重构数据库模块实现延迟初始化

- 使用Global Object Pattern设计模式
- 实现数据库连接的延迟初始化
- 添加类型注解支持IDE类型推导
- 确保环境变量在bot.py加载后再连接数据库

🤖 Generated with [Claude Code](https://claude.ai/code)
Co-Authored-By: Claude <noreply@anthropic.com>

src/common/database.py

@@ -1,73 +1,53 @@
-from typing import Optional
+import os
+from typing import cast
 from pymongo import MongoClient
-from pymongo.database import Database as MongoDatabase
+from pymongo.database import Database
 
-class Database:
-    _instance: Optional["Database"] = None
-    
-    def __init__(
-        self,
-        host: str,
-        port: int,
-        db_name: str,
-        username: Optional[str] = None,
-        password: Optional[str] = None,
-        auth_source: Optional[str] = None,
-        uri: Optional[str] = None,
-    ):
-        if uri and uri.startswith("mongodb://"):
-            # 优先使用URI连接
-            self.client = MongoClient(uri)
-        elif username and password:
-            # 如果有用户名和密码，使用认证连接
-            self.client = MongoClient(
-                host, port, username=username, password=password, authSource=auth_source
-            )
-        else:
-            # 否则使用无认证连接
-            self.client = MongoClient(host, port)
-        self.db: MongoDatabase = self.client[db_name]
-        
-    @classmethod
-    def initialize(
-        cls,
-        host: str,
-        port: int,
-        db_name: str,
-        username: Optional[str] = None,
-        password: Optional[str] = None,
-        auth_source: Optional[str] = None,
-        uri: Optional[str] = None,
-    ) -> MongoDatabase:
-        if cls._instance is None:
-            cls._instance = cls(
-                host, port, db_name, username, password, auth_source, uri
-            )
-        return cls._instance.db
-        
-    @classmethod
-    def get_instance(cls) -> MongoDatabase:
-        if cls._instance is None:
-            raise RuntimeError("Database not initialized")
-        return cls._instance.db
+_client = None
+_db = None
 
 
-    #测试用
-    
-    def get_random_group_messages(self, group_id: str, limit: int = 5):
-        # 先随机获取一条消息
-        random_message = list(self.db.messages.aggregate([
-            {"$match": {"group_id": group_id}},
-            {"$sample": {"size": 1}}
-        ]))[0]
-        
-        # 获取该消息之后的消息
-        subsequent_messages = list(self.db.messages.find({
-            "group_id": group_id,
-            "time": {"$gt": random_message["time"]}
-        }).sort("time", 1).limit(limit))
-        
-        # 将随机消息和后续消息合并
-        messages = [random_message] + subsequent_messages
-        
-        return messages
+def __create_database_instance():
+    uri = os.getenv("MONGODB_URI")
+    host = os.getenv("MONGODB_HOST", "127.0.0.1")
+    port = int(os.getenv("MONGODB_PORT", "27017"))
+    db_name = os.getenv("DATABASE_NAME", "MegBot")
+    username = os.getenv("MONGODB_USERNAME")
+    password = os.getenv("MONGODB_PASSWORD")
+    auth_source = os.getenv("MONGODB_AUTH_SOURCE")
+
+    if uri and uri.startswith("mongodb://"):
+        # 优先使用URI连接
+        return MongoClient(uri)
+
+    if username and password:
+        # 如果有用户名和密码，使用认证连接
+        return MongoClient(
+            host, port, username=username, password=password, authSource=auth_source
+        )
+
+    # 否则使用无认证连接
+    return MongoClient(host, port)
+
+
+def get_db():
+    """获取数据库连接实例，延迟初始化。"""
+    global _client, _db
+    if _client is None:
+        _client = __create_database_instance()
+        _db = _client[os.getenv("DATABASE_NAME", "MegBot")]
+    return _db
+
+
+class DBWrapper:
+    """数据库代理类，保持接口兼容性同时实现懒加载。"""
+
+    def __getattr__(self, name):
+        return getattr(get_db(), name)
+
+    def __getitem__(self, key):
+        return get_db()[key]
+
+
+# 全局数据库访问点
+db: Database = DBWrapper()