Add a class-based GATT adapter

bumble/att.py

@@ -759,13 +759,13 @@ class AttributeValue:
     def __init__(
         self,
         read: Union[
-            Callable[[Optional[Connection]], bytes],
-            Callable[[Optional[Connection]], Awaitable[bytes]],
+            Callable[[Optional[Connection]], Any],
+            Callable[[Optional[Connection]], Awaitable[Any]],
             None,
         ] = None,
         write: Union[
-            Callable[[Optional[Connection], bytes], None],
-            Callable[[Optional[Connection], bytes], Awaitable[None]],
+            Callable[[Optional[Connection], Any], None],
+            Callable[[Optional[Connection], Any], Awaitable[None]],
             None,
         ] = None,
     ):
@@ -824,13 +824,13 @@ def from_string(cls, permissions_str: str) -> Attribute.Permissions:
     READ_REQUIRES_AUTHORIZATION = Permissions.READ_REQUIRES_AUTHORIZATION
     WRITE_REQUIRES_AUTHORIZATION = Permissions.WRITE_REQUIRES_AUTHORIZATION
 
-    value: Union[bytes, AttributeValue]
+    value: Any
 
     def __init__(
         self,
         attribute_type: Union[str, bytes, UUID],
         permissions: Union[str, Attribute.Permissions],
-        value: Union[str, bytes, AttributeValue] = b'',
+        value: Any = b'',
     ) -> None:
         EventEmitter.__init__(self)
         self.handle = 0
@@ -848,11 +848,7 @@ def __init__(
         else:
             self.type = attribute_type
 
-        # Convert the value to a byte array
-        if isinstance(value, str):
-            self.value = bytes(value, 'utf-8')
-        else:
-            self.value = value
+        self.value = value
 
     def encode_value(self, value: Any) -> bytes:
         return value
@@ -895,6 +891,8 @@ async def read_value(self, connection: Optional[Connection]) -> bytes:
         else:
             value = self.value
 
+        self.emit('read', connection, value)
+
         return self.encode_value(value)
 
     async def write_value(self, connection: Connection, value_bytes: bytes) -> None:

bumble/gatt.py

@@ -28,19 +28,23 @@
 import logging
 import struct
 from typing import (
+    Any,
     Callable,
     Dict,
     Iterable,
     List,
     Optional,
     Sequence,
+    SupportsBytes,
+    Type,
     Union,
     TYPE_CHECKING,
 )
 
 from bumble.colors import color
 from bumble.core import BaseBumbleError, UUID
 from bumble.att import Attribute, AttributeValue
+from bumble.utils import ByteSerializable
 
 if TYPE_CHECKING:
     from bumble.gatt_client import AttributeProxy
@@ -343,7 +347,7 @@ class Service(Attribute):
     def __init__(
         self,
         uuid: Union[str, UUID],
-        characteristics: List[Characteristic],
+        characteristics: Iterable[Characteristic],
         primary=True,
         included_services: Iterable[Service] = (),
     ) -> None:
@@ -362,7 +366,7 @@ def __init__(
         )
         self.uuid = uuid
         self.included_services = list(included_services)
-        self.characteristics = characteristics[:]
+        self.characteristics = list(characteristics)
         self.primary = primary
 
     def get_advertising_data(self) -> Optional[bytes]:
@@ -393,7 +397,7 @@ class TemplateService(Service):
 
     def __init__(
         self,
-        characteristics: List[Characteristic],
+        characteristics: Iterable[Characteristic],
         primary: bool = True,
         included_services: Iterable[Service] = (),
     ) -> None:
@@ -490,7 +494,7 @@ def __init__(
         uuid: Union[str, bytes, UUID],
         properties: Characteristic.Properties,
         permissions: Union[str, Attribute.Permissions],
-        value: Union[str, bytes, CharacteristicValue] = b'',
+        value: Any = b'',
         descriptors: Sequence[Descriptor] = (),
     ):
         super().__init__(uuid, permissions, value)
@@ -525,7 +529,11 @@ class CharacteristicDeclaration(Attribute):
 
     characteristic: Characteristic
 
-    def __init__(self, characteristic: Characteristic, value_handle: int) -> None:
+    def __init__(
+        self,
+        characteristic: Characteristic,
+        value_handle: int,
+    ) -> None:
         declaration_bytes = (
             struct.pack('<BH', characteristic.properties, value_handle)
             + characteristic.uuid.to_pdu_bytes()
@@ -705,7 +713,7 @@ class MappedCharacteristicAdapter(PackedCharacteristicAdapter):
     '''
     Adapter that packs/unpacks characteristic values according to a standard
     Python `struct` format.
-    The adapted `read_value` and `write_value` methods return/accept aa dictionary which
+    The adapted `read_value` and `write_value` methods return/accept a dictionary which
     is packed/unpacked according to format, with the arguments extracted from the
     dictionary by key, in the same order as they occur in the `keys` parameter.
     '''
@@ -735,6 +743,24 @@ def decode_value(self, value: bytes) -> str:
         return value.decode('utf-8')
 
 
+# -----------------------------------------------------------------------------
+class SerializableCharacteristicAdapter(CharacteristicAdapter):
+    '''
+    Adapter that converts any class to/from bytes using the class'
+    `to_bytes` and `__bytes__` methods, respectively.
+    '''
+
+    def __init__(self, characteristic, cls: Type[ByteSerializable]):
+        super().__init__(characteristic)
+        self.cls = cls
+
+    def encode_value(self, value: SupportsBytes) -> bytes:
+        return bytes(value)
+
+    def decode_value(self, value: bytes) -> Any:
+        return self.cls.from_bytes(value)
+
+
 # -----------------------------------------------------------------------------
 class Descriptor(Attribute):
     '''

bumble/gatt_server.py

@@ -28,7 +28,17 @@
 import logging
 from collections import defaultdict
 import struct
-from typing import List, Tuple, Optional, TypeVar, Type, Dict, Iterable, TYPE_CHECKING
+from typing import (
+    Dict,
+    Iterable,
+    List,
+    Optional,
+    Tuple,
+    TypeVar,
+    Type,
+    Union,
+    TYPE_CHECKING,
+)
 from pyee import EventEmitter
 
 from bumble.colors import color
@@ -68,6 +78,7 @@
     GATT_REQUEST_TIMEOUT,
     GATT_SECONDARY_SERVICE_ATTRIBUTE_TYPE,
     Characteristic,
+    CharacteristicAdapter,
     CharacteristicDeclaration,
     CharacteristicValue,
     IncludedServiceDeclaration,

bumble/profiles/aics.py

@@ -17,6 +17,7 @@
 # -----------------------------------------------------------------------------
 # Imports
 # -----------------------------------------------------------------------------
+from __future__ import annotations
 import logging
 import struct
 
@@ -28,10 +29,11 @@
 from bumble.att import ATT_Error
 from bumble.gatt import (
     Characteristic,
-    DelegatedCharacteristicAdapter,
+    SerializableCharacteristicAdapter,
+    PackedCharacteristicAdapter,
     TemplateService,
     CharacteristicValue,
-    PackedCharacteristicAdapter,
+    UTF8CharacteristicAdapter,
     GATT_AUDIO_INPUT_CONTROL_SERVICE,
     GATT_AUDIO_INPUT_STATE_CHARACTERISTIC,
     GATT_GAIN_SETTINGS_ATTRIBUTE_CHARACTERISTIC,
@@ -154,9 +156,6 @@ async def notify_subscribers_via_connection(self, connection: Connection) -> Non
             attribute=self.attribute_value, value=bytes(self)
         )
 
-    def on_read(self, _connection: Optional[Connection]) -> bytes:
-        return bytes(self)
-
 
 @dataclass
 class GainSettingsProperties:
@@ -173,7 +172,7 @@ def from_bytes(cls, data: bytes):
         (gain_settings_unit, gain_settings_minimum, gain_settings_maximum) = (
             struct.unpack('BBB', data)
         )
-        GainSettingsProperties(
+        return GainSettingsProperties(
             gain_settings_unit, gain_settings_minimum, gain_settings_maximum
         )
 
@@ -186,9 +185,6 @@ def __bytes__(self) -> bytes:
             ]
         )
 
-    def on_read(self, _connection: Optional[Connection]) -> bytes:
-        return bytes(self)
-
 
 @dataclass
 class AudioInputControlPoint:
@@ -321,21 +317,14 @@ class AudioInputDescription:
     audio_input_description: str = "Bluetooth"
     attribute_value: Optional[CharacteristicValue] = None
 
-    @classmethod
-    def from_bytes(cls, data: bytes):
-        return cls(audio_input_description=data.decode('utf-8'))
-
-    def __bytes__(self) -> bytes:
-        return self.audio_input_description.encode('utf-8')
-
-    def on_read(self, _connection: Optional[Connection]) -> bytes:
-        return self.audio_input_description.encode('utf-8')
+    def on_read(self, _connection: Optional[Connection]) -> str:
+        return self.audio_input_description
 
-    async def on_write(self, connection: Optional[Connection], value: bytes) -> None:
+    async def on_write(self, connection: Optional[Connection], value: str) -> None:
         assert connection
         assert self.attribute_value
 
-        self.audio_input_description = value.decode('utf-8')
+        self.audio_input_description = value
         await connection.device.notify_subscribers(
             attribute=self.attribute_value, value=value
         )
@@ -375,34 +364,37 @@ def __init__(
             self.audio_input_state, self.gain_settings_properties
         )
 
-        self.audio_input_state_characteristic = DelegatedCharacteristicAdapter(
+        self.audio_input_state_characteristic = SerializableCharacteristicAdapter(
             Characteristic(
                 uuid=GATT_AUDIO_INPUT_STATE_CHARACTERISTIC,
                 properties=Characteristic.Properties.READ
                 | Characteristic.Properties.NOTIFY,
                 permissions=Characteristic.Permissions.READ_REQUIRES_ENCRYPTION,
-                value=CharacteristicValue(read=self.audio_input_state.on_read),
+                value=self.audio_input_state,
             ),
-            encode=lambda value: bytes(value),
+            AudioInputState,
         )
         self.audio_input_state.attribute_value = (
             self.audio_input_state_characteristic.value
         )
 
-        self.gain_settings_properties_characteristic = DelegatedCharacteristicAdapter(
-            Characteristic(
-                uuid=GATT_GAIN_SETTINGS_ATTRIBUTE_CHARACTERISTIC,
-                properties=Characteristic.Properties.READ,
-                permissions=Characteristic.Permissions.READ_REQUIRES_ENCRYPTION,
-                value=CharacteristicValue(read=self.gain_settings_properties.on_read),
+        self.gain_settings_properties_characteristic = (
+            SerializableCharacteristicAdapter(
+                Characteristic(
+                    uuid=GATT_GAIN_SETTINGS_ATTRIBUTE_CHARACTERISTIC,
+                    properties=Characteristic.Properties.READ,
+                    permissions=Characteristic.Permissions.READ_REQUIRES_ENCRYPTION,
+                    value=self.gain_settings_properties,
+                ),
+                GainSettingsProperties,
             )
         )
 
         self.audio_input_type_characteristic = Characteristic(
             uuid=GATT_AUDIO_INPUT_TYPE_CHARACTERISTIC,
             properties=Characteristic.Properties.READ,
             permissions=Characteristic.Permissions.READ_REQUIRES_ENCRYPTION,
-            value=audio_input_type,
+            value=bytes(audio_input_type, 'utf-8'),
         )
 
         self.audio_input_status_characteristic = Characteristic(
@@ -412,18 +404,14 @@ def __init__(
             value=bytes([self.audio_input_status]),
         )
 
-        self.audio_input_control_point_characteristic = DelegatedCharacteristicAdapter(
-            Characteristic(
-                uuid=GATT_AUDIO_INPUT_CONTROL_POINT_CHARACTERISTIC,
-                properties=Characteristic.Properties.WRITE,
-                permissions=Characteristic.Permissions.WRITE_REQUIRES_ENCRYPTION,
-                value=CharacteristicValue(
-                    write=self.audio_input_control_point.on_write
-                ),
-            )
+        self.audio_input_control_point_characteristic = Characteristic(
+            uuid=GATT_AUDIO_INPUT_CONTROL_POINT_CHARACTERISTIC,
+            properties=Characteristic.Properties.WRITE,
+            permissions=Characteristic.Permissions.WRITE_REQUIRES_ENCRYPTION,
+            value=CharacteristicValue(write=self.audio_input_control_point.on_write),
         )
 
-        self.audio_input_description_characteristic = DelegatedCharacteristicAdapter(
+        self.audio_input_description_characteristic = UTF8CharacteristicAdapter(
             Characteristic(
                 uuid=GATT_AUDIO_INPUT_DESCRIPTION_CHARACTERISTIC,
                 properties=Characteristic.Properties.READ
@@ -469,8 +457,8 @@ def __init__(self, service_proxy: ServiceProxy) -> None:
             )
         ):
             raise gatt.InvalidServiceError("Audio Input State Characteristic not found")
-        self.audio_input_state = DelegatedCharacteristicAdapter(
-            characteristic=characteristics[0], decode=AudioInputState.from_bytes
+        self.audio_input_state = SerializableCharacteristicAdapter(
+            characteristics[0], AudioInputState
         )
 
         if not (
@@ -481,9 +469,8 @@ def __init__(self, service_proxy: ServiceProxy) -> None:
             raise gatt.InvalidServiceError(
                 "Gain Settings Attribute Characteristic not found"
             )
-        self.gain_settings_properties = PackedCharacteristicAdapter(
-            characteristics[0],
-            'BBB',
+        self.gain_settings_properties = SerializableCharacteristicAdapter(
+            characteristics[0], GainSettingsProperties
         )
 
         if not (
@@ -494,10 +481,7 @@ def __init__(self, service_proxy: ServiceProxy) -> None:
             raise gatt.InvalidServiceError(
                 "Audio Input Status Characteristic not found"
             )
-        self.audio_input_status = PackedCharacteristicAdapter(
-            characteristics[0],
-            'B',
-        )
+        self.audio_input_status = PackedCharacteristicAdapter(characteristics[0], 'B')
 
         if not (
             characteristics := service_proxy.get_characteristics_by_uuid(
@@ -517,4 +501,4 @@ def __init__(self, service_proxy: ServiceProxy) -> None:
             raise gatt.InvalidServiceError(
                 "Audio Input Description Characteristic not found"
             )
-        self.audio_input_description = characteristics[0]
+        self.audio_input_description = UTF8CharacteristicAdapter(characteristics[0])