using System;

using System.Collections.Generic;

using System.Diagnostics;

using System.IO;

using System.Xml.Linq;

using System.Xml.XPath;

using System.Reflection;



namespace SharpObjects.EventBus

{

    public static class EventBusManager

    {

        public const string guid = "_{313DD131-BA38-4370-B301-44110922F64B}";

        public const string EventBusId = "event_bus" + guid;



        public const string ConfigurationFileName = "SharpObjects.EventBus.config";

        public const string EventBusDescriptorFileName = "SharpObjects.EventBusDescriptor.json";

        private const string SharpObjectsApplicationFolderTemplate = "{0}\\SharpObjects\\";



        private static EventBusDescirptor eventBusDescriptor = null;

        private static IEventBus eventBusInstance = null;



        public static IEventBus EventBus

        {

            get

            {

                if (System.Web.HttpContext.Current == null)

                {

                    if(eventBusInstance == null)

                    {

                        Initialize();

                    }



                    return eventBusInstance;

                }

                else

                {

                    if (eventBusDescriptor.IsApplicationWide)

                    {



                        IEventBus eventBus = (IEventBus)System.Web.HttpContext.Current.Application[EventBusId];



                        if(eventBus == null)

                        {

                            Initialize();

                        }



                        return (IEventBus)System.Web.HttpContext.Current.Application[EventBusId];

                    }

                    else

                    {

                        IEventBus eventBus = (IEventBus)System.Web.HttpContext.Current.Session[EventBusId];



                        if(eventBus == null)

                        {

                            Initialize();

                        }



                        return (IEventBus)System.Web.HttpContext.Current.Session[EventBusId];

                    }

                }  

            }

        }



        private static void SetEventBus(IEventBus eventBus)

        {

            if (System.Web.HttpContext.Current == null)

            {

                eventBusInstance = eventBus;

            }

            else

            {

                if(eventBusDescriptor.IsApplicationWide)

                {

                    System.Web.HttpContext.Current.Application[EventBusId] = eventBus;

                }

                else

                {

                    System.Web.HttpContext.Current.Session[EventBusId] = eventBus;

                }

            }        

        }



        /*

        SharpObjects.EventBus.config file format:



        <?xml version="1.0" encoding="utf-8" ?>

        <configuration>

          <event_bus>

            <assembly>SharpObjects.EventBus.dll</assembly>

            <type>SharpObjects.EventBus.EventBus</type>

            <!-- arguments to pass to the constructor if any -->

            <arguments>

            </arguments>

                <argiment>argument 1</argument>

                <argiment>argument 2</argument>

          </event_bus>

        </configuration>

        

        

        SharpObjects.EventBusDescriptor.json file sample:

        

        {

	        "AssemblyPath":"SharpObjects.EventBus.dll",

	        "TypeName":"SharpObjects.EventBus.EventBus",

	        "Arguments":null

        }

        

        */



        static void Initialize()

        {

            string location = "SharpObjects.EventBus.EventBusFactory()";



            try

            {

                eventBusDescriptor = new EventBusDescirptor()

                                         {

                                             AssemblyPath = "SharpObjects.EventBus.dll",

                                             TypeName = "SharpObjects.EventBus.EventBus"

                                         };

                SetEventBus(new EventBus());

                



                Assembly currentAssembly = Assembly.GetExecutingAssembly();



                if(currentAssembly != null)

                {

                    string configFilePath = currentAssembly.Location;

                    string assemblyDirectory = Path.GetDirectoryName(configFilePath);

                    configFilePath = assemblyDirectory + "\\" + ConfigurationFileName;

                    string eventBusDescriptorFilePath = assemblyDirectory + "\\" + EventBusDescriptorFileName;





                    if(File.Exists(eventBusDescriptorFilePath))

                    {

                        eventBusDescriptor = GetEventBusDescriptorFromJsonDescriptor(eventBusDescriptorFilePath,

                                                                                     assemblyDirectory);    

                    }



                    if (eventBusDescriptor == null && File.Exists(configFilePath))

                    {

                        eventBusDescriptor = GetEventBusDescriptorFromXmlConfigFile(configFilePath, assemblyDirectory);

                    }



                    if (eventBusDescriptor != null)

                    {

                        Assembly assembly = Assembly.LoadFrom(eventBusDescriptor.AssemblyPath);



                        if (assembly == null)

                        {

                            return;

                        }



                        Type type = assembly.GetType(eventBusDescriptor.TypeName);



                        if (type == null)

                        {

                            return;

                        }



                        IEventBus eventBus = (IEventBus)Activator.CreateInstance(type, eventBusDescriptor.Arguments);

                        SetEventBus(eventBus);

                    }

                }

            }

            catch (Exception ex)

            {

                string message = string.Format("SharpObjects.EventBus ERROR.\nLOCATION:{0}\n\n {1}\n\nSTACK TRACE:\n\n{2}",

                                               location, ex.Message, ex.StackTrace);

                EventLog.WriteEntry("SharpObjects", message , EventLogEntryType.Error);

            }

        }



        private static EventBusDescirptor GetEventBusDescriptorFromJsonDescriptor(string eventBusDescriptorFilePath, string assemblyDirectory)

        {

            string location = "SharpObjects.EventBus.GetEventBusDescriptorFromJsonDescriptor()";



            try

            {

                string json = File.ReadAllText(eventBusDescriptorFilePath);

                EventBusDescirptor eventBusDescriptor =

                    (EventBusDescirptor) JsonSerialization.Deserialize<EventBusDescirptor>(json);



                if (!Path.IsPathRooted(eventBusDescriptor.AssemblyPath))

                {

                    eventBusDescriptor.AssemblyPath = assemblyDirectory + "\\" + eventBusDescriptor.AssemblyPath;

                }



                if (!File.Exists(eventBusDescriptor.AssemblyPath))

                {

                    return null;

                }



                return eventBusDescriptor;

            }

            catch (Exception ex)

            {

                string message = string.Format("SharpObjects.EventBus ERROR.\nLOCATION:{0}\n\n {1}\n\nSTACK TRACE:\n\n{2}",

                                               location, ex.Message, ex.StackTrace);

                EventLog.WriteEntry("SharpObjects", message, EventLogEntryType.Error);

            }



            return null;

        }



        private static EventBusDescirptor GetEventBusDescriptorFromXmlConfigFile(string configFilePath, string assemblyDirectory)

        {

            string location = "SharpObjects.EventBus.GetEventBusDescriptorFromXmlConfigFile()";



            try

            {

                EventBusDescirptor eventBusDescirptor = new EventBusDescirptor();



                XElement root = XElement.Load(configFilePath);



                XElement assemblyElement = root.XPathSelectElement("/event_bus/assembly");

                XElement typeElement = root.XPathSelectElement("/event_bus/type");

                XElement isApplicationwideElement = root.XPathSelectElement("/event_bus/is_applicatoinwide");



                if (assemblyElement == null || typeElement == null)

                {

                    return null;

                }



                string assemblyPath = assemblyElement.Value.Trim();



                if (!Path.IsPathRooted(assemblyPath))

                {

                    assemblyPath = assemblyDirectory + "\\" + assemblyPath;

                }



                if (!File.Exists(assemblyPath))

                {

                    return null;

                }



                eventBusDescirptor.AssemblyPath = assemblyPath;

                eventBusDescirptor.TypeName = typeElement.Value.Trim();



                if(isApplicationwideElement != null)

                {

                    if(isApplicationwideElement.Value.Trim().ToLower() == "false")

                    {

                        eventBusDescirptor.IsApplicationWide = false;

                    }

                }



                IEnumerable<XElement> argumentCollection =

                    root.XPathSelectElements("/event_bus/arguments/argument");

                List<object> argumentList = new List<object>();

                argumentList.AddRange(argumentCollection);



                if (argumentList.Count > 0)

                {

                    foreach (XElement argumentElement in argumentCollection)

                    {

                        argumentList.Add(argumentElement.Value);

                    }



                    eventBusDescirptor.Arguments = argumentList.ToArray();

                }



                return eventBusDescirptor;

            }

            catch (Exception ex)

            {

                string message = string.Format("SharpObjects.EventBus ERROR.\nLOCATION:{0}\n\n {1}\n\nSTACK TRACE:\n\n{2}",

                                               location, ex.Message, ex.StackTrace);

                EventLog.WriteEntry("SharpObjects", message, EventLogEntryType.Error);

            }



            return null;

        }



    }

}