import re # Import Regex tools
import string # Import string tools
ciphertext = input("Please type in your cipher text:") # Set variable cipertext to the input from user.
ciphertext = re.sub (r'([^a-zA-Z ]+?)', '', ciphertext) # Remove all non-letters.
ciphertext = ciphertext.lower() # Make it all lowercase.
letters = list(string.ascii_lowercase) # Use a list of lowercase letters. https://stackoverflow.com/questions/43918437/how-to-iterate-through-the-alphabet
letterCount = 0 # Set variable for keeping track of which letter in the ciphertext we're on.
letterPos = 0 # Set variable for keeping track of the letter's position in the alphabet.
answer = "" # The solution.
shiftNum = input("Please enter the shift used:") # Get input

for c in ciphertext: # For every letter in the ciphertext
    #Upletters = list(string.ascii_uppercase)
    while letterPos < 26: # While the letter's position in the alphabet is less than
        if ciphertext[letterCount] == letters[letterPos]: # Match the letter in the ciphertext to a letter in the alphabet and once they match, continue.
            letter = int(letterPos) + int(shiftNum) # Take the position of the letter and the shift number.  NOTE: catch spaces.
            if letter > 25:
                letter = letter - 26
            if letter < 0:
                letter = letter + 26
            answer = answer + letters[letter]

        letterPos = letterPos + 1
    if letterPos > 25:
        letterPos = letterPos - 26

    letterCount = letterCount + 1

print("\nYour enciphered text is: " + answer)

#alphabet = '"abcd","e","f","g","h","i","j","k","l","m","n","o","p","q","r","s","t","u","v","w","x","y","z"' #old alphabet string for an array in JS
#print(re.sub (r'([^a-zA-Z]+?)', '', alphabet)) # strip everything except letters

'''
On line #4
This feeds a regex to re.sub literally "If it doesn't match letters or spaces, convert it to nothing, process this variable."
Scrub extranous info or typos.
r marks it as a string literal (no escaping needed)
[] indicates a set of characters, special characters become normal.
^ = start of the string. In a set like this, it matches anything that is not in the string.
a-z matches lowercase letters.
Z-Z matches caps letters
 matches a space
+? essential means "try to match this till you can't"
More info: https://docs.python.org/3/library/re.html
'''

'''
### Stackoverflow thanks to:
First char of string: https://stackoverflow.com/questions/48973202/how-to-get-first-char-of-string-in-python
Length of string: https://stackoverflow.com/questions/4967580/how-to-get-the-size-of-a-string-in-python
Regex to scrub var of extranous info/symbols: https://stackoverflow.com/questions/44315941/regex-to-strip-all-numbers-and-special-characters-but-space-and-letters
Proper syntax for if blocks: https://stackoverflow.com/questions/37376516/python-check-if-multiple-variables-have-the-same-value
https://www.tutorialspoint.com/python/python_if_else.htm
Find substring in a string: https://stackoverflow.com/questions/3437059/does-python-have-a-string-contains-substring-method
'''