import threading
from dataclasses import dataclass, field
from typing import Dict, Optional, Any
from datetime import datetime
from utils.get_logger import setup_logger

logger = setup_logger(__name__)


class TaskCancelledException(Exception):
    """任务被取消异常"""
    pass


@dataclass
class TaskContext:
    """任务上下文 - 存储单个任务的状态信息"""
    task_id: str    # 任务ID 
    user_id: str = ""   # 用户ID
    knowledge_id: str = "" # 知识库ID
    is_cancelled: bool = False  # 任务取消标志 
    created_at: datetime = field(default_factory=datetime.now) # 任务创建时间
    reporter: Optional[Any] = None # 进度报告器
    # 记录已插入的数据，用于取消时清理
    inserted_doc_ids: list = field(default_factory=list)
    inserted_to_milvus: bool = False # 是否已插入到 Milvus
    inserted_to_mysql_slice: bool = False # 是否已插入到 MySQL slice
    inserted_to_mysql_image: bool = False # 是否已插入到 MySQL image


class TaskRegistry:
    """
    全局任务注册表（单例模式）
    
    用于跟踪所有正在执行的任务，支持通过 task_id 查找和取消任务
    """
    _instance = None
    _lock = threading.Lock()
    
    def __new__(cls):
        if cls._instance is None:
            with cls._lock:
                if cls._instance is None:
                    cls._instance = super().__new__(cls)
                    cls._instance._tasks: Dict[str, TaskContext] = {}
                    cls._instance._task_lock = threading.Lock()
        return cls._instance
    
    def register(self, task_id: str, user_id: str = "", knowledge_id: str = "") -> TaskContext:
        """
        注册新任务
        
        输入:
            task_id: 任务唯一标识（通常是 document_id）
            user_id: 用户ID
            knowledge_id: 知识库ID
            
        输出:
            TaskContext: 任务上下文对象
        """
        with self._task_lock:
            # 如果已存在，先清理旧的
            if task_id in self._tasks:
                logger.warning(f"任务 {task_id} 已存在，将覆盖旧任务")
            
            ctx = TaskContext(
                task_id=task_id, 
                user_id=user_id,
                knowledge_id=knowledge_id
            )
            self._tasks[task_id] = ctx
            logger.info(f"任务注册成功: task_id={task_id}, knowledge_id={knowledge_id}")
            return ctx
    
    def get(self, task_id: str) -> Optional[TaskContext]:
        """获取任务上下文"""
        with self._task_lock:
            return self._tasks.get(task_id)
    
    def cancel(self, task_id: str) -> tuple[bool, str]:
        """
        取消任务
        
        输入:
            task_id: 任务ID
            
        输出:
            (success, message): 是否成功及消息
        """
        with self._task_lock:
            ctx = self._tasks.get(task_id)
            
            if not ctx:
                return False, "任务不存在或已完成"
            
            if ctx.is_cancelled:
                return False, "任务已被取消"
            
            # 设置取消标志
            ctx.is_cancelled = True
            
            # 停止进度上报
            if ctx.reporter:
                ctx.reporter.is_completed = True
            
            logger.info(f"任务取消标志已设置: task_id={task_id}")
            return True, "取消信号已发送"
    
    def unregister(self, task_id: str):
        """注销任务（任务完成或取消后调用）"""
        with self._task_lock:
            ctx = self._tasks.pop(task_id, None)
            if ctx:
                logger.info(f"任务注销成功: task_id={task_id}")
    
    def is_cancelled(self, task_id: str) -> bool:
        """检查任务是否已取消"""
        with self._task_lock:
            ctx = self._tasks.get(task_id)
            return ctx.is_cancelled if ctx else False
    
    def get_all_tasks(self) -> Dict[str, dict]:
        """获取所有活跃任务的信息（用于调试）"""
        with self._task_lock:
            return {
                task_id: {
                    "user_id": ctx.user_id,
                    "knowledge_id": ctx.knowledge_id,
                    "is_cancelled": ctx.is_cancelled,
                    "created_at": ctx.created_at.isoformat(),
                }
                for task_id, ctx in self._tasks.items()
            }


# 全局单例实例
task_registry = TaskRegistry()