"""会话管理器"""
from datetime import datetime
from typing import List, Dict, Any

from database import DatabaseManager, Session, Message


class SessionManager:
    """会话管理器"""

    def __init__(self, db_path: str = None):
        """
        初始化会话管理器

        Args:
            db_path: 数据库路径，默认为 chat_sessions.db
        """
        self.db_manager = DatabaseManager(db_path or 'chat_sessions.db')
        self.Session = Session
        self.Message = Message

    def get_or_create_session(self, name: str, **kwargs) -> Session:
        """
        获取或创建会话

        Args:
            name: 会话名称
            **kwargs: 会话参数（model, system_prompt, metadata）

        Returns:
            Session对象
        """
        # 尝试获取现有会话
        session = self.Session.get_or_none(self.Session.name == name)

        if session:
            return session

        # 创建新会话
        defaults = {
            'model': kwargs.get('model', 'deepseek-chat'),
            'system_prompt': kwargs.get('system_prompt', '你是一个乐于助人的助手。'),
            'metadata': kwargs.get('metadata', {})
        }

        session = self.Session.create(
            name=name,
            **defaults
        )

        # 添加系统提示作为第一条消息
        if defaults['system_prompt']:
            self.Message.create(
                session=session,
                role='system',
                content=defaults['system_prompt']
            )

        return session

    def add_message(self, session_name: str, role: str, content: str,
                    tokens: int = 0, metadata: Dict = None) -> str:
        """
        添加消息到会话

        Args:
            session_name: 会话名称
            role: 消息角色（user/assistant/system）
            content: 消息内容
            tokens: token数量
            metadata: 元数据

        Returns:
            消息内容
        """
        session = self.get_or_create_session(session_name)

        self.Message.create(
            session=session,
            role=role,
            content=content,
            tokens=tokens,
            timestamp=datetime.now(),
            metadata=metadata or {}
        )

        # 更新会话时间戳
        session.update_timestamp()

        return content

    def get_session_history(self, session_name: str, limit: int = 20) -> List[Dict]:
        """
        获取会话历史

        Args:
            session_name: 会话名称
            limit: 返回消息数量限制

        Returns:
            消息历史列表
        """
        session = self.Session.get_or_none(self.Session.name == session_name)
        if not session:
            return []

        messages = (self.Message
                    .select()
                    .where(self.Message.session == session)
                    .order_by(self.Message.timestamp.asc())
                    .limit(limit))

        return [
            {'role': msg.role, 'content': msg.content}
            for msg in messages
        ]

    def get_session_info(self, session_name: str) -> Dict:
        """
        获取会话信息

        Args:
            session_name: 会话名称

        Returns:
            会话信息字典
        """
        session = self.Session.get_or_none(self.Session.name == session_name)
        if not session:
            return {}

        messages = session.messages
        message_count = messages.count()
        user_messages = messages.where(self.Message.role == 'user').count()
        assistant_messages = messages.where(self.Message.role == 'assistant').count()

        return {
            'name': session.name,
            'model': session.model,
            'system_prompt': session.system_prompt,
            'message_count': message_count,
            'user_messages': user_messages,
            'assistant_messages': assistant_messages,
            'created_at': session.created_at.isoformat(),
            'updated_at': session.updated_at.isoformat(),
            'metadata': session.metadata
        }

    def list_sessions(self) -> List[Dict]:
        """
        列出所有会话

        Returns:
            会话列表
        """
        sessions = self.Session.select().order_by(self.Session.updated_at.desc())

        return [
            {
                'name': session.name,
                'message_count': session.messages.count(),
                'updated_at': session.updated_at.isoformat()
            }
            for session in sessions
        ]

    def clear_session_history(self, session_name: str, keep_system: bool = True) -> bool:
        """
        清空会话历史（保留系统提示）

        Args:
            session_name: 会话名称
            keep_system: 是否保留系统提示

        Returns:
            是否成功
        """
        session = self.Session.get_or_none(self.Session.name == session_name)
        if not session:
            return False

        # 删除消息
        query = session.messages
        if keep_system:
            query = query.where(self.Message.role != 'system')

        query.delete().execute()

        # 重新添加系统提示（如果需要）
        if keep_system and session.system_prompt:
            messages = session.messages.where(self.Message.role == 'system')
            if not messages.exists():
                self.add_message(
                    session_name=session_name,
                    role='system',
                    content=session.system_prompt
                )

        return True

    def close(self):
        """关闭数据库连接"""
        self.db_manager.close()