huge commit for advanced stats feature.

broke data out into its own library.
may be breaking changes with existing plugins

Data/Helpers/DataValueCache.cs

@@ -0,0 +1,84 @@
+using System;
+using System.Collections.Generic;
+using System.Threading.Tasks;
+using Data.Abstractions;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.Extensions.Logging;
+
+namespace Data.Helpers
+{
+    public class DataValueCache<T, V> : IDataValueCache<T, V> where T : class
+    {
+        private readonly ILogger _logger;
+        private readonly IDatabaseContextFactory _contextFactory;
+        private readonly Dictionary<string, CacheState> _cacheStates = new Dictionary<string, CacheState>();
+        private const int DefaultExpireMinutes = 15;
+
+        private class CacheState
+        {
+            public string Key { get; set; }
+            public DateTime LastRetrieval { get; set; }
+            public TimeSpan ExpirationTime { get; set; }
+            public Func<DbSet<T>, Task<V>> Getter { get; set; }
+            public V Value { get; set; }
+            public bool IsExpired => (DateTime.Now - LastRetrieval.Add(ExpirationTime)).TotalSeconds > 0;
+        }
+        
+        public DataValueCache(ILogger<DataValueCache<T, V>> logger, IDatabaseContextFactory contextFactory)
+        {
+            _logger = logger;
+            _contextFactory = contextFactory;
+        }
+        
+        public void SetCacheItem(Func<DbSet<T>, Task<V>> getter, string key, TimeSpan? expirationTime = null)
+        {
+            if (_cacheStates.ContainsKey(key))
+            {
+                _logger.LogDebug("Cache key {key} is already added", key);
+                return;
+            }
+                 
+            var state = new CacheState()
+            {
+                Key = key,
+                Getter = getter,
+                ExpirationTime = expirationTime ?? TimeSpan.FromMinutes(DefaultExpireMinutes)
+            };
+  
+            _cacheStates.Add(key, state);
+        }
+        
+        public async Task<V> GetCacheItem(string keyName)
+        {
+            if (!_cacheStates.ContainsKey(keyName))
+            {
+                throw new ArgumentException("No cache found for key {key}", keyName);
+            }
+
+            var state = _cacheStates[keyName];
+
+            if (state.IsExpired)
+            {
+                await RunCacheUpdate(state);
+            }
+
+            return state.Value;
+        }
+
+        private async Task RunCacheUpdate(CacheState state)
+        {
+            try
+            {
+                await using var context = _contextFactory.CreateContext(false);
+                var set = context.Set<T>();
+                var value = await state.Getter(set);
+                state.Value = value;
+                state.LastRetrieval = DateTime.Now;
+            }
+            catch (Exception ex)
+            {
+                _logger.LogError(ex, "Could not get cached value for {key}", state.Key);
+            }
+        }
+    }
+}