#!/usr/local/bin/python

import sys
import re
import os

from optparse import OptionParser

# Options
class Parser(OptionParser):
    def __init__(self):
	OptionParser.__init__(self, usage="%prog [options] file.pem")
	self.add_option('--cert', dest='cert', default='./cert.pem', 
		help='File to extract certificate into, default: [%default]')
	self.add_option('--key', dest='key', default='./key.pem', 
		help='File to extract key into, default: [%default]')
	self.add_option('--force', action='store_true', dest='force',
		default=False,
		help=('Overwite existing certificate and key files. ' + \
			'default: [%default]'))

class diversion:
    '''
    Wraps up the reqular expression to start and end a diversion, as well as
    the open file that gets the lines.
    '''
    def __init__(self, start, end, fn):
	self.start = re.compile(start)
	self.end = re.compile(end)
	self.f = open(fn, 'w')

# Option validation
parser = Parser()
opts, args = parser.parse_args()

if len(args) == 1:
    combo = args[0]
else:
    parser.print_help()
    sys.exit('\nMust have one file argument')

if not opts.force:
    for fn in (opts.cert, opts.key):
	if os.access(fn, os.F_OK):
	    sys.exit('%s exists.  --force to overwite it' % fn)

try:
    # Initialize the diversions
    divs = [diversion(s, e, fn) for s, e,fn in (
	('\s*-----BEGIN RSA PRIVATE KEY-----$', 
	    '\s*-----END RSA PRIVATE KEY-----$',
	    opts.key),
	('\s*-----BEGIN CERTIFICATE-----$', 
	    '\s*-----END CERTIFICATE-----$',
	    opts.cert))]

    # walk through the file, beginning a diversion when a start regexp matches
    # until the end regexp matches.  While in the two regexps, print each line
    # to the ipen diversion file (including the two matches).
    active = None
    f = open(combo, 'r')
    for l in f:
	if active:
	    if active.end.match(l):
		print >>active.f, l,
		active = None
	else:
	    for d in divs:
		if d.start.match(l):
		    active = d
		    break
	if active: print >>active.f, l,

# This clause catches all file opening problems, including the diversion opens
except EnvironmentError, e:
    sys.exit("%s: %s" % (e.strerror, e.filename or '?!'))

# This is probably unnecessary.  Close all the diversion files.
for d in divs: d.f.close()