cp10000`, `:cp10006`, `:cp10007`, `:cp10029`, `:cp10079`, `:cp10081`
  * `:utf8`, `:utf16`, `:utf16le`, `:utf16be`, `:utf32`, `:utf32le`, `:utf32be`
 
  ## Options

  * return: `:list`, `:binary`
  * error: `:strict`, `:ignore`, `:replace`
  * replace: `non_neg_integer`
  * bom: `true`, `false`

  ## License
  Copyright (c) 2014 woxtu

  Licensed under the Boost Software License, Version 1.0.
  """

  def start do
    :mbcs.start
  end
 
  def stop do
    :mbcs.stop
  end

  def encode(string, to, options \\ [])

  def encode(string, to, options) when is_bitstring(string) do
    to_list = if String.valid?(string), do: &to_char_list/1, else: &:erlang.bitstring_to_list/1

    encode(to_list.(string), to, options)
  end

  def encode(string, to, options) when is_list(string) do
    case :mbcs.encode(string, to, options) do
      {:error, reason} -> {:error, reason}
      result -> {:ok, result}
    end
  end

  def encode!(string, to, options \\ [])

  def encode!(string, to, options) when is_bitstring(string) do
    to_list = if String.valid?(string), do: &to_char_list/1, else: &:erlang.bitstring_to_list/1

    encode!(to_list.(string), to, options)
  end

  def encode!(string, to, options) when is_list(string) do
    case :mbcs.encode(string, to, options) do
      {:error, reason} -> raise to_error(reason)
      result -> result
    end
  end

  def decode(string, from, options \\ []) do
    case :mbcs.decode(string, from, options) do
      {:error, reason} -> {:error, reason}
      result -> if options[:return] == :list, do: {:ok, result}, else: {:ok, List.to_string(result)}
    end
  end

  def decode!(string, from, options \\ []) do
    case :mbcs.decode(string, from, options) do
      {:error, reason} -> raise to_error(reason)
      result -> if options[:return] == :list, do: result, else: List.to_string(result)
    end
  end

  def from_to(string, from, to, options \\ []) do
    case :mbcs.from_to(string, from, to, options) do
      {:error, reason} -> {:error, reason}
      result -> {:ok, result}
    end
  end

  def from_to!(string, from, to, options \\ []) do
    case :mbcs.from_to(string, from, to, options) do
      {:error, reason} -> raise to_error(reason)
      result -> result
    end
  end

  defmodule UnknownOptionError, do: defexception [:message]
  defmodule UnknownEncodingError, do: defexception [:message]
  defmodule UnmappingUnicodeError, do: defexception [:message]
  defmodule IllegalListError, do: defexception [:message]
  defmodule UndefinedCharacterError, do: defexception [:message]
  defmodule UnmappingCharacterError, do: defexception [:message]
  defmodule IncompleteMultibyteSequenceError, do: defexception [:message]
  defmodule UnmappingMultibyteCharacterError, do: defexception [:message]
  defmodule UnknownError, do: defexception [:message]

  defp to_error({:unknown_option, [option: option]}) do
    UnknownOptionError.exception(message: "option #{inspect option}")
  end

  defp to_error({:unkonwn_encoding, [encoding: encoding]}) do
    UnknownEncodingError.exception(message: "encoding #{inspect encoding}")
  end

  defp to_error({:unmapping_unicode, [unicode: code, pos: pos]}) do
    UnmappingUnicodeError.exception(message: "code #{code} in position #{pos}")
  end

  defp to_error({:illegal_list, [list: list, line: line]}) do
    IllegalListError.exception(message: "list #{inspect list} at line #{line}")
  end

  defp to_error({:undefined_character, [character: character, pos: pos]}) do
    UndefinedCharacterError.exception(message: "character #{character} in position #{pos}")
  end

  defp to_error({:unmapping_character, [character: character, pos: pos]}) do
    UnmappingCharacterError.exception(message: "character #{character} in position #{pos}")
  end

  defp to_error({:incomplete_multibyte_sequence, [leadbyte: leadbyte, pos: pos]}) do
    IncompleteMultibyteSequenceError.exception(message: "leadbyte #{leadbyte} in position #{pos}")
  end

  defp to_error({:unmapping_multibyte_character, [multibyte_character: character, pos: pos]}) do
    UnmappingMultibyteCharacterError.exception(message: "character #{character} in position #{pos}")
  end

  defp to_error(reason) do
    UnknownError.exception(message: inspect reason)
  end
end