Abstract away cache. 2 implementations: redis and memory

src/NadekoBot/Common/Cache/IBotCache.cs

@@ -0,0 +1,47 @@
+using OneOf;
+using OneOf.Types;
+
+namespace NadekoBot.Common;
+
+public interface IBotCache
+{
+    /// <summary>
+    /// Adds an item to the cache
+    /// </summary>
+    /// <param name="key">Key to add</param>
+    /// <param name="value">Value to add to the cache</param>
+    /// <param name="expiry">Optional expiry</param>
+    /// <param name="overwrite">Whether old value should be overwritten</param>
+    /// <typeparam name="T">Type of the value</typeparam>
+    /// <returns>Returns whether add was sucessful. Always true unless ovewrite = false</returns>
+    ValueTask<bool> AddAsync<T>(TypedKey<T> key, T value, TimeSpan? expiry = null, bool overwrite = true);
+    
+    /// <summary>
+    /// Get an element from the cache
+    /// </summary>
+    /// <param name="key">Key</param>
+    /// <typeparam name="T">Type of the value</typeparam>
+    /// <returns>Either a value or <see cref="None"/></returns>
+    ValueTask<OneOf<T, None>> GetAsync<T>(TypedKey<T> key);
+    
+    /// <summary>
+    /// Remove a key from the cache
+    /// </summary>
+    /// <param name="key">Key to remove</param>
+    /// <typeparam name="T">Type of the value</typeparam>
+    /// <returns>Whether there was item</returns>
+    ValueTask<bool> RemoveAsync<T>(TypedKey<T> key);
+
+    /// <summary>
+    /// Get the key if it exists or add a new one
+    /// </summary>
+    /// <param name="key">Key to get and potentially add</param>
+    /// <param name="createFactory">Value creation factory</param>
+    /// <param name="expiry">Optional expiry</param>
+    /// <typeparam name="T">Type of the value</typeparam>
+    /// <returns>The retrieved or newly added value</returns>
+    ValueTask<T?> GetOrAddAsync<T>(
+        TypedKey<T> key,
+        Func<Task<T?>> createFactory,
+        TimeSpan? expiry = null);
+}