Add Metadata LTV serializer and adapt Unicast

bumble/profiles/le_audio.py

@@ -17,33 +17,67 @@
 # -----------------------------------------------------------------------------
 from __future__ import annotations
 import dataclasses
-from typing import List
+import struct
+from typing import List, Type
 from typing_extensions import Self
 
+from bumble import utils
+
 
 # -----------------------------------------------------------------------------
 # Classes
 # -----------------------------------------------------------------------------
 @dataclasses.dataclass
 class Metadata:
+    '''Bluetooth Assigned Numbers, Section 6.12.6 - Metadata LTV structures.
+
+    As Metadata fields may extend, and Spec doesn't forbid duplication, we don't parse
+    Metadata into a key-value style dataclass here. Rather, we encourage users to parse
+    again outside the lib.
+    '''
+
+    class Tag(utils.OpenIntEnum):
+        # fmt: off
+        PREFERRED_AUDIO_CONTEXTS                 = 0x01
+        STREAMING_AUDIO_CONTEXTS                 = 0x02
+        PROGRAM_INFO                             = 0x03
+        LANGUAGE                                 = 0x04
+        CCID_LIST                                = 0x05
+        PARENTAL_RATING                          = 0x06
+        PROGRAM_INFO_URI                         = 0x07
+        AUDIO_ACTIVE_STATE                       = 0x08
+        BROADCAST_AUDIO_IMMEDIATE_RENDERING_FLAG = 0x09
+        ASSISTED_LISTENING_STREAM                = 0x0A
+        BROADCAST_NAME                           = 0x0B
+        EXTENDED_METADATA                        = 0xFE
+        VENDOR_SPECIFIC                          = 0xFF
+
     @dataclasses.dataclass
     class Entry:
-        tag: int
+        tag: Metadata.Tag
         data: bytes
 
-    entries: List[Entry]
+        @classmethod
+        def from_bytes(cls: Type[Self], data: bytes) -> Self:
+            return cls(tag=Metadata.Tag(data[0]), data=data[1:])
+
+        def __bytes__(self) -> bytes:
+            return bytes([len(self.data) + 1, self.tag]) + self.data
+
+    entries: List[Entry] = dataclasses.field(default_factory=list)
 
     @classmethod
-    def from_bytes(cls, data: bytes) -> Self:
+    def from_bytes(cls: Type[Self], data: bytes) -> Self:
         entries = []
         offset = 0
         length = len(data)
-        while length >= 2:
+        while offset < length:
             entry_length = data[offset]
-            entry_tag = data[offset + 1]
-            entry_data = data[offset + 2 : offset + 2 + entry_length - 1]
-            entries.append(cls.Entry(entry_tag, entry_data))
-            length -= entry_length
+            offset += 1
+            entries.append(cls.Entry.from_bytes(data[offset : offset + entry_length]))
             offset += entry_length
 
         return cls(entries)
+
+    def __bytes__(self) -> bytes:
+        return b''.join([bytes(entry) for entry in self.entries])