# phone_letters_to_numbers
class String
  
  # Converts a phone number with letters to numbers
  # Ex. AAA-FFFF => 222-3333
  def convert_to_phone_number
    letters = 'abcdefghijklmnopqrstuvwxyz'
    numbers = '22233344455566677778889999'
    self.downcase.tr(letters, numbers)
  end
  
  # Converts the given string to the sequence of
  # numbers that you would need to push to create
  # that string. Shift = *, Space = #
  # Input: "Hello hi"
  # Output: "*44 33 555 555 666 # 44 444"
  def how_to_text
    letters    = 'abcdefghijklmnopqrstuvwxyz '
    numbers    = '22233344455566677778889999#'
    multiplier = '123123123123123123412312341'
    str = ''
    self.each_byte do |char|
      char = char.chr      
      if char =~ /[A-Z]/
        str += '*'
        char.downcase!
      end
      str += if letters.include? char
        index = letters.index(char)
        numbers[index].chr * multiplier[index].chr.to_i
      else
        char
      end + " "
    end
    str.chop
  end
  
  # Converts the given numeric sequence back to
  # a text string.
  # Input: "*44 33 555 555 666 # 44 444"
  # Output: "Hello hi"
  def decode_text
    letters = 'abcdefghijklmnopqrstuvwxyz '
    numbers = '22233344455566677778889999#'
    str = ''
    self.split.each do |part|
      shift = part[0].eql?(?*) ? true : false
      part = part[1,part.length] if shift
      pos = numbers.index(part) + (part.length-1)
      str += if shift
        letters[pos].chr.upcase
      else
        letters[pos].chr
      end
    end
    str
  end
  
end