Assist Pipeline stream TTS when supported and long response (#145264)

* Assist Pipeline stream TTS when supported and long response

* Indicate in run-start if streaming supported

* Simplify a little bit

* Trigger streaming based on characters

* 60

tests/components/assist_pipeline/test_pipeline.py

@@ -1575,8 +1575,9 @@ async def test_pipeline_language_used_instead_of_conversation_language(
 
 
 @pytest.mark.parametrize(
-    ("to_stream_tts", "expected_chunks"),
+    ("to_stream_tts", "expected_chunks", "chunk_text"),
     [
+        # Size below STREAM_RESPONSE_CHUNKS
         (
             [
                 "hello,",
@@ -1588,7 +1589,33 @@ async def test_pipeline_language_used_instead_of_conversation_language(
                 "you",
                 "?",
             ],
-            1,
+            # We are not streaming, so 0 chunks via streaming method
+            0,
+            "",
+        ),
+        # Size above STREAM_RESPONSE_CHUNKS
+        (
+            [
+                "hello, ",
+                "how ",
+                "are ",
+                "you",
+                "? ",
+                "I'm ",
+                "doing ",
+                "well",
+                ", ",
+                "thank ",
+                "you",
+                ". ",
+                "What ",
+                "about ",
+                "you",
+                "?",
+            ],
+            # We are streamed, so equal to count above list items
+            16,
+            "hello, how are you? I'm doing well, thank you. What about you?",
         ),
     ],
 )
@@ -1602,6 +1629,7 @@ async def test_chat_log_tts_streaming(
     pipeline_data: assist_pipeline.pipeline.PipelineData,
     to_stream_tts: list[str],
     expected_chunks: int,
+    chunk_text: str,
 ) -> None:
     """Test that chat log events are streamed to the TTS entity."""
     events: list[assist_pipeline.PipelineEvent] = []
@@ -1627,22 +1655,41 @@ async def test_chat_log_tts_streaming(
         ),
     )
 
+    received_tts = []
+
+    async def async_stream_tts_audio(
+        request: tts.TTSAudioRequest,
+    ) -> tts.TTSAudioResponse:
+        """Mock stream TTS audio."""
+
+        async def gen_data():
+            async for msg in request.message_gen:
+                received_tts.append(msg)
+                yield msg.encode()
+
+        return tts.TTSAudioResponse(
+            extension="mp3",
+            data_gen=gen_data(),
+        )
+
     async def async_get_tts_audio(
         message: str,
         language: str,
         options: dict[str, Any] | None = None,
-    ) -> tts.TTSAudioResponse:
+    ) -> tts.TtsAudioType:
         """Mock get TTS audio."""
         return ("mp3", b"".join([chunk.encode() for chunk in to_stream_tts]))
 
     mock_tts_entity.async_get_tts_audio = async_get_tts_audio
+    mock_tts_entity.async_stream_tts_audio = async_stream_tts_audio
+    mock_tts_entity.async_supports_streaming_input = Mock(return_value=True)
 
     with patch(
         "homeassistant.components.assist_pipeline.pipeline.conversation.async_get_agent_info",
         return_value=conversation.AgentInfo(
             id="test-agent",
             name="Test Agent",
-            supports_streaming=False,
+            supports_streaming=True,
         ),
     ):
         await pipeline_input.validate()
@@ -1707,6 +1754,7 @@ async def test_chat_log_tts_streaming(
 
     streamed_text = "".join(to_stream_tts)
     assert tts_result == streamed_text
-    assert expected_chunks == 1
+    assert len(received_tts) == expected_chunks
+    assert "".join(received_tts) == chunk_text
 
     assert process_events(events) == snapshot