ai生成设计书文档，并解决文档中指出的部分bug

websocket/connectionManager.js

@@ -1,3 +1,5 @@
+const WebSocket = require("ws");
+
 const onlineUsers = new Map();
 
 // 保存用户连接
@@ -30,9 +32,13 @@ function getOnlineUsers() {
 function broadcast(data) {
   const message = JSON.stringify(data);
 
-  for (const ws of onlineUsers.values()) {
+  for (const [username, ws] of onlineUsers) {
     if (ws.readyState === WebSocket.OPEN) {
-      ws.send(message);
+      ws.send(message, (error) => {
+        if (error) {
+          console.error(`向用户 ${username} 广播失败：`, error);
+        }
+      });
     }
   }
 }

websocket/index.js

@@ -138,38 +138,35 @@ function handleSendMessage(senderName, data) {
       }
       return;
     }
-  });
+    // 数据库确认写入后，才确认发送并推送给接收者
+    const senderWs = getConnection(senderName);
+    if (senderWs) {
+      senderWs.send(
+        JSON.stringify({
+          type: "sendSuccess",
+          messageId: messageId
+        })
+      );
+    }
 
-  // 告诉发送者：服务器已经保存成功
-  const senderWs = getConnection(senderName);
-  if (senderWs) {
-    senderWs.send(
+    const receiverWs = getConnection(receiverName);
+    if (!receiverWs) {
+      console.log(`${receiverName} 当前不在线`);
+      return;
+    }
+
+    receiverWs.send(
       JSON.stringify({
-        type: "sendSuccess",
-        messageId: messageId
+        type: "newMessage",
+        message: {
+          messageId,
+          senderName,
+          receiverName,
+          content
+        },
       })
     );
-  }
-
-  // 找到接收者的WebSocket
-  const receiverWs = getConnection(receiverName);
-  if (!receiverWs) {
-    console.log(`${receiverName} 当前不在线`);
-    return;
-  }
-
-  // 推送消息
-  receiverWs.send(
-    JSON.stringify({
-      type: "newMessage",
-      message: {
-        messageId,
-        senderName,
-        receiverName,
-        content
-      },
-    })
-  );
+  });
 }
 
 function handleAck(receiverName, data) {