Merge pull request #7 from simulation-tree/dev/system-attributes

System attributes

Author: popcron

README.md

@@ -2,7 +2,7 @@
 
 [![Test](https://github.com/simulation-tree/simulation/actions/workflows/test.yml/badge.svg)](https://github.com/simulation-tree/simulation/actions/workflows/test.yml)
 
-Library providing a way to organize and update systems with support for message handling.
+Library providing a way to broadcast messages to added listeners.
 
 ### Running simulators
 
@@ -18,21 +18,16 @@ public static void Main()
     simulator.Remove<ProgramSystems>();
 }
 
-public class ProgramSystems : ISystem, IDisposable
+public class ProgramSystems : IDisposable
 {
     public ProgramSystems()
     {
-        //initialize
+        //before addition
     }
 
     public void Dispose()
     {
-        //clean up
-    }
-
-    void ISystem.Update(Simulator simulator, double deltaTime)
-    {
-        //do work
+        //after removal
     }
 }
 ```
@@ -50,7 +45,6 @@ public partial class ListenerSystem : IListener<float>
 {
     void IListener<float>.Receive(ref float message)
     {
-        //do something with this
     }
 }
 ```
@@ -76,6 +70,32 @@ public struct LoadRequest
 }
 ```
 
+### Global simulator
+
+Another way to have listeners and broadcasting setup, is using the included `GlobalSimulator` type.
+This approach is slimmer than with the `Simulator`, at the cost of the listeners being global to the entire
+runtime.
+```cs
+public class Program
+{
+    public static void Main()
+    {
+        GlobalSimulatorLoader.Load();
+        GlobalSimulator.Broadcast(32f);
+        GlobalSimulator.Broadcast(32f);
+        GlobalSimulator.Broadcast(32f);
+    }
+}
+
+public static class Systems
+{
+    [Listener<float>]
+    public static void Update(ref float message)
+    {
+    }
+}
+```
+
 ### Contributing and design
 
 This library is created for composing behaviour of programs using systems, ideally created by

core/Attributes/ListenerAttribute.cs

@@ -0,0 +1,12 @@
+using System;
+
+namespace Simulation
+{
+    /// <summary>
+    /// Attribute to mark static methods as listeners for messages of type <typeparamref name="T"/>.
+    /// </summary>
+    [AttributeUsage(AttributeTargets.Method)]
+    public class ListenerAttribute<T> : Attribute where T : unmanaged
+    {
+    }
+}

core/GlobalSimulator.cs

@@ -0,0 +1,87 @@
+using System;
+using System.Collections.Generic;
+
+namespace Simulation
+{
+    /// <summary>
+    /// Dispatches messages for static methods with the <see cref="ListenerAttribute{T}"/>.
+    /// </summary>
+    public static class GlobalSimulator
+    {
+        private static readonly List<Action> clearFunctions = new();
+
+        /// <summary>
+        /// Registers a listener for messages of type <typeparamref name="T"/>.
+        /// </summary>
+        public static void Register<T>(Receive<T> receive) where T : unmanaged
+        {
+            Array.Resize(ref Listeners<T>.list, Listeners<T>.list.Length + 1);
+            Listeners<T>.list[^1] = receive;
+        }
+
+        /// <summary>
+        /// Registers a <paramref name="listener"/>.
+        /// </summary>
+        public static void Register<T>(IListener<T> listener) where T : unmanaged
+        {
+            Receive<T> receive = listener.Receive;
+            Array.Resize(ref Listeners<T>.list, Listeners<T>.list.Length + 1);
+            Listeners<T>.list[^1] = receive;
+        }
+
+        /// <summary>
+        /// Resets the global simulator to initial state, with no listeners registered.
+        /// </summary>
+        public static void Reset()
+        {
+            foreach (Action clearFunction in clearFunctions)
+            {
+                clearFunction();
+            }
+        }
+
+        /// <summary>
+        /// Broadcasts the given <paramref name="message"/>.
+        /// </summary>
+        public static void Broadcast<T>(T message) where T : unmanaged
+        {
+            int length = Listeners<T>.list.Length;
+            for (int i = 0; i < length; i++)
+            {
+                Listeners<T>.list[i](ref message);
+            }
+        }
+
+        /// <summary>
+        /// Broadcasts the given <paramref name="message"/>.
+        /// </summary>
+        public static void Broadcast<T>(ref T message) where T : unmanaged
+        {
+            int length = Listeners<T>.list.Length;
+            for (int i = 0; i < length; i++)
+            {
+                Listeners<T>.list[i](ref message);
+            }
+        }
+
+        private static class Listeners<T> where T : unmanaged
+        {
+            public static Receive<T>[] list = [];
+
+            static Listeners()
+            {
+                clearFunctions.Add(Reset);
+            }
+
+            public static void Reset()
+            {
+                Array.Resize(ref list, 0);
+            }
+        }
+
+        /// <summary>
+        /// Delegate for message receivers.
+        /// </summary>
+        public delegate void Receive<T>(ref T message) where T : unmanaged;
+    }
+}

generator/Constants.cs

@@ -1,7 +1,4 @@
-using System.Runtime.CompilerServices;
-
-[assembly: InternalsVisibleTo("Simulation.Generator.Tests")]
-namespace Simulation
+namespace Simulation
 {
     internal static class Constants
     {
@@ -10,5 +7,8 @@ internal static class Constants
         public const string ListenerInterfaceTypeName = Namespace + ".IListener";
         public const string SystemBankTypeNameFormat = "{0}SystemBank";
         public const string PluralSystemBankTypeNameFormat = "{0}SystemsBank";
+        public const string GlobalSimulatorTypeName = "GlobalSimulator";
+        public const string GlobalSimulatorLoaderTypeName = GlobalSimulatorTypeName + "Loader";
+        public const string ListenerAttributeTypeName = "ListenerAttribute";
     }
 }