using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Text;
using System.Xml;
using System.Xml.Schema;

namespace Wayne.Lib.Log
{
    /// <summary>
    /// The Log config handles the application-wide setup for the logging. It is read from a
    /// XML file that should be in accordance with the LogConfig.xsd schema.
    /// </summary>
    internal class LogConfig : IDisposable
    {
        #region Private Class LogConfigWrapper

        private class LogConfigWrapper
        {
            public LogConfigWrapper(LogConfig logConfig, XmlNode logConfigNode, string ns)
            {
                LogConfigBuilder = new LogConfigBuilder(logConfigNode, ns);

                foreach (LogConfigOutput output in LogConfigBuilder.Outputs)
                    LogWriters.Add(logConfig.GetLogWriter(LogConfigBuilder.Name, output));
            }

            public readonly LogConfigBuilder LogConfigBuilder;
            public readonly List<LogWriter> LogWriters = new List<LogWriter>();

            public override string ToString()
            {
                return LogConfigBuilder.ToString();
            }
        }

        #endregion

        #region Fields

        private bool disposed;
        private readonly string ns;
        private readonly System.Xml.Schema.XmlSchema schema;
        private readonly object configReadingLock = new object();
        private readonly Dictionary<EntityCategory, LogWriter[]> logWriterPreparedDict = new Dictionary<EntityCategory, LogWriter[]>();
        private readonly Dictionary<IIdentifiableEntity, Dictionary<object, EntityCategory>> cachedEntityCategoryDict = new Dictionary<IIdentifiableEntity, Dictionary<object, EntityCategory>>();

        private readonly List<LogWriter> createdLogWriters = new List<LogWriter>();
        private readonly List<LogConfigWrapper> logConfigWrappers = new List<LogConfigWrapper>();
        private readonly System.Threading.Timer cleaningTimer;

        #endregion

        #region Construction & Finalizer

        /// <summary>
        /// Initializes a new instance of the LogConfig class.
        /// </summary>
        internal LogConfig()
        {
            // Read the LogConfig.xsd file from an embedded resource stream and validate it.
            bool schemaValid = true;
            StringBuilder errors = new StringBuilder();

            using(var logConfigSchemaStream = Assemblies.GetManifestResourceStreamWithPartialName("LogConfig.xsd", System.Reflection.Assembly.GetExecutingAssembly()))
            {
                schema = XmlSchema.Read(logConfigSchemaStream,
                    (
                        delegate(object sender, ValidationEventArgs args)
                        {
                            Debug.WriteLine(args.Message);
                            if (args.Severity == XmlSeverityType.Error)
                            {
                                schemaValid = false;
                                errors.Append(args.Message);
                                errors.Append("\r\n");
                            }
                        }
                        ));
            }

            if ((schema == null) || !schemaValid)
            {
                Debug.WriteLine("Schema LogConfig was not valid!!!!");
                Debug.WriteLine(errors.ToString());
                throw new LogException(LogExceptionType.CorruptConfigSchemaFile, errors.ToString());
            }
            ns = schema.TargetNamespace;
            cleaningTimer = new System.Threading.Timer(PerformListCleaning, null, 120000, 120000); // Every second minute.
        }

        /// <summary>
        /// Finalizer.
        /// </summary>
        ~LogConfig()
        {
            Dispose(false);
        }

        #endregion

        #region IDisposable Members

        /// <summary>
        /// Disposes the LogConfig's resources.
        /// </summary>
        public void Dispose()
        {
            Dispose(true);
            GC.SuppressFinalize(this);
        }

        /// <summary>
        /// Internal dispose method.
        /// </summary>
        /// <param name="disposing"></param>
        private void Dispose(bool disposing)
        {
            if (!disposed)
            {
                disposed = true;
                if (disposing)
                {
                    lock (configReadingLock)
                    {
                        CloseAllLogWritersLocked("Shutting down logger.");
                    }
                    cleaningTimer.Dispose();
                }
            }
        }

        #endregion

        #region Properties

        public bool IsConfigured
        {
            get { return logConfigWrappers.Count > 0; }
        }

        #endregion

        #region Methods: Refresh

        /// <summary>
        /// Refreshes the log configuration from the configuration xml file.
        /// </summary>
        /// <param name="configFiles">A list of config files (the file is in the form of a string[]).</param>
        /// <param name="leftoverLogLinesConfigOutputList"></param>
        /// <param name="leftoverLogEntitiesConfigOutputList"></param>
        /// <exception cref="Exception">If no log configuration file is specified.</exception>
        /// <exception cref="Exception">If the specified log configuration file is missing.</exception>
        /// <exception cref="Exception">If the log configuration file is invalid.</exception>
        internal void Refresh(List<string[]> configFiles, LogConfigOutput[] leftoverLogLinesConfigOutputList, LogConfigOutput[] leftoverLogEntitiesConfigOutputList)
        {
            if (disposed)
                return;

            lock (configReadingLock)
            {
                CloseAllLogWritersLocked("Configuration Refreshed.");

                logConfigWrappers.Clear();
                foreach (string[] configFile in configFiles)
                {
                    XmlDocument logConfigXml = new XmlDocument();

                    // Load and validate the config file.
                    bool valid = true;
                    try
                    {
                        logConfigXml.Schemas.Add(schema);
                        logConfigXml.LoadXml(string.Join("\r\n", configFile));
                        if (logConfigXml.DocumentElement != null)
                        {
                            XmlAttribute namespaceAttribute = logConfigXml.DocumentElement.Attributes["xmlns"];
                            if ((namespaceAttribute == null) || !namespaceAttribute.Value.Equals(schema.TargetNamespace, StringComparison.InvariantCultureIgnoreCase))
                            {
                                System.Diagnostics.Debug.WriteLine(string.Concat("The log config XML doesn't have the correct namespace. Wanted: \"", schema.TargetNamespace, "\", was: \"", namespaceAttribute.Value, "\""));
                                valid = false;
                            }
                            else
                            {
                                logConfigXml.Validate((
                                    delegate(object sender, System.Xml.Schema.ValidationEventArgs args)
                                    {
                                        System.Diagnostics.Debug.WriteLine(args.Message);
                                        valid = false;
                                    }));
                            }
                        }
                    }
                    catch (XmlException) { }
                    if (!valid)
                        throw new LogException(LogExceptionType.InvalidLogConfigFile, string.Join("\r\n", configFile));

                    XmlNode logConfigFileNode = logConfigXml["LogConfigFile", ns];
                    if (logConfigFileNode != null)
                    {
                        foreach (XmlNode logConfigNode in logConfigFileNode.ChildNodes)
                        {
                            if ((logConfigNode.NodeType == XmlNodeType.Element) && (logConfigNode.LocalName == "LogConfig"))
                            {
                                XmlAttribute enabledAttribute = logConfigNode.Attributes["Enabled"];
                                if ((enabledAttribute != null) && !XmlConvert.ToBoolean(enabledAttribute.Value))
                                    continue;
                                logConfigWrappers.Add(new LogConfigWrapper(this, logConfigNode, ns));
                            }
                        }
                    }
                }               
            }
        }

        /// <summary>
        /// Closes all LogWriters. NOTE! Must be called under the lock of configReadingLock!
        /// </summary>
        /// <param name="reason"></param>
        private void CloseAllLogWritersLocked(string reason)
        {
            // Empty the buffered log writers.
            foreach (LogWriter logWriter in createdLogWriters)
                logWriter.Dispose(reason);

            // Clear all lists and dictionaries.
            createdLogWriters.Clear();
            logWriterPreparedDict.Clear();
            cachedEntityCategoryDict.Clear();
        }

        #endregion

        #region Methods: GetLogWriters

        /// <summary>
        /// Returns a list of log writers to be used with the specified identifiable entity.
        /// </summary>
        /// <param name="entityCategory"></param>
        /// <returns></returns>
        internal LogWriter[] GetLogWriters(EntityCategory entityCategory)
        {
            if (disposed)
                return new LogWriter[0];

            LogWriter[] cachedLogWriters;
            lock (configReadingLock)
            {
                if (!logWriterPreparedDict.TryGetValue(entityCategory, out cachedLogWriters))
                {
                    List<LogWriter> logWriterList = new List<LogWriter>();

                    foreach (LogConfigWrapper logConfigWrapper in logConfigWrappers)
                    {
                        DebugLogLevel debugLogLevel;
                        if (logConfigWrapper.LogConfigBuilder.MatchFilter(entityCategory, out debugLogLevel))
                        {
                            foreach (LogWriter logWriter in logConfigWrapper.LogWriters)
                            {
                                if (!logWriterList.Contains(logWriter))
                                {
                                    logWriter.CacheFilterData(entityCategory, debugLogLevel);
                                    logWriterList.Add(logWriter);
                                }
                            }                    
                        }
                    }

                    cachedLogWriters = logWriterList.ToArray();
					if(!logWriterPreparedDict.ContainsKey(entityCategory))
					{
						logWriterPreparedDict.Add(entityCategory, cachedLogWriters);
					}
                }
            }
            return cachedLogWriters;
        }

        /// <summary>
        /// Get all active log writers.
        /// </summary>
        /// <returns></returns>
        internal LogWriter[] GetLogWriters()
        {
            if (disposed)
                return new LogWriter[0];

            lock (configReadingLock)
            {
                return createdLogWriters.ToArray();
            }
        }

        #endregion

        #region Methods: GetLogWriter

        /// <summary>
        /// Get (or creates) the appropriate logwriter depending on the output type and the output parameters.
        /// </summary>
        private LogWriter GetLogWriter(string logName, LogConfigOutput output)
        {
            if (disposed)
                return null;

            LogConfigTextFileOutput logConfigTextFileOutput = output as LogConfigTextFileOutput;
            if (logConfigTextFileOutput != null)
            {
                foreach (LogWriter createdLogWriter in createdLogWriters)
                {
                    TextFileLogWriter textFileLogWriter = createdLogWriter as TextFileLogWriter;
                    if ((textFileLogWriter != null) && textFileLogWriter.LogConfigTextFilePath.Equals(logConfigTextFileOutput.LogConfigTextFilePath))
                        return textFileLogWriter;
                }
                TextFileLogWriter newLogWriter = new TextFileLogWriter(logName, logConfigTextFileOutput);
                createdLogWriters.Add(newLogWriter);
                return newLogWriter;
            }


            LogConfigEventLogSubscriptionOutput logConfigEventLogSubscriptionOutput = output as LogConfigEventLogSubscriptionOutput;
            if (logConfigEventLogSubscriptionOutput != null)
            {
                foreach (LogWriter createdLogWriter in createdLogWriters)
                {
                    EventLogSubscriptionLogWriter eventSubscriberSupplierLogWriter = createdLogWriter as EventLogSubscriptionLogWriter;
                    if ((eventSubscriberSupplierLogWriter != null) &&
                        (eventSubscriberSupplierLogWriter.SubscriberId.Equals(logConfigEventLogSubscriptionOutput.SubscriberId)) &&
                        (eventSubscriberSupplierLogWriter.StorageType.Equals(logConfigEventLogSubscriptionOutput.StorageType))
                        )
                    {
                        return eventSubscriberSupplierLogWriter;
                    }
                }
                EventLogSubscriptionLogWriter newLogWriter = new EventLogSubscriptionLogWriter(logName, logConfigEventLogSubscriptionOutput);
                createdLogWriters.Add(newLogWriter);
                return newLogWriter;
            }


            LogConfigExternalLogWriterOutput logConfigExternalLogWriterOutput = output as LogConfigExternalLogWriterOutput;
            if (logConfigExternalLogWriterOutput != null)
            {
                foreach (LogWriter createdLogWriter in createdLogWriters)
                {
                    ExternalLogWriterWrapper externalLogWriter = createdLogWriter as ExternalLogWriterWrapper;
                    if ((externalLogWriter != null) &&
                        externalLogWriter.ExternalLogType.Equals(logConfigExternalLogWriterOutput.ExternalLogType, StringComparison.CurrentCultureIgnoreCase) &&
                        externalLogWriter.ExternalLogName.Equals(logConfigExternalLogWriterOutput.ExternalLogName, StringComparison.CurrentCultureIgnoreCase))
                    {
                        return externalLogWriter;
                    }
                }
                ExternalLogWriterWrapper newLogWriter = new ExternalLogWriterWrapper(logName, logConfigExternalLogWriterOutput);
                createdLogWriters.Add(newLogWriter);
                return newLogWriter;
            }

            return null;
        }

        #endregion

        #region Methods: Find Filter Nodes


        #endregion

        #region Methods: GetEntityCategory

        internal EntityCategory GetEntityCategory(IIdentifiableEntity entity, object category)
        {
            EntityCategory result = null;
            if (entity == null)
                entity = IdentifiableEntity.Empty;

            if (category == null)
                category = string.Empty;

            lock (configReadingLock)
            {
                //Dictionary<object, EntityCategory> entityCategoriesDict;
				//if (cachedEntityCategoryDict.TryGetValue(entity, out entityCategoriesDict))
				//{
					//if (!entityCategoriesDict.TryGetValue(category, out result))
					//{
                        result = new EntityCategory(entity, category);
					//    entityCategoriesDict[category] = result;
					//}
				//}
				//else
				//{
				//    result = new EntityCategory(entity, category);
				//    entityCategoriesDict = new Dictionary<object, EntityCategory>();
				//    entityCategoriesDict[category] = result;
				//    cachedEntityCategoryDict[entity] = entityCategoriesDict;
				//}
            }

            result.Touch();
            return result;
        }

        #endregion

        #region Methods: Cleaning of internal lists

        private void PerformListCleaning(object o)
        {
            lock (configReadingLock)
            {
                DateTime oldestAllowedTouch = DateTime.Now.AddMinutes(-5); // 5 minutes is the longest time an untouched EntityCategory is cached in the log library.

                #region Clean the logWriterPreparedDict and the cachedEntityCategoryDict.

                List<EntityCategory> entityCategoriesToRemove = new List<EntityCategory>();
                foreach (EntityCategory entityCategory in logWriterPreparedDict.Keys)
                {
                    if (entityCategory.LastTouched < oldestAllowedTouch)
                        entityCategoriesToRemove.Add(entityCategory);
                }

                //Remove from the dict.
                foreach (EntityCategory entityCategoryToRemove in entityCategoriesToRemove)
                {
                    logWriterPreparedDict.Remove(entityCategoryToRemove);

                    Dictionary<object, EntityCategory> entityCategoriesDict;
                    if (cachedEntityCategoryDict.TryGetValue(entityCategoryToRemove.Entity, out entityCategoriesDict))
                    {
                        entityCategoriesDict.Remove(entityCategoryToRemove.Category);
                        if (entityCategoriesDict.Count == 0)
                            cachedEntityCategoryDict.Remove(entityCategoryToRemove.Entity);
                    }
                }

                #endregion

                foreach (LogWriter logWriter in createdLogWriters)
                    logWriter.PerformListCleaning(oldestAllowedTouch);
            }
        }

        #endregion

        #region Methods: UnregisterEntity

        internal void UnregisterEntity(IIdentifiableEntity entity)
        {
            lock (configReadingLock)
            {
                #region Clean the logWriterPreparedDict

                List<EntityCategory> entityCategoriesToRemove = new List<EntityCategory>();
                foreach (EntityCategory entityCategory in logWriterPreparedDict.Keys)
                {
                    if (IdentifiableEntity.Equals(entityCategory.Entity, entity))
                        entityCategoriesToRemove.Add(entityCategory);
                }

                //Remove from the list.
                foreach (EntityCategory entityCategoryToRemove in entityCategoriesToRemove)
                    logWriterPreparedDict.Remove(entityCategoryToRemove);

                #endregion

                foreach (LogWriter logWriter in createdLogWriters)
                    logWriter.RemoveEntity(entity);
            }
        }

        #endregion
    }
}