#! /usr/bin/env python3
"""pwgen generates passwords for your needs.

Usage: pwgen [OPTION...]

  -c, --chars STRING               define a charset
  -C, --charset ascii|hex|alphanum use a predefined charset (default=ascii)
  -h, --help                       display this help
  -l, --length INTEGER             passwords length (default=64)
  -n, --number INTEGER             number of passwords (default=1)"""

# imports
from random import SystemRandom
import getopt
import sys

# usage exception
class Usage(Exception):
	def __init__(self, msg):
		self.msg = msg

# main function
def main(argv=None):
	if argv is None:
		argv = sys.argv
	try:
		# parse command line options
		try:
			opts, argv = getopt.getopt(argv[1:], "c:C:hl:n:", ["chars=", "charset=", "help", "length=", "number="])
		except getopt.error as msg:
			raise Usage(msg)
		
		# define default args
		chars = " !\"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz{|}~"
		length = 64
		number = 1
		
		# process options		
		for opt, arg in opts:
		
			if opt in ("-c", "--chars"):
				try:
					chars = str(arg)
				except ValueError as err:
					raise Usage(err)
			
			if opt in ("-C", "--charset"):
				if(arg == "alphanum"):
					chars = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"
				elif(arg == "ascii"):
					chars = " !\"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz{|}~"
				elif(arg == "hex"):
					chars = "0123456789ABCDEF"
			
			if opt in ("-h", "--help"):
				print(__doc__)
				return 0
		
			if opt in ("-l", "--length"):
				try:
					length = int(arg)
				except ValueError as err:
					raise Usage(err)
					
			if opt in ("-n", "--number"):
				try:
					number = int(arg)
				except ValueError as err:
					raise Usage(err)
		
		# generate passwords
		random = SystemRandom()
		for i in range(number):
			print("".join([random.choice(chars) for i in range(length)]))

		# print last character indicator to stderr
		print(' ' * (length - 1) + '^', file=sys.stderr)
			
	except Usage as err:
		print(err.msg, file=sys.stderr)
		print("for help use --help", file=sys.stderr)
		return 2

if __name__ == "__main__":
	sys.exit(main())