# -*- coding: UTF-8 -*-
# Copyright (c) 2007 - 2010, Pascal Volk
# See COPYING for distribution information.

"""
    VirtualMailManager.Config

    VMM's configuration module for simplified configuration access.
"""


from ConfigParser import \
     Error, MissingSectionHeaderError, NoOptionError, NoSectionError, \
     ParsingError, RawConfigParser
from cStringIO import StringIO# TODO: move interactive stff to cli

from VirtualMailManager import exec_ok, get_unicode, is_dir
from VirtualMailManager.constants.ERROR import CONF_ERROR
from VirtualMailManager.Exceptions import VMMConfigException


class BadOptionError(Error):
    """Raised when a option isn't in the format 'section.option'."""
    pass


class ConfigValueError(Error):
    """Raised when creating or validating of new values fails."""
    pass


class NoDefaultError(Error):
    """Raised when the requested option has no default value."""

    def __init__(self, section, option):
        Error.__init__(self, 'Option %r in section %r has no default value' %
                             (option, section))


class LazyConfig(RawConfigParser):
    """The **lazy** derivate of the `RawConfigParser`.

    There are two additional getters:

    `pget()`
      The polymorphic getter, which returns a option's value with the
      appropriate type.
    `dget()`
      Like `LazyConfig.pget()`, but returns the option's default, from
      `LazyConfig._cfg['sectionname']['optionname'].default`, if the
      option is not configured in a ini-like configuration file.

    `set()` differs from `RawConfigParser`'s `set()` method. `set()` takes
    the `section` and `option` arguments combined to a single string in the
    form "section.option".
    """

    def __init__(self):
        RawConfigParser.__init__(self)
        self._modified = False
        self._cfg = {
            'sectionname': {
                'optionname': LazyConfigOption(int, 1, self.getint)
            }
        }
        """sample _cfg dictionary. Create your own in your derived class."""

    def bool_new(self, value):
        """Converts the string `value` into a `bool` and returns it.

        | '1', 'on', 'yes' and 'true' will become `True`
        | '0', 'off', 'no' and 'false' will become `False`

        Throws a `ConfigValueError` for all other values, except bools.
        """
        if isinstance(value, bool):
            return value
        if value.lower() in self._boolean_states:
            return self._boolean_states[value.lower()]
        else:
            raise ConfigValueError(_(u"Not a boolean: '%s'") %
                                   get_unicode(value))

    def getboolean(self, section, option):
        """Returns the boolean value of the option, in the given section.

        For a boolean True, the value must be set to '1', 'on', 'yes',
        'true' or True. For a boolean False, the value must set to '0',
        'off', 'no', 'false' or False.
        If the option has another value assigned this method will raise a
        ValueError.
        """
        # if the setting was modified it may be still a boolean value lets see
        tmp = self.get(section, option)
        if isinstance(tmp, bool):
            return tmp
        if not tmp.lower() in self._boolean_states:
            raise ValueError, 'Not a boolean: %s' % tmp
        return self._boolean_states[tmp.lower()]

    def _get_section_option(self, section_option):
        """splits ``section_option`` (section\ **.**\ option) in two parts
        and returns them as list ``[section, option]``, if:

            * it likes the format of ``section_option``
            * the ``section`` is known
            * the ``option`` is known

        Else one of the following exceptions will be thrown:

            * `BadOptionError`
            * `NoSectionError`
            * `NoOptionError`
        """
        sect_opt = section_option.lower().split('.')
        # TODO: cache it
        if len(sect_opt) != 2:# do we need a regexp to check the format?
            raise BadOptionError(
                        _(u"Bad format: '%s' - expected: section.option") %
                                 get_unicode(section_option))
        if not sect_opt[0] in self._cfg:
            raise NoSectionError(sect_opt[0])
        if not sect_opt[1] in self._cfg[sect_opt[0]]:
            raise NoOptionError(sect_opt[1], sect_opt[0])
        return sect_opt

    def items(self, section):
        """returns an iterable that returns key, value ``tuples`` from the
        given ``section``."""
        if section in self._sections:# check if the section was parsed
            d2 = self._sections[section]
        elif not section in self._cfg:
            raise NoSectionError(section)
        else:
            return ((k, self._cfg[section][k].default) \
                    for k in self._cfg[section].iterkeys())
        # still here? Get defaults and merge defaults with configured setting
        d = dict((k, self._cfg[section][k].default) \
                 for k in self._cfg[section].iterkeys())
        d.update(d2)
        if '__name__' in d:
            del d['__name__']
        return d.iteritems()

    def dget(self, option):
        """Returns the value of the `option`.

        If the option could not be found in the configuration file, the
        configured default value, from ``LazyConfig._cfg`` will be
        returned.

        Arguments:

        `option` : string
            the configuration option in the form
            "``section``\ **.**\ ``option``"

        Throws a `NoDefaultError`, if no default value was passed to
        `LazyConfigOption.__init__()` for the `option`.
        """
        section, option = self._get_section_option(option)
        try:
            return self._cfg[section][option].getter(section, option)
        except (NoSectionError, NoOptionError):
            if not self._cfg[section][option].default is None:# may be False
                return self._cfg[section][option].default
            else:
                raise NoDefaultError(section, option)

    def pget(self, option):
        """Returns the value of the `option`."""
        section, option = self._get_section_option(option)
        return self._cfg[section][option].getter(section, option)

    def set(self, option, value):
        """Set the `value` of the `option`.

        Throws a `ValueError` if `value` couldn't be converted using
        `LazyConfigOption.cls`"""
        section, option = self._get_section_option(option)
        val = self._cfg[section][option].cls(value)
        if self._cfg[section][option].validate:
            val = self._cfg[section][option].validate(val)
        if not RawConfigParser.has_section(self, section):
            self.add_section(section)
        RawConfigParser.set(self, section, option, val)
        self._modified = True

    def has_section(self, section):
        """Checks if `section` is a known configuration section."""
        return section.lower() in self._cfg

    def has_option(self, option):
        """Checks if the option (section.option) is a known configuration
        option."""
        try:
            self._get_section_option(option)
            return True
        except(BadOptionError, NoSectionError, NoOptionError):
            return False

    def sections(self):
        """Returns an iterator object for all configuration sections."""
        return self._cfg.iterkeys()


class LazyConfigOption(object):
    """A simple container class for configuration settings.

    `LazyConfigOption` instances are required by `LazyConfig` instances,
    and instances of classes derived from `LazyConfig`, like the
    `Config` class.
    """
    __slots__ = ('__cls', '__default', '__getter', '__validate')

    def __init__(self, cls, default, getter, validate=None):
        """Creates a new `LazyConfigOption` instance.

        Arguments:

        `cls` : type
          The class/type of the option's value
        `default`
          Default value of the option. Use ``None`` if the option should not
          have a default value.
        `getter` : callable
          A method's name of `RawConfigParser` and derived classes, to get a
          option's value, e.g. `self.getint`.
        `validate` : NoneType or a callable
          None or any method, that takes one argument, in order to check the
          value, when `LazyConfig.set()` is called.
        """
        self.__cls = cls
        if not default is None:# enforce the type of the default value
            self.__default = self.__cls(default)
        else:
            self.__default = default
        if not callable(getter):
            raise TypeError('getter has to be a callable, got a %r' %
                            getter.__class__.__name__)
        self.__getter = getter
        if validate and not callable(validate):
            raise TypeError('validate has to be callable or None, got a %r' %
                            validate.__class__.__name__)
        self.__validate = validate

    @property
    def cls(self):
        """The class of the option's value e.g. `str`, `unicode` or `bool`"""
        return self.__cls

    @property
    def default(self):
        """The option's default value, may be `None`"""
        return self.__default

    @property
    def getter(self):
        """The getter method or function to get the option's value"""
        return self.__getter

    @property
    def validate(self):
        """A method or function to validate the value"""
        return self.__validate


class Config(LazyConfig):
    """This class is for reading vmm's configuration file."""

    def __init__(self, filename):
        """Creates a new Config instance

        Arguments:

        `filename` : str
          path to the configuration file
        """
        LazyConfig.__init__(self)
        self._cfgFileName = filename
        self._cfgFile = None
        self.__missing = {}

        LCO = LazyConfigOption
        bool_t = self.bool_new
        self._cfg = {
            'account': {
                'delete_directory': LCO(bool_t, False, self.getboolean),
                'directory_mode':   LCO(int,    448,   self.getint),
                'disk_usage':       LCO(bool_t, False, self.getboolean),
                'password_length':  LCO(int,    8,     self.getint),
                'random_password':  LCO(bool_t, False, self.getboolean),
                'imap' :            LCO(bool_t, True,  self.getboolean),
                'pop3' :            LCO(bool_t, True,  self.getboolean),
                'sieve':            LCO(bool_t, True,  self.getboolean),
                'smtp' :            LCO(bool_t, True,  self.getboolean),
            },
            'bin': {
                'dovecotpw': LCO(str, '/usr/sbin/dovecotpw', self.get, exec_ok),
                'du':        LCO(str, '/usr/bin/du',        self.get, exec_ok),
                'postconf':  LCO(str, '/usr/sbin/postconf', self.get, exec_ok),
            },
            'database': {
                'host': LCO(str, 'localhost', self.get),
                'name': LCO(str, 'mailsys',   self.get),
                'pass': LCO(str, None,        self.get),
                'user': LCO(str, None,        self.get),
            },
            'domain': {
                'auto_postmaster':  LCO(bool_t, True,  self.getboolean),
                'delete_directory': LCO(bool_t, False, self.getboolean),
                'directory_mode':   LCO(int,    504,   self.getint),
                'force_deletion':   LCO(bool_t, False, self.getboolean),
            },
            'maildir': {
                'folders': LCO(str, 'Drafts:Sent:Templates:Trash', self.get),
                'name':    LCO(str, 'Maildir',                     self.get),
            },
            'misc': {
                'base_directory':  LCO(str, '/srv/mail', self.get, is_dir),
                'dovecot_version': LCO(int, 12,          self.getint),
                'gid_mail':        LCO(int, 8,           self.getint),
                'password_scheme': LCO(str, 'CRAM-MD5',  self.get,
                                       self.known_scheme),
                'transport':       LCO(str, 'dovecot:',  self.get),
            },
        }

    def configure(self, sections):
        raise NotImplementedError

    def load(self):
        """Loads the configuration, read only.

        Raises a VMMConfigException if the configuration syntax is invalid.
        """
        try:
            self._cfgFile = open(self._cfgFileName, 'r')
            self.readfp(self._cfgFile)
        except (MissingSectionHeaderError, ParsingError), e:
            raise VMMConfigException(str(e), CONF_ERROR)
        finally:
            if self._cfgFile and not self._cfgFile.closed:
                self._cfgFile.close()

    def check(self):
        """Performs a configuration check.

        Raises a VMMConfigException if the check fails.
        """
        # TODO: There are only two settings w/o defaults.
        #       So there is no need for cStringIO
        if not self.__chkCfg():
            errmsg = StringIO()
            errmsg.write(_(u'Missing options, which have no default value.\n'))
            errmsg.write(_(u'Using configuration file: %s\n') %
                         self._cfgFileName)
            for section, options in self.__missing.iteritems():
                errmsg.write(_(u'* Section: %s\n') % section)
                for option in options:
                    errmsg.write((u'    %s\n') % option)
            raise VMMConfigException(errmsg.getvalue(), CONF_ERROR)

    def known_scheme(self, scheme):
        """Converts `scheme` to upper case and checks if is known by
        Dovecot (listed in VirtualMailManager.SCHEMES).

        Throws a `ConfigValueError` if the scheme is not listed in
        VirtualMailManager.SCHEMES.
        """
        scheme = scheme.upper()
        # TODO: VMM.SCHEMES

    def unicode(self, section, option):
        """Returns the value of the `option` from `section`, converted to
        Unicode."""
        return get_unicode(self.get(section, option))

    def __chkCfg(self):
        """Checks all section's options for settings w/o a default value.

        Returns `True` if everything is fine, else `False`."""
        errors = False
        for section in self._cfg.iterkeys():
            missing = []
            for option, value in self._cfg[section].iteritems():
                if (value.default is None and
                    not RawConfigParser.has_option(self, section, option)):
                        missing.append(option)
                        errors = True
            if missing:
                self.__missing[section] = missing
        return not errors