# coding: utf-8

from argparse import ArgumentParser
from unidecode import unidecode
from re import sub


def checkArguments():
    args = ArgumentParser(description='Cryptanalyst')
    args.add_argument('-f', '--filename', help='Text to analyze')
    return args.parse_args()

def main():
	args = checkArguments()

	# Read file	
	dataFile = str()
	with open(args.filename, 'r') as f:
		data = f.readlines()

		for d in data:
			u = unidecode(d.lower(), 'utf-8')
			dataFile += sub(r'[^a-z]', '', u)

	# Get number of letters
	totalLetters = 0
	for letter in dataFile:
		totalLetters += 1

	counts = []

	for i in range (0, 26):
		counts.append(0)

	# Count the number of letter in our text	
	letterToAscii = ord('a') # Get the ASCII code
	for i in dataFile:
		l = ord(i) - letterToAscii
		if l >= 0 and l <= 26:
			counts[l] += 1

	# Get the sum
	sum = 0
	for i in range (0, 26):
		sum += counts[i] * (counts[i] - 1)

	ic = sum / (totalLetters * (totalLetters - 1))
	print(f"Index of coincidence: {ic}")
	
if __name__ == "__main__":
	main()