def encode value, offset = 13
	cypher = ""
	value.each_char do |c|
		if c.ord <= 90 && c.ord >= 65
			cypher << ((((c.ord - 65)+ offset) % 26) + 65)
		elsif c.ord <= 122 && c.ord >= 91
			cypher << ((((c.ord - 97)+ offset) % 26) + 97)
		else
			cypher << c
		end
	end
	cypher
end

def decode value, offset = 13
	decypher = ""
	value.each_char do | c |
		if c.ord <= 90 && c.ord >= 65
			decypher << ((((c.ord - 65)-offset) % 26) + 65)
		elsif c.ord <= 122 && c.ord >= 91
			decypher << ((((c.ord - 97)-offset) % 26) + 97)
		else
			decypher << c
		end
	end
	decypher
end

def code (file, offset = 13)
	input = File.open('assignment.txt', "r")
	output = File.open('assignment.txt', "a")
	input.each_line do |line|
		if line[0] == "e"
			line = line[2..-1]
			output.write(encode(line, offset))
		elsif line[0] == "d"
			line = line[2..-1]
			output.write(decode(line, offset))
		else
			puts "Not a thing"
		end
	end
	input.close
	output.close
end

code("decypher",13)