From fbfad9fbf5e061cb7c658dada3c4014c9796021c Mon Sep 17 00:00:00 2001
From: Andrew Godwin
Date: Thu, 10 Nov 2022 23:42:43 -0700
Subject: Inbound and outbound follows basic working

---
 stator/graph.py  | 27 ++++++++++++++++-----------
 stator/models.py | 20 +++++++++++++++++---
 stator/runner.py |  6 +++---
 3 files changed, 36 insertions(+), 17 deletions(-)

(limited to 'stator')

diff --git a/stator/graph.py b/stator/graph.py
index 7a8455c..00ef1c4 100644
--- a/stator/graph.py
+++ b/stator/graph.py
@@ -41,6 +41,7 @@ class StateGraph:
                 initial_state = state
             # Collect terminal states
             if state.terminal:
+                state.externally_progressed = True
                 terminal_states.add(state)
                 # Ensure they do NOT have a handler
                 try:
@@ -52,17 +53,18 @@ class StateGraph:
                         f"Terminal state '{state}' should not have a handler method ({state.handler_name})"
                     )
             else:
-                # Ensure non-terminal states have a try interval and a handler
-                if not state.try_interval:
-                    raise ValueError(
-                        f"State '{state}' has no try_interval and is not terminal"
-                    )
-                try:
-                    state.handler
-                except AttributeError:
-                    raise ValueError(
-                        f"State '{state}' does not have a handler method ({state.handler_name})"
-                    )
+                # Ensure non-terminal/manual states have a try interval and a handler
+                if not state.externally_progressed:
+                    if not state.try_interval:
+                        raise ValueError(
+                            f"State '{state}' has no try_interval and is not terminal or manual"
+                        )
+                    try:
+                        state.handler
+                    except AttributeError:
+                        raise ValueError(
+                            f"State '{state}' does not have a handler method ({state.handler_name})"
+                        )
         if initial_state is None:
             raise ValueError("The graph has no initial state")
         cls.initial_state = initial_state
@@ -80,9 +82,11 @@ class State:
         self,
         try_interval: Optional[float] = None,
         handler_name: Optional[str] = None,
+        externally_progressed: bool = False,
     ):
         self.try_interval = try_interval
         self.handler_name = handler_name
+        self.externally_progressed = externally_progressed
         self.parents: Set["State"] = set()
         self.children: Set["State"] = set()
 
@@ -118,6 +122,7 @@ class State:
 
     @property
     def handler(self) -> Callable[[Any], Optional[str]]:
+        # Retrieve it by name off the graph
         if self.handler_name is None:
             raise AttributeError("No handler defined")
         return getattr(self.graph, self.handler_name)
diff --git a/stator/models.py b/stator/models.py
index 50ee622..072a3ed 100644
--- a/stator/models.py
+++ b/stator/models.py
@@ -80,7 +80,7 @@ class StatorModel(models.Model):
         q = models.Q()
         for state in cls.state_graph.states.values():
             state = cast(State, state)
-            if not state.terminal:
+            if not state.externally_progressed:
                 q = q | models.Q(
                     (
                         models.Q(
@@ -135,17 +135,31 @@ class StatorModel(models.Model):
         self.state_ready = True
         self.save()
 
-    async def atransition_attempt(self) -> Optional[str]:
+    async def atransition_attempt(self) -> Optional[State]:
         """
         Attempts to transition the current state by running its handler(s).
         """
+        current_state = self.state_graph.states[self.state]
+        # If it's a manual progression state don't even try
+        # We shouldn't really be here in this case, but it could be a race condition
+        if current_state.externally_progressed:
+            print("Externally progressed state!")
+            return None
         try:
-            next_state = await self.state_graph.states[self.state].handler(self)
+            next_state = await current_state.handler(self)
         except BaseException as e:
             await StatorError.acreate_from_instance(self, e)
             traceback.print_exc()
         else:
             if next_state:
+                # Ensure it's a State object
+                if isinstance(next_state, str):
+                    next_state = self.state_graph.states[next_state]
+                # Ensure it's a child
+                if next_state not in current_state.children:
+                    raise ValueError(
+                        f"Cannot transition from {current_state} to {next_state} - not a declared transition"
+                    )
                 await self.atransition_perform(next_state)
                 return next_state
         await self.__class__.objects.filter(pk=self.pk).aupdate(
diff --git a/stator/runner.py b/stator/runner.py
index 1392e4d..0b42b27 100644
--- a/stator/runner.py
+++ b/stator/runner.py
@@ -50,9 +50,6 @@ class StatorRunner:
                         min(space_remaining, self.MAX_TASKS_PER_MODEL),
                         timezone.now() + datetime.timedelta(seconds=self.LOCK_TIMEOUT),
                     ):
-                        print(
-                            f"Attempting transition on {instance._meta.label_lower}#{instance.pk}"
-                        )
                         self.tasks.append(
                             asyncio.create_task(self.run_transition(instance))
                         )
@@ -76,6 +73,9 @@ class StatorRunner:
         Wrapper for atransition_attempt with fallback error handling
         """
         try:
+            print(
+                f"Attempting transition on {instance._meta.label_lower}#{instance.pk} from state {instance.state}"
+            )
             await instance.atransition_attempt()
         except BaseException:
             traceback.print_exc()
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