"""
Finalize 节点 - 轻量后处理
"""

from typing import Dict, Any, Optional
from langchain_core.runnables.config import RunnableConfig
from langchain_core.messages import AIMessage

from backend.app.main_graph.state import AgentState
from backend.app.logger import info


async def finalize_node(state: AgentState, config: Optional[RunnableConfig] = None) -> Dict[str, Any]:
    """
    Finalize 节点：轻量后处理

    职责：
    1. 从 messages 中提取最后一条 AIMessage.content 作为最终回复
    2. 汇总元数据：步数、使用的工具、停止原因
    3. 如果 final_reply 为空且有 stop_reason，生成说明文本
    """
    info("[Finalize] 执行后处理")

    # 获取最终回复
    final_reply = ""
    for msg in reversed(state.messages):
        if isinstance(msg, AIMessage) and msg.content:
            final_reply = msg.content
            break

    # 获取停止原因
    stop_reason = getattr(state, "stop_reason", "")
    if not final_reply and stop_reason:
        # 如果没有回复但有停止原因，生成说明
        reason_messages = {
            "loop_detected": "[系统] 检测到工具调用循环，已终止。",
            "max_steps": "[系统] 已达到最大步数限制。",
        }
        final_reply = reason_messages.get(stop_reason, f"[系统] 已终止，原因: {stop_reason}")

    # 汇总元数据
    metadata = {
        "steps_taken": getattr(state, "current_step", 0),
        "tools_used": getattr(state, "tools_used", []),
        "stop_reason": stop_reason,
        "llm_calls": getattr(state, "llm_calls", 0),
    }

    info(f"[Finalize] 完成 - steps: {metadata['steps_taken']}, tools: {len(metadata['tools_used'])}")

    return {
        "final_reply": final_reply,
        "metadata": metadata,
    }