"""
会话记忆管理器

管理每个用户的对话上下文，支持多轮对话状态机。
内存缓存，10 分钟 TTL 自动清除。
"""

import time
from typing import Dict, List, Optional

from app.utils.logger import logger

SESSION_TTL = 600  # 10 分钟


class UserSession:
    """单个用户的会话上下文"""

    def __init__(self, user_id: str):
        self.user_id = user_id
        self.state = "idle"  # idle / waiting_location / waiting_confirm / waiting_close_photo
        self.pending_image_url = ""      # 暂存的图片 COS key
        self.pending_analysis = ""       # VLM 分析结果描述
        self.pending_alarm_type = ""     # VLM 识别的告警类型
        self.pending_order_id = ""       # 待结单的工单 ID
        self.pending_alarm_id = ""       # 关联的告警 ID
        self.history: List[Dict] = []    # 对话历史 [{"role": "user/assistant", "content": ...}]
        self.updated_at = time.time()

    def is_expired(self) -> bool:
        return time.time() - self.updated_at > SESSION_TTL

    def touch(self):
        self.updated_at = time.time()

    def reset(self):
        """重置状态机（保留 history）"""
        self.state = "idle"
        self.pending_image_url = ""
        self.pending_analysis = ""
        self.pending_alarm_type = ""
        self.pending_order_id = ""
        self.pending_alarm_id = ""

    def add_history(self, role: str, content):
        """添加对话记录，content 可以是 str 或 list（多模态）"""
        self.history.append({"role": role, "content": content})
        # 保留最近 10 轮（20 条消息）
        if len(self.history) > 20:
            self.history = self.history[-20:]
        self.touch()

    def get_history_for_vlm(self) -> List[Dict]:
        """获取用于 VLM 调用的 history（过滤掉过大的图片内容）"""
        return self.history.copy()


class SessionManager:
    """全局会话管理器（单例）"""

    def __init__(self):
        self._sessions: Dict[str, UserSession] = {}
        self._last_cleanup = time.time()

    def get(self, user_id: str) -> UserSession:
        """获取或创建用户会话"""
        # 定期清理过期会话（每 5 分钟）
        if time.time() - self._last_cleanup > 300:
            self._cleanup_expired()

        session = self._sessions.get(user_id)
        if session and not session.is_expired():
            session.touch()
            return session

        # 过期或不存在，创建新会话
        session = UserSession(user_id)
        self._sessions[user_id] = session
        return session

    def clear(self, user_id: str):
        """清除用户会话"""
        if user_id in self._sessions:
            self._sessions[user_id].reset()
            self._sessions[user_id].history.clear()

    def _cleanup_expired(self):
        """清理过期会话"""
        expired = [uid for uid, s in self._sessions.items() if s.is_expired()]
        for uid in expired:
            del self._sessions[uid]
        if expired:
            logger.debug(f"清理 {len(expired)} 个过期会话")
        self._last_cleanup = time.time()

    @property
    def active_count(self) -> int:
        return sum(1 for s in self._sessions.values() if not s.is_expired())


_session_manager: Optional[SessionManager] = None


def get_session_manager() -> SessionManager:
    global _session_manager
    if _session_manager is None:
        _session_manager = SessionManager()
    return _session_manager