feat: improve key alignment efficiency

findmy/accessory.py

@@ -61,9 +61,11 @@ def get_max_index(self, dt: datetime) -> int:
     @abstractmethod
     def update_alignment(self, dt: datetime, index: int) -> None:
         """
-        Update alignment of the accessory.
+        Update alignment of the accessory based on a key index that was observed at a specific time.
 
-        Alignment can be updated based on a LocationReport that was observed at a specific index.
+        Implementations of this method should consider that this method may be called
+        multiple times, sometimes with seemingly conflicting data: the same index may be
+        observed at different times, or multiple indices may be observed at the same time.
         """
         raise NotImplementedError
 
@@ -222,8 +224,13 @@ def get_max_index(self, dt: datetime) -> int:
 
     @override
     def update_alignment(self, dt: datetime, index: int) -> None:
-        if dt < self._alignment_date:
-            # we only care about the most recent report
+        if dt < self._alignment_date or index < self._alignment_index:
+            # We only care about the most recent report and index.
+            # Multiple calls to this method may be made with
+            # possibly conflicting data, so we just ignore
+            # anything that seems to go backwards in time or index.
+            # Saving the newest data is at least likely to be stable
+            # over multiple fetches.
             return
 
         logger.info("Updating alignment based on report observed at index %i", index)

findmy/reports/reports.py

@@ -431,7 +431,7 @@ async def _fetch_accessory_report(
         # state variables
         cur_keys_primary: set[str] = set()
         cur_keys_secondary: set[str] = set()
-        cur_index = accessory.get_min_index(start_date)
+        cur_index = accessory.get_max_index(start_date)
         ret: set[LocationReport] = set()
 
         async def _fetch() -> set[LocationReport]:
@@ -446,17 +446,15 @@ async def _fetch() -> set[LocationReport]:
                 report.decrypt(key)
 
                 # update alignment data on every report
-                # if a key maps to multiple indices, only feed it the maximum index,
-                # since apple only returns the latest reports per request.
-                # This makes the value more likely to be stable.
-                accessory.update_alignment(report.timestamp, max(key_to_ind[key]))
+                for i in key_to_ind[key]:
+                    accessory.update_alignment(report.timestamp, i)
 
             cur_keys_primary.clear()
             cur_keys_secondary.clear()
 
             return set(new_reports)
 
-        while cur_index <= accessory.get_max_index(end_date):
+        while cur_index >= accessory.get_min_index(end_date):
             key_batch = accessory.keys_at(cur_index)
 
             # split into primary and secondary keys
@@ -483,7 +481,7 @@ async def _fetch() -> set[LocationReport]:
             cur_keys_primary |= new_keys_primary
             cur_keys_secondary |= new_keys_secondary
 
-            cur_index += 1
+            cur_index -= 1
 
         if cur_keys_primary or cur_keys_secondary:
             # fetch remaining keys