using System;
using System.Diagnostics;
using System.IO;
using System.Runtime.Serialization.Formatters.Binary;
using System.Security.Cryptography;
using System.Text;
using System.Web.Caching;
using MongoDB.Driver;
using SN.Setting;

namespace SN.Caching.OutputCaching
{
    public class DocumentDatabaseOutputCacheProvider: OutputCacheProvider
    {
        readonly MongoCollection _cacheItems;

        public DocumentDatabaseOutputCacheProvider()
        {
            MongoServerSettings settings = new MongoServerSettings { Server = new MongoServerAddress(Settings.Instance.Get("Caching.OutputCache", "MongoDBName"), 27017) };
            MongoServer server = new MongoServer(settings);


            MongoDatabase mongo = server.GetDatabase("OutputCacheDB");
            _cacheItems = mongo.GetCollection("CacheItems");
        }

        public override  object Get(string key)
        {
            Debug.WriteLine(string.Format("Cache.Get({0})", key));

            key = Md5(key);

            var query = MongoDB.Driver.Builders.Query.EQ("_id", key);

            var cacheItem = _cacheItems.FindOneAs<CacheItem>(query);

            if (cacheItem != null)
            {
                if (cacheItem.Expiration.ToUniversalTime() <= DateTime.UtcNow)
                {
                    _cacheItems.Remove(query);
                }
                else
                {
                    return Deserialize(cacheItem.Item);
                }
            }

            return null;
        }

        public override object Add(string key, object entry, DateTime utcExpiry)
        {
            Debug.WriteLine("Cache.Add({0}, {1}, {2})", key, entry, utcExpiry);

            key = Md5(key);

            if (utcExpiry == DateTime.MaxValue)
                utcExpiry = DateTime.UtcNow.AddMinutes(5);

            var query = MongoDB.Driver.Builders.Query.EQ("_id", key);

            var cacheItem = _cacheItems.FindOneAs<CacheItem>(query);

            if (cacheItem != null)
            {
                if (cacheItem.Expiration.ToUniversalTime() <= DateTime.UtcNow)
                {
                    _cacheItems.Remove(query);
                }
                else
                {
                    return Deserialize(cacheItem.Item);
                }
            }

            _cacheItems.Insert(new CacheItem
            {
                Id = key,
                Item = Serialize(entry),
                Expiration = utcExpiry
            });

            return entry;
        }

        public override void Set(string key, object entry, DateTime utcExpiry)
        {
            Debug.WriteLine("Cache.Set({0}, {1}, {2})", key, entry, utcExpiry);

            key = Md5(key);

            var query = MongoDB.Driver.Builders.Query.EQ("_id", key);

            var cacheItem = _cacheItems.FindOneAs<CacheItem>(query);

            if (cacheItem != null)
            {
                cacheItem.Item = Serialize(entry);
                cacheItem.Expiration = utcExpiry;
                _cacheItems.Save(cacheItem);
            }
            else
            {
                _cacheItems.Insert(new CacheItem
                {
                    Id = key,
                    Item = Serialize(entry),
                    Expiration = utcExpiry
                });
            }
        }

        public override void Remove(string key)
        {
            Debug.WriteLine("Cache.Remove({0})", key);

            var query = MongoDB.Driver.Builders.Query.EQ("_id", key);


            _cacheItems.Remove(query);
        }

        private static string Md5(string value)
        {
            var cryptoServiceProvider = new MD5CryptoServiceProvider();
            var bytes = Encoding.UTF8.GetBytes(value);
            var builder = new StringBuilder();

            bytes = cryptoServiceProvider.ComputeHash(bytes);

            foreach (var b in bytes)
                builder.Append(b.ToString("x2").ToLower());

            return builder.ToString();
        }

        private static byte[] Serialize(object entry)
        {
            var formatter = new BinaryFormatter();
            var stream = new MemoryStream();
            formatter.Serialize(stream, entry);

            return stream.ToArray();
        }

        private static object Deserialize(byte[] serializedEntry)
        {
            var formatter = new BinaryFormatter();
            var stream = new MemoryStream(serializedEntry);

            return formatter.Deserialize(stream);
        }


    }
}