# -*- coding: UTF-8 -*-

# Copyright (c) 2008 - 2010, Pascal Volk

# See COPYING for distribution information.

"""A small - r/o - wrapper class for Postfix' postconf."""

import re

from subprocess import Popen, PIPE

import VirtualMailManager.constants.ERROR as ERR

from VirtualMailManager.errors import VMMError

RE_PC_PARAMS = """^\w+$"""

RE_PC_VARIABLES = r"""\$\b\w+\b"""

class Postconf(object):

    __slots__ = ('__bin', '__val', '__varFinder')

    def __init__(self, postconf_bin):

        """Creates a new Postconf instance.

        Keyword arguments:

        postconf_bin -- absolute path to the Postfix postconf binary (str)

        """

        self.__bin = postconf_bin

        self.__val = ''

        self.__varFinder = re.compile(RE_PC_VARIABLES)

    def read(self, parameter, expand_vars=True):

        """Returns the parameters value.

        If expand_vars is True (default), all variables in the value will be

        expanded:

        e.g. mydestination -> mail.example.com, localhost.example.com, localhost

        Otherwise the value may contain one or more variables.

        e.g. mydestination -> $myhostname, localhost.$mydomain, localhost

        Keyword arguments:

        parameter -- the name of a Postfix configuration parameter (str)

        expand_vars -- default True (bool)

        """

        if not re.match(RE_PC_PARAMS, parameter):

            raise VMMError(_(u"The value '%s' doesn't look like a valid "

                             u"postfix configuration parameter name.") %

                           parameter, ERR.VMM_ERROR)

        self.__val = self.__read(parameter)

        if expand_vars:

            self.__expandVars()

        return self.__val

    def __expandVars(self):

        while True:

            pvars = set(self.__varFinder.findall(self.__val))

            pvars_len = len(pvars)

            if pvars_len < 1:

                break

            if pvars_len > 1:

                self.__expandMultiVars(self.__readMulti(pvars))

                continue

            pvars = pvars.pop()

            self.__val = self.__val.replace(pvars, self.__read(pvars[1:]))

    def __expandMultiVars(self, old_new):

        for old, new in old_new.items():

            self.__val = self.__val.replace('$'+old, new)

    def __read(self, parameter):

        out, err = Popen([self.__bin, '-h', parameter], stdout=PIPE,

                stderr=PIPE).communicate()

        if len(err):

            raise VMMError(err.strip(), ERR.VMM_ERROR)

        return out.strip()

    def __readMulti(self, parameters):

        cmd = [self.__bin]

        cmd.extend(parameter[1:] for parameter in parameters)

        out, err = Popen(cmd, stdout=PIPE, stderr=PIPE).communicate()

        if len(err):

            raise VMMError(err.strip(), ERR.VMM_ERROR)

        par_val = {}

        for line in out.splitlines():

            par, val = line.split(' = ')

            par_val[par] = val

        return par_val