misc: add property watcher

Shokofin/Utils/PropertyWatcher.cs

@@ -0,0 +1,47 @@
+using System;
+using System.Threading.Tasks;
+
+namespace Shokofin.Utils;
+
+public class PropertyWatcher<T>
+{
+    private readonly Func<T> _valueGetter;
+
+    private bool _continueMonitoring;
+
+    public T LastKnownValue { get; private set; }
+
+    public event EventHandler<T> OnValueChanged;
+
+    public PropertyWatcher(Func<T> valueGetter)
+    {
+        _valueGetter = valueGetter;
+        LastKnownValue = _valueGetter();
+    }
+
+    public void StartMonitoring(int delayInMilliseconds)
+    {
+        _continueMonitoring = true;
+        LastKnownValue = _valueGetter();
+        Task.Run(async () => {
+            while (_continueMonitoring) {
+                await Task.Delay(delayInMilliseconds);
+                CheckForChange();
+            }
+        });
+    }
+
+    public void StopMonitoring()
+    {
+        _continueMonitoring = false;
+    }
+
+    private void CheckForChange()
+    {
+        var currentValue = _valueGetter()!;
+        if (!LastKnownValue!.Equals(currentValue)) {
+            OnValueChanged?.Invoke(null, currentValue);
+            LastKnownValue = currentValue;
+        }
+    }
+}