Fix up async wrappers. Comment out gevent stuff for now

capnp/async.pyx

@@ -25,30 +25,81 @@ cdef class EventLoop:
         Py_INCREF(func)
         return Promise()._init(async.evalLater(self.thisptr, <PyObject *>func))
 
-    cdef wait(self, async.PyPromise * promise):
-        return self.thisptr.wait(movePromise(deref(promise)))
+    cpdef wait(self, Promise promise) except+:
+        if promise.is_consumed:
+            raise RuntimeError('Promise was already used in a consuming operation. You can no longer use this Promise object')
+
+        ret = self.thisptr.wait(movePromise(deref(promise.thisptr)))
+        promise.is_consumed = True
+
+        return ret
+
+    cpdef there(self, Promise promise, object func, object error_func=None):
+        if promise.is_consumed:
+            raise RuntimeError('Promise was already used in a consuming operation. You can no longer use this Promise object')
 
-    cdef there(self, async.PyPromise * promise, object func, object error_func):
         Py_INCREF(func)
         Py_INCREF(error_func)
-        return Promise()._init(async.there(self.thisptr, deref(promise), <PyObject *>func, <PyObject *>error_func))
+        return Promise()._init(async.there(self.thisptr, deref(promise.thisptr), <PyObject *>func, <PyObject *>error_func))
 
-
-cdef EventLoop c_event_loop = EventLoop()
-event_loop = c_event_loop
+    cpdef yield_end(self):
+        return Promise()._init(async.yield_end(self.thisptr))
 
 cdef class Promise:
     cdef async.PyPromise * thisptr
+    cdef public bint is_consumed
+
+    def __init__(self):
+        self.is_consumed = True
+
     cdef _init(self, async.PyPromise other):
+        self.is_consumed = False
         self.thisptr = new async.PyPromise(movePromise(other))
         return self
 
     def __dealloc__(self):
         del self.thisptr
 
-    def wait(self):
-        return c_event_loop.wait(self.thisptr)
+    cpdef wait(self) except+:
+        if self.is_consumed:
+            raise RuntimeError('Promise was already used in a consuming operation. You can no longer use this Promise object')
 
-    def then(self, func, error_func=None):
-        return c_event_loop.there(self.thisptr, func, error_func)
+        ret = <object>self.thisptr.wait()
+        self.is_consumed = True
 
+        return ret
+
+    cpdef then(self, func, error_func=None) except+:
+        if self.is_consumed:
+            raise RuntimeError('Promise was already used in a consuming operation. You can no longer use this Promise object')
+
+        Py_INCREF(func)
+        Py_INCREF(error_func)
+
+        return Promise()._init(async.then(deref(self.thisptr), <PyObject *>func, <PyObject *>error_func))
+
+# from gevent.event import Event, AsyncResult
+# import gevent
+
+# cdef object _event = Event()
+# cdef object _start_loop = AsyncResult()
+
+# def _start_event_loop():
+#     loop = EventLoop()
+#     _start_loop.set(loop)
+#     _event.wait()
+#     _event.clear()
+
+# _event_loop_greenlet = gevent.spawn(_start_event_loop)
+
+# event_loop = _start_loop.get()
+# _event.set()
+
+# cdef public void _gevent_eventloop_prepare_to_sleep():
+#     _event.clear()
+
+# cdef public void _gevent_eventloop_sleep():
+#     _event.wait()
+
+# cdef public void _gevent_eventloop_wake():
+#     _event.set()