import logging

class ConfigParser:

    def __init__(self):

        self.args = {}       # config file arguments

        self.registered_args = {}

        self.log = logging.getLogger('config')

    def add_argument(self, name, type=str, default=None):

        self.registered_args[name] = {'type':type, 'default':default}

    def load(self, fname):

        # parse config file

        with open(fname) as f:

            exec(f.read(), self.args)

        # check contents

        return self.check()

    def check(self):

        ok = True

        for key in self.args.keys():

            if key == '__builtins__':

                continue

            if key in self.registered_args:

                # arg registered, check type

                type = self.registered_args[key]['type']

                if not isinstance(self.args[key], type):

                    ok = False

                    self.log.error("Bad type of config parameter '%s': is %s but should be %s",

                        key, type(self.args[key]), type)

            else:

                # arg not registered

                    ok = False

                    self.log.error("Unknown config parameter '%s'.", key)

        return ok

    def __getattr__(self, name):

        if name in self.args:

            return self.args[name]

        # raise error if not found

        raise AttributeError()