Implemented theme crud and basic theme loading

Moonlight.Api/Services/FrontendService.cs

@@ -0,0 +1,50 @@
+using Microsoft.EntityFrameworkCore;
+using Microsoft.Extensions.Caching.Memory;
+using Microsoft.Extensions.Options;
+using Moonlight.Api.Configuration;
+using Moonlight.Api.Database;
+using Moonlight.Api.Database.Entities;
+using Moonlight.Api.Models;
+
+namespace Moonlight.Api.Services;
+
+public class FrontendService
+{
+    private readonly IMemoryCache Cache;
+    private readonly DatabaseRepository<Theme> ThemeRepository;
+    private readonly IOptions<FrontendOptions> Options;
+    
+    private const string CacheKey = $"Moonlight.{nameof(FrontendService)}.{nameof(GetConfigurationAsync)}";
+
+    public FrontendService(IMemoryCache cache, DatabaseRepository<Theme> themeRepository, IOptions<FrontendOptions> options)
+    {
+        Cache = cache;
+        ThemeRepository = themeRepository;
+        Options = options;
+    }
+
+    public async Task<FrontendConfiguration> GetConfigurationAsync()
+    {
+        if (Cache.TryGetValue(CacheKey, out FrontendConfiguration? value))
+        {
+            if (value != null)
+                return value;
+        }
+
+        var theme = await ThemeRepository
+            .Query()
+            .FirstOrDefaultAsync(x => x.IsEnabled);
+
+        var config = new FrontendConfiguration("Moonlight", theme?.CssContent);
+
+        Cache.Set(CacheKey, config, TimeSpan.FromMinutes(Options.Value.CacheMinutes));
+
+        return config;
+    }
+
+    public Task ResetCacheAsync()
+    {
+        Cache.Remove(CacheKey);
+        return Task.CompletedTask;
+    }
+}