using System;
using System.Web;

namespace Umbraco.Core.Cache
{
    /// <summary>
    /// Class that is exposed by the ApplicationContext for application wide caching purposes
    /// </summary>
    public class CacheHelper
    {
        public static CacheHelper NoCache { get; } = new CacheHelper(NullCacheProvider.Instance, NullCacheProvider.Instance, NullCacheProvider.Instance, new IsolatedRuntimeCache(_ => NullCacheProvider.Instance));

        /// <summary>
        /// Creates a cache helper with disabled caches
        /// </summary>
        /// <returns></returns>
        /// <remarks>
        /// Good for unit testing
        /// </remarks>
        public static CacheHelper CreateDisabledCacheHelper()
        {
            // do *not* return NoCache
            // NoCache is a special instance that is detected by RepositoryBase and disables all cache policies
            // CreateDisabledCacheHelper is used in tests to use no cache, *but* keep all cache policies
            return new CacheHelper(NullCacheProvider.Instance, NullCacheProvider.Instance, NullCacheProvider.Instance, new IsolatedRuntimeCache(_ => NullCacheProvider.Instance));
        }

        /// <summary>
        /// Initializes a new instance for use in the web
        /// </summary>
        public CacheHelper()
            : this(
                new HttpRuntimeCacheProvider(HttpRuntime.Cache),
                new StaticCacheProvider(),
                new HttpRequestCacheProvider(),
                new IsolatedRuntimeCache(t => new ObjectCacheRuntimeCacheProvider()))
        {
        }

        /// <summary>
        /// Initializes a new instance for use in the web
        /// </summary>
        /// <param name="cache"></param>
        public CacheHelper(System.Web.Caching.Cache cache)
            : this(
                new HttpRuntimeCacheProvider(cache),
                new StaticCacheProvider(),
                new HttpRequestCacheProvider(),
                new IsolatedRuntimeCache(t => new ObjectCacheRuntimeCacheProvider()))
        {
        }


        /// <summary>
        /// Initializes a new instance based on the provided providers
        /// </summary>
        /// <param name="httpCacheProvider"></param>
        /// <param name="staticCacheProvider"></param>
        /// <param name="requestCacheProvider"></param>
        /// <param name="isolatedCacheManager"></param>
        public CacheHelper(
            IRuntimeCacheProvider httpCacheProvider,
            ICacheProvider staticCacheProvider,
            ICacheProvider requestCacheProvider,
            IsolatedRuntimeCache isolatedCacheManager)
        {
            if (httpCacheProvider == null) throw new ArgumentNullException("httpCacheProvider");
            if (staticCacheProvider == null) throw new ArgumentNullException("staticCacheProvider");
            if (requestCacheProvider == null) throw new ArgumentNullException("requestCacheProvider");
            if (isolatedCacheManager == null) throw new ArgumentNullException("isolatedCacheManager");
            RuntimeCache = httpCacheProvider;
            StaticCache = staticCacheProvider;
            RequestCache = requestCacheProvider;
            IsolatedRuntimeCache = isolatedCacheManager;
        }

        /// <summary>
        /// Returns the current Request cache
        /// </summary>
        public ICacheProvider RequestCache { get; internal set; }

        /// <summary>
        /// Returns the current Runtime cache
        /// </summary>
        public ICacheProvider StaticCache { get; internal set; }

        /// <summary>
        /// Returns the current Runtime cache
        /// </summary>
        public IRuntimeCacheProvider RuntimeCache { get; internal set; }

        /// <summary>
        /// Returns the current Isolated Runtime cache manager
        /// </summary>
        public IsolatedRuntimeCache IsolatedRuntimeCache { get; internal set; }

    }

}