class String

def to_full_characters(alpha: true, number: true, symbol: false)
  result = String.new
  return result if self.blank?
  (0...self.size).each do |i|
    half_ord = self[i].ord
    full_ord = half_ord + 0xfee0
    char_ord = case half_ord
               when 0x20 then 0x3000
               when ('0'.ord)..('9'.ord) then number ? full_ord : half_ord
               when ('A'.ord)..('Z'.ord) then alpha ? full_ord : half_ord
               when ('a'.ord)..('z'.ord) then alpha ? full_ord : half_ord
               when ('!'.ord)..('~'.ord) then symbol ? full_ord : half_ord
               else half_ord
               end
    result << char_ord.chr('UTF-8')
  end
  result
end

def to_half_characters(alpha: true, number: true, symbol: false)
  result = String.new
  return result if self.blank?
  (0...self.size).each do |i|
    full_ord = self[i].ord
    half_ord = full_ord - 0xfee0
    char_ord = case full_ord
               when 0x3000 then 0x20
               when ('0'.ord + 0xfee0)..('9'.ord + 0xfee0) then number ? half_ord : full_ord
               when ('A'.ord + 0xfee0)..('Z'.ord + 0xfee0) then alpha ? half_ord : full_ord
               when ('a'.ord + 0xfee0)..('z'.ord + 0xfee0) then alpha ? half_ord : full_ord
               when ('!'.ord + 0xfee0)..('~'.ord + 0xfee0) then symbol ? half_ord : full_ord
               else full_ord
               end
    result << char_ord.chr('UTF-8')
  end
  result
end