add warning text on acronym conflict

osu.Game.Tournament/Screens/Editors/TeamEditorScreen.cs

@@ -71,6 +71,8 @@ namespace osu.Game.Tournament.Screens.Editors
             [Resolved]
             private LadderInfo ladderInfo { get; set; } = null!;
 
+            private readonly SettingsTextBox acronymTextBox;
+
             public TeamRow(TournamentTeam team, TournamentScreen parent)
             {
                 Model = team;
@@ -112,7 +114,7 @@ namespace osu.Game.Tournament.Screens.Editors
                                 Width = 0.2f,
                                 Current = Model.FullName
                             },
-                            new SettingsTextBox
+                            acronymTextBox = new SettingsTextBox
                             {
                                 LabelText = "Acronym",
                                 Width = 0.2f,
@@ -177,6 +179,28 @@ namespace osu.Game.Tournament.Screens.Editors
                 };
             }
 
+            protected override void LoadComplete()
+            {
+                base.LoadComplete();
+
+                Model.Acronym.BindValueChanged(acronym =>
+                {
+                    var matchingTeams = ladderInfo.Teams
+                                                  .Where(t => t.Acronym.Value == acronym.NewValue && t != Model)
+                                                  .ToList();
+
+                    if (matchingTeams.Count > 0)
+                    {
+                        acronymTextBox.SetNoticeText(
+                            $"Acronym '{acronym.NewValue}' is already in use by team{(matchingTeams.Count > 1 ? "s" : "")}:\n"
+                            + $"{string.Join(",\n", matchingTeams)}", true);
+                        return;
+                    }
+
+                    acronymTextBox.ClearNoticeText();
+                }, true);
+            }
+
             private partial class LastYearPlacementSlider : RoundedSliderBar<int>
             {
                 public override LocalisableString TooltipText => Current.Value == 0 ? "N/A" : base.TooltipText;