fix:修复已知问题

backend/IM_API/Services/MessageService.cs

@@ -11,6 +11,7 @@ using IM_API.VOs.Message;
 using MassTransit;
 using Microsoft.EntityFrameworkCore;
 using StackExchange.Redis;
+using System.Text.Json;
 using System.Text.RegularExpressions;
 using static MassTransit.Monitoring.Performance.BuiltInCounters;
 using static Microsoft.EntityFrameworkCore.DbLoggerCategory;
@@ -26,9 +27,11 @@ namespace IM_API.Services
         //private readonly IEventBus _eventBus;
         private readonly IPublishEndpoint _endpoint;
         private readonly ISequenceIdService _sequenceIdService;
+        private readonly IUserService _userService;
         public MessageService(
             ImContext context, ILogger<MessageService> logger, IMapper mapper,
-            IPublishEndpoint publishEndpoint, ISequenceIdService sequenceIdService
+            IPublishEndpoint publishEndpoint, ISequenceIdService sequenceIdService,
+            IUserService userService
             )
         {
             _context = context;
@@ -37,6 +40,7 @@ namespace IM_API.Services
             //_eventBus = eventBus;
             _endpoint = publishEndpoint;
             _sequenceIdService = sequenceIdService;
+            _userService = userService;
         }
 
         public async Task<List<MessageBaseVo>> GetMessagesAsync(int userId,MessageQueryDto dto)
@@ -48,6 +52,7 @@ namespace IM_API.Services
             if (conversation is null) throw new BaseException(CodeDefine.CONVERSATION_NOT_FOUND);
 
             var baseQuery = _context.Messages.Where(x => x.StreamKey == conversation.StreamKey);
+            List<MessageBaseVo> messages = new List<MessageBaseVo>();
             if (dto.Direction == 0) // Before: 找比锚点小的，按倒序排
             {
                 if (dto.Cursor.HasValue)
@@ -59,20 +64,41 @@ namespace IM_API.Services
                     .Select(m => _mapper.Map<MessageBaseVo>(m))
                     .ToListAsync();
 
-                return list.OrderBy(s => s.SequenceId).ToList();
+                messages = list.OrderBy(s => s.SequenceId).ToList();
             }
             else // After: 找比锚点大的，按正序排（用于补洞或刷新）
             {
                 // 如果 Cursor 为空且是 After，逻辑上说不通，通常直接返回空或报错
                 if (!dto.Cursor.HasValue) return new List<MessageBaseVo>();
 
-                return await baseQuery
+                messages = await baseQuery
                     .Where(m => m.SequenceId > dto.Cursor.Value)
                     .OrderBy(m => m.SequenceId) // 按时间线正序
                     .Take(dto.Limit)
                     .Select(m => _mapper.Map<MessageBaseVo>(m))
                     .ToListAsync();
             }
+            //取发送者信息，用于前端展示
+            if(messages.Count > 0)
+            {
+                var ids = messages
+                    .Select(s => s.SenderId)
+                    .Distinct()
+                    .ToList();
+                var userinfoList = await _userService.GetUserInfoListAsync(ids);
+                // 转为字典，提高查询效率
+                var userDict = userinfoList.ToDictionary(x => x.Id, x => x);
+
+                foreach (var item in messages)
+                {
+                    if(userDict.TryGetValue(item.SenderId, out var user))
+                    {
+                        item.SenderName = user.NickName;
+                        item.SenderAvatar = user.Avatar ?? "";
+                    }
+                }
+            }
+            return messages;
         }
 
         public Task<int> GetUnreadCountAsync(int userId)