refactor(responses): move stuff into some utils and add unit tests (#3158)

# What does this PR do?
Refactors the OpenAI response conversion utilities by moving helper functions from `openai_responses.py` to `utils.py`. Adds unit tests.

tests/unit/providers/agents/meta_reference/test_response_conversion_utils.py

@@ -0,0 +1,310 @@
+# Copyright (c) Meta Platforms, Inc. and affiliates.
+# All rights reserved.
+#
+# This source code is licensed under the terms described in the LICENSE file in
+# the root directory of this source tree.
+
+
+import pytest
+
+from llama_stack.apis.agents.openai_responses import (
+    OpenAIResponseInputFunctionToolCallOutput,
+    OpenAIResponseInputMessageContentImage,
+    OpenAIResponseInputMessageContentText,
+    OpenAIResponseInputToolFunction,
+    OpenAIResponseInputToolWebSearch,
+    OpenAIResponseMessage,
+    OpenAIResponseOutputMessageContentOutputText,
+    OpenAIResponseOutputMessageFunctionToolCall,
+    OpenAIResponseText,
+    OpenAIResponseTextFormat,
+)
+from llama_stack.apis.inference import (
+    OpenAIAssistantMessageParam,
+    OpenAIChatCompletionContentPartImageParam,
+    OpenAIChatCompletionContentPartTextParam,
+    OpenAIChatCompletionToolCall,
+    OpenAIChatCompletionToolCallFunction,
+    OpenAIChoice,
+    OpenAIDeveloperMessageParam,
+    OpenAIResponseFormatJSONObject,
+    OpenAIResponseFormatJSONSchema,
+    OpenAIResponseFormatText,
+    OpenAISystemMessageParam,
+    OpenAIToolMessageParam,
+    OpenAIUserMessageParam,
+)
+from llama_stack.providers.inline.agents.meta_reference.responses.utils import (
+    convert_chat_choice_to_response_message,
+    convert_response_content_to_chat_content,
+    convert_response_input_to_chat_messages,
+    convert_response_text_to_chat_response_format,
+    get_message_type_by_role,
+    is_function_tool_call,
+)
+
+
+class TestConvertChatChoiceToResponseMessage:
+    @pytest.mark.asyncio
+    async def test_convert_string_content(self):
+        choice = OpenAIChoice(
+            message=OpenAIAssistantMessageParam(content="Test message"),
+            finish_reason="stop",
+            index=0,
+        )
+
+        result = await convert_chat_choice_to_response_message(choice)
+
+        assert result.role == "assistant"
+        assert result.status == "completed"
+        assert len(result.content) == 1
+        assert isinstance(result.content[0], OpenAIResponseOutputMessageContentOutputText)
+        assert result.content[0].text == "Test message"
+
+    @pytest.mark.asyncio
+    async def test_convert_text_param_content(self):
+        choice = OpenAIChoice(
+            message=OpenAIAssistantMessageParam(
+                content=[OpenAIChatCompletionContentPartTextParam(text="Test text param")]
+            ),
+            finish_reason="stop",
+            index=0,
+        )
+
+        with pytest.raises(ValueError) as exc_info:
+            await convert_chat_choice_to_response_message(choice)
+
+        assert "does not yet support output content type" in str(exc_info.value)
+
+
+class TestConvertResponseContentToChatContent:
+    @pytest.mark.asyncio
+    async def test_convert_string_content(self):
+        result = await convert_response_content_to_chat_content("Simple string")
+        assert result == "Simple string"
+
+    @pytest.mark.asyncio
+    async def test_convert_text_content_parts(self):
+        content = [
+            OpenAIResponseInputMessageContentText(text="First part"),
+            OpenAIResponseOutputMessageContentOutputText(text="Second part"),
+        ]
+
+        result = await convert_response_content_to_chat_content(content)
+
+        assert len(result) == 2
+        assert isinstance(result[0], OpenAIChatCompletionContentPartTextParam)
+        assert result[0].text == "First part"
+        assert isinstance(result[1], OpenAIChatCompletionContentPartTextParam)
+        assert result[1].text == "Second part"
+
+    @pytest.mark.asyncio
+    async def test_convert_image_content(self):
+        content = [OpenAIResponseInputMessageContentImage(image_url="https://example.com/image.jpg", detail="high")]
+
+        result = await convert_response_content_to_chat_content(content)
+
+        assert len(result) == 1
+        assert isinstance(result[0], OpenAIChatCompletionContentPartImageParam)
+        assert result[0].image_url.url == "https://example.com/image.jpg"
+        assert result[0].image_url.detail == "high"
+
+
+class TestConvertResponseInputToChatMessages:
+    @pytest.mark.asyncio
+    async def test_convert_string_input(self):
+        result = await convert_response_input_to_chat_messages("User message")
+
+        assert len(result) == 1
+        assert isinstance(result[0], OpenAIUserMessageParam)
+        assert result[0].content == "User message"
+
+    @pytest.mark.asyncio
+    async def test_convert_function_tool_call_output(self):
+        input_items = [
+            OpenAIResponseInputFunctionToolCallOutput(
+                output="Tool output",
+                call_id="call_123",
+            )
+        ]
+
+        result = await convert_response_input_to_chat_messages(input_items)
+
+        assert len(result) == 1
+        assert isinstance(result[0], OpenAIToolMessageParam)
+        assert result[0].content == "Tool output"
+        assert result[0].tool_call_id == "call_123"
+
+    @pytest.mark.asyncio
+    async def test_convert_function_tool_call(self):
+        input_items = [
+            OpenAIResponseOutputMessageFunctionToolCall(
+                call_id="call_456",
+                name="test_function",
+                arguments='{"param": "value"}',
+            )
+        ]
+
+        result = await convert_response_input_to_chat_messages(input_items)
+
+        assert len(result) == 1
+        assert isinstance(result[0], OpenAIAssistantMessageParam)
+        assert len(result[0].tool_calls) == 1
+        assert result[0].tool_calls[0].id == "call_456"
+        assert result[0].tool_calls[0].function.name == "test_function"
+        assert result[0].tool_calls[0].function.arguments == '{"param": "value"}'
+
+    @pytest.mark.asyncio
+    async def test_convert_response_message(self):
+        input_items = [
+            OpenAIResponseMessage(
+                role="user",
+                content=[OpenAIResponseInputMessageContentText(text="User text")],
+            )
+        ]
+
+        result = await convert_response_input_to_chat_messages(input_items)
+
+        assert len(result) == 1
+        assert isinstance(result[0], OpenAIUserMessageParam)
+        # Content should be converted to chat content format
+        assert len(result[0].content) == 1
+        assert result[0].content[0].text == "User text"
+
+
+class TestConvertResponseTextToChatResponseFormat:
+    @pytest.mark.asyncio
+    async def test_convert_text_format(self):
+        text = OpenAIResponseText(format=OpenAIResponseTextFormat(type="text"))
+        result = await convert_response_text_to_chat_response_format(text)
+
+        assert isinstance(result, OpenAIResponseFormatText)
+        assert result.type == "text"
+
+    @pytest.mark.asyncio
+    async def test_convert_json_object_format(self):
+        text = OpenAIResponseText(format={"type": "json_object"})
+        result = await convert_response_text_to_chat_response_format(text)
+
+        assert isinstance(result, OpenAIResponseFormatJSONObject)
+
+    @pytest.mark.asyncio
+    async def test_convert_json_schema_format(self):
+        schema_def = {"type": "object", "properties": {"test": {"type": "string"}}}
+        text = OpenAIResponseText(
+            format={
+                "type": "json_schema",
+                "name": "test_schema",
+                "schema": schema_def,
+            }
+        )
+        result = await convert_response_text_to_chat_response_format(text)
+
+        assert isinstance(result, OpenAIResponseFormatJSONSchema)
+        assert result.json_schema["name"] == "test_schema"
+        assert result.json_schema["schema"] == schema_def
+
+    @pytest.mark.asyncio
+    async def test_default_text_format(self):
+        text = OpenAIResponseText()
+        result = await convert_response_text_to_chat_response_format(text)
+
+        assert isinstance(result, OpenAIResponseFormatText)
+        assert result.type == "text"
+
+
+class TestGetMessageTypeByRole:
+    @pytest.mark.asyncio
+    async def test_user_role(self):
+        result = await get_message_type_by_role("user")
+        assert result == OpenAIUserMessageParam
+
+    @pytest.mark.asyncio
+    async def test_system_role(self):
+        result = await get_message_type_by_role("system")
+        assert result == OpenAISystemMessageParam
+
+    @pytest.mark.asyncio
+    async def test_assistant_role(self):
+        result = await get_message_type_by_role("assistant")
+        assert result == OpenAIAssistantMessageParam
+
+    @pytest.mark.asyncio
+    async def test_developer_role(self):
+        result = await get_message_type_by_role("developer")
+        assert result == OpenAIDeveloperMessageParam
+
+    @pytest.mark.asyncio
+    async def test_unknown_role(self):
+        result = await get_message_type_by_role("unknown")
+        assert result is None
+
+
+class TestIsFunctionToolCall:
+    def test_is_function_tool_call_true(self):
+        tool_call = OpenAIChatCompletionToolCall(
+            index=0,
+            id="call_123",
+            function=OpenAIChatCompletionToolCallFunction(
+                name="test_function",
+                arguments="{}",
+            ),
+        )
+        tools = [
+            OpenAIResponseInputToolFunction(
+                type="function", name="test_function", parameters={"type": "object", "properties": {}}
+            ),
+            OpenAIResponseInputToolWebSearch(type="web_search"),
+        ]
+
+        result = is_function_tool_call(tool_call, tools)
+        assert result is True
+
+    def test_is_function_tool_call_false_different_name(self):
+        tool_call = OpenAIChatCompletionToolCall(
+            index=0,
+            id="call_123",
+            function=OpenAIChatCompletionToolCallFunction(
+                name="other_function",
+                arguments="{}",
+            ),
+        )
+        tools = [
+            OpenAIResponseInputToolFunction(
+                type="function", name="test_function", parameters={"type": "object", "properties": {}}
+            ),
+        ]
+
+        result = is_function_tool_call(tool_call, tools)
+        assert result is False
+
+    def test_is_function_tool_call_false_no_function(self):
+        tool_call = OpenAIChatCompletionToolCall(
+            index=0,
+            id="call_123",
+            function=None,
+        )
+        tools = [
+            OpenAIResponseInputToolFunction(
+                type="function", name="test_function", parameters={"type": "object", "properties": {}}
+            ),
+        ]
+
+        result = is_function_tool_call(tool_call, tools)
+        assert result is False
+
+    def test_is_function_tool_call_false_wrong_type(self):
+        tool_call = OpenAIChatCompletionToolCall(
+            index=0,
+            id="call_123",
+            function=OpenAIChatCompletionToolCallFunction(
+                name="web_search",
+                arguments="{}",
+            ),
+        )
+        tools = [
+            OpenAIResponseInputToolWebSearch(type="web_search"),
+        ]
+
+        result = is_function_tool_call(tool_call, tools)
+        assert result is False