namespace Epic.Infrastructure {
    using System;
    using System.Linq;
    using Nancy;
    using Nancy.ErrorHandling;
    using Nancy.ViewEngines;

    public class EpicErrorHandler : CustomRazorErrorHandler {
        public EpicErrorHandler(IViewFactory factory, IViewLocationCache cache) : base(factory, cache) {}

        public override bool HandlesStatusCode(HttpStatusCode statusCode, NancyContext context) {
            return statusCode == HttpStatusCode.NotFound || statusCode == HttpStatusCode.InternalServerError;
        }

        public override void Handle(HttpStatusCode statusCode, NancyContext context) {
            switch (statusCode) {
                case HttpStatusCode.NotFound:
                    RenderView(context, "404");
                    break;
                case HttpStatusCode.InternalServerError:
                    RenderView(context, "500");
                    break;
            }
            context.Response.StatusCode = statusCode;
        }
    }

    public abstract class CustomRazorErrorHandler : IErrorHandler {
        private readonly IViewLocationCache _cache;
        private readonly IViewFactory _factory;

        protected CustomRazorErrorHandler(IViewFactory factory, IViewLocationCache cache) {
            _factory = factory;
            _cache = cache;
        }

        #region IErrorHandler Members

        public abstract bool HandlesStatusCode(HttpStatusCode statusCode, NancyContext context);
        public abstract void Handle(HttpStatusCode statusCode, NancyContext context);

        #endregion

        protected void RenderView(NancyContext context, string viewName, dynamic model = null) {
            bool foundMatchingView = _cache.Any(x =>
                                                x.Name.Equals(viewName) &&
                                                x.Extension.Equals("cshtml", StringComparison.OrdinalIgnoreCase));

            if (foundMatchingView) {
                var viewContext = new ViewLocationContext {Context = context};

                context.Response = _factory.RenderView(viewName, model, viewContext);
            }
        }
    }
}