Profile fetching now working on state machine

6 files changed, 121 insertions, 172 deletions

diff --git a/stator/admin.py b/stator/admin.py
index 025f225..790fc38 100644
--- a/stator/admin.py
+++ b/stator/admin.py
@@ -10,8 +10,7 @@ class DomainAdmin(admin.ModelAdmin):
         "date",
         "model_label",
         "instance_pk",
-        "from_state",
-        "to_state",
+        "state",
         "error",
     ]
     ordering = ["-date"]
diff --git a/stator/graph.py b/stator/graph.py
index 7fc23f7..7a8455c 100644
--- a/stator/graph.py
+++ b/stator/graph.py
@@ -1,16 +1,4 @@
-from typing import (
-    Any,
-    Callable,
-    ClassVar,
-    Dict,
-    List,
-    Optional,
-    Set,
-    Tuple,
-    Type,
-    Union,
-    cast,
-)
+from typing import Any, Callable, ClassVar, Dict, List, Optional, Set, Tuple, Type
 
 
 class StateGraph:
@@ -44,20 +32,43 @@ class StateGraph:
         terminal_states = set()
         initial_state = None
         for state in cls.states.values():
+            # Check for multiple initial states
             if state.initial:
                 if initial_state:
                     raise ValueError(
                         f"The graph has more than one initial state: {initial_state} and {state}"
                     )
                 initial_state = state
+            # Collect terminal states
             if state.terminal:
                 terminal_states.add(state)
+                # Ensure they do NOT have a handler
+                try:
+                    state.handler
+                except AttributeError:
+                    pass
+                else:
+                    raise ValueError(
+                        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})"
+                    )
         if initial_state is None:
             raise ValueError("The graph has no initial state")
         cls.initial_state = initial_state
         cls.terminal_states = terminal_states
         # Generate choices
-        cls.choices = [(state, name) for name, state in cls.states.items()]
+        cls.choices = [(name, name) for name in cls.states.keys()]
 
 
 class State:
@@ -65,49 +76,37 @@ class State:
     Represents an individual state
     """
 
-    def __init__(self, try_interval: float = 300):
+    def __init__(
+        self,
+        try_interval: Optional[float] = None,
+        handler_name: Optional[str] = None,
+    ):
         self.try_interval = try_interval
+        self.handler_name = handler_name
         self.parents: Set["State"] = set()
-        self.children: Dict["State", "Transition"] = {}
+        self.children: Set["State"] = set()
 
     def _add_to_graph(self, graph: Type[StateGraph], name: str):
         self.graph = graph
         self.name = name
         self.graph.states[name] = self
+        if self.handler_name is None:
+            self.handler_name = f"handle_{self.name}"
 
     def __repr__(self):
         return f"<State {self.name}>"
 
-    def __str__(self):
-        return self.name
-
-    def __len__(self):
-        return len(self.name)
-
-    def add_transition(
-        self,
-        other: "State",
-        handler: Optional[Callable] = None,
-        priority: int = 0,
-    ) -> Callable:
-        def decorator(handler: Callable[[Any], bool]):
-            self.children[other] = Transition(
-                self,
-                other,
-                handler,
-                priority=priority,
-            )
-            other.parents.add(self)
-            return handler
+    def __eq__(self, other):
+        if isinstance(other, State):
+            return self is other
+        return self.name == other
 
-        # If we're not being called as a decorator, invoke it immediately
-        if handler is not None:
-            decorator(handler)
-        return decorator
+    def __hash__(self):
+        return hash(id(self))
 
-    def add_manual_transition(self, other: "State"):
-        self.children[other] = ManualTransition(self, other)
-        other.parents.add(self)
+    def transitions_to(self, other: "State"):
+        self.children.add(other)
+        other.parents.add(other)
 
     @property
     def initial(self):
@@ -117,59 +116,8 @@ class State:
     def terminal(self):
         return not self.children
 
-    def transitions(self, automatic_only=False) -> List["Transition"]:
-        """
-        Returns all transitions from this State in priority order
-        """
-        if automatic_only:
-            transitions = [t for t in self.children.values() if t.automatic]
-        else:
-            transitions = list(self.children.values())
-        return sorted(transitions, key=lambda t: t.priority, reverse=True)
-
-
-class Transition:
-    """
-    A possible transition from one state to another
-    """
-
-    def __init__(
-        self,
-        from_state: State,
-        to_state: State,
-        handler: Union[str, Callable],
-        priority: int = 0,
-    ):
-        self.from_state = from_state
-        self.to_state = to_state
-        self.handler = handler
-        self.priority = priority
-        self.automatic = True
-
-    def get_handler(self) -> Callable:
-        """
-        Returns the handler (it might need resolving from a string)
-        """
-        if isinstance(self.handler, str):
-            self.handler = getattr(self.from_state.graph, self.handler)
-        return cast(Callable, self.handler)
-
-    def __repr__(self):
-        return f"<Transition {self.from_state} -> {self.to_state}>"
-
-
-class ManualTransition(Transition):
-    """
-    A possible transition from one state to another that cannot be done by
-    the stator task runner, and must come from an external source.
-    """
-
-    def __init__(
-        self,
-        from_state: State,
-        to_state: State,
-    ):
-        self.from_state = from_state
-        self.to_state = to_state
-        self.priority = 0
-        self.automatic = False
+    @property
+    def handler(self) -> Callable[[Any], Optional[str]]:
+        if self.handler_name is None:
+            raise AttributeError("No handler defined")
+        return getattr(self.graph, self.handler_name)
diff --git a/stator/migrations/0001_initial.py b/stator/migrations/0001_initial.py
index d56ed5c..f7d652e 100644
--- a/stator/migrations/0001_initial.py
+++ b/stator/migrations/0001_initial.py
@@ -1,4 +1,4 @@
-# Generated by Django 4.1.3 on 2022-11-10 03:24
+# Generated by Django 4.1.3 on 2022-11-10 05:56
 
 from django.db import migrations, models
 
@@ -24,8 +24,7 @@ class Migration(migrations.Migration):
                 ),
                 ("model_label", models.CharField(max_length=200)),
                 ("instance_pk", models.CharField(max_length=200)),
-                ("from_state", models.CharField(max_length=200)),
-                ("to_state", models.CharField(max_length=200)),
+                ("state", models.CharField(max_length=200)),
                 ("date", models.DateTimeField(auto_now_add=True)),
                 ("error", models.TextField()),
                 ("error_details", models.TextField(blank=True, null=True)),
diff --git a/stator/models.py b/stator/models.py
index 235b18c..50ee622 100644
--- a/stator/models.py
+++ b/stator/models.py
@@ -1,13 +1,13 @@
 import datetime
 import traceback
-from typing import ClassVar, List, Optional, Type, cast
+from typing import ClassVar, List, Optional, Type, Union, cast
 
 from asgiref.sync import sync_to_async
 from django.db import models, transaction
 from django.utils import timezone
 from django.utils.functional import classproperty
 
-from stator.graph import State, StateGraph, Transition
+from stator.graph import State, StateGraph
 
 
 class StateField(models.CharField):
@@ -29,16 +29,6 @@ class StateField(models.CharField):
         kwargs["graph"] = self.graph
         return name, path, args, kwargs
 
-    def from_db_value(self, value, expression, connection):
-        if value is None:
-            return value
-        return self.graph.states[value]
-
-    def to_python(self, value):
-        if isinstance(value, State) or value is None:
-            return value
-        return self.graph.states[value]
-
     def get_prep_value(self, value):
         if isinstance(value, State):
             return value.name
@@ -95,7 +85,9 @@ class StatorModel(models.Model):
                     (
                         models.Q(
                             state_attempted__lte=timezone.now()
-                            - datetime.timedelta(seconds=state.try_interval)
+                            - datetime.timedelta(
+                                seconds=cast(float, state.try_interval)
+                            )
                         )
                         | models.Q(state_attempted__isnull=True)
                     ),
@@ -117,7 +109,7 @@ class StatorModel(models.Model):
                 ].select_for_update()
             )
             cls.objects.filter(pk__in=[i.pk for i in selected]).update(
-                state_locked_until=timezone.now()
+                state_locked_until=lock_expiry
             )
         return selected
 
@@ -143,36 +135,36 @@ class StatorModel(models.Model):
         self.state_ready = True
         self.save()
 
-    async def atransition_attempt(self) -> bool:
+    async def atransition_attempt(self) -> Optional[str]:
         """
         Attempts to transition the current state by running its handler(s).
         """
-        # Try each transition in priority order
-        for transition in self.state.transitions(automatic_only=True):
-            try:
-                success = await transition.get_handler()(self)
-            except BaseException as e:
-                await StatorError.acreate_from_instance(self, transition, e)
-                traceback.print_exc()
-                continue
-            if success:
-                await self.atransition_perform(transition.to_state.name)
-                return True
+        try:
+            next_state = await self.state_graph.states[self.state].handler(self)
+        except BaseException as e:
+            await StatorError.acreate_from_instance(self, e)
+            traceback.print_exc()
+        else:
+            if next_state:
+                await self.atransition_perform(next_state)
+                return next_state
         await self.__class__.objects.filter(pk=self.pk).aupdate(
             state_attempted=timezone.now(),
             state_locked_until=None,
             state_ready=False,
         )
-        return False
+        return None
 
-    def transition_perform(self, state_name):
+    def transition_perform(self, state: Union[State, str]):
         """
         Transitions the instance to the given state name, forcibly.
         """
-        if state_name not in self.state_graph.states:
-            raise ValueError(f"Invalid state {state_name}")
+        if isinstance(state, State):
+            state = state.name
+        if state not in self.state_graph.states:
+            raise ValueError(f"Invalid state {state}")
         self.__class__.objects.filter(pk=self.pk).update(
-            state=state_name,
+            state=state,
             state_changed=timezone.now(),
             state_attempted=None,
             state_locked_until=None,
@@ -194,11 +186,8 @@ class StatorError(models.Model):
     # The primary key of that model (probably int or str)
     instance_pk = models.CharField(max_length=200)
 
-    # The state we moved from
-    from_state = models.CharField(max_length=200)
-
-    # The state we moved to (or tried to)
-    to_state = models.CharField(max_length=200)
+    # The state we were on
+    state = models.CharField(max_length=200)
 
     # When it happened
     date = models.DateTimeField(auto_now_add=True)
@@ -213,14 +202,12 @@ class StatorError(models.Model):
     async def acreate_from_instance(
         cls,
         instance: StatorModel,
-        transition: Transition,
         exception: Optional[BaseException] = None,
     ):
         return await cls.objects.acreate(
             model_label=instance._meta.label_lower,
             instance_pk=str(instance.pk),
-            from_state=transition.from_state,
-            to_state=transition.to_state,
+            state=instance.state,
             error=str(exception),
             error_details=traceback.format_exc(),
         )
diff --git a/stator/runner.py b/stator/runner.py
index f9c726e..1392e4d 100644
--- a/stator/runner.py
+++ b/stator/runner.py
@@ -1,6 +1,7 @@
 import asyncio
 import datetime
 import time
+import traceback
 import uuid
 from typing import List, Type
 
@@ -53,7 +54,7 @@ class StatorRunner:
                             f"Attempting transition on {instance._meta.label_lower}#{instance.pk}"
                         )
                         self.tasks.append(
-                            asyncio.create_task(instance.atransition_attempt())
+                            asyncio.create_task(self.run_transition(instance))
                         )
                         self.handled += 1
                         space_remaining -= 1
@@ -70,5 +71,17 @@ class StatorRunner:
         print("Complete")
         return self.handled
 
+    async def run_transition(self, instance: StatorModel):
+        """
+        Wrapper for atransition_attempt with fallback error handling
+        """
+        try:
+            await instance.atransition_attempt()
+        except BaseException:
+            traceback.print_exc()
+
     def remove_completed_tasks(self):
+        """
+        Removes all completed asyncio.Tasks from our local in-progress list
+        """
         self.tasks = [t for t in self.tasks if not t.done()]
diff --git a/stator/tests/test_graph.py b/stator/tests/test_graph.py
index 0a7113d..c66f441 100644
--- a/stator/tests/test_graph.py
+++ b/stator/tests/test_graph.py
@@ -9,39 +9,29 @@ def test_declare():
     lookups.
     """
 
-    fake_handler = lambda: True
-
     class TestGraph(StateGraph):
-        initial = State()
-        second = State()
+        initial = State(try_interval=3600)
+        second = State(try_interval=1)
         third = State()
-        fourth = State()
-        final = State()
-
-        initial.add_transition(second, 60, handler=fake_handler)
-        second.add_transition(third, 60, handler="check_third")
 
-        def check_third(cls):
-            return True
+        initial.transitions_to(second)
+        second.transitions_to(third)
 
-        @third.add_transition(fourth, 60)
-        def check_fourth(cls):
-            return True
+        @classmethod
+        def handle_initial(cls):
+            pass
 
-        fourth.add_manual_transition(final)
+        @classmethod
+        def handle_second(cls):
+            pass
 
     assert TestGraph.initial_state == TestGraph.initial
-    assert TestGraph.terminal_states == {TestGraph.final}
+    assert TestGraph.terminal_states == {TestGraph.third}
 
-    assert TestGraph.initial.children[TestGraph.second].get_handler() == fake_handler
-    assert (
-        TestGraph.second.children[TestGraph.third].get_handler()
-        == TestGraph.check_third
-    )
-    assert (
-        TestGraph.third.children[TestGraph.fourth].get_handler().__name__
-        == "check_fourth"
-    )
+    assert TestGraph.initial.handler == TestGraph.handle_initial
+    assert TestGraph.initial.try_interval == 3600
+    assert TestGraph.second.handler == TestGraph.handle_second
+    assert TestGraph.second.try_interval == 1
 
 
 def test_bad_declarations():
@@ -62,5 +52,18 @@ def test_bad_declarations():
             loop = State()
             loop2 = State()
 
-            loop.add_transition(loop2, 1, handler="fake")
-            loop2.add_transition(loop, 1, handler="fake")
+            loop.transitions_to(loop2)
+            loop2.transitions_to(loop)
+
+
+def test_state():
+    """
+    Tests basic values of the State class
+    """
+
+    class TestGraph(StateGraph):
+        initial = State()
+
+    assert "initial" == TestGraph.initial
+    assert TestGraph.initial == "initial"
+    assert TestGraph.initial == TestGraph.initial