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fsm: Support asynchronous transitions via coroutine enter/exit funcs
Fixes #1037
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@ -13,6 +13,8 @@ from direct.showbase.MessengerGlobal import messenger
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from direct.showbase import PythonUtil
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from direct.directnotify import DirectNotifyGlobal
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from direct.stdpy.threading import RLock
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from panda3d.core import AsyncTaskManager, AsyncFuture, PythonTask
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import types
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class FSMException(Exception):
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@ -27,6 +29,19 @@ class RequestDenied(FSMException):
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pass
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class Transition(tuple):
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"""Used for the return value of fsm.request(). Behaves like a tuple, for
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historical reasons."""
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_future = None
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def __await__(self):
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if self._future:
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yield self._future
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return tuple(self)
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class FSM(DirectObject):
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"""
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A Finite State Machine. This is intended to be the base class
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@ -154,6 +169,9 @@ class FSM(DirectObject):
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# must be approved by some filter function.
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defaultTransitions = None
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__doneFuture = AsyncFuture()
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__doneFuture.set_result(None)
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# An enum class for special states like the DEFAULT or ANY state,
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# that should be treatened by the FSM in a special way
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class EnumStates():
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@ -247,7 +265,13 @@ class FSM(DirectObject):
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def forceTransition(self, request, *args):
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"""Changes unconditionally to the indicated state. This
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bypasses the filterState() function, and just calls
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exitState() followed by enterState()."""
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exitState() followed by enterState().
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If the FSM is currently undergoing a transition, this will
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queue up the new transition.
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Returns a future, which can be used to await the transition.
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"""
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self.fsmLock.acquire()
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try:
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@ -257,11 +281,13 @@ class FSM(DirectObject):
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if not self.state:
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# Queue up the request.
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self.__requestQueue.append(PythonUtil.Functor(
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self.forceTransition, request, *args))
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return
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fut = AsyncFuture()
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self.__requestQueue.append((PythonUtil.Functor(
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self.forceTransition, request, *args), fut))
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return fut
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self.__setState(request, *args)
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result = self.__setState(request, *args)
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return result._future or self.__doneFuture
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finally:
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self.fsmLock.release()
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@ -275,6 +301,10 @@ class FSM(DirectObject):
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request is queued up and will be executed when the current
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transition finishes. Multiple requests will queue up in
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sequence.
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The return value of this function can be used in an `await`
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expression to suspend the current coroutine until the
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transition is done.
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"""
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self.fsmLock.acquire()
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@ -284,12 +314,15 @@ class FSM(DirectObject):
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self._name, request, str(args)[1:]))
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if not self.state:
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# Queue up the request.
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self.__requestQueue.append(PythonUtil.Functor(
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self.demand, request, *args))
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return
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fut = AsyncFuture()
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self.__requestQueue.append((PythonUtil.Functor(
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self.demand, request, *args), fut))
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return fut
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if not self.request(request, *args):
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result = self.request(request, *args)
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if not result:
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raise RequestDenied("%s (from state: %s)" % (request, self.state))
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return result._future or self.__doneFuture
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finally:
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self.fsmLock.release()
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@ -314,7 +347,12 @@ class FSM(DirectObject):
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executing an enterState or exitState function), an
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`AlreadyInTransition` exception is raised (but see `demand()`,
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which will queue these requests up and apply when the
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transition is complete)."""
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transition is complete).
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If the previous state's exitFunc or the new state's enterFunc
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is a coroutine, the state change may not have been applied by
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the time request() returns, but you can use `await` on the
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return value to await the transition."""
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self.fsmLock.acquire()
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try:
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@ -331,7 +369,7 @@ class FSM(DirectObject):
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result = (result,) + args
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# Otherwise, assume it's a (name, *args) tuple
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self.__setState(*result)
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return self.__setState(*result)
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return result
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finally:
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@ -441,11 +479,11 @@ class FSM(DirectObject):
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try:
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if self.stateArray:
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if not self.state in self.stateArray:
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self.request(self.stateArray[0])
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return self.request(self.stateArray[0])
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else:
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cur_index = self.stateArray.index(self.state)
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new_index = (cur_index + 1) % len(self.stateArray)
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self.request(self.stateArray[new_index], args)
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return self.request(self.stateArray[new_index], args)
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else:
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assert self.notifier.debug(
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"stateArray empty. Can't switch to next.")
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@ -459,11 +497,11 @@ class FSM(DirectObject):
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try:
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if self.stateArray:
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if not self.state in self.stateArray:
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self.request(self.stateArray[0])
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return self.request(self.stateArray[0])
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else:
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cur_index = self.stateArray.index(self.state)
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new_index = (cur_index - 1) % len(self.stateArray)
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self.request(self.stateArray[new_index], args)
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return self.request(self.stateArray[new_index], args)
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else:
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assert self.notifier.debug(
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"stateArray empty. Can't switch to next.")
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@ -471,8 +509,26 @@ class FSM(DirectObject):
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self.fsmLock.release()
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def __setState(self, newState, *args):
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# Internal function to change unconditionally to the indicated
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# state.
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# Internal function to change unconditionally to the indicated state.
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transition = Transition((newState,) + args)
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# See if we can transition immediately by polling the coroutine.
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coro = self.__transition(newState, *args)
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try:
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coro.send(None)
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except StopIteration:
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# We managed to apply this straight away.
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return transition
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# Continue the state transition in a task.
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task = PythonTask(coro)
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mgr = AsyncTaskManager.get_global_ptr()
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mgr.add(task)
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transition._future = task
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return transition
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async def __transition(self, newState, *args):
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assert self.state
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assert self.notify.debug("%s to state %s." % (self._name, newState))
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@ -482,8 +538,13 @@ class FSM(DirectObject):
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try:
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if not self.__callFromToFunc(self.oldState, self.newState, *args):
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self.__callExitFunc(self.oldState)
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self.__callEnterFunc(self.newState, *args)
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result = self.__callExitFunc(self.oldState)
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if isinstance(result, types.CoroutineType):
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await result
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result = self.__callEnterFunc(self.newState, *args)
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if isinstance(result, types.CoroutineType):
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await result
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except:
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# If we got an exception during the enter or exit methods,
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# go directly to state "InternalError" and raise up the
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@ -503,9 +564,10 @@ class FSM(DirectObject):
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del self.newState
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if self.__requestQueue:
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request = self.__requestQueue.pop(0)
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request, fut = self.__requestQueue.pop(0)
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assert self.notify.debug("%s continued queued request." % (self._name))
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request()
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await request()
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fut.set_result(None)
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def __callEnterFunc(self, name, *args):
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# Calls the appropriate enter function when transitioning into
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@ -517,7 +579,7 @@ class FSM(DirectObject):
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# If there's no matching enterFoo() function, call
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# defaultEnter() instead.
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func = self.defaultEnter
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func(*args)
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return func(*args)
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def __callFromToFunc(self, oldState, newState, *args):
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# Calls the appropriate fromTo function when transitioning into
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@ -540,7 +602,7 @@ class FSM(DirectObject):
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# If there's no matching exitFoo() function, call
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# defaultExit() instead.
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func = self.defaultExit
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func()
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return func()
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def __repr__(self):
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return self.__str__()
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