using System;
using System.Configuration;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using ChadSoft.Web.ResponseFilters;

namespace ChadSoft.Web.Modules
{
    public class PluggableNavigationModule : IHttpModule
    {
        private static Control _NavigationControl;
        public static Control NavigationControl
        {
            get 
            {
                if (_NavigationControl == null)
                    _NavigationControl = createNavigationControl();
                return _NavigationControl;
            }
        }

        public void Init(HttpApplication context)
        {
            context.PostReleaseRequestState += context_PostReleaseRequestState;
        }

        public void Dispose() {  }

        static void context_PostReleaseRequestState(object sender, EventArgs e)
        {
            RenderNavigation((HttpApplication)sender);
        }

        private static void RenderNavigation(HttpApplication app)
        {
            app.Response.Filter = new PluggableNavigationResponseFilter(
                app.Response.Filter, NavigationControl);
        }

        private static Control createNavigationControl()
        {
            var controlTypeName = ConfigurationManager.
                AppSettings["PluggableNavigation.NavigationControlType"];

            if (string.IsNullOrEmpty(controlTypeName))
                return new ErrorMessage(ErrorType.EmptyTypeName);

            var controlType = Type.GetType(controlTypeName, false);
            if (controlType == null)
                return new ErrorMessage(ErrorType.InvalidTypeName);

            var control = Activator.CreateInstance(controlType) as Control;
            return control ?? new ErrorMessage(ErrorType.CouldNotCreateInstance);
        }


        enum ErrorType
        {
            EmptyTypeName,
            InvalidTypeName,
            CouldNotCreateInstance
        }

        private class ErrorMessage : Label
        {
            private readonly ErrorType _error;

            public ErrorMessage(ErrorType error)
            {
                _error = error;

                Style["color"] = "red";
                Style["font-size"] = "large";
                Style["font-weight"] = "bold";
            }

            public override string Text
            {
                get
                {
                    var text = string.Empty;

                    // TODO: It'd probably be nice if these messages were resources...
                    switch (_error)
                    {
                        case (ErrorType.EmptyTypeName):
                            text = "The PluggableNavigationModule has been activated, however you did not specify a control type to be used as the navigation control.  Please specify the type name in the 'PluggableNavigation.NavigationControlType' AppSetting or remove this module.";
                            break;
                        case (ErrorType.InvalidTypeName):
                            text = "The PluggableNavigation.NavigationControlType you specified is invalid or cannot be found.";
                            break;
                        case (ErrorType.CouldNotCreateInstance):
                            text = "Unable to create an instance of the PluggableNavigation.NavigationControlType you specified (however we were able to find its Type).";
                            break;
                    }

                    return text;
                }
                set { }
            }

        }
    }
}