Added class CharacteristicDeclaration, gatt_server getters

* Converted CharacteristicDeclaration implementation to class
* Added ability to get a gatt_server attribute by service UUID, characteristics UUID, descriptor UUID

bumble/gatt_server.py

@@ -26,6 +26,7 @@
 import asyncio
 import logging
 from collections import defaultdict
+from typing import Tuple, Optional
 from pyee import EventEmitter
 from colors import color
 
@@ -79,6 +80,63 @@ class Server(EventEmitter):
                 return attribute
         return None
 
+    def get_service_attribute(self, service_uuid: UUID) -> Optional[Service]:
+        return next(
+            (
+                attribute
+                for attribute in self.attributes
+                if attribute.type == GATT_PRIMARY_SERVICE_ATTRIBUTE_TYPE
+                and attribute.uuid == service_uuid
+            ),
+            None,
+        )
+
+    def get_characteristic_attributes(
+        self, service_uuid: UUID, characteristic_uuid: UUID
+    ) -> Optional[Tuple[CharacteristicDeclaration, Characteristic]]:
+        service_handle = self.get_service_attribute(service_uuid)
+        if not service_handle:
+            return None
+
+        return next(
+            (
+                (attribute, self.get_attribute(attribute.characteristic.handle))
+                for attribute in map(
+                    self.get_attribute,
+                    range(service_handle.handle, service_handle.end_group_handle + 1),
+                )
+                if attribute.type == GATT_CHARACTERISTIC_ATTRIBUTE_TYPE
+                and attribute.characteristic.uuid == characteristic_uuid
+            ),
+            None,
+        )
+
+    def get_descriptor_attribute(
+        self, service_uuid: UUID, characteristic_uuid: UUID, descriptor_uuid: UUID
+    ) -> Optional[Descriptor]:
+        characteristics = self.get_characteristic_attributes(
+            service_uuid, characteristic_uuid
+        )
+        if not characteristics:
+            return None
+
+        (_, characteristic_value) = characteristics
+
+        return next(
+            (
+                attribute
+                for attribute in map(
+                    self.get_attribute,
+                    range(
+                        characteristic_value.handle + 1,
+                        characteristic_value.end_group_handle + 1,
+                    ),
+                )
+                if attribute.type == descriptor_uuid
+            ),
+            None,
+        )
+
     def add_attribute(self, attribute):
         # Assign a handle to this attribute
         attribute.handle = self.next_handle()
@@ -95,16 +153,9 @@ class Server(EventEmitter):
 
         # Add all characteristics
         for characteristic in service.characteristics:
-            # Add a Characteristic Declaration (Vol 3, Part G - 3.3.1 Characteristic Declaration)
-            declaration_bytes = struct.pack(
-                '<BH',
-                characteristic.properties,
-                self.next_handle() + 1,  # The value will be the next attribute after this declaration
-            ) + characteristic.uuid.to_pdu_bytes()
-            characteristic_declaration = Attribute(
-                GATT_CHARACTERISTIC_ATTRIBUTE_TYPE,
-                Attribute.READABLE,
-                declaration_bytes
+            # Add a Characteristic Declaration
+            characteristic_declaration = CharacteristicDeclaration(
+                characteristic, self.next_handle() + 1
             )
             self.add_attribute(characteristic_declaration)