using System;
using Microsoft.Practices.EnterpriseLibrary.Caching;

namespace Website.Caching
{
    public abstract class CacheBase
    {
        private const string KEY_FORMAT = "{0}_{1}";

        protected internal readonly ICacheManager cache;
        private readonly string prefix;

        protected CacheBase(string prefix) : this(null, prefix)
        {
        }
        protected CacheBase(ICacheManager cache, string prefix)
        {
            if (cache == null)
            {
                // Try to get the default cache manager
                cache = CacheFactory.GetCacheManager();
                
                // If it's still null, bail out now
                if (cache == null)
                    throw new ArgumentNullException("cache", 
                        "No cache manager was provided! Try configuring a Default Cache manager");
            }

            this.cache = cache;
            this.prefix = prefix;
        }

        protected object this[string key]
        {
            get
            {
                var customKey = GetCustomKey(key);
                return cache.Contains(customKey) ? cache[customKey] : null;
            }
            set
            {
                // You can't set an empty key!
                if (string.IsNullOrEmpty(key))
                    return;

                var customKey = GetCustomKey(key);
                // See if we've got anything in there now
                if (cache.Contains(customKey))
                    cache.Remove(customKey);

                // Can only cache non-null values
                if (value != null)
                    cache.Add(customKey, value);
            }
        }

        public void ClearCachedItems()
        {
            cache.Flush();
        }

        protected internal string GetCustomKey(string key)
        {
            if (string.IsNullOrEmpty(key))
                throw new ArgumentNullException("key", "Cache keys can not be null or empty!");
                
            return string.Format(KEY_FORMAT, prefix, key);
        }
    }

    public abstract class CacheBase<T> : CacheBase
    {
        protected CacheBase(ICacheManager cache, string prefix)
            : base(cache, prefix)
        {
        }

        protected new T this[string key]
        {
            get { return (T)base[key]; }
            set { base[key] = value; }
        }
        
    }
}