CacheExtentions

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Caching;

namespace Core.Web {
    /// <summary>
    /// Extra syntax sugar for System.Web.Caching.Cache
    /// </summary>
    public static class CacheExtentions {

        /// <summary>
        /// Gets a cache value by key, if value is null then return will be the defaultValue
        /// </summary>
        /// <typeparam name="T">Type of Item in the value</typeparam>
        /// <param name="cache"></param>
        /// <param name="key"></param>
        /// <param name="defaultValue">value if value is null</param>
        /// <returns>Cached item or default value</returns>
        public static T Get<T>(this Cache cache,string key,T defaultValue = default(T)) {

            object raw = cache[key];
            if(raw == null)
                return defaultValue;

            return (T)Convert.ChangeType(raw,typeof(T));
        }

        /// <summary>
        /// TryGet pattern for cache
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="cache"></param>
        /// <param name="key"></param>
        /// <param name="cacheValue"></param>
        /// <returns></returns>
        public static bool TryGet<T>(this Cache cache,string key,out T cacheValue) {

            object raw = cache[key];
            if(raw == null) {
                cacheValue = default(T);
                return false;
            }

            cacheValue = (T)Convert.ChangeType(raw,typeof(T));

            return cacheValue != null;
        }

        /// <summary>
        /// Adds the cached item via the returnValueFunc() delegate to insert/replace the results into the cache
        /// </summary>
        public static void AddOrUpdate<T>(this Cache cache
            ,string key
            ,Func<T> returnValueFunc
            ,CacheDependency dependencies = null
            ,DateTime? absoluteExpiration = null
            ,TimeSpan? slidingExpiration = null
            ,CacheItemPriority priority = CacheItemPriority.Normal
            ,CacheItemRemovedCallback onRemoveCallback = null,bool enabled = true) {

            object raw = null;
            if(enabled)
                raw = cache[key];

            if(raw == null) {
                if(returnValueFunc == null)
                    return;

                T item = returnValueFunc();

                if(enabled)
                    cache.Insert(key,item
                        ,dependencies
                        ,absoluteExpiration.HasValue ? absoluteExpiration.Value : Cache.NoAbsoluteExpiration
                        ,slidingExpiration.HasValue ? slidingExpiration.Value : Cache.NoSlidingExpiration
                        ,priority
                        ,onRemoveCallback);

                return;
            }
        }
        /// <summary>
        /// Returns the cached item or call the returnValueFunc() delegate to insert the results into the cache
        /// </summary>
        /// <returns>Cached Item or Item return from the  returnValueFunc delegate</returns>
        public static T GetOrAdd<T>(this Cache cache
            ,string key
            ,Func<T> returnValueFunc
            ,CacheDependency dependencies = null
            ,DateTime? absoluteExpiration = null
            ,TimeSpan? slidingExpiration = null
            ,CacheItemPriority priority = CacheItemPriority.Normal
            ,CacheItemRemovedCallback onRemoveCallback = null,bool enabled = true) {

            object raw = null;
            if(enabled)
                raw = cache[key];

            if(raw == null) {
                if(returnValueFunc == null)
                    return default(T);

                T item = returnValueFunc();

                if(enabled)
                    cache.Insert(key,item
                        ,dependencies
                        ,absoluteExpiration.HasValue ? absoluteExpiration.Value : Cache.NoAbsoluteExpiration
                        ,slidingExpiration.HasValue ? slidingExpiration.Value : Cache.NoSlidingExpiration
                        ,priority
                        ,onRemoveCallback);

                return item;
            }
            else {
                return (T)Convert.ChangeType(raw,typeof(T));
            }
        }
    }
}