Implement LLM Chat API with tool calling support (#21731)

* Implement initial tools definiton APIs

* Add initial chat completion API with tool support

* Implement other providers

* Cleanup

frigate/genai/__init__.py

@@ -292,6 +292,64 @@ Guidelines:
         """Get the context window size for this provider in tokens."""
         return 4096
 
+    def chat_with_tools(
+        self,
+        messages: list[dict[str, Any]],
+        tools: Optional[list[dict[str, Any]]] = None,
+        tool_choice: Optional[str] = "auto",
+    ) -> dict[str, Any]:
+        """
+        Send chat messages to LLM with optional tool definitions.
+
+        This method handles conversation-style interactions with the LLM,
+        including function calling/tool usage capabilities.
+
+        Args:
+            messages: List of message dictionaries. Each message should have:
+                - 'role': str - One of 'user', 'assistant', 'system', or 'tool'
+                - 'content': str - The message content
+                - 'tool_call_id': Optional[str] - For tool responses, the ID of the tool call
+                - 'name': Optional[str] - For tool messages, the tool name
+            tools: Optional list of tool definitions in OpenAI-compatible format.
+                   Each tool should have 'type': 'function' and 'function' with:
+                   - 'name': str - Tool name
+                   - 'description': str - Tool description
+                   - 'parameters': dict - JSON schema for parameters
+            tool_choice: How the model should handle tools:
+                - 'auto': Model decides whether to call tools
+                - 'none': Model must not call tools
+                - 'required': Model must call at least one tool
+                - Or a dict specifying a specific tool to call
+            **kwargs: Additional provider-specific parameters.
+
+        Returns:
+            Dictionary with:
+            - 'content': Optional[str] - The text response from the LLM, None if tool calls
+            - 'tool_calls': Optional[List[Dict]] - List of tool calls if LLM wants to call tools.
+              Each tool call dict has:
+                - 'id': str - Unique identifier for this tool call
+                - 'name': str - Tool name to call
+                - 'arguments': dict - Arguments for the tool call (parsed JSON)
+            - 'finish_reason': str - Reason generation stopped:
+                - 'stop': Normal completion
+                - 'tool_calls': LLM wants to call tools
+                - 'length': Hit token limit
+                - 'error': An error occurred
+
+        Raises:
+            NotImplementedError: If the provider doesn't implement this method.
+        """
+        # Base implementation - each provider should override this
+        logger.warning(
+            f"{self.__class__.__name__} does not support chat_with_tools. "
+            "This method should be overridden by the provider implementation."
+        )
+        return {
+            "content": None,
+            "tool_calls": None,
+            "finish_reason": "error",
+        }
+
 
 def get_genai_client(config: FrigateConfig) -> Optional[GenAIClient]:
     """Get the GenAI client."""