Initial commit

Assets/Pacore/Runtime/Threading/ThreadDispatcher.cs

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+using System.Collections.Concurrent;
+using PashaBibko.Pacore.Attributes;
+using UnityEngine;
+using System;
+using System.Collections;
+using System.Diagnostics;
+using System.Threading;
+using System.Threading.Tasks;
+using Debug = UnityEngine.Debug;
+
+namespace PashaBibko.Pacore.Threading
+{
+    [CreateInstanceOnStart] public class ThreadDispatcher : MonoBehaviour
+    {
+        private static ConcurrentQueue<IEnumerator> MainThreadMultistepQueue { get; } = new();
+        private static ConcurrentQueue<Action> MainThreadImmediateQueue { get; } = new();
+        private static ConcurrentQueue<Action> BackgroundQueue { get; } = new();
+
+        private static SemaphoreSlim Semaphore { get; } = new(initialCount: 4);
+        private static int IsBackgroundProcessing; // Pseudo boolean
+
+        private static IEnumerator ActiveMultistepRoutine { get; set; }
+        private static ThreadDispatcher Instance;
+        
+        private const long MAIN_THREAD_MS_MAX = 5;
+        
+        private void Awake()
+        {
+            /* Makes sure there is only one instance */
+            if (Instance is not null)
+            {
+                Debug.LogError($"Cannot have multiple instances of [{nameof(ThreadDispatcher)}]");
+                return;
+            }
+
+            Instance = this;
+        }
+
+        private void OnDestroy()
+        {
+            Instance = null; // Allows the Dispatcher to be destroyed
+        }
+
+        public static void QueueMultistep(IEnumerator routine) => MainThreadMultistepQueue.Enqueue(routine);
+        public static void QueueImmediate(Action action) => MainThreadImmediateQueue.Enqueue(action);
+
+        public static void QueueBackground(Action action)
+        {
+            /* Adds to the queue and runs if there are no active threads */
+            BackgroundQueue.Enqueue(action);
+            TriggerBackgroundProcessing();
+        }
+
+        private static void TriggerBackgroundProcessing()
+        {
+            /* Makes sure there are not too many threads queued */
+            if (Interlocked.Exchange(ref IsBackgroundProcessing, 1) != 1)
+            {
+                Task.Run(ProcessBackgroundQueue);
+            }
+        }
+
+        private static async Task ProcessBackgroundQueue()
+        {
+            /* Empties the queue of all tasks */
+            while (BackgroundQueue.TryDequeue(out Action task))
+            {
+                await Semaphore.WaitAsync();
+                _ = Task.Run(() =>
+                {
+                    ThreadSafe.Try
+                    (
+                        action: task,
+                        final: () => Semaphore.Release()
+                    );
+                });
+            }
+            
+            /* Cleans up to allow for future procession */
+            Interlocked.Exchange(ref IsBackgroundProcessing, 0);
+            if (!BackgroundQueue.IsEmpty) // Items may be queued during cleanup
+            {
+                TriggerBackgroundProcessing();
+            }
+        }
+
+        private void Update()
+        {
+            /* Runs the Actions in the immediate queue */
+            Stopwatch sw = Stopwatch.StartNew(); // Used to make sure not too much processing is done in one go
+            while (MainThreadImmediateQueue.TryDequeue(out Action current) && sw.ElapsedMilliseconds < MAIN_THREAD_MS_MAX)
+            {
+                current.Invoke();
+            }
+            
+            /* Runs the multistep actions (if there is still time) */
+            while (sw.ElapsedMilliseconds < MAIN_THREAD_MS_MAX)
+            {
+                /* Gets a new routine if there is none active */
+                if (ActiveMultistepRoutine == null)
+                {
+                    if (!MainThreadMultistepQueue.TryDequeue(out IEnumerator next))
+                    {
+                        return; // There is none left so we can return early
+                    }
+                    
+                    ActiveMultistepRoutine = next;
+                }
+                
+                /* Runs the next step in the routine */
+                if (!ActiveMultistepRoutine.MoveNext())
+                {
+                    ActiveMultistepRoutine = null; // [MoveNext() -> false] means the routine has ended
+                }
+            }
+        }
+    }
+}

Assets/Pacore/Runtime/Threading/ThreadDispatcher.cs.meta

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+fileFormatVersion: 2
+guid: dea7202d2750b6d4fb932511a26c0b50

Assets/Pacore/Runtime/Threading/ThreadEnforcer.cs

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+using System.Runtime.CompilerServices;
+using System.Threading;
+using UnityEngine;
+using System;
+
+namespace PashaBibko.Pacore.Threading
+{
+    public static partial class ThreadSafe
+    {
+        private static SynchronizationContext MainThreadContext { get; set; }
+
+        public class IncorrectThreadException : Exception
+        {
+            public IncorrectThreadException(string message)
+                : base(message)
+            {
+            }
+        }
+
+        [RuntimeInitializeOnLoadMethod(RuntimeInitializeLoadType.AfterAssembliesLoaded)]
+        private static void CaptureMainThreadContext()
+        {
+            MainThreadContext = SynchronizationContext.Current;
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static void EnforceMainThread()
+        {
+            if (SynchronizationContext.Current != MainThreadContext)
+            {
+                throw new IncorrectThreadException("Main thread function was called on a background thread");
+            }
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static void EnforceBackgroundThread()
+        {
+            if (SynchronizationContext.Current == MainThreadContext)
+            {
+                throw new IncorrectThreadException("Background thread function was called on the main thread");
+            }
+        }
+    }
+}

Assets/Pacore/Runtime/Threading/ThreadEnforcer.cs.meta

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+fileFormatVersion: 2
+guid: 1ef7f28549bf1594eab8e277cfcdfab7

Assets/Pacore/Runtime/Threading/ThreadSafeTry.cs

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+using System.Runtime.CompilerServices;
+using UnityEngine;
+using System;
+
+namespace PashaBibko.Pacore.Threading
+{
+    public static partial class ThreadSafe
+    {
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static void Try(Action action, Action final = null)
+        {
+            try { action(); }
+
+            /* Makes sure any exceptions are caught and logged properly */
+            catch (Exception ex)
+            {
+                ThreadDispatcher.QueueImmediate(() => Debug.Log($"Exception: [{ex.Message}]"));
+                throw;
+            }
+
+            finally { final?.Invoke(); }
+        }
+    }
+}

Assets/Pacore/Runtime/Threading/ThreadSafeTry.cs.meta

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+fileFormatVersion: 2
+guid: c8f7e0d910af34342aefbb654c8b7acf