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"""

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    Support for loading config files with twisted.python.usage

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"""

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from twisted.python import usage

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import traceback

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class ConfigMapper (dict) :

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    """

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        Provides access to a usage.Options's keys via python names.

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    """

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    IGNORED_NAMES = ('__doc__', )

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    def __init__ (self, opts, defaults=None) :

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        """

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            opts        - store the values from the config file into the given dict

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            defaults    - (optional) update any pre-exisitng values from the config file into the given dict

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        """

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        self.opts = opts

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        self.defaults = defaults

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    def _map_name (self, name) :

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        return name.replace('_', '-')

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    def __getitem__ (self, name) :

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        """

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            Map from foo_bar -> foo-bar

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        """

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        return self.opts[self._map_name(name)]

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    def __setitem__ (self, name, value) :

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        """

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            Map from foo_bar -> foo-bar

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        """

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        store = self.opts

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        # filter out certain keys

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        if name in self.IGNORED_NAMES :

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            # skip things like __doc__

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            return

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        # translate name

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        name = self._map_name(name)

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        if name in self.opts :

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            # normal long opt

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            pass

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        else :

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            # fail

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            raise NameError(name)

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        # store

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        store[name] = value

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        if self.defaults is not None and name in self.defaults :

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            self.defaults[name] = value

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class ConfigOptions (usage.Options) :

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    """

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        Provide a --config param to read in new values/defaults for any defined options from the given config file

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    """

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    def opt_config (self, path) :

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        """

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            Read the given configuration file

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        """

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        # set up env for the config module

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        globals = {}

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        locals = ConfigMapper(self.opts, self.defaults)

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        try :

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            # run config

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            execfile(path, globals, locals)

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        except :

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            # XXX: raising a usage.error prints out --help

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            raise usage.error("Error reading config file: %s\n%s" % (path, traceback.format_exc()))

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    opt_c = opt_config

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