refactor: reorganize LLM handler structure and improve tool call parsing

application/llm/handlers/google.py

@@ -0,0 +1,78 @@
+import uuid
+from typing import Any, Dict, Generator
+
+from application.llm.handlers.base import LLMHandler, LLMResponse, ToolCall
+
+
+class GoogleLLMHandler(LLMHandler):
+    """Handler for Google's GenAI API."""
+
+    def parse_response(self, response: Any) -> LLMResponse:
+        """Parse Google response into standardized format."""
+
+        if isinstance(response, str):
+            return LLMResponse(
+                content=response,
+                tool_calls=[],
+                finish_reason="stop",
+                raw_response=response,
+            )
+
+        if hasattr(response, "candidates"):
+            parts = response.candidates[0].content.parts if response.candidates else []
+            tool_calls = [
+                ToolCall(
+                    id=str(uuid.uuid4()),
+                    name=part.function_call.name,
+                    arguments=part.function_call.args,
+                )
+                for part in parts
+                if hasattr(part, "function_call") and part.function_call is not None
+            ]
+
+            content = " ".join(
+                part.text
+                for part in parts
+                if hasattr(part, "text") and part.text is not None
+            )
+            return LLMResponse(
+                content=content,
+                tool_calls=tool_calls,
+                finish_reason="tool_calls" if tool_calls else "stop",
+                raw_response=response,
+            )
+
+        else:
+            tool_calls = []
+            if hasattr(response, "function_call"):
+                tool_calls.append(
+                    ToolCall(
+                        id=str(uuid.uuid4()),
+                        name=response.function_call.name,
+                        arguments=response.function_call.args,
+                    )
+                )
+            return LLMResponse(
+                content=response.text if hasattr(response, "text") else "",
+                tool_calls=tool_calls,
+                finish_reason="tool_calls" if tool_calls else "stop",
+                raw_response=response,
+            )
+
+    def create_tool_message(self, tool_call: ToolCall, result: Any) -> Dict:
+        """Create Google-style tool message."""
+        from google.genai import types
+
+        return {
+            "role": "tool",
+            "content": [
+                types.Part.from_function_response(
+                    name=tool_call.name, response={"result": result}
+                ).to_json_dict()
+            ],
+        }
+
+    def _iterate_stream(self, response: Any) -> Generator:
+        """Iterate through Google streaming response."""
+        for chunk in response:
+            yield chunk