using System.IO.Compression;
using System.Web;
using System.Web.Mvc;

namespace Website.Filters
{
    public class CompressableAttribute : ActionFilterAttribute
    {
        private bool _enabled = Parse.AppSetting<bool>("EnableContentCompression");
        public bool Enabled
        {
            get { return _enabled; }
            set { _enabled = value; }
        }

        public override void OnActionExecuting(ActionExecutingContext filterContext)
        {
            // Check first to see if we should even think about compressing 
            // this request at all.  If not, just return now.
            if(!Enabled) 
                return;

            var response = filterContext.HttpContext.Response;
            switch (GetCompressionType(filterContext.HttpContext.Request))
            {
                case(CompressionType.Deflate):
                    response.AppendHeader("Content-encoding", "deflate");
                    response.Filter = new DeflateStream(response.Filter, CompressionMode.Compress);
                    break;
                case(CompressionType.GZip):
                    response.AppendHeader("Content-encoding", "gzip");
                    response.Filter = new GZipStream(response.Filter, CompressionMode.Compress);
                    break;
            }
        }

        private static CompressionType GetCompressionType(HttpRequestBase request)
        {
            // Get the type of compression (if any) the client has given us.
            var acceptedEncodings = (request.ServerVariables["HTTP_ACCEPT_ENCODING"] ?? string.Empty).ToLowerInvariant();

            // If we didn't get anything, just bail out now.
            if (string.IsNullOrEmpty(acceptedEncodings))
                return CompressionType.None;

            // Otherwise, try to figure out if it's a compression type we know about...
            var compressionType = CompressionType.None;

            // Look at the header value(s) and see if they match anything we're looking for
            if (acceptedEncodings.Contains("gzip") || acceptedEncodings.Contains("*"))
                compressionType = CompressionType.GZip;
            else if (acceptedEncodings.Contains("deflate"))
                compressionType = CompressionType.Deflate;

            return compressionType;
        }

        enum CompressionType
        {
            Deflate,
            GZip,
            None
        }
    }

}