add state action

share/models.py

@@ -1,6 +1,7 @@
 import logging
 import typing
-from datetime import date
+from datetime import date, timedelta
+from functools import singledispatchmethod
 
 from django.contrib.auth import get_user_model
 from django.db import OperationalError, models, transaction
@@ -122,6 +123,7 @@ class Donation(models.Model):
         default=states.PendingApprovalState.state_id(),
         choices=states.DonationStateEnum.choices,
     )
+    estimated_delivery_days = models.PositiveSmallIntegerField()
     excepted_delivery_date = models.DateField(null=True)
     events = models.JSONField(default=list)
     created_by = models.ForeignKey(User, on_delete=models.CASCADE)
@@ -132,13 +134,26 @@ class Donation(models.Model):
     def required_item_name(self) -> str:
         return self.required_item.name
 
+    @singledispatchmethod
+    def perform_action(self, arg):
+        raise NotImplementedError("Unknown action")
+
+    @perform_action.register
+    def _approval_action(self, action: states.ApprovalAction):
+        self.excepted_delivery_date = date.today() + timedelta(
+            days=self.estimated_delivery_days
+        )
+
     def calc_state(self) -> states.State:
         current_state = states.get_state(self.state)
         for raw_event in self.events:
             e = states.get_event(raw_event)
             if e.timestamp < self.modified_at.timestamp():
                 continue
-            current_state = current_state.apply(e)
+            current_state, action = current_state.apply(e)
+            if action is not None:
+                self.perform_action(action)
+
         return current_state
 
     def set_event(self, user, raw_event: typing.Dict):

share/states.py

@@ -6,6 +6,18 @@
 from pydantic import BaseModel, Field, validator
 
 
+class Action:
+    pass
+
+
+class ApprovalAction(Action):
+    pass
+
+
+class CancelAction(Action):
+    pass
+
+
 class Event(BaseModel):
     name: str = ""
     timestamp: float = Field(default_factory=time.time)
@@ -38,7 +50,7 @@ class DonationCancelledEvent(Event):
 
 class State(ABC):
     @abstractmethod
-    def apply(self, event: Event) -> "State":
+    def apply(self, event: Event) -> typing.Tuple["State", typing.Optional[Action]]:
         raise NotImplementedError()
 
     @classmethod
@@ -47,52 +59,52 @@ def state_id(cls) -> str:
 
 
 class InvalidState(State):
-    def apply(self, event: Event) -> State:
-        return InvalidState()
+    def apply(self, event: Event) -> typing.Tuple["State", typing.Optional[Action]]:
+        return InvalidState(), None
 
 
 class CancelledState(State):
-    def apply(self, event: Event) -> State:
-        return CancelledState()
+    def apply(self, event: Event) -> typing.Tuple["State", typing.Optional[Action]]:
+        return CancelledState(), CancelAction()
 
 
 class CollectingState(State):
-    def apply(self, event: Event) -> State:
-        return CancelledState()
+    def apply(self, event: Event) -> typing.Tuple["State", typing.Optional[Action]]:
+        return CancelledState(), None
 
 
 class PendingApprovalState(State):
-    def apply(self, event: Event) -> State:
+    def apply(self, event: Event) -> typing.Tuple["State", typing.Optional[Action]]:
         if event.name == DonationApprovedEvent.event_id():
-            return PendingDispatchState()
+            return PendingDispatchState(), ApprovalAction()
         elif event.name == DonationCancelledEvent.event_id():
-            return CancelledState()
+            return CancelledState(), None
         else:
-            return InvalidState()
+            return InvalidState(), None
 
 
 class PendingDispatchState(State):
-    def apply(self, event: Event) -> State:
+    def apply(self, event: Event) -> typing.Tuple["State", typing.Optional[Action]]:
         if event.name == DonationDispatchedEvent.event_id():
-            return DoneState()
+            return DoneState(), None
             # return PendingDeliveryState()
         elif event.name == DonationCancelledEvent.event_id():
-            return CancelledState()
+            return CancelledState(), None
         else:
-            return InvalidState()
+            return InvalidState(), None
 
 
 class PendingDeliveryState(State):
-    def apply(self, event: Event) -> State:
+    def apply(self, event: Event) -> typing.Tuple["State", typing.Optional[Action]]:
         if event.name == DonationDeliveredEvent.event_id():
-            return DoneState()
+            return DoneState(), None
         else:
-            return InvalidState()
+            return InvalidState(), None
 
 
 class DoneState(State):
-    def apply(self, event: Event) -> State:
-        return InvalidState()
+    def apply(self, event: Event) -> typing.Tuple["State", typing.Optional[Action]]:
+        return InvalidState(), None
 
 
 class DonationStateMachine: