Refactor response handling for clarity and consistency.

Simplified how responses and tool calls are appended to conversations. Adjusted structure in message formatting to better align with tool call requirements, ensuring consistent data representation.

response.go

@@ -25,27 +25,29 @@ func (r ResponseChoice) toRaw() map[string]any {
 		calls = append(calls, call.toRaw())
 	}
 
-	res["calls"] = calls
+	res["tool_calls"] = calls
 
 	return res
 }
 
 func (r ResponseChoice) toChatCompletionMessages() []openai.ChatCompletionMessage {
-	var res []openai.ChatCompletionMessage
+	var res = openai.ChatCompletionMessage{
+		Role:    openai.ChatMessageRoleAssistant,
+		Content: r.Content,
+		Refusal: r.Refusal,
+	}
 
 	for _, call := range r.Calls {
-		res = append(res, call.toChatCompletionMessages()...)
-	}
-
-	if r.Refusal != "" || r.Content != "" {
-		res = append(res, openai.ChatCompletionMessage{
-			Role:    openai.ChatMessageRoleAssistant,
-			Content: r.Content,
-			Refusal: r.Refusal,
+		res.ToolCalls = append(res.ToolCalls, openai.ToolCall{
+			ID:   call.ID,
+			Type: openai.ToolTypeFunction,
+			Function: openai.FunctionCall{
+				Name:      call.FunctionCall.Name,
+				Arguments: call.FunctionCall.Arguments,
+			},
 		})
 	}
-
-	return res
+	return []openai.ChatCompletionMessage{res}
 }
 
 func (r ResponseChoice) toInput() []Input {