deluge/deluge/config.py

#
# config.py
#
# Copyright (C) 2008 Andrew Resch <andrewresch@gmail.com>
#
# Deluge is free software.
#
# You may redistribute it and/or modify it under the terms of the
# GNU General Public License, as published by the Free Software
# Foundation; either version 3 of the License, or (at your option)
# any later version.
#
# deluge 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 deluge.    If not, write to:
# 	The Free Software Foundation, Inc.,
# 	51 Franklin Street, Fifth Floor
# 	Boston, MA    02110-1301, USA.
#


"""
Deluge Config Module
"""

import cPickle as pickle
import shutil
import os

import deluge.common
from deluge.log import LOG as log

json = deluge.common.json

def prop(func):
    """Function decorator for defining property attributes

    The decorated function is expected to return a dictionary
    containing one or more of the following pairs:
        fget - function for getting attribute value
        fset - function for setting attribute value
        fdel - function for deleting attribute
    This can be conveniently constructed by the locals() builtin
    function; see:
    http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/205183
    """
    return property(doc=func.__doc__, **func())

class Config(object):
    """
    This class is used to access/create/modify config files

    :param filename: the name of the config file
    :param defaults: dictionary of default values
    :param config_dir: the path to the config directory

    """
    def __init__(self, filename, defaults=None, config_dir=None):
        self.__config = {}
        self.__previous_config = {}
        self.__set_functions = {}
        self.__change_callback = None
        # This will get set with a reactor.callLater whenever a config option
        # is set.
        self.__save_timer = None

        if defaults:
            self.__config = defaults

        # Load the config from file in the config_dir
        if config_dir:
            self.__config_file = os.path.join(config_dir, filename)
        else:
            self.__config_file = deluge.common.get_default_config_dir(filename)

        self.load()

    def __setitem__(self, key, value):
        """
        See
        :meth:`set_item`
        """

        return self.set_item(key, value)

    def set_item(self, key, value):
        """
        Sets item 'key' to 'value' in the config dictionary, but does not allow
        changing the item's type unless it is None

        :param key: string, item to change to change
        :param value: the value to change item to, must be same type as what is currently in the config

        :raises ValueError: raised when the type of value is not the same as what is currently in the config

        **Usage**

        >>> config = Config("test.conf")
        >>> config["test"] = 5
        >>> config["test"]
        5

        """
        if not self.__config.has_key(key):
            self.__config[key] = value
            log.debug("Setting '%s' to %s of %s", key, value, type(value))
            return

        if self.__config[key] == value:
            return

        # Do not allow the type to change unless it is None
        oldtype, newtype = type(self.__config[key]), type(value)

        if value is not None and oldtype != type(None) and oldtype != newtype:
            try:
                value = oldtype(value)
            except ValueError:
                log.warning("Type '%s' invalid for '%s'", newtype, key)
                raise

        log.debug("Setting '%s' to %s of %s", key, value, type(value))

        # Make a copy of the current config prior to changing it
        self.__previous_config.update(self.__config)
        self.__config[key] = value
        # Run the set_function for this key if any
        from twisted.internet import reactor
        try:
            reactor.callLater(0, self.__set_functions[key], key, value)
        except KeyError:
            pass
        try:
            reactor.callLater(0, self.__change_callback, key, value)
        except:
            pass

        # We set the save_timer for 5 seconds if not already set
        if not self.__save_timer or not self.__save_timer.active():
            self.__save_timer = reactor.callLater(5, self.save)

    def __getitem__(self, key):
        """
        See
        :meth:`get_item`
        """
        return self.get_item(key)

    def get_item(self, key):
        """
        Gets the value of item 'key'

        :param key: the item for which you want it's value
        :return: the value of item 'key'

        :raises KeyError: if 'key' is not in the config dictionary

        **Usage**

        >>> config = Config("test.conf", defaults={"test": 5})
        >>> config["test"]
        5

        """
        return self.__config[key]

    def register_change_callback(self, callback):
        """
        Registers a callback function that will be called when a value is changed in the config dictionary

        :param callback: the function, callback(key, value)

        **Usage**

        >>> config = Config("test.conf", defaults={"test": 5})
        >>> def cb(key, value):
        ...     print key, value
        ...
        >>> config.register_change_callback(cb)

        """
        self.__change_callback = callback

    def register_set_function(self, key, function, apply_now=True):
        """
        Register a function to be called when a config value changes

        :param key: the item to monitor for change
        :param function: the function to call when the value changes, f(key, value)
        :keyword apply_now: if True, the function will be called after it's registered

        **Usage**

        >>> config = Config("test.conf", defaults={"test": 5})
        >>> def cb(key, value):
        ...     print key, value
        ...
        >>> config.register_set_function("test", cb, apply_now=True)
        test 5

        """
        log.debug("Registering function for %s key..", key)
        self.__set_functions[key] = function
        # Run the function now if apply_now is set
        if apply_now:
            self.__set_functions[key](key, self.__config[key])
        return

    def apply_all(self):
        """
        Calls all set functions

        **Usage**

        >>> config = Config("test.conf", defaults={"test": 5})
        >>> def cb(key, value):
        ...     print key, value
        ...
        >>> config.register_set_function("test", cb, apply_now=False)
        >>> config.apply_all()
        test 5

        """
        log.debug("Calling all set functions..")
        for key, value in self.__set_functions.iteritems():
            value(key, self.__config[key])

    def load(self, filename=None):
        """
        Load a config file

        :param filename: if None, uses filename set in object initialization


        """
        if not filename:
            filename = self.__config_file
        try:
            self.__config.update(json.load(open(filename, "r")))
        except Exception, e:
            try:
                self.__config.update(pickle.load(open(filename, "r")))
            except Exception, e:
                log.warning("Unable to load config file: %s", filename)

        log.debug("Config %s loaded: %s", filename, self.__config)

    def save(self, filename=None):
        """
        Save configuration to disk

        :param filename: if None, uses filename set in object initiliazation

        """
        if not filename:
            filename = self.__config_file
        # Check to see if the current config differs from the one on disk
        # We will only write a new config file if there is a difference
        try:
            if self.__config == json.load(open(filename, "r")):
                # The config has not changed so lets just return
                self.__save_timer = None
                return
        except Exception, e:
            log.warning("Unable to open config file: %s", filename)

        self.__save_timer = None

        # Save the new config and make sure it's written to disk
        try:
            log.debug("Saving new config file %s", filename + ".new")
            f = open(filename + ".new", "w")
            json.dump(self.__config, f, indent=2)
            f.flush()
            os.fsync(f.fileno())
            f.close()
        except Exception, e:
            log.error("Error writing new config file: %s", e)
            return

        # Make a backup of the old config
        try:
            log.debug("Backing up old config file to %s~", filename)
            shutil.move(filename, filename + "~")
        except Exception, e:
            log.error("Error backing up old config..")

        # The new config file has been written successfully, so let's move it over
        # the existing one.
        try:
            log.debug("Moving new config file %s to %s..", filename + ".new", filename)
            shutil.move(filename + ".new", filename)
        except Exception, e:
            log.error("Error moving new config file: %s", e)
            return

    @prop
    def config():
        """The config dictionary"""
        def fget(self):
            return self.__config
        def fdel(self):
            return self.save()
        return locals()