Updated audio image extraction logic. Added caching classes.

Harmonia.Core/Caching/Cache.cs

@@ -0,0 +1,40 @@
+namespace Harmonia.Core.Caching;
+
+public abstract class Cache<TKey, TValue> : ICache<TKey, TValue> where TKey : notnull
+{
+    protected abstract TValue? TryGetValue(object key);
+    protected abstract TValue? Fetch(TKey key);
+    protected abstract void AddToCache(object key, TValue value);
+
+    public TValue? Get(TKey key)
+    {
+        object? actualKey = GetKey(key);
+
+        if (actualKey == null)
+            return default;
+
+        return TryGetValue(actualKey) ?? Refresh(key);
+    }
+
+    public TValue? Refresh(TKey key)
+    {
+        object? actualKey = GetKey(key);
+
+        if (actualKey == null)
+            return default;
+
+        TValue? value = Fetch(key);
+
+        if (value == null)
+            return default;
+
+        AddToCache(actualKey, value);
+
+        return value;
+    }
+
+    protected virtual object? GetKey(TKey key)
+    {
+        return key;
+    }
+}