// Copyright (c) AlphaSierraPapa for the SharpDevelop Team (for details please see \doc\copyright.txt)
// This code is distributed under the GNU LGPL (for details please see \doc\license.txt)

using System;
using System.IO;
using System.Text;
using System.Threading;
using System.Xml;

namespace ICSharpCode.Core
{
	public static class PropertyService
	{
		static string propertyFileName;
		static string propertyXmlRootNodeName;
		
		static string configDirectory;
		static string dataDirectory;
		
		static Properties properties;
		
		public static bool Initialized {
			get { return properties != null; }
		}
		
		public static void InitializeServiceForUnitTests()
		{
			properties = null;
			InitializeService(null, null, null);
		}

		public static void InitializeService(string configDirectory, string dataDirectory, string propertiesName)
		{
			if (properties != null)
				throw new InvalidOperationException("Service is already initialized.");
			properties = new Properties();
			PropertyService.configDirectory = configDirectory;
			PropertyService.dataDirectory = dataDirectory;
			propertyXmlRootNodeName = propertiesName;
			propertyFileName = propertiesName + ".xml";
			properties.PropertyChanged += new PropertyChangedEventHandler(PropertiesPropertyChanged);
		}
		
		public static string ConfigDirectory {
			get {
				return configDirectory;
			}
		}
		
		public static string DataDirectory {
			get {
				return dataDirectory;
			}
		}
		
		public static string Get(string property)
		{
			return properties[property];
		}
		
		public static T Get<T>(string property, T defaultValue)
		{
			return properties.Get(property, defaultValue);
		}
		
		public static void Set<T>(string property, T value)
		{
			properties.Set(property, value);
		}
		
		public static void Load()
		{
			if (properties == null)
				throw new InvalidOperationException("Service is not initialized.");
			if (string.IsNullOrEmpty(configDirectory) || string.IsNullOrEmpty(propertyXmlRootNodeName))
				throw new InvalidOperationException("No file name was specified on service creation");
			if (!Directory.Exists(configDirectory)) {
				Directory.CreateDirectory(configDirectory);
			}
			
			if (!LoadPropertiesFromStream(Path.Combine(configDirectory, propertyFileName))) {
				LoadPropertiesFromStream(Path.Combine(DataDirectory, "options", propertyFileName));
			}
		}
		
		public static bool LoadPropertiesFromStream(string fileName)
		{
			if (!File.Exists(fileName)) {
				return false;
			}
			try {
				using (LockPropertyFile()) {
					using (XmlTextReader reader = new XmlTextReader(fileName)) {
						while (reader.Read()){
							if (reader.IsStartElement()) {
								if (reader.LocalName == propertyXmlRootNodeName) {
									properties.ReadProperties(reader, propertyXmlRootNodeName);
									return true;
								}
							}
						}
					}
				}
			} catch (XmlException ex) {
				MessageService.ShowError("Error loading properties: " + ex.Message + "\nSettings have been restored to default values.");
			}
			return false;
		}
		
		public static void Save()
		{
			if (string.IsNullOrEmpty(configDirectory) || string.IsNullOrEmpty(propertyXmlRootNodeName))
				throw new InvalidOperationException("No file name was specified on service creation");
			using (MemoryStream ms = new MemoryStream()) {
				XmlTextWriter writer = new XmlTextWriter(ms, Encoding.UTF8);
				writer.Formatting = Formatting.Indented;
				writer.WriteStartElement(propertyXmlRootNodeName);
				properties.WriteProperties(writer);
				writer.WriteEndElement();
				writer.Flush();
				
				ms.Position = 0;
				string fileName = Path.Combine(configDirectory, propertyFileName);
				using (LockPropertyFile()) {
					using (FileStream fs = new FileStream(fileName, FileMode.Create, FileAccess.Write, FileShare.None)) {
						ms.WriteTo(fs);
					}
				}
			}
		}
		
		/// <summary>
		/// Acquires an exclusive lock on the properties file so that it can be opened safely.
		/// </summary>
		public static IDisposable LockPropertyFile()
		{
			Mutex mutex = new Mutex(false, "PropertyServiceSave-30F32619-F92D-4BC0-BF49-AA18BF4AC313");
			mutex.WaitOne();
			return new CallbackOnDispose(
				delegate {
					mutex.ReleaseMutex();
					mutex.Close();
				});
		}
		
		static void PropertiesPropertyChanged(object sender, PropertyChangedEventArgs e)
		{
			if (PropertyChanged != null) {
				PropertyChanged(null, e);
			}
		}
		
		public static event PropertyChangedEventHandler PropertyChanged;
	}
}