using Microsoft.Practices.EnterpriseLibrary.Caching;

namespace Website.Caching
{
    /// <summary>
    /// A simple wrapper around any IContentProvider that provides caching of the information
    /// provided by that provider.
    /// </summary>
    public class CachingContentProvider : CacheBase<IContent>, IContentProvider
    {
        private const string CACHE_MANAGER_PREFIX = "ContentProvider";
        private const string ID_KEY_FORMAT = "ContentID_{0}";
        private static readonly object __CACHE_LOCK = new object();

        private readonly IContentProvider _provider;

        protected IContent this[int contentId]
        {
            get { return this[string.Format(ID_KEY_FORMAT, contentId)]; }
            set { this[string.Format(ID_KEY_FORMAT, contentId)] = value; }
        }

        public CachingContentProvider(IContentProvider provider) : this(provider, null)
        {
            
        }

        public CachingContentProvider(IContentProvider provider, ICacheManager cache)
            : base(cache, CACHE_MANAGER_PREFIX)
        {
            _provider = provider;
        }

        public IContent GetById(int id)
        {
            var content = this[id];
            if (content == null)
            {
                lock (__CACHE_LOCK)
                {
                    if (this[id] == null)
                        this[id] = _provider.GetById(id); 
                }
                content = this[id];
            }
            return content;
        }

        public IContent GetByAlias(string alias)
        {
            var content = this[alias];
            if (content == null)
            {
                lock (__CACHE_LOCK)
                {
                    if (this[alias] == null)
                        this[alias] = _provider.GetByAlias(alias); 
                }
                content = this[alias];
            }
            return content;
        }

        public void Save(IContent content)
        {
            _provider.Save(content);

            lock (__CACHE_LOCK)
            {
                // Clear the cached version (if any) so that 
                // it is reloaded from the source on the next request
                this[content.ID] = null;
                
                if(!string.IsNullOrEmpty(content.Alias))
                    this[content.Alias] = null;
            }
        }
    }
}