Ombi/src/Ombi.Helpers/MediaCacheService.cs

using System;
using System.Collections.Generic;
using System.Threading.Tasks;
using LazyCache;
using Microsoft.Extensions.Caching.Memory;

namespace Ombi.Helpers
{
    public interface IMediaCacheService
    {
        Task<T> GetOrAddAsync<T>(string cacheKey, System.Func<Task<T>> factory, DateTimeOffset absoluteExpiration = default);
        Task Purge();
    }
    public class MediaCacheService : CacheService, IMediaCacheService
    {
        private const string CacheKey = "MediaCacheServiceKeys";

        public MediaCacheService(IMemoryCache memoryCache) : base(memoryCache)
        {
        }

        public async override Task<T> GetOrAddAsync<T>(string cacheKey, System.Func<Task<T>> factory, DateTimeOffset absoluteExpiration = default)
        {
            if (absoluteExpiration == default)
            {
                absoluteExpiration = DateTimeOffset.Now.AddHours(1);
            }

            if (_memoryCache.TryGetValue<T>($"MediaCacheService_{cacheKey}", out var result))
            {
                return (T)result;
            }

            // Not in the cache, so add this Key into our MediaServiceCache
            UpdateLocalCache(cacheKey);

            return await _memoryCache.GetOrCreateAsync<T>(cacheKey, entry =>
            {
                entry.AbsoluteExpiration = absoluteExpiration;
                return factory();
            });
        }

        private void UpdateLocalCache(string cacheKey)
        {
            var mediaServiceCache = _memoryCache.Get<List<string>>(CacheKey);
            if (mediaServiceCache == null)
            {
                mediaServiceCache = new List<string>();
            }
            mediaServiceCache.Add(cacheKey);
            _memoryCache.Remove(CacheKey);
            _memoryCache.Set(CacheKey, mediaServiceCache);
        }

        public Task Purge()
        {
            var keys = _memoryCache.Get<List<string>>(CacheKey);
            if (keys == null)
            {
                return Task.CompletedTask;
            }
            foreach (var key in keys)
            {
                base.Remove(key);
            }
            return Task.CompletedTask;
        }

    }
}