Implement Sequential Hooking and Notification for Multiplayer Button Click

SSMP/Api/Client/IUiManager.cs

@@ -1,3 +1,5 @@
+using System;
+
 namespace SSMP.Api.Client;
 
 /// <summary>
@@ -8,4 +10,41 @@ public interface IUiManager {
     /// The message box that shows information related to SSMP.
     /// </summary>
     IChatBox ChatBox { get; }
+
+    /// <summary>
+    /// Fired when the multiplayer button is pressed, before any blocking hooks run.
+    /// Use this for fire-and-forget reactions such as logging or showing a notification.
+    /// </summary>
+    event Action? MultiplayerButtonPressed;
+
+    /// <summary>
+    /// Registers a hook that is invoked when the multiplayer button is pressed.
+    /// </summary>
+    /// <remarks>
+    /// Hooks are executed in reverse order (last registered runs first).
+    ///
+    /// Example (informational hook):
+    /// <code>
+    /// RegisterMultiplayerMenuHook(next => {
+    ///     MyNonMandatoryDependencyPopup.Show(
+    ///         "Addon X unavailable",
+    ///         onAccept:  _ => {continue;  },
+    ///         onDecline: _ => { continue; });
+    ///     });
+    /// </code>
+    ///
+    /// Example (blocking hook):
+    /// <code>
+    /// RegisterMultiplayerMenuHook(next => {
+    ///     MyMandatoryDependencyPopup.Show(
+    ///         "Addon X unavailable",
+    ///         onConfirm: agreed => { if (agreed) continue; });
+    ///         onDecline: agreed => { if (!agreed) return;  });
+    ///     });
+    /// </code>
+    /// </remarks>
+    /// <param name="hook">
+    /// The hook to register. Receives a callback to invoke when ready to proceed.
+    /// </param>
+    void RegisterMultiplayerMenuHook(Action<Action> hook);
 }

SSMP/Ui/UiManager.cs

@@ -142,6 +142,9 @@ internal class UiManager : IUiManager {
     /// </summary>
     public event Action? RequestClientDisconnectEvent;
 
+    /// <inheritdoc />
+    public event Action? MultiplayerButtonPressed;
+
     #endregion
 
     #region Fields
@@ -207,6 +210,12 @@ internal class UiManager : IUiManager {
     /// </summary>
     private bool _isSlotSelectionActive;
 
+    /// <summary>
+    /// The head of the multiplayer menu hook chain.
+    /// Starts as the bare transition; each registered hook wraps it.
+    /// </summary>
+    private Action _multiplayerMenuChain;
+
     #endregion
 
     #region Properties
@@ -243,6 +252,13 @@ public IChatBox ChatBox {
     public UiManager(ModSettings modSettings, NetClient netClient) {
         _modSettings = modSettings;
         _netClient = netClient;
+        _multiplayerMenuChain = () => UM.StartCoroutine(GoToMultiplayerMenu());
+    }
+
+    /// <inheritdoc />
+    public void RegisterMultiplayerMenuHook(Action<Action> hook) {
+        var previous = _multiplayerMenuChain;
+        _multiplayerMenuChain = () => hook(previous);
     }
 
     #endregion
@@ -738,7 +754,7 @@ private void ConfigureButtonTriggers(GameObject button) {
         if (eventTrigger == null) return;
 
         eventTrigger.triggers.Clear();
-        AddButtonTriggers(eventTrigger, () => UM.StartCoroutine(GoToMultiplayerMenu()));
+        AddButtonTriggers(eventTrigger, OnMultiplayerMenuRequested);
     }
 
     /// <summary>
@@ -777,6 +793,14 @@ private void SetNavigation(MenuButton button, MenuButton? selectOnUp = null, Men
         button.navigation = nav;
     }
 
+    /// <summary>
+    /// Handles the multiplayer menu request by firing the notification event, then invoking the hook chain.
+    /// </summary>
+    private void OnMultiplayerMenuRequested() {
+        MultiplayerButtonPressed?.Invoke();
+        _multiplayerMenuChain.Invoke();
+    }
+
     #endregion
 
     #region Menu Navigation