feat: consider connection slots when selecting connection path (#293)

Author: bdraco

src/habluetooth/__init__.py

@@ -1,5 +1,7 @@
 __version__ = "5.3.1"
 
+from bleak_retry_connector import Allocations
+
 from .advertisement_tracker import (
     TRACKER_BUFFERING_WOBBLE_SECONDS,
     AdvertisementTracker,
@@ -45,6 +47,7 @@
     "TRACKER_BUFFERING_WOBBLE_SECONDS",
     "UNAVAILABLE_TRACK_SECONDS",
     "AdvertisementTracker",
+    "Allocations",
     "BaseHaRemoteScanner",
     "BaseHaScanner",
     "BluetoothManager",

src/habluetooth/base_scanner.py

@@ -11,7 +11,7 @@
 
 from bleak.backends.device import BLEDevice
 from bleak.backends.scanner import AdvertisementData
-from bleak_retry_connector import NO_RSSI_VALUE
+from bleak_retry_connector import NO_RSSI_VALUE, Allocations
 from bluetooth_adapters import adapter_human_name
 from bluetooth_data_tools import monotonic_time_coarse, parse_advertisement_data_bytes
 
@@ -169,20 +169,51 @@ def _clear_connect_failure(self, address: str) -> None:
         """Clear a connect failure."""
         self._connect_failures.pop(address, None)
 
+    def get_allocations(self) -> Allocations | None:
+        """
+        Get current connection slot allocations for this scanner.
+
+        Returns:
+            Allocations object with free/limit/allocated info, or None if not available.
+
+        Note:
+            Subclasses should override this method to provide their allocation info.
+            For local adapters, this will be overridden in HaScanner to query
+            BleakSlotManager.
+            For remote scanners, they should override to return their own tracking.
+
+        """
+        return None
+
     def _score_connection_paths(
         self, rssi_diff: _int, scanner_device: BluetoothScannerDevice
     ) -> float:
-        """Score the connection paths."""
+        """Score the connection paths considering slot availability."""
         address = scanner_device.ble_device.address
         score = scanner_device.advertisement.rssi or NO_RSSI_VALUE
         scanner_connections_in_progress = len(self._connect_in_progress)
         previous_failures = self._connect_failures.get(address, 0)
+
+        # Penalize scanners with connections in progress
         if scanner_connections_in_progress:
             # Very large penalty for multiple connections in progress
             # to avoid overloading the adapter
             score -= rssi_diff * scanner_connections_in_progress * 1.01
+
+        # Penalize based on previous failures
         if previous_failures:
             score -= rssi_diff * previous_failures * 0.51
+
+        # Consider connection slot availability
+        allocation = self.get_allocations()
+        if allocation and allocation.slots > 0:
+            if allocation.free == 0:
+                # No slots available - return NO_RSSI_VALUE to indicate unavailable
+                return NO_RSSI_VALUE
+            if allocation.free == 1:
+                # Last slot available - small penalty to prefer adapters with more slots
+                score -= rssi_diff * 0.76
+
         return score
 
     def _connections_in_progress(self) -> int:

src/habluetooth/scanner.py

@@ -16,7 +16,7 @@
 from bleak.assigned_numbers import AdvertisementDataType
 from bleak.backends.device import BLEDevice
 from bleak.backends.scanner import AdvertisementData, AdvertisementDataCallback
-from bleak_retry_connector import restore_discoveries
+from bleak_retry_connector import Allocations, restore_discoveries
 from bleak_retry_connector.bluez import stop_discovery
 from bluetooth_adapters import DEFAULT_ADDRESS
 from bluetooth_data_tools import monotonic_time_coarse
@@ -253,6 +253,12 @@ def get_discovered_device_advertisement_data(
         """Return the advertisement data for a discovered device."""
         return self.discovered_devices_and_advertisement_data.get(address)
 
+    def get_allocations(self) -> Allocations | None:
+        """Get current connection slot allocations from BleakSlotManager."""
+        if self._manager and self._manager.slot_manager:
+            return self._manager.slot_manager.get_allocations(self.adapter)
+        return None
+
     def async_setup(self) -> CALLBACK_TYPE:
         """Set up the scanner."""
         super().async_setup()