聊天：精简未读消息数的处理逻辑

shared/db/ChatInfo.ts

@@ -8,6 +8,8 @@ export class PrivateChatRec {
   lastReadTime: Date; // 最后查看时间，用来检查未读消息数
   @prop({ required: true })
   lastChatTime: Date; // 最后聊天时间
+  @prop({ required: true, default: 0 })
+  unreadCnt: number; // 未读消息数
 }
 
 /**
@@ -50,8 +52,13 @@ export default class ChatInfo extends BaseModel {
     return result;
   }
 
-  public static async updateReadTime(roleId: string, targetRoleId: string, time: Date) {
-    const result: ChatInfoType = await ChatInfoModel.findOneAndUpdate({ roleId, 'recentPrivateChats.targetRoleId': targetRoleId }, { 'recentPrivateChats.$.lastReadTime': time }, { new: true }).select('-_id').lean();
+  public static async updateReadInfo(roleId: string, targetRoleId: string, time: Date) {
+    const result: ChatInfoType = await ChatInfoModel
+      .findOneAndUpdate(
+        { roleId, 'recentPrivateChats.targetRoleId': targetRoleId },
+        { 'recentPrivateChats.$.lastReadTime': time, 'recentPrivateChats.$.unreadCnt': 0 },
+        { new: true })
+      .select('-_id').lean();
     return result;
   }
 }