#!/usr/bin/env python3

import sys
import argparse
import re


def option_type(s, pat = re.compile(r'\w+=.*')):
  if not pat.match(s): raise argparse.ArgumentTypeError
  return s


parser = argparse.ArgumentParser(description = 'Edit config file.')
parser.add_argument('config', help = 'The configuration file to edit.')
parser.add_argument('options', nargs = '*', type = option_type,
                    metavar = '<name>=<value>', help = 'An option to set.')
args = parser.parse_args()


# Parse config lines and options
lines = []
options = {}
optRE = re.compile(r'(\w+)\s*=\s*([^#]+)(#.*)?')


class Line:
  def __init__(self, text, name = None, value = None, comment = None):
    self.text = text
    self.name = name
    self.value = value
    self.comment = comment


  def __str__(self):
    if self.name is not None:
      if self.value.strip():
        text = '%s=%s' % (self.name, self.value)
        if self.comment: text += ' # ' + self.comment
        text += '\n'
        return text

      else: return ''

    return self.text


with open(args.config, 'r') as f:
  for line in f:
    m = optRE.match(line.strip())

    if m: name, value, comment = m.groups()
    else: name, value, comment = None, None, None

    l = Line(line, name, value, comment)
    lines.append(l)
    if name is not None: options[name] = l


# Save original config
config = ''.join(map(str, lines))


# Set options
first = True
for opt in args.options:
  name, value = opt.split('=', 1)

  if name in options: options[name].value = value
  else:
    if first and len(lines) and str(lines[:-1]).strip() != '':
      first = False
      lines.append(Line('\n'))

    lines.append(Line(None, name, value, None))


# Assemble new config
new_config = ''.join(map(str, lines))


if new_config != config:
  with open(args.config, 'w') as f:
    f.write(new_config)