caesar_cipher.rb

#Caesar Cipher
#Simple text cipher that shifts letters a fixed number of positions

def caesar_cipher_encrypt(string, shift)
	
	#Alphabet Arrays
	alpha = ("a".."z").to_a
	alphaBig = ("A".."Z").to_a
	new_string = ""

	#Do shift on each letter one at a time
	string.split(//).each do |letter|
		
		#See if letter should be shifted, shift using function
		if alpha.include? letter
			new_letter = letterShift(letter, alpha, shift)
		elsif alphaBig.include? letter
			new_letter = letterShift(letter, alphaBig, shift)
		else
			new_letter = letter
		end
		new_string += new_letter

	end
	new_string
end

def caeser_cipher_decrypt(string, shift)
	caesar_cipher_encrypt(string, 0-shift)
end

def letterShift(letter, array, shift)
#captures letter shift logic

	index = array.index(letter)
	new_index = (index + shift)%(array.length)
	new_letter = array[new_index]
end

##Tests##
message = "HI"
puts "-----Test 1-----" 
key1 = 2
encrypted_message1 = caesar_cipher_encrypt(message, key1)
puts "Encrypted Message 1: #{encrypted_message1}"
decrypted_message1 = caeser_cipher_decrypt(encrypted_message1, key1)
puts "Decrypted message 1: #{decrypted_message1}"

puts "-----Test 2-----" 
message = "HI"
key2 = 20
encrypted_message2 = caesar_cipher_encrypt(message, key2)
puts "Encrypted Message 2: #{encrypted_message2}"
decrypted_message2 = caeser_cipher_decrypt(encrypted_message2, key2)
puts "Decrypted message 1: #{decrypted_message2}"