mecab

defmodule Mecab do
  @moduledoc """
  Elixir bindings for MeCab, a morphological analyzer.

  Each parser function returns a list of map.
  The map's keys meanings is as follows.

  - surface_form: 表層形
  - part_of_speech: 品詞
  - part_of_speech_subcategory1: 品詞細分類1
  - part_of_speech_subcategory2: 品詞細分類2
  - part_of_speech_subcategory3: 品詞細分類3
  - conjugation_form: 活用形
  - conjugation: 活用型
  - lexical_form: 原形
  - yomi: 読み
  - pronunciation: 発音

  Note: To distinguish things clearly, we call this module "Mecab" and
  a mecab command either "MeCab" or "mecab".
  """

  @doc """
  Parse given string and returns an list of map.

  ## Examples

      iex> Mecab.parse("今日は晴れです")
      [%{"conjugation" => "*", "conjugation_form" => "*", "lexical_form" => "今日",
         "part_of_speech" => "名詞", "part_of_speech_subcategory1" => "副詞可能",
         "part_of_speech_subcategory2" => "*", "part_of_speech_subcategory3" => "*",
         "pronunciation" => "キョー", "surface_form" => "今日", "yomi" => "キョウ"},
       %{"conjugation" => "*", "conjugation_form" => "*", "lexical_form" => "は",
         "part_of_speech" => "助詞", "part_of_speech_subcategory1" => "係助詞",
         "part_of_speech_subcategory2" => "*", "part_of_speech_subcategory3" => "*",
         "pronunciation" => "ワ", "surface_form" => "は", "yomi" => "ハ"},
       %{"conjugation" => "*", "conjugation_form" => "*", "lexical_form" => "晴れ",
         "part_of_speech" => "名詞", "part_of_speech_subcategory1" => "一般",
         "part_of_speech_subcategory2" => "*", "part_of_speech_subcategory3" => "*",
         "pronunciation" => "ハレ", "surface_form" => "晴れ", "yomi" => "ハレ"},
       %{"conjugation" => "基本形", "conjugation_form" => "特殊・デス", "lexical_form" => "です",
         "part_of_speech" => "助動詞", "part_of_speech_subcategory1" => "*",
         "part_of_speech_subcategory2" => "*", "part_of_speech_subcategory3" => "*",
         "pronunciation" => "デス", "surface_form" => "です", "yomi" => "デス"},
       %{"conjugation" => "", "conjugation_form" => "", "lexical_form" => "",
         "part_of_speech" => "", "part_of_speech_subcategory1" => "",
         "part_of_speech_subcategory2" => "", "part_of_speech_subcategory3" => "",
         "pronunciation" => "", "surface_form" => "EOS", "yomi" => ""}]

  """

  @spec parse(String.t, Keyword.t) :: [Map.t, ...]

  def parse(str, option \\ []) do
    read_from_file = option[:from_file]
    mecab_option = option[:mecab_option]

    command =
      case read_from_file do
        true ->
          "mecab '#{str}' #{mecab_option}"
        x when x == nil or x == false ->
          """
          cat <<EOS.907a600613b96a88c04a | mecab #{mecab_option}
          #{str}
          EOS.907a600613b96a88c04a
          """
      end

    command
    |> to_char_list
    |> :os.cmd
    |> to_string
    |> String.trim
    |> String.split("\n")
    |> Enum.map(fn line ->
        Regex.named_captures(~r/
          ^
          (?<surface_form>[^\t]+)
          (?:
            \s
            (?<part_of_speech>[^,]+),
            (?<part_of_speech_subcategory1>[^,]*),
            (?<part_of_speech_subcategory2>[^,]*),
            (?<part_of_speech_subcategory3>[^,]*),
            (?<conjugation_form>[^,]*),
            (?<conjugation>[^,]*),
            (?<lexical_form>[^,]*),
            (?<yomi>[^,]*),
            (?<pronunciation>[^,]*)
          )?
          $
          /x, line)
      end)
  end


  @doc """
  Parse given file and returns an list of map.

  In addition to Mecab.parse(filepath, from_file: true), this function checks
  if a given filepath is exists.

  ## Examples

      iex> File.read!("sample.txt")
      "今日は晴れです。\\n明日は雨でしょう。\\n"

      iex> Mecab.read("sample.txt")
      {:ok,
       [%{"surface_form" => "今日", "part_of_speech" => "名詞", ...},
        %{"surface_form" => "は", "part_of_speech" => "助詞", ...},
        %{"surface_form" => "晴れ", "part_of_speech" => "名詞", ...},
        %{"surface_form" => "です", "part_of_speech" => "助動詞", ...},
        %{"surface_form" => "。", "part_of_speech" => "記号", ...},
        %{"surface_form" => "EOS", ...},
        %{"surface_form" => "明日", "part_of_speech" => "名詞", ...},
        %{"surface_form" => "は", "part_of_speech" => "助詞", ...},
        %{"surface_form" => "雨", "part_of_speech" => "名詞", ...},
        %{"surface_form" => "でしょ", "part_of_speech" => "助動詞", ...},
        %{"surface_form" => "う", "part_of_speech" => "助動詞", ...},
        %{"surface_form" => "。", "part_of_speech" => "記号", ...},
        %{"surface_form" => "EOS", ...}]}

      iex> Mecab.read("not_found.txt")
      {:error, "no such a file or directory: not_found.txt"}
  """

  @spec read(String.t, Keyword.t) :: {:ok, [Map.t, ...]} | {:error, String.t}

  def read(path, option \\ []) do
    case File.exists?(path) do
      true ->
        {:ok, parse(path, [from_file: true] ++ option)}
      false ->
        {:error, "no such a file or directory: #{path}"}
    end
  end


  @doc """
  Parse given file and returns an list of map.

  ## Examples

      iex> File.read!("sample.txt")
      "今日は晴れです。\\n明日は雨でしょう。\\n"

      iex> Mecab.read!("sample.txt")
      [%{"surface_form" => "今日", "part_of_speech" => "名詞", ...},
       %{"surface_form" => "は", "part_of_speech" => "助詞", ...},
       %{"surface_form" => "晴れ", "part_of_speech" => "名詞", ...},
       %{"surface_form" => "です", "part_of_speech" => "助動詞", ...},
       %{"surface_form" => "。", "part_of_speech" => "記号", ...},
       %{"surface_form" => "EOS", ...},
       %{"surface_form" => "明日", "part_of_speech" => "名詞", ...},
       %{"surface_form" => "は", "part_of_speech" => "助詞", ...},
       %{"surface_form" => "雨", "part_of_speech" => "名詞", ...},
       %{"surface_form" => "でしょ", "part_of_speech" => "助動詞", ...},
       %{"surface_form" => "う", "part_of_speech" => "助動詞", ...},
       %{"surface_form" => "。", "part_of_speech" => "記号", ...},
       %{"surface_form" => "EOS", ...}]
  """

  @spec read!(String.t, Keyword.t) :: [Map.t, ...]

  def read!(path, option \\ []) do
    if !File.exists?(path) do
      raise "no such a file or directory: #{path}"
    end
    parse(path, [from_file: true] ++ option)
  end

end