event.py

#!/usr/bin/env python3
#
# Copyright 2016 Red Hat, Inc.
#
# Authors:
#     Fam Zheng <famz@redhat.com>
#
# This work is licensed under the MIT License.  Please see the LICENSE file or
# http://opensource.org/licenses/MIT.

"""
The patchew event framework
"""

_handlers = {}

_events = {}


def register_handler(event, handler):
    """Register an event hander. It will be called when the event is emitted.
    If event is None, all events will be dispatched to the handler"""
    _handlers.setdefault(event, [])
    _handlers[event].append(handler)


def declare_event(event, **params):
    """Declare an event that the caller will emit later, with kwarg names as
    the event argument names, and values as the descriptions."""
    assert event not in _events
    _events[event] = params


def emit_event(event, **params):
    """Emit an event that was previously declared, and call all the registered
    handlers."""
    assert event in _events
    for keyword in params:
        assert keyword in _events[event]
    for handler in _handlers.get(event, []) + _handlers.get(None, []):
        try:
            handler(event, **params)
        except:
            import traceback

            traceback.print_exc()


def get_events_info():
    return _events.copy()