"""用于处理 LangGraph checkpoint 相关的工具函数"""

import logging
from typing import List, Dict, Any, Optional
from langgraph.checkpoint.memory import MemorySaver

logger = logging.getLogger('app')


async def get_checkpoint_history(checkpointer: MemorySaver, thread_id: str) -> List:
    """
    从 checkpointer 获取指定 thread_id 的历史聊天记录

    Args:
        checkpointer: MemorySaver 实例
        thread_id: 线程ID（通常是 session_id）

    Returns:
        List[Dict]: 历史消息列表，如果没有历史记录或出错则返回空列表
    """
    if not checkpointer or not thread_id:
        logger.debug(f"No checkpointer or thread_id: checkpointer={bool(checkpointer)}, thread_id={thread_id}")
        return []

    try:
        config = {"configurable": {"thread_id": thread_id}}
        checkpoint_tuple = await checkpointer.aget_tuple(config)

        if checkpoint_tuple is None or checkpoint_tuple.checkpoint is None:
            logger.debug(f"No checkpoint found for thread_id: {thread_id}")
            return []

        # 从 checkpoint 中提取消息历史
        checkpoint_data = checkpoint_tuple.checkpoint

        # LangGraph checkpoint 中的消息通常在 channel_values['messages'] 中
        if "channel_values" not in checkpoint_data:
            logger.debug(f"No channel_values in checkpoint for thread_id: {thread_id}")
            return []

        channel_values = checkpoint_data["channel_values"]

        if isinstance(channel_values, dict) and "messages" in channel_values:
            history_messages = channel_values["messages"]
            converted = history_messages
            logger.info(f"Loaded {len(converted)} messages from checkpoint for thread_id: {thread_id}")
            return converted
        elif isinstance(channel_values, list):
            # 有些情况下 channel_values 直接是消息列表
            converted = channel_values
            logger.info(f"Loaded {len(converted)} messages from checkpoint for thread_id: {thread_id}")
            return converted
        else:
            logger.debug(f"Unexpected channel_values format: {type(channel_values)}")
            return []

    except Exception as e:
        import traceback
        logger.error(f"Error getting checkpoint history for thread_id {thread_id}: {e}")
        logger.error(f"Full traceback: {traceback.format_exc()}")
        return []


async def prepare_checkpoint_message(config, checkpointer):
    """
    准备 checkpoint 相关的消息：
    1. 获取并过滤历史记录（去除包含双引号/think的消息）
    2. 根据是否有历史决定发送哪些消息
    """
    if not config.session_id or not checkpointer or len(config.messages) == 0:
        logger.debug("No session_id/checkpointer or empty messages, skipping checkpoint")
        return

    # 获取历史记录
    history = await get_checkpoint_history(checkpointer, config.session_id)
    has_history = len(history) > 0

    # 处理历史记录：过滤并保留最近20条
    if has_history:
        filtered_history = [
            h for h in history
            if getattr(h, "type", None) in ("human", "ai")
            and "<think>" not in str(getattr(h, "content", "")).lower()
        ]
        logger.info(f"Filtered {len(filtered_history)} human/ai messages from history")
        config._session_history = filtered_history[-20:]

    # 处理要发送的消息：有历史只发最后一条用户消息，否则全发
    if has_history:
        last_user_msg = next((m for m in reversed(config.messages) if m.get('role') == 'user'), None)
        if last_user_msg:
            config.messages = [last_user_msg]
            logger.info(f"Has history, sending last user message: {last_user_msg.get('content', '')[:50]}...")
    else:
        logger.info(f"No history, sending all {len(config.messages)} messages")