ruby class for ISBN

isbn.rb

class ISBN
	attr_reader :isbn

	# =initialize
	def initialize(isbn)
		@isbn = isbn.strip.gsub(/[\s\-]/, "")# {{{
		@type = nil
		@type_checked = false
	end# }}}

	# =set_isbn
	def set_isbn(isbn)
		@isbn = isbn# {{{ 
		@type = nil
		@type_checked = false
	end# }}}

	# =get_type
	def get_type
		unless @type_checked# {{{
			len = @isbn.length
			case len
			when 10
				if /^[0123457][0-9]{8}[0-9Xx]$/ =~ @isbn and check_isbn10
					@type = :isbn10
				end
			when 13
				if /^(978|979)[0-9]{10}/ =~ @isbn and check_isbn13
					@type = :isbn13
				end
			end
			@type_checked = true
		end
		@type
	end# }}}

	# =to_isbn10
	def to_isbn10
		if get_type == :isbn13# {{{
			tmp = @isbn[3..11]
			cd = get_check_digit_for_isbn10(tmp)
			"#{tmp}#{cd}"
		else
			@isbn
		end
	end# }}}

	# =to_isbn13
	def to_isbn13
		if get_type == :isbn10# {{{
			tmp = "978#{@isbn[0..8]}"
			cd = get_check_digit_for_isbn13(tmp)
			"#{tmp}#{cd}"
		else
			@isbn
		end
	end# }}}

	private
	# =check_isbn10
	def check_isbn10
		cd = (@isbn[9..9].downcase == "x") ? 10 : @isbn[9..9].to_i# {{{
		(cd == get_check_digit_for_isbn10(@isbn)) ? true : false
	end# }}}

	# =checK_isbn13
	def check_isbn13
		cd = @isbn[12..12].to_i# {{{
		(cd == get_check_digit_for_isbn13(@isbn)) ? true : false
	end# }}}

	# =get_check_digit_for_isbn10
	def get_check_digit_for_isbn10(isbn_str)
		total = 0# {{{
		isbn_str[0..8].split(//).each_with_index do |chr, index|
			total += (10 - index) * chr.to_i
		end
		11 - (total % 11)
	end# }}}

	# =get_check_digit_for_isbn13
	def get_check_digit_for_isbn13(isbn_str)
		total = 0# {{{
		isbn_str[0..11].split(//).each_with_index do |chr, index|
			total += (index % 2 == 0 ? 1 : 3) * chr.to_i
		end
		res = 10 - (total % 10)
		res_s = res.to_s
		(res_s[res_s.length - 1].chr == "0") ? 0 : res
	end# }}}
end