class String
  CHARACTER_MAPPING = {
    'ك' => 'ک',
    'دِ' => 'د',
    'بِ' => 'ب',
    'زِ' => 'ز',
    'ذِ' => 'ذ',
    'شِ' => 'ش',
    'سِ' => 'س',
    'ى' => 'ی',
    'ي' => 'ی',
    '١' => '۱',
    '٢' => '۲',
    '٣' => '۳',
    '٤' => '۴',
    '٥' => '۵',
    '٦' => '۶',
    '٧' => '۷',
    '٨' => '۸',
    '٩' => '۹',
    '٠' => '۰'
  }.freeze

  def to_persian
    gsub(Regexp.union(CHARACTER_MAPPING.keys), CHARACTER_MAPPING)
  end

  def percent_match(mold)
    mold = mold.to_s.to_persian
    str = self.to_persian
    char_cost = (100.to_f / length).round(2)
    matching = 0
    str_index = 0
    mold_index = 0
    str.each_char.with_index do |_char, index|
      break if mold[mold_index].blank?

      if mold[mold_index] != str[str_index]
        mold_index = index - 1 if mold.length < str.length
        str_index = index - 1 if mold.length > str.length
      else
        matching += char_cost
      end
      str_index += 1
      mold_index += 1
    end
    matching.round
  end
end