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

# Copyright (c) 2008 - 2014, Pascal Volk

# See COPYING for distribution information.

"""

    VirtualMailManager.ext.postconf

    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

    Wrapper class for Postfix's postconf.

    Postconf instances can be used to read actual values of configuration

    parameters or edit the value of a configuration parameter.

    postconf.read(parameter) -> value

    postconf.edit(parameter, value)

"""

import re

from subprocess import Popen, PIPE

from VirtualMailManager.errors import VMMError

from VirtualMailManager.constants import VMM_ERROR

_ = lambda msg: msg

class Postconf(object):

    """Wrapper class for Postfix's postconf."""

    __slots__ = ('_bin', '_val')

    _parameter_re = re.compile(r'^\w+$', re.ASCII)

    _variables_re = re.compile(r'\$\b\w+\b', re.ASCII)

    def __init__(self, postconf_bin):

        """Creates a new Postconf instance.

        Argument:

        `postconf_bin` : str

          absolute path to the Postfix postconf binary.

        """

        self._bin = postconf_bin

        self._val = ''

    def edit(self, parameter, value):

        """Set the `parameter`'s value to `value`.

        Arguments:

        `parameter` : str

          the name of a Postfix configuration parameter

        `value` : str

          the parameter's new value.

        """

        self._check_parameter(parameter)

        stderr = Popen((self._bin, '-e', parameter + '=' + str(value)),

                       stderr=PIPE).communicate()[1]

        if stderr:

            raise VMMError(stderr.strip().decode(), VMM_ERROR)

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

        """Returns the parameter's 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

        Arguments:

        `parameter` : str

          the name of a Postfix configuration parameter.

        `expand_vars` : bool

          indicates if variables should be expanded or not, default True

        """

        self._check_parameter(parameter)

        self._val = self._read(parameter)

        if expand_vars:

            self._expand_vars()

        return self._val

    def _check_parameter(self, parameter):

        """Check that the `parameter` looks like a configuration parameter.

        If not, a VMMError will be raised."""

        if not self.__class__._parameter_re.match(parameter):

            raise VMMError(_("The value '%s' does not look like a valid "

                             "Postfix configuration parameter name.") %

                           parameter, VMM_ERROR)

    def _expand_vars(self):

        """Expand the $variables in self._val to their values."""

        while True:

            pvars = set(self.__class__._variables_re.findall(self._val))

            if not pvars:

                break

            if len(pvars) > 1:

                self._expand_multi_vars(self._read_multi(pvars))

                continue

            pvars = pvars.pop()

            self._val = self._val.replace(pvars, self._read(pvars[1:]))

    def _expand_multi_vars(self, old_new):

        """Replace all $vars in self._val with their values."""

        for old, new in old_new.items():

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

    def _read(self, parameter):

        """Ask postconf for the value of a single configuration parameter."""

        stdout, stderr = Popen([self._bin, '-h', parameter], stdout=PIPE,

                               stderr=PIPE).communicate()

        if stderr:

            raise VMMError(stderr.strip().decode(), VMM_ERROR)

        return stdout.strip().decode()

    def _read_multi(self, parameters):

        """Ask postconf for multiple configuration parameters. Returns a dict

        parameter: value items."""

        cmd = [self._bin]

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

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

        if stderr:

            raise VMMError(stderr.strip().decode(), VMM_ERROR)

        par_val = {}

        for line in stdout.decode().splitlines():

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

            par_val[par] = val

        return par_val

del _