[core] Refactor engine

This is going to be a bit more comprehensive than anticipated. In order
to cleanly refactor the core and the engine, basically start from
scratch with the implementation.

Goals:

* Test coverage
* Maintain backwards compatibility with module interface as much as
  possible (but still make modules easier to code)
* Simplicity

see #23

bumblebee/output.py

@@ -1,121 +0,0 @@
-import os
-import inspect
-import threading
-import bumblebee.util
-
-def output(args):
-    import bumblebee.outputs.i3
-    return bumblebee.outputs.i3.Output(args)
-
-class Widget(object):
-    def __init__(self, obj, text, instance=None):
-        self._obj = obj
-        self._text = text
-        self._store = {}
-        self._instance = instance
-
-        obj._output.register_widget(self.instance(), self)
-
-    def set(self, key, value):
-        self._store[key] = value
-
-    def get(self, key, default=None):
-        return self._store.get(key, default)
-
-    def state(self):
-        return self._obj.state(self)
-
-    def warning(self):
-        return self._obj.warning(self)
-
-    def critical(self):
-        return self._obj.critical(self)
-
-    def module(self):
-        return self._obj.__module__.split(".")[-1]
-
-    def instance(self):
-        return self._instance if self._instance else getattr(self._obj, "instance")(self)
-
-    def text(self):
-        return self._text
-
-class Command(object):
-    def __init__(self, command, event, widget):
-        self._command = command
-        self._event = event
-        self._widget = widget
-
-    def __call__(self, *args, **kwargs):
-        if not isinstance(self._command, list):
-            self._command = [ self._command ]
-
-        for cmd in self._command:
-            if not cmd: continue
-            if inspect.ismethod(cmd):
-                cmd(self._event, self._widget)
-            else:
-                c = cmd.format(*args, **kwargs)
-                bumblebee.util.execute(c, False)
-
-class Output(object):
-    def __init__(self, config):
-        self._config = config
-        self._callbacks = {}
-        self._wait = threading.Condition()
-        self._wait.acquire()
-        self._widgets = {}
-
-    def register_widget(self, identity, widget):
-        self._widgets[identity] = widget
-
-    def redraw(self):
-        self._wait.acquire()
-        self._wait.notify()
-        self._wait.release()
-
-    def add_callback(self, cmd, button, module=None):
-        if module:
-            module = module.replace("bumblebee.modules.", "")
-
-        if self._callbacks.get((button, module)): return
-
-        self._callbacks[(
-            button,
-            module,
-        )] = cmd
-
-    def callback(self, event):
-        cb = self._callbacks.get((
-            event.get("button", -1),
-            None,
-        ), None)
-        cb = self._callbacks.get((
-            event.get("button", -1),
-            event.get("instance", event.get("module", None)),
-        ), cb)
-
-        identity = event.get("instance", event.get("module", None))
-        return Command(cb, event, self._widgets.get(identity, None))
-
-    def wait(self):
-        self._wait.wait(self._config.parameter("interval", 1))
-
-    def draw(self, widgets, theme):
-        if not type(widgets) is list:
-            widgets = [ widgets ]
-        self._draw(widgets, theme)
-
-    def start(self):
-        pass
-
-    def _draw(self, widgets, theme):
-        pass
-
-    def flush(self):
-        pass
-
-    def stop(self):
-        pass
-
-# vim: tabstop=8 expandtab shiftwidth=4 softtabstop=4