#!/usr/bin/env python3

from string import ascii_uppercase
from string import digits

#### Variables for Rail Fence Transposion  ####
# numbe of rows
k = 3
cipher_text_list = []
cipher_text_list_element = ''
count_char = 1
i = 0
decrypted_text = ''

#### Variables for ROT  #### 
rot=5
clear_text = ""

with open("cipher_text.txt", "r") as f:
    # we need to remove last char
    cipher_text = f.read()

#### Rail Fence Transposition  ####

# Compute real text length 
text_length = len(cipher_text)
print(f"Length of text with spaces is: {text_length}")

# Compute block length
block_length = int(text_length / k)

print(f"Length of text with spaces is: {text_length}, length of block is: {block_length}")


# Create list with k-number fields
for pismeno in cipher_text:        
    if count_char % block_length != 0:
        cipher_text_list_element = cipher_text_list_element + pismeno
    elif count_char % block_length == 0:
        cipher_text_list_element = cipher_text_list_element + pismeno
        cipher_text_list.append(cipher_text_list_element)
        cipher_text_list_element = ''

    count_char+=1

# Display list
print("\nThis is Rail Fence Transposition Cipher list")
print(cipher_text_list, "\n")

# Read first char from list element than move to another element and read first char until end of list
# then read second char from element and move to anther element when you read the second char
# do it k times

while i < block_length:
    for element in cipher_text_list:
        decrypted_text+=element[i]
    i+=1

print(f"\nThis is decrypted text encrypted by Rail Fence Transposition Cipher that is input into ROT{rot} de-cipher: ")
print(decrypted_text, "\n")

#### ROT Decryption ###

cipher_text = decrypted_text

# print(f"Cipher text is: '{cipher_text}'")

# Generate variable ABC..XYZ0123..9
template = "(,;'<.$![@" + ascii_uppercase + '}>+:&-%]*\\ ' + digits + '_"?=`/~#|){'

print(f"Template for ROT{rot} is: {template}")

# Get length of template
len_template = len(template)
print(f"Length of template is: '{len_template}'")

for pismeno in cipher_text:
    # get index of pismeno and add length of rot cipher
    rot_position = template.find(pismeno) - rot
    print(f"Char is: {pismeno} and rot position is: {rot_position}")

    if rot_position < 0:
        clear_text += template[len_template+rot_position]
    elif rot_position >= 0:
        clear_text += template[rot_position]

# Print clear_text
print(clear_text)