From 2eff4364c983c899ed2967a783ecb7119f322636 Mon Sep 17 00:00:00 2001
From: LittleSheep <littlesheep.code@hotmail.com>
Date: Sat, 24 May 2025 02:12:32 +0800
Subject: [PATCH] :sparkles: Sort chat rooms by last message created at

---
 DysonNetwork.Sphere/Chat/ChatRoomController.cs |  1 +
 DysonNetwork.Sphere/Chat/ChatRoomService.cs    | 18 ++++++++++++++++++
 2 files changed, 19 insertions(+)

diff --git a/DysonNetwork.Sphere/Chat/ChatRoomController.cs b/DysonNetwork.Sphere/Chat/ChatRoomController.cs
index 5df6cb2..802dd07 100644
--- a/DysonNetwork.Sphere/Chat/ChatRoomController.cs
+++ b/DysonNetwork.Sphere/Chat/ChatRoomController.cs
@@ -54,6 +54,7 @@ public class ChatRoomController(
             .Select(m => m.ChatRoom)
             .ToListAsync();
         chatRooms = await crs.LoadDirectMessageMembers(chatRooms, userId);
+        chatRooms = await crs.SortChatRoomByLastMessage(chatRooms);
 
         return Ok(chatRooms);
     }
diff --git a/DysonNetwork.Sphere/Chat/ChatRoomService.cs b/DysonNetwork.Sphere/Chat/ChatRoomService.cs
index d556a79..5fa91fc 100644
--- a/DysonNetwork.Sphere/Chat/ChatRoomService.cs
+++ b/DysonNetwork.Sphere/Chat/ChatRoomService.cs
@@ -1,6 +1,7 @@
 using DysonNetwork.Sphere.Account;
 using Microsoft.EntityFrameworkCore;
 using Microsoft.Extensions.Caching.Memory;
+using NodaTime;
 
 namespace DysonNetwork.Sphere.Chat;
 
@@ -32,6 +33,23 @@ public class ChatRoomService(AppDatabase db, IMemoryCache cache)
         var cacheKey = string.Format(RoomMembersCacheKey, roomId);
         cache.Remove(cacheKey);
     }
+
+    public async Task<List<ChatRoom>> SortChatRoomByLastMessage(List<ChatRoom> rooms)
+    {
+        var roomIds = rooms.Select(r => r.Id).ToList();
+        var lastMessages = await db.ChatMessages
+            .Where(m => roomIds.Contains(m.ChatRoomId))
+            .GroupBy(m => m.ChatRoomId)
+            .Select(g => new { RoomId = g.Key, CreatedAt = g.Max(m => m.CreatedAt) })
+            .ToDictionaryAsync(g => g.RoomId, m => m.CreatedAt);
+    
+        var now = SystemClock.Instance.GetCurrentInstant();
+        var sortedRooms = rooms
+            .OrderByDescending(r => lastMessages.TryGetValue(r.Id, out var time) ? time : now)
+            .ToList();
+            
+        return sortedRooms;
+    }
     
     public async Task<List<ChatRoom>> LoadDirectMessageMembers(List<ChatRoom> rooms, Guid userId)
     {