"""
会话服务
处理会话相关的业务逻辑
"""
from typing import Optional, List
from datetime import datetime
from app.models import db, Session, Agent
from app.services.scheduler import AgentScheduler


class SessionService:
    """会话服务"""
    
    def __init__(self, scheduler_strategy: str = 'weighted_round_robin'):
        self.scheduler = AgentScheduler(scheduler_strategy)
    
    def create_session(
        self,
        user_id: str,
        title: str = None,
        agent_id: str = None,
        channel_type: str = 'web',
        context: dict = None
    ) -> Session:
        """创建新会话"""
        # 如果没有指定 Agent，调度一个
        if not agent_id:
            from app.models import Agent
            agents = Agent.query.all()
            selected_agent = self.scheduler.select_agent(agents, context)
            agent_id = selected_agent.id if selected_agent else None
        
        # 创建会话
        session = Session(
            user_id=user_id,
            primary_agent_id=agent_id,
            title=title or f"Session {datetime.utcnow().strftime('%Y-%m-%d %H:%M')}",
            channel_type=channel_type,
            status='active'
        )
        
        db.session.add(session)
        
        # 更新 Agent 会话数
        if agent_id:
            agent = Agent.query.get(agent_id)
            if agent:
                agent.current_sessions += 1
        
        db.session.commit()
        
        return session
    
    def close_session(self, session_id: str, user_id: str = None) -> Optional[Session]:
        """关闭会话"""
        session = Session.query.get(session_id)
        if not session:
            return None
        
        # 验证权限
        if user_id and session.user_id != user_id:
            return None
        
        session.status = 'closed'
        session.updated_at = datetime.utcnow()
        
        # 更新 Agent 会话数
        if session.primary_agent_id:
            agent = Agent.query.get(session.primary_agent_id)
            if agent and agent.current_sessions > 0:
                agent.current_sessions -= 1
        
        db.session.commit()
        
        return session
    
    def get_user_sessions(self, user_id: str, status: str = None) -> List[Session]:
        """获取用户会话列表"""
        query = Session.query.filter_by(user_id=user_id)
        
        if status:
            query = query.filter_by(status=status)
        
        return query.order_by(Session.created_at.desc()).all()
    
    def get_session(self, session_id: str, user_id: str = None) -> Optional[Session]:
        """获取会话详情"""
        session = Session.query.get(session_id)
        
        if not session:
            return None
        
        if user_id and session.user_id != user_id:
            return None
        
        return session
    
    def update_session_activity(self, session_id: str) -> bool:
        """更新会话活跃时间"""
        session = Session.query.get(session_id)
        if not session:
            return False
        
        session.last_active_at = datetime.utcnow()
        session.message_count += 1
        db.session.commit()
        
        return True
    
    def assign_agent(self, session_id: str, agent_id: str) -> Optional[Session]:
        """分配 Agent 到会话"""
        session = Session.query.get(session_id)
        if not session:
            return None
        
        # 验证 Agent 是否在线
        agent = Agent.query.get(agent_id)
        if not agent or agent.status != 'online':
            return None
        
        # 更新会话
        old_agent_id = session.primary_agent_id
        session.primary_agent_id = agent_id
        
        # 更新新旧 Agent 的会话数
        if old_agent_id:
            old_agent = Agent.query.get(old_agent_id)
            if old_agent and old_agent.current_sessions > 0:
                old_agent.current_sessions -= 1
        
        agent.current_sessions += 1
        
        db.session.commit()
        
        return session
    
    def add_participant(self, session_id: str, agent_id: str) -> Optional[Session]:
        """添加参与 Agent"""
        session = Session.query.get(session_id)
        if not session:
            return None
        
        # 获取当前参与列表
        participants = session.participating_agent_ids or []
        
        if agent_id not in participants:
            participants.append(agent_id)
            session.participating_agent_ids = participants
        
        db.session.commit()
        
        return session
    
    def remove_participant(self, session_id: str, agent_id: str) -> Optional[Session]:
        """移除参与 Agent"""
        session = Session.query.get(session_id)
        if not session:
            return None
        
        participants = session.participating_agent_ids or []
        
        if agent_id in participants:
            participants.remove(agent_id)
            session.participating_agent_ids = participants
        
        db.session.commit()
        
        return session