#!/usr/bin/python2
import sys, readline

#Which characters should be translated? Uncomment as many lines as you like.
increment = ''
#Lowercase letters.
increment+= 'abcdefghijklmnopqrstuvwxyz'
#Uppercase letters
increment+= 'abcdefghijklmnopqrstuvwxyz'.upper()
#Numbers
#increment+= '1234567890'
#Whitespace
#increment+= ' \t\n'
#Basic punctuation
#increment+= '.,\'\"?'
#Advanced punctuation
#increment+= '`~!@#$%^&*_+-=|\\;:/<>'
#Braces
#increment+= '{}[]()'


def main():
	#Parse arguments
	global mode
	cyphertext, transpose, mode, output = args()
	
	#Print out the cypher, as interpreted.
	print >> sys.stderr, "Transpostion pattern: "+transpose+'\n'
	
	#Parse the cyphertext.
	final = parse(cyphertext, transpose)

	print final

	if output != '': 
		writer = open(output, 'w')
		writer.write(final)
		writer.close()

def args():
	help = """One time pad decoder. Run as otp.py <options>

Encoding, passphrase, and cyphertext must be specified. 
 Other arguments are optional.
If multiple arguments override each other, 
 the last one takes precedence. 
If there are spaces in filenames, passwords, 
 or other text, enclose the argument in quotes.
 
Options:
	-d Decode text
	-e Encode text
	
	-pf <passfile> Specify a password file.
	-p  <password> Specify a passphrase.
	
	-cf <cypherfile> File to decode.
	-c  <cyphertext> Text to decode.
	
	-o <filename> File to output encrypted text to. (optional)
	
	-h This help text.
	"""
	
	#Output is returned, so must be something.
	output = ''
	
	for x in range(len(sys.argv)):
		arg = sys.argv[x]

		#Encrypt/decrypt
		if arg == '-d': mode = -1
		if arg == '-e': mode = 1

		#Passphrase
		if arg == '-p':  passphrase = sys.argv[x+1]
		if arg == '-pf': passphrase = open(sys.argv[x+1], 'r').read()

		#Cyphertext
		if arg == '-c':  cypher = sys.argv[x+1]
		if arg == '-cf': cypher = open(sys.argv[x+1], 'r').read()
		
		#Output
		if arg == '-o': output = sys.argv[x+1]
		
		#Help
		if arg == '-h':	print >> sys.stderr, help
		
	try:
		return cypher, passphrase, mode, output
	except: 
		print "Missing required arguments! Check your syntax.\n\n".upper()+help
		exit()
	
#Parses the cypher, for a given starting index, a given transposition matrix, 
#and given cyphertext.
def parse(string, transpose):
	index = 0
	newstring = ''
	for char in string:
		#Translate this character?
		if (char in increment):
			newstring += translate(char, transpose[index])
			index = (index + 1 ) % len(transpose)
			
		else: newstring += char
	return newstring


#Translates a character by an offset. Supports any alpha characters. Numbers #and symbols will wonk.
def translate(char, offset):

	if (offset.islower()):   offset = ord(offset) - ord('a')
	elif (offset.isupper()): offset = ord(offset) - ord('A')
	
	if (char.islower()):   fix = ord('a')
	elif (char.isupper()): fix = ord('A')
	elif (char.isdigit()): fix = ord('0') #Not sure if this'll work... XXX
	
	if (char.isalpha()): mod = 26
	elif (char.isdigit()): mod = 10
	
	#If fix is still 0, weird stuff will happen here. Everything will map to 
	#ASCII 0-26, which is garbage. And it won't unmap.
	val = ((ord(char) - fix + (mode * offset)) % mod) + fix
	return chr(val)
main()