'''
Caesar's cipher

Introduction

No doubt you will have seen the ennciphering/deciphering methods with 
shifting the alphabet. For example, A becomes D, B becomes E, etc. 
This is something you can do in Python.

We start with a message, written in a string. 
'''

message = 'CAESARSDECIPHERING'

'''
Have you ever heared of ASCII (American Standard Code for 
Information Interchange)? Each character or string has a numerical ASCII value.
For A it is 65, for Z it is 95. To convert from ASCII to a string in Python, 
you use the `chr()` function, whose name originates from the word 'character.'

The code below generates a variable `Str`, which holds the alphabet:

'''

alphabet = np.arange(65,91)
Str = []

for ii in alphabet: 
    Str.append(chr(ii))

Str=''.join(Str)
print(Str)

'''
In order to decipher our message, we need a variable `Str_decipher`, for 
which the variable `Str` is shifted. In this case we use a shift (Caesar 
number) of 2. 
'''

caesar_num = 2  # Between 0 and 25
Str_decipher = Str[caesar_num:] + Str[:caesar_num]
print(Str_decipher)

'''
In order to encrypt, we need to:
* go over each character in the string
* find the location in the regular alphabet (`Str`), with `Str.index(character)`
* find the corresponding character in the new alphabet (`Str_decipher`)
* append that character to the encrypted message
'''

new_message = []

for ii in message:
    index = Str.index(ii) # Go over each character in the string
    new_character = Str_decipher[index]  # Find the location in the regular alphabet
    new_message.append(new_character)  # Extract the corresponding character in the new alphabet

new_message=''.join(new_message) # Stitches all characters in the array to one string

print(new_message)

'''
Exercise A: Deciphering function

You have seen how to encrypt. The challenge is now to decrypt a message.

Let's start by making code which takes as input the Caesar number and 
`message_to_decipher`, and outputs the `message_original`. 
Name your function `Caesar_decipher`.
'''

message = 'EGCUCTUFGEKRJGTKPI' 
caesar_num = 2 

def Caesar_decipher(message,caesar_num):
    
# Your code here


'''
Exercise B: Caesar number

Can you decipher without the value of the Caesar number given?
'''

message_to_decipher = 'KVCQOBFSORKWHVCIHGDOQSG'

# Your code here