import os
import json
import logging
from typing import Dict, List, Optional
import uuid
try:
    import redis
except ImportError:
    redis = None

from config import CACHE_CONFIG
from database.models import TaskQueue, SessionLocal

# 配置日志
logging.basicConfig(level=logging.INFO)
logger = logging.getLogger(__name__)

class QueueManager:
    """
    队列管理器
    支持Redis队列，自动降级为文件队列（基于SQLite），最后降级为内存队列
    """
    
    _instance = None
    
    def __new__(cls):
        if cls._instance is None:
            cls._instance = super(QueueManager, cls).__new__(cls)
            cls._instance._initialize()
        return cls._instance
    
    def _initialize(self):
        self.backend = CACHE_CONFIG.get("backend", "memory")
        self.config = CACHE_CONFIG.get("redis", {})
        self.redis_available = False
        
        if self.backend == "redis" and redis is not None:
            try:
                # 初始化Redis连接池
                pool = redis.ConnectionPool(
                    host=self.config.get("host", "localhost"),
                    port=self.config.get("port", 6379),
                    password=self.config.get("password"),
                    db=self.config.get("db", 0),
                    max_connections=self.config.get("max_connections", 100),
                    socket_timeout=self.config.get("socket_timeout", 5)
                )
                self.client = redis.Redis(connection_pool=pool)
                # 测试连接
                self.client.ping()
                self.redis_available = True
                logger.info("Redis连接成功，已启用Redis队列模式")
            except Exception as e:
                logger.error(f"Redis连接失败: {e}，将使用文件队列作为降级方案")
                self.backend = "file"
                self.redis_available = False
        elif self.backend == "redis" and redis is None:
             logger.warning("未检测到redis库，自动降级为文件队列")
             self.backend = "file"
             self.redis_available = False
        
        if self.backend == "memory":
             logger.info("使用内存队列模式")
             self.memory_queue = []
        elif self.backend == "file":
             logger.info("使用文件队列模式 (SQLite)")

    def _get_db(self):
        return SessionLocal()

    def _enqueue_file(self, queue_name: str, item: str) -> bool:
        db = self._get_db()
        try:
            task = TaskQueue(
                task_id=str(uuid.uuid4()),
                queue_name=queue_name,
                payload=item,
                status="queued"
            )
            db.add(task)
            db.commit()
            return True
        except Exception as e:
            logger.error(f"文件入队失败: {e}")
            db.rollback()
            return False
        finally:
            db.close()

    def _dequeue_file(self, queue_name: str) -> Optional[str]:
        db = self._get_db()
        try:
            # 获取最早的一个queued任务
            task = db.query(TaskQueue).filter(
                TaskQueue.queue_name == queue_name,
                TaskQueue.status == "queued"
            ).order_by(TaskQueue.created_at.asc()).first()

            if task:
                # 模拟出队（删除任务）
                payload = task.payload
                db.delete(task)
                db.commit()
                return payload
            return None
        except Exception as e:
            logger.error(f"文件出队失败: {e}")
            db.rollback()
            return None
        finally:
            db.close()

    def enqueue(self, queue_name: str, item: str) -> bool:
        """入队"""
        # 优先尝试Redis
        if self.redis_available:
            try:
                self.client.rpush(queue_name, item)
                return True
            except Exception as e:
                logger.error(f"Redis入队异常: {e}，尝试降级到文件队列")
                self.redis_available = False # 标记Redis不可用
                # 降级到文件
                return self._enqueue_file(queue_name, item)
        
        # 降级策略
        if self.backend == "file" or (not self.redis_available and self.backend == "redis"):
            return self._enqueue_file(queue_name, item)
        else:
            # 内存模式
            try:
                self.memory_queue.append({"queue": queue_name, "item": item})
                return True
            except Exception as e:
                logger.error(f"内存入队失败: {e}")
                return False
            
    def dequeue(self, queue_name: str) -> Optional[str]:
        """出队"""
        # 优先尝试Redis
        if self.redis_available:
            try:
                # 阻塞式出队，超时时间1秒
                result = self.client.blpop(queue_name, timeout=1)
                if result:
                    return result[1].decode('utf-8')
                return None
            except Exception as e:
                logger.error(f"Redis出队异常: {e}，尝试降级到文件队列")
                self.redis_available = False
                return self._dequeue_file(queue_name)
        
        # 降级策略
        if self.backend == "file" or (not self.redis_available and self.backend == "redis"):
             return self._dequeue_file(queue_name)
        else:
            # 内存模式
            try:
                for i, task in enumerate(self.memory_queue):
                    if task["queue"] == queue_name:
                        return self.memory_queue.pop(i)["item"]
                return None
            except Exception as e:
                logger.error(f"内存出队失败: {e}")
                return None
            
    def get_queue_length(self, queue_name: str) -> int:
        """获取队列长度"""
        try:
            if self.redis_available:
                return self.client.llen(queue_name)
            elif self.backend == "file" or (not self.redis_available and self.backend == "redis"):
                 db = self._get_db()
                 try:
                     count = db.query(TaskQueue).filter(
                         TaskQueue.queue_name == queue_name,
                         TaskQueue.status == "queued"
                     ).count()
                     return count
                 finally:
                     db.close()
            else:
                return len([t for t in self.memory_queue if t["queue"] == queue_name])
        except Exception as e:
            logger.error(f"获取队列长度失败: {e}")
            return 0

# 全局实例
queue_manager = QueueManager()