[Add] Add event engine

.gitignore

@@ -1,10 +1,10 @@
+# Python
+*.pyc
+
 # IDE
 .vscode
 .idea
 
-# Python
-.pyc
-.pyo
-
+# Temp
 build
 dist

vnpy/event/__init__.py

@@ -0,0 +1 @@
+from engine import Event, EventEngine, EVENT_TIMER

vnpy/event/engine.py

@@ -0,0 +1,139 @@
+from queue import Queue, Empty
+from threading import Thread, Timer
+from collections import defaultdict
+from time import sleep
+from typing import Any, Callable
+
+EVENT_TIMER = "eTimer"
+
+
+class Event:
+    """
+    Event object consists of a type string which is used 
+    by event engine for distributing event, and a data 
+    object which contains the real data. 
+    """
+
+    def __init__(self, type: str, data: Any = None):
+        """"""
+        self.type = type
+        self.data = data
+
+
+# Defines handler function to be used in event engine.
+HandlerType = Callable[[Event], None]
+
+
+class EventEngine:
+    """
+    Event engine distributes event object based on its type 
+    to those handlers registered.
+
+    It also generates timer event by every interval seconds,
+    which can be used for timing purpose.
+    """
+
+    def __init__(self, interval: int = 1):
+        """
+        Timer event is generated every 1 second by default, if
+        interval not specified.
+        """
+        self._interval = interval
+        self._queue = Queue()
+        self._active = False
+        self._thread = Thread(target=self._run)
+        self._timer = Thread(target=self._run_timer)
+        self._handlers = defaultdict(list)
+        self._general_handlers = []
+
+    def _run(self):
+        """
+        Get event from queue and then process it.
+        """
+        while self._active:
+            try:
+                event = self._queue.get(block=True, timeout=1)
+                self._process(event)
+            except Empty:
+                pass
+
+    def _process(self, event: Event):
+        """
+        First ditribute event to those handlers registered listening
+        to this type. 
+        
+        Then distrubute event to those general handlers which listens
+        to all types.
+        """
+        if event.type in self._handlers:
+            [handler(event) for handler in self._handlers[event.type]]
+
+        if self._general_handlers:
+            [handler(event) for handler in self._general_handlers]
+
+    def _run_timer(self):
+        """
+        Sleep by interval second(s) and then generate a timer event.
+        """
+        while self._active:
+            sleep(self._interval)
+            event = Event(EVENT_TIMER)
+            self.put(event)
+
+    def start(self):
+        """
+        Start event engine to process events and generate timer events.
+        """
+        self._active = True
+        self._thread.start()
+        self._timer.start()
+
+    def stop(self):
+        """
+        Stop event engine.
+        """
+        self._active = False
+        self._timer.join()
+        self._thread.join()
+
+    def put(self, event: Event):
+        """
+        Put an event object into event queue.
+        """
+        self._queue.put(event)
+
+    def register(self, type: str, handler: HandlerType):
+        """
+        Register a new handler function for a specific event type. Every 
+        function can only be registered once for each event type.
+        """
+        handler_list = self._handlers[type]
+        if handler not in handler_list:
+            handler_list.append(handler)
+
+    def unregister(self, type: str, handler: HandlerType):
+        """
+        Unregister an existing handler function from event engine.
+        """
+        handler_list = self._handlers[type]
+
+        if handler in handler_list:
+            handler_list.remove(handler)
+
+        if not handler_list:
+            self._handlers.pop(type)
+
+    def register_general(self, handler: HandlerType):
+        """
+        Register a new handler function for all event types. Every 
+        function can only be registered once for each event type.
+        """
+        if handler not in self._general_handlers:
+            self._general_handlers.append(handler)
+
+    def unregister_general(self, handler: HandlerType):
+        """
+        Unregister an existing general handler function.
+        """
+        if handler in self._general_handlers:
+            self._general_handlers.remove(handler)