[stg] Bring in MemoryCache

Because I'm too lazy to rework it.

Author: Haselnussbomber

LeveHelper/Caches/ItemQuantityCache.cs

@@ -1,5 +1,5 @@
 using FFXIVClientStructs.FFXIV.Client.Game;
-using HaselCommon.Cache;
+using LeveHelper.Utils;
 
 namespace LeveHelper.Caches;
 

LeveHelper/Caches/LeveIssuerCache.cs

@@ -1,7 +1,7 @@
 using System.Collections.Generic;
 using System.Linq;
-using HaselCommon.Cache;
 using HaselCommon.Services;
+using LeveHelper.Utils;
 using Lumina.Excel.Sheets;
 
 namespace LeveHelper.Caches;

LeveHelper/Caches/ResidentLevelCache.cs

@@ -1,5 +1,5 @@
-using HaselCommon.Cache;
 using HaselCommon.Services;
+using LeveHelper.Utils;
 using Lumina.Excel.Sheets;
 
 namespace LeveHelper.Caches;

LeveHelper/Utils/MemoryCache.cs

@@ -0,0 +1,55 @@
+using System.Collections.Concurrent;
+using System.Diagnostics.CodeAnalysis;
+using HaselCommon.Extensions;
+
+namespace LeveHelper.Utils;
+
+public abstract class MemoryCache<TKey, TValue> where TKey : notnull, IEquatable<TKey>
+{
+    protected readonly ConcurrentDictionary<TKey, TValue?> Data = [];
+
+    public virtual void Dispose()
+    {
+        Clear();
+    }
+
+    public abstract TValue? CreateEntry(TKey key);
+
+    public virtual TValue? GetValue(TKey key)
+    {
+        TryGetValue(key, out var value);
+        return value;
+    }
+
+    public virtual bool TryGetValue(TKey key, [NotNullWhen(returnValue: true)] out TValue? value)
+    {
+        if (Data.TryGetValue(key, out var _value))
+        {
+            if (_value == null)
+            {
+                value = default;
+                return false;
+            }
+
+            value = _value!;
+            return true;
+        }
+
+        var entry = CreateEntry(key);
+
+        Data.TryAdd(key, entry);
+
+        value = entry;
+        return entry != null;
+    }
+
+    public virtual bool Remove(TKey key)
+    {
+        return Data.TryRemove(key, out var _);
+    }
+
+    public virtual void Clear()
+    {
+        Data.Dispose();
+    }
+}