From bc1c76d746d01281ecaa3c6937e1990fd1dcdcfc Mon Sep 17 00:00:00 2001
From: Syntriax <Syntriax@gmail.com>
Date: Sun, 6 Jul 2025 22:22:57 +0300
Subject: [PATCH] feat: added priorities to events

---
 Engine.Core/Helpers/Event.cs | 186 +++++++++++++++++++++++++++++------
 1 file changed, 156 insertions(+), 30 deletions(-)

diff --git a/Engine.Core/Helpers/Event.cs b/Engine.Core/Helpers/Event.cs
index 7f818e5..c8221f4 100644
--- a/Engine.Core/Helpers/Event.cs
+++ b/Engine.Core/Helpers/Event.cs
@@ -45,30 +45,71 @@ namespace Syntriax.Engine.Core;
 /// </summary>
 public class Event
 {
-    private readonly List<EventHandler> listeners = null!;
-    private readonly List<EventHandler> onceListeners = null!;
+    // We use Ascending order because draw calls are running from last to first
+    private static readonly Comparer<ListenerData> SortByAscendingPriority = Comparer<ListenerData>.Create((x, y) => x.Priority.CompareTo(y.Priority));
+
+    private readonly List<ListenerData> listeners = null!;
+    private readonly List<ListenerData> onceListeners = null!;
 
     /// <summary>
     /// Subscribes the callback to be invoked whenever the event is triggered.
     /// </summary>
     /// <param name="listener">The callback to be called when the event is triggered.</param>
-    public void AddListener(EventHandler listener) => listeners.Add(listener);
+    /// <param name="priority">Priority of the callback.</param>
+    public void AddListener(EventHandler listener, int priority = 0)
+    {
+        ListenerData listenerData = new(listener, priority);
+
+        int insertIndex = listeners.BinarySearch(listenerData, SortByAscendingPriority);
+        if (insertIndex < 0)
+            insertIndex = ~insertIndex;
+
+        listeners.Insert(insertIndex, listenerData);
+    }
+
     /// <summary>
     /// Subscribes the callback to be invoked the next time the event is triggered. The callback will be called only once.
     /// </summary>
     /// <param name="listener">The callback to be called the next time the event is triggered.</param>
-    public void AddOneTimeListener(EventHandler listener) => onceListeners.Add(listener);
+    /// <param name="priority">Priority of the callback.</param>
+    public void AddOneTimeListener(EventHandler listener, int priority = 0)
+    {
+        ListenerData listenerData = new(listener, priority);
+
+        int insertIndex = onceListeners.BinarySearch(listenerData, SortByAscendingPriority);
+        if (insertIndex < 0)
+            insertIndex = ~insertIndex;
+
+        onceListeners.Insert(insertIndex, listenerData);
+    }
 
     /// <summary>
     /// Unsubscribes the callback that was previously registered by <see cref="AddListener(EventHandler)"/>.
     /// </summary>
     /// <param name="listener">The callback that was previously registered by <see cref="AddListener(EventHandler)"/></param>
-    public void RemoveListener(EventHandler listener) => listeners.Remove(listener);
+    public void RemoveListener(EventHandler listener)
+    {
+        for (int i = listeners.Count - 1; i >= 0; i--)
+            if (listeners[i].Callback == listener)
+            {
+                listeners.RemoveAt(i);
+                return;
+            }
+    }
+
     /// <summary>
     /// Unsubscribes the callback that was previously registered by <see cref="AddOneTimeListener(EventHandler)"/>.
     /// </summary>
     /// <param name="listener">The callback that was previously registered by <see cref="AddOneTimeListener(EventHandler)"/></param>
-    public void RemoveOneTimeListener(EventHandler listener) => onceListeners.Remove(listener);
+    public void RemoveOneTimeListener(EventHandler listener)
+    {
+        for (int i = 0; i < onceListeners.Count; i++)
+            if (onceListeners[i].Callback == listener)
+            {
+                onceListeners.RemoveAt(i);
+                return;
+            }
+    }
 
     /// <summary>
     /// Unsubscribes all listeners that was previously registered by either <see cref="AddListener(EventHandler)"/> or <see cref="AddOneTimeListener(EventHandler)"/>.
@@ -81,19 +122,19 @@ public class Event
     public void Invoke()
     {
         for (int i = listeners.Count - 1; i >= 0; i--)
-            try { listeners[i].Invoke(); }
+            try { listeners[i].Callback.Invoke(); }
             catch (Exception exception)
             {
-                string methodCallRepresentation = $"{listeners[i].Method.DeclaringType?.FullName}.{listeners[i].Method.Name}()";
+                string methodCallRepresentation = $"{listeners[i].Callback.Method.DeclaringType?.FullName}.{listeners[i].Callback.Method.Name}()";
                 Console.WriteLine($"Unexpected exception on invocation of method {methodCallRepresentation}:{Environment.NewLine}{exception.InnerException}");
             }
 
         for (int i = onceListeners.Count - 1; i >= 0; i--)
         {
-            try { onceListeners[i].Invoke(); }
+            try { onceListeners[i].Callback.Invoke(); }
             catch (Exception exception)
             {
-                string methodCallRepresentation = $"{onceListeners[i].Method.DeclaringType?.FullName}.{onceListeners[i].Method.Name}()";
+                string methodCallRepresentation = $"{onceListeners[i].Callback.Method.DeclaringType?.FullName}.{onceListeners[i].Callback.Method.Name}()";
                 Console.WriteLine($"Unexpected exception on invocation of method {methodCallRepresentation}:{Environment.NewLine}{exception.InnerException}");
             }
             onceListeners.RemoveAt(i);
@@ -113,6 +154,7 @@ public class Event
     }
 
     public delegate void EventHandler();
+    private record struct ListenerData(EventHandler Callback, int Priority);
 }
 
 /// <summary>
@@ -159,30 +201,71 @@ public class Event
 /// <typeparam name="TSender">Sender type</typeparam>
 public class Event<TSender>
 {
-    private readonly List<EventHandler> listeners = null!;
-    private readonly List<EventHandler> onceListeners = null!;
+    // We use Ascending order because draw calls are running from last to first
+    private static readonly Comparer<ListenerData> SortByAscendingPriority = Comparer<ListenerData>.Create((x, y) => x.Priority.CompareTo(y.Priority));
+
+    private readonly List<ListenerData> listeners = null!;
+    private readonly List<ListenerData> onceListeners = null!;
 
     /// <summary>
     /// Subscribes the callback to be invoked whenever the event is triggered.
     /// </summary>
     /// <param name="listener">The callback to be called when the event is triggered.</param>
-    public void AddListener(EventHandler listener) => listeners.Add(listener);
+    /// <param name="priority">Priority of the callback.</param>
+    public void AddListener(EventHandler listener, int priority = 0)
+    {
+        ListenerData listenerData = new(listener, priority);
+
+        int insertIndex = listeners.BinarySearch(listenerData, SortByAscendingPriority);
+        if (insertIndex < 0)
+            insertIndex = ~insertIndex;
+
+        listeners.Insert(insertIndex, listenerData);
+    }
+
     /// <summary>
     /// Subscribes the callback to be invoked the next time the event is triggered. The callback will be called only once.
     /// </summary>
     /// <param name="listener">The callback to be called the next time the event is triggered.</param>
-    public void AddOneTimeListener(EventHandler listener) => onceListeners.Add(listener);
+    /// <param name="priority">Priority of the callback.</param>
+    public void AddOneTimeListener(EventHandler listener, int priority = 0)
+    {
+        ListenerData listenerData = new(listener, priority);
+
+        int insertIndex = onceListeners.BinarySearch(listenerData, SortByAscendingPriority);
+        if (insertIndex < 0)
+            insertIndex = ~insertIndex;
+
+        onceListeners.Insert(insertIndex, listenerData);
+    }
 
     /// <summary>
     /// Unsubscribes the callback that was previously registered by <see cref="AddListener(EventHandler)"/>.
     /// </summary>
     /// <param name="listener">The callback that was previously registered by <see cref="AddListener(EventHandler)"/></param>
-    public void RemoveListener(EventHandler listener) => listeners.Remove(listener);
+    public void RemoveListener(EventHandler listener)
+    {
+        for (int i = listeners.Count - 1; i >= 0; i--)
+            if (listeners[i].Callback == listener)
+            {
+                listeners.RemoveAt(i);
+                return;
+            }
+    }
+
     /// <summary>
     /// Unsubscribes the callback that was previously registered by <see cref="AddOneTimeListener(EventHandler)"/>.
     /// </summary>
     /// <param name="listener">The callback that was previously registered by <see cref="AddOneTimeListener(EventHandler)"/></param>
-    public void RemoveOneTimeListener(EventHandler listener) => onceListeners.Remove(listener);
+    public void RemoveOneTimeListener(EventHandler listener)
+    {
+        for (int i = 0; i < onceListeners.Count; i++)
+            if (onceListeners[i].Callback == listener)
+            {
+                onceListeners.RemoveAt(i);
+                return;
+            }
+    }
 
     /// <summary>
     /// Unsubscribes all listeners that was previously registered by either <see cref="AddListener(EventHandler)"/> or <see cref="AddOneTimeListener(EventHandler)"/>.
@@ -196,19 +279,19 @@ public class Event<TSender>
     public void Invoke(TSender sender)
     {
         for (int i = listeners.Count - 1; i >= 0; i--)
-            try { listeners[i].Invoke(sender); }
+            try { listeners[i].Callback.Invoke(sender); }
             catch (Exception exception)
             {
-                string methodCallRepresentation = $"{listeners[i].Method.DeclaringType?.FullName}.{listeners[i].Method.Name}({sender})";
+                string methodCallRepresentation = $"{listeners[i].Callback.Method.DeclaringType?.FullName}.{listeners[i].Callback.Method.Name}({sender})";
                 Console.WriteLine($"Unexpected exception on invocation of method {methodCallRepresentation}:{Environment.NewLine}{exception.InnerException}");
             }
 
         for (int i = onceListeners.Count - 1; i >= 0; i--)
         {
-            try { onceListeners[i].Invoke(sender); }
+            try { onceListeners[i].Callback.Invoke(sender); }
             catch (Exception exception)
             {
-                string methodCallRepresentation = $"{onceListeners[i].Method.DeclaringType?.FullName}.{onceListeners[i].Method.Name}({sender})";
+                string methodCallRepresentation = $"{onceListeners[i].Callback.Method.DeclaringType?.FullName}.{onceListeners[i].Callback.Method.Name}({sender})";
                 Console.WriteLine($"Unexpected exception on invocation of method {methodCallRepresentation}:{Environment.NewLine}{exception.InnerException}");
             }
             onceListeners.RemoveAt(i);
@@ -228,6 +311,7 @@ public class Event<TSender>
     }
 
     public delegate void EventHandler(TSender sender);
+    private record struct ListenerData(EventHandler Callback, int Priority);
 }
 
 /// <summary>
@@ -281,30 +365,71 @@ public class Event<TSender>
 /// <typeparam name="TSender">Sender type</typeparam>
 public class Event<TSender, TArguments>
 {
-    private readonly List<EventHandler> listeners = null!;
-    private readonly List<EventHandler> onceListeners = null!;
+    // We use Ascending order because draw calls are running from last to first
+    private static readonly Comparer<ListenerData> SortByAscendingPriority = Comparer<ListenerData>.Create((x, y) => x.Priority.CompareTo(y.Priority));
+
+    private readonly List<ListenerData> listeners = null!;
+    private readonly List<ListenerData> onceListeners = null!;
 
     /// <summary>
     /// Subscribes the callback to be invoked whenever the event is triggered.
     /// </summary>
     /// <param name="listener">The callback to be called when the event is triggered.</param>
-    public void AddListener(EventHandler listener) => listeners.Add(listener);
+    /// <param name="priority">Priority of the callback.</param>
+    public void AddListener(EventHandler listener, int priority = 0)
+    {
+        ListenerData listenerData = new(listener, priority);
+
+        int insertIndex = listeners.BinarySearch(listenerData, SortByAscendingPriority);
+        if (insertIndex < 0)
+            insertIndex = ~insertIndex;
+
+        listeners.Insert(insertIndex, listenerData);
+    }
+
     /// <summary>
     /// Subscribes the callback to be invoked the next time the event is triggered. The callback will be called only once.
     /// </summary>
     /// <param name="listener">The callback to be called the next time the event is triggered.</param>
-    public void AddOneTimeListener(EventHandler listener) => onceListeners.Add(listener);
+    /// <param name="priority">Priority of the callback.</param>
+    public void AddOneTimeListener(EventHandler listener, int priority = 0)
+    {
+        ListenerData listenerData = new(listener, priority);
+
+        int insertIndex = onceListeners.BinarySearch(listenerData, SortByAscendingPriority);
+        if (insertIndex < 0)
+            insertIndex = ~insertIndex;
+
+        onceListeners.Insert(insertIndex, listenerData);
+    }
 
     /// <summary>
     /// Unsubscribes the callback that was previously registered by <see cref="AddListener(EventHandler)"/>.
     /// </summary>
     /// <param name="listener">The callback that was previously registered by <see cref="AddListener(EventHandler)"/></param>
-    public void RemoveListener(EventHandler listener) => listeners.Remove(listener);
+    public void RemoveListener(EventHandler listener)
+    {
+        for (int i = listeners.Count - 1; i >= 0; i--)
+            if (listeners[i].Callback == listener)
+            {
+                listeners.RemoveAt(i);
+                return;
+            }
+    }
+
     /// <summary>
     /// Unsubscribes the callback that was previously registered by <see cref="AddOneTimeListener(EventHandler)"/>.
     /// </summary>
     /// <param name="listener">The callback that was previously registered by <see cref="AddOneTimeListener(EventHandler)"/></param>
-    public void RemoveOneTimeListener(EventHandler listener) => onceListeners.Remove(listener);
+    public void RemoveOneTimeListener(EventHandler listener)
+    {
+        for (int i = 0; i < onceListeners.Count; i++)
+            if (onceListeners[i].Callback == listener)
+            {
+                onceListeners.RemoveAt(i);
+                return;
+            }
+    }
 
     /// <summary>
     /// Unsubscribes all listeners that was previously registered by either <see cref="AddListener(EventHandler)"/> or <see cref="AddOneTimeListener(EventHandler)"/>.
@@ -319,19 +444,19 @@ public class Event<TSender, TArguments>
     public void Invoke(TSender sender, TArguments args)
     {
         for (int i = listeners.Count - 1; i >= 0; i--)
-            try { listeners[i].Invoke(sender, args); }
+            try { listeners[i].Callback.Invoke(sender, args); }
             catch (Exception exception)
             {
-                string methodCallRepresentation = $"{listeners[i].Method.DeclaringType?.FullName}.{listeners[i].Method.Name}({string.Join(", ", sender, args)})";
+                string methodCallRepresentation = $"{listeners[i].Callback.Method.DeclaringType?.FullName}.{listeners[i].Callback.Method.Name}({string.Join(", ", sender, args)})";
                 Console.WriteLine($"Unexpected exception on invocation of method {methodCallRepresentation}:{Environment.NewLine}{exception.InnerException}");
             }
 
         for (int i = onceListeners.Count - 1; i >= 0; i--)
         {
-            try { onceListeners[i].Invoke(sender, args); }
+            try { onceListeners[i].Callback.Invoke(sender, args); }
             catch (Exception exception)
             {
-                string methodCallRepresentation = $"{onceListeners[i].Method.DeclaringType?.FullName}.{onceListeners[i].Method.Name}({string.Join(", ", sender, args)})";
+                string methodCallRepresentation = $"{onceListeners[i].Callback.Method.DeclaringType?.FullName}.{onceListeners[i].Callback.Method.Name}({string.Join(", ", sender, args)})";
                 Console.WriteLine($"Unexpected exception on invocation of method {methodCallRepresentation}:{Environment.NewLine}{exception.InnerException}");
             }
             onceListeners.RemoveAt(i);
@@ -351,4 +476,5 @@ public class Event<TSender, TArguments>
     }
 
     public delegate void EventHandler(TSender sender, TArguments args);
+    private record struct ListenerData(EventHandler Callback, int Priority);
 }