Abstract away cache. 2 implementations: redis and memory

src/NadekoBot/Common/Cache/BotCacheExtensions.cs

@@ -0,0 +1,46 @@
+using OneOf;
+using OneOf.Types;
+
+namespace NadekoBot.Common;
+
+public static class BotCacheExtensions
+{
+    public static async ValueTask<T?> GetOrDefaultAsync<T>(this IBotCache cache, TypedKey<T> key)
+    {
+        var result = await cache.GetAsync(key);
+        if (result.TryGetValue(out var val))
+            return val;
+
+        return default;
+    }
+    
+    private static TypedKey<byte[]> GetImgKey(Uri uri)
+        => new($"image:{uri}");
+
+    public static ValueTask SetImageDataAsync(this IBotCache c, string key, byte[] data)
+        => c.SetImageDataAsync(new Uri(key), data);
+    public static async ValueTask SetImageDataAsync(this IBotCache c, Uri key, byte[] data)
+        => await c.AddAsync(GetImgKey(key), data, expiry: TimeSpan.FromHours(48));
+
+    public static async ValueTask<OneOf<byte[], None>> GetImageDataAsync(this IBotCache c, Uri key)
+        => await c.GetAsync(GetImgKey(key));
+
+    public static async Task<TimeSpan?> GetRatelimitAsync(
+        this IBotCache c,
+        TypedKey<long> key,
+        TimeSpan length)
+    {
+        var now = DateTime.UtcNow;
+        var nowB = now.ToBinary();
+
+        var cachedValue = await c.GetOrAddAsync(key,
+            () => Task.FromResult(now.ToBinary()),
+            expiry: length);
+
+        if (cachedValue == nowB)
+            return null;
+
+        var diff = now - DateTime.FromBinary(cachedValue);
+        return length - diff;
+    }
+}