from collections import OrderedDict

class Event:

    """Base class for events."""

    def __init__(self, event_name=None, arg_names=(), arg_values=()):

        self.name = event_name

        self.args = OrderedDict(zip(arg_names, arg_values))

    def __getattr__(self, item):

        if item in self.args:

            return self.args[item]

        else:

            raise AttributeError(item)

    def __getitem__(self, key):

        return self.args[key]

    def __repr__(self):

        return '{}({})'.format(self.__class__.__name__,

                               ', '.join("%s=%r" % (k,v) for k,v

                                         in self.args.items()))

class ResizeEvent(Event):

    def __init__(self, w, h):

        Event.__init__(self, 'resize', ('w', 'h'), (w, h))

class KeypressEvent(Event):

    def __init__(self, keyname, char, mods):

        Event.__init__(self, 'keypress',

                       ('keyname', 'char', 'mods'),

                       (keyname, char, mods))

    def mod_key(self, sep='+'):

        """Return combined key with modifiers.

        E.g. "shift+tab"

        Order of modifiers is fixed: ctrl, alt, meta, shift

        """

        res = []

        for mod in ('ctrl', 'alt', 'meta', 'shift'):

            if mod in self.mods:

                res.append(mod)

        res.append(self.keyname or self.char)

        return sep.join(res)