StaticAssetResolver.cs

using System.Diagnostics;
using System.IO;
using System.Web.Caching;
using Newtonsoft.Json;;

namespace Sitecore.StaticAssets.Infrastructure
{
  public class StaticAssetResolver
  {
    private readonly string _assetsJsonPath;
    private readonly Cache _cache;

    private const string CacheKey = "assetsJsonDictionary";

    public StaticAssetResolver(string assetsJsonPath, Cache cache)
    {
      _assetsJsonPath = assetsJsonPath;
      _cache = cache;
    }

    public string GetActualPath(string assetPath)
    {
      var assets = _cache.Get(CacheKey) as AssetCollection;
      
      if (assets == null)
      {
        assets = GetAssetsFromFile();
        _cache.Insert(CacheKey, assets, new CacheDependency(assetsJsonPath));
        
        Trace.TraceInformation("Assets cache miss");
      }
      else
      {
        Trace.TraceInformation("Assets cache hit");
      }
      
      return assets[assetPath];
    }

    private AssetCollection GetAssetsFromFile()
    {
      return JsonConvert.DeserializeObject<AssetCollection>(File.ReadAllText(_assetsJsonPath));
    }
  }
}