fix: release consumed restore references and explain deletion protection [skip ci]

pigway_frame_flow/display/service.py

@@ -205,6 +205,27 @@ class DisplayService:
         )
         return self.db.one("SELECT * FROM device_state WHERE device_id=?", (id,))
 
+    def clear_self_restore_reference(self, device_id, device):
+        # A confirmed return to the managed image consumes its restore target.
+        # Keep references while an override or an uncertain write still needs them.
+        image_id = device.current_content.id
+        if (
+            device.status == "offline"
+            or not device.current_content.synced
+            or image_id is None
+        ):
+            return
+        with self.lock:
+            self.db.execute(
+                """UPDATE device_state SET previous_image_id=NULL
+                WHERE device_id=? AND previous_image_id=? AND managed_image_id=?
+                AND base_image_id IS NULL
+                AND NOT EXISTS (SELECT 1 FROM overrides WHERE device_id=?)
+                AND NOT EXISTS (SELECT 1 FROM operations WHERE device_id=?
+                    AND write_started=1 AND status IN ('UPLOADING','SYNCING','UNKNOWN'))""",
+                (device_id, image_id, image_id, device_id, device_id),
+            )
+
     def content_asset(self, content, device_id=None, operation_id=None):
         if isinstance(content, AutoCollageContent):
             from pigway_frame_flow.extensions.auto_collage import prepare
@@ -376,6 +397,7 @@ class DisplayService:
 
     def current_content(self, device_id):
         device = self.registry.get(device_id).device()
+        self.clear_self_restore_reference(device_id, device)
         image_id = device.current_content.id
         row = self.db.one(
             "SELECT * FROM image_sources WHERE device_id=? AND image_id=?",
@@ -513,6 +535,8 @@ class DisplayService:
         previous = device.current_content.id
         state = self.state(device_id)
         if action == "delete":
+            self.clear_self_restore_reference(device_id, device)
+            state = self.state(device_id)
             image_id = payload["image_id"]
             if payload.get("cloud_cleanup"):
                 if (
@@ -551,7 +575,12 @@ class DisplayService:
                 )
             }
             if image_id in protected and not payload.get("purge"):
-                raise FlowError(E.CONFLICT, "Image is needed for restoration", 409)
+                raise FlowError(
+                    E.CONFLICT,
+                    "Image is needed for restoration",
+                    409,
+                    {"reason": "RESTORE_IMAGE_PROTECTED"},
+                )
             if image_id == previous and not payload["confirm_current"]:
                 raise FlowError(E.CONFLICT, "Current image needs confirmation", 409)
             self._start_write(id)
@@ -743,6 +772,7 @@ class DisplayService:
                     and device.current_content.synced
                 ):
                     self.update(op["id"], "COMPLETED")
+                    self.clear_self_restore_reference(op["device_id"], device)
                     self.cloud_library.confirm(op["id"])
                     self.db.history(op, "COMPLETED")
                     self.db.event("operation.completed", {"operation_id": op["id"]})
@@ -768,6 +798,7 @@ class DisplayService:
                     and device.current_content.synced
                 ):
                     self.update(op["id"], "COMPLETED")
+                    self.clear_self_restore_reference(op["device_id"], device)
                     self.cloud_library.confirm(op["id"])
                     self.db.history(op, "COMPLETED")
                     self.db.event("operation.completed", {"operation_id": op["id"]})