~azzar1/unity/add-show-desktop-key

# IVLE - Informatics Virtual Learning Environment

# Copyright (C) 2007-2009 The University of Melbourne

#

# This program is free software; you can redistribute it and/or modify

# it under the terms of the GNU General Public License as published by

# the Free Software Foundation; either version 2 of the License, or

# (at your option) any later version.

#

# This program is distributed in the hope that it will be useful,

# but WITHOUT ANY WARRANTY; without even the implied warranty of

# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

# GNU General Public License for more details.

#

# You should have received a copy of the GNU General Public License

# along with this program; if not, write to the Free Software

# Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA

# Author: Matt Giuca, Will Grant

"""

Provides programmatic access to the IVLE configuration file.

"""

import os

from configobj import ConfigObj

from validate import Validator

__all__ = ["ConfigError", "Config"]

class ConfigError(Exception):

    """

    An error reading or writing the configuration file.

    """

    pass

def search_conffile():

    """

    Search for the config file, and return it as a filename.

    1. Environment var IVLECONF (full filename).

    2. ./etc/ivle.conf

    3. /etc/ivle/ivle.conf

    Raises a ConfigError on error.

    """

    if 'IVLECONF' in os.environ:

        fname = os.environ['IVLECONF']

        if os.path.exists(fname):

            return fname

    if os.path.exists('./etc/ivle.conf'):

        return './etc/ivle.conf'

    if os.path.exists('/etc/ivle/ivle.conf'):

        return '/etc/ivle/ivle.conf'

    raise ConfigError("Could not find IVLE config file")

_NO_VALUE = []

class Config(ConfigObj):

    """

    The configuration object. Can be instantiated with no arguments (will

    implicitly find the ivle.conf file and load it).

    Automatically validates the file against the spec (found in

    ./ivle-spec.conf relative to this module).

    """

    def __init__(self, blank=False, *args, **kwargs):

        """Initialises a new Config object. Searches for the config file,

        loads it, and validates it.

        @param blank: If blank=True, will create a blank config instead, and

        not search for the config file.

        @raise ConfigError: If the config file cannot be found.

        """

        specfile = os.path.join(os.path.dirname(__file__), 'ivle-spec.conf')

        if blank:

            super(Config, self).__init__(configspec=specfile, *args, **kwargs)

        else:

            conffile = search_conffile()

            super(Config, self).__init__(infile=conffile, configspec=specfile,

                                         *args, **kwargs)

            # XXX This doesn't raise errors if it doesn't validate

            self.validate(Validator())

    def set_by_path(self, path, value=_NO_VALUE, comment=None):

        """Writes a value to an option, given a '/'-separated path.

        @param path: '/'-separated path to configuration option.

        @param value: Optional - value to write to the option.

        @param comment: Optional - comment string (lines separated by '\n's).

        """

        path = path.split('/')

        # Iterate over each segment of the path, and find the section in conf

        # file to insert the value into (use all but the last path segment)

        conf_section = self

        for seg in path[:-1]:

            # Create the section if it isn't there

            if seg not in conf_section:

                conf_section[seg] = {}

            conf_section = conf_section[seg]

        # The final path segment names the key to insert into

        keyname = path[-1]

        if value is not _NO_VALUE:

            conf_section[keyname] = value

        if comment is not None:

            conf_section.comments[keyname] = comment.split('\n')

    def get_by_path(self, path):

        """Gets an option's value, given a '/'-separated path.

        @param path: '/'-separated path to configuration option.

        @raise KeyError: if no config option is at that path.

        """

        # Iterate over each segment of the path, and find the value in conf file

        value = self

        for seg in path.split('/'):

            value = value[seg]      # May raise KeyError

        return value