snack based ncurses script for configuring ubuntu networking, first pass

netconf.py

from __future__ import with_statement
import snack, ipaddr, optparse, re, shlex

parser = optparse.OptionParser()
parser.add_option('--no-cancel', action='store_true', dest='no_cancel', help='Do not display a cancel button')
parser.add_option('--title', action='store', dest='title', default='Configure Networking', help='set the form title')
parser.add_option('--interface', action='store', dest='interface', default='eth0', help='interface to edit')
parser.add_option('--interfaces-file', action='store', dest='interfaces_file', default='/etc/network/interfaces', help='target interfaces file to edit')
parser.add_option('--dns-file', action='store', dest='dns_file', default='/etc/resolvconf/resolv.conf.d/base', help='target dns file to edit')

options, args = parser.parse_args()

def bind(object, **kwargs):
  for key, value in kwargs.items():
    setattr(object, key, value)
  return object

VALUES = dict()
ERRORS = dict()
OUTPUT = dict()

screen = snack.SnackScreen()

def LabelledEntry(name, label):
  return (
    bind(snack.Label(label), name=name, label=label, form=dict(padding=(2, 0, 1, 0), anchorRight=1)),
    bind(snack.Entry(width=20), name=name, form=dict(padding=(0, 0, 1, 0)))
  )

def to_ip_address(s):
  try:
    return ipaddr.IPAddress(s)
  except ValueError:
    return None

def to_ip_network(address, netmask):
  try:
    return ipaddr.IPNetwork('%s/%s' % (address, netmask))
  except ValueError:
    return None

try:
  screen.pushHelpLine(' <Tab>/<Alt-Tab> between elements  |  * Optional Address')

  while True:
    fields = [
      LabelledEntry('address', 'IP Address '),
      LabelledEntry('netmask', 'Netmask '),
      LabelledEntry('gateway', 'Gateway '),
      LabelledEntry('dns[0]', 'Primary DNS '),
      LabelledEntry('dns[1]', '* Secondary DNS '),
    ]
    
    form = snack.GridForm(screen, options.title, 1, 2)

    grid = snack.Grid(max(len(row) for row in fields), len(fields))

    if not options.no_cancel:
      button_grid = snack.Grid(2, 1)
      button_grid.setField(bind(snack.Button('OK'), name='ok'), 0, 0, padding=(0, 2, 2, 0))
      button_grid.setField(bind(snack.Button('Canel'), name='cancel'), 1, 0, padding=(2, 2, 0, 0))
    else:
      button_grid = snack.Grid(1, 1)
      button_grid.setField(bind(snack.Button('OK'), name='ok'), 0, 0, padding=(0, 2, 0, 0))

    if len(ERRORS) > 0:
      screen.pushHelpLine(' <Tab>/<Alt-Tab> between elements  |  * Optional Address  |  ! Invalid Address')

    for y, row in enumerate(fields):
      for x, field in enumerate(row):
        if isinstance(field, snack.Entry):
          field.set(VALUES.get(field.name, ''))
        elif isinstance(field, snack.Label) and hasattr(field, 'name') and field.name in ERRORS:
          field.setText('! ' + field.label)
        grid.setField(field, x, y, **field.__dict__.get('form', {}))

    form.add(grid, 0, 0)
    form.add(button_grid, 0, 1)

    result = form.runOnce()
    
    for row in fields:
      for field in row:
        if isinstance(field, snack.Entry):
          VALUES[field.name] = field.value()

    if len(ERRORS) > 0:
      screen.popHelpLine()

    ERRORS = dict()

    address = to_ip_address(VALUES['address'])
    if not address: ERRORS['address'] = True
    else:
      OUTPUT['address'] = address
      network = to_ip_network(address, VALUES['netmask'])
      if not network: ERRORS['netmask'] = True
      else: OUTPUT['netmask'] = network.netmask

    for key in ['gateway', 'dns[0]']:
      address = to_ip_address(VALUES[key])
      if not address: ERRORS[key] = True
      else: OUTPUT[key] = address

    for key in ['dns[1]']:
      if len(VALUES[key]) > 0:
        address = to_ip_address(VALUES[key])
        if not address: ERRORS[key] = True
        else: OUTPUT[key] = address

    if result.name == 'cancel': break
    if len(ERRORS) == 0:
      with open(options.interfaces_file, 'r') as f:
        tokens = ' '.join(shlex.split(f.read(), comments=True))
        tokens = re.compile(' (?=auto|iface)').split(tokens)
        # filter out the interface we are working on
        tokens = [interface for interface in tokens if not re.search('^(?:auto|iface) %(interface)s' % options.__dict__, interface)]

      with open(options.interfaces_file, 'w+') as f:
        result = []
        result.append('iface %(interface)s inet static' % options.__dict__)
        result.append('address %(address)s netmask %(netmask)s gateway %(gateway)s' % OUTPUT)
        result.append('dns-nameservers %(dns[0])s' % OUTPUT)
        if 'dns[1]' in OUTPUT:
          result.append(' %(dns[1])s' % OUTPUT)
        tokens.append(' '.join(result))
        print >> f, '\n'.join(tokens)

      break
  
finally:
  screen.finish()