Don't allow deletion of the selected character slot.

Content.Server/Database/ServerDbBase.cs

@@ -39,21 +39,22 @@ namespace Content.Server.Database
         {
             await using var db = await GetDb();
 
-            var prefs = await db.DbContext.Preference.SingleAsync(p => p.UserId == userId.UserId);
+            await SetSelectedCharacterSlotAsync(userId, index, db.DbContext);
-            prefs.SelectedCharacterSlot = index;
 
             await db.DbContext.SaveChangesAsync();
         }
 
         public async Task SaveCharacterSlotAsync(NetUserId userId, ICharacterProfile? profile, int slot)
         {
+            await using var db = await GetDb();
+
             if (profile is null)
             {
-                await DeleteCharacterSlotAsync(userId, slot);
+                DeleteCharacterSlot(db.DbContext, userId, slot);
+                await db.DbContext.SaveChangesAsync();
                 return;
             }
 
-            await using var db = await GetDb();
             if (!(profile is HumanoidCharacterProfile humanoid))
             {
                 // TODO: Handle other ICharacterProfile implementations properly
@@ -80,17 +81,12 @@ namespace Content.Server.Database
             await db.DbContext.SaveChangesAsync();
         }
 
-        private async Task DeleteCharacterSlotAsync(NetUserId userId, int slot)
+        private static void DeleteCharacterSlot(ServerDbContext db, NetUserId userId, int slot)
         {
-            await using var db = await GetDb();
+            db.Preference
-
-            db.DbContext
-                .Preference
                 .Single(p => p.UserId == userId.UserId)
                 .Profiles
                 .RemoveAll(h => h.Slot == slot);
-
-            await db.DbContext.SaveChangesAsync();
         }
 
         public async Task<PlayerPreferences> InitPrefsAsync(NetUserId userId, ICharacterProfile defaultProfile)
@@ -113,6 +109,22 @@ namespace Content.Server.Database
             return new PlayerPreferences(new[] {new KeyValuePair<int, ICharacterProfile>(0, defaultProfile)}, 0);
         }
 
+        public async Task DeleteSlotAndSetSelectedIndex(NetUserId userId, int deleteSlot, int newSlot)
+        {
+            await using var db = await GetDb();
+
+            DeleteCharacterSlot(db.DbContext, userId, deleteSlot);
+            await SetSelectedCharacterSlotAsync(userId, newSlot, db.DbContext);
+
+            await db.DbContext.SaveChangesAsync();
+        }
+
+        private static async Task SetSelectedCharacterSlotAsync(NetUserId userId, int newSlot, ServerDbContext db)
+        {
+            var prefs = await db.Preference.SingleAsync(p => p.UserId == userId.UserId);
+            prefs.SelectedCharacterSlot = newSlot;
+        }
+
         private static HumanoidCharacterProfile ConvertProfiles(Profile profile)
         {
             var jobs = profile.Jobs.ToDictionary(j => j.JobName, j => (JobPriority) j.Priority);
@@ -188,6 +200,7 @@ namespace Content.Server.Database
             await db.DbContext.SaveChangesAsync();
         }
 
+
         /*
          * BAN STUFF
          */

Content.Server/Database/ServerDbManager.cs

@@ -1,4 +1,4 @@
-using System;
+using System;
 using System.IO;
 using System.Net;
 using System.Threading.Tasks;
@@ -28,6 +28,8 @@ namespace Content.Server.Database
         Task<PlayerPreferences> InitPrefsAsync(NetUserId userId, ICharacterProfile defaultProfile);
         Task SaveSelectedCharacterIndexAsync(NetUserId userId, int index);
         Task SaveCharacterSlotAsync(NetUserId userId, ICharacterProfile? profile, int slot);
+        // Single method for two operations for transaction.
+        Task DeleteSlotAndSetSelectedIndex(NetUserId userId, int deleteSlot, int newSlot);
         Task<PlayerPreferences?> GetPlayerPreferencesAsync(NetUserId userId);
 
         // Username assignment (for guest accounts, so they persist GUID)
@@ -95,6 +97,11 @@ namespace Content.Server.Database
             return _db.SaveCharacterSlotAsync(userId, profile, slot);
         }
 
+        public Task DeleteSlotAndSetSelectedIndex(NetUserId userId, int deleteSlot, int newSlot)
+        {
+            return _db.DeleteSlotAndSetSelectedIndex(userId, deleteSlot, newSlot);
+        }
+
         public Task<PlayerPreferences?> GetPlayerPreferencesAsync(NetUserId userId)
         {
             return _db.GetPlayerPreferencesAsync(userId);

Content.Server/Preferences/ServerPreferencesManager.cs

@@ -131,14 +131,36 @@ namespace Content.Server.Preferences
 
             var curPrefs = prefsData.Prefs!;
 
+            // If they try to delete the slot they have selected then we switch to another one.
+            // Of course, that's only if they HAVE another slot.
+            int? nextSlot = null;
+            if (curPrefs.SelectedCharacterIndex == slot)
+            {
+                var (ns, profile) = curPrefs.Characters.FirstOrDefault(p => p.Key != message.Slot);
+                if (profile == null)
+                {
+                    // Only slot left, can't delete.
+                    return;
+                }
+
+                nextSlot = ns;
+            }
+
             var arr = new Dictionary<int, ICharacterProfile>(curPrefs.Characters);
             arr.Remove(slot);
 
-            prefsData.Prefs = new PlayerPreferences(arr, slot);
+            prefsData.Prefs = new PlayerPreferences(arr, nextSlot ?? curPrefs.SelectedCharacterIndex);
 
             if (ShouldStorePrefs(message.MsgChannel.AuthType))
             {
-                await _db.SaveCharacterSlotAsync(message.MsgChannel.UserId, null, message.Slot);
+                if (nextSlot != null)
+                {
+                    await _db.DeleteSlotAndSetSelectedIndex(userId, slot, nextSlot.Value);
+                }
+                else
+                {
+                    await _db.SaveCharacterSlotAsync(userId, null, slot);
+                }
             }
         }