using System.Collections.Generic;
using System.Xml.Linq;
using Microsoft.Win32;

namespace VB.TimeZoneInformation
{
    /// <summary>

    /// Date: 02/18/2008
    /// Created By: Vladimir Burmistrovich
    /// Exports all of the information about time zones from the Windows registry to an XML file
    /// </summary>
    public class TimeZoneExporter
    {
        private List<TimeZoneInformationStruct> timezones; // a list of all the timezones in the
                                                           // registry
        private const string fileName = "timezones.xml"; // the filename to export to

        /// <summary>
        /// The entry point of the program
        /// </summary>
        /// <param name="args">The standard args parameter. It's not used in this program.</param>
        static void Main(string[] args)
        {
            TimeZoneExporter exporter = new TimeZoneExporter();
            exporter.SetTimeZoneInfo();
            exporter.Export();
        }

        /// <summary>
        /// Exports all of the time zone information to the XML file. Uses the new LINQ
        /// functionality of .NET 3.5
        /// </summary>
        private void Export()
        {
            XDocument xmlDoc = new XDocument();
            XElement timezonesEl = new XElement("TimeZones");
            foreach (TimeZoneInformationStruct tz in timezones)
            {
                XElement timezone = new XElement("TimeZone");
                XElement display = new XElement("Display", tz.Display);
                XElement dlt = new XElement("Dlt", tz.Dlt);
                XElement std = new XElement("Std", tz.Std);
                XElement tzi = new XElement("TziBytes");
                foreach (byte b in tz.Tzi) // Since Tzi is a byte array, export each byte
                                           // separately for easier importing later

                {
                    XElement tzibyte = new XElement("TziByte", b);
                    tzi.Add(tzibyte);
                }
                timezone.Add(display);
                timezone.Add(dlt);
                timezone.Add(std);
                timezone.Add(tzi);

                timezonesEl.Add(timezone);
            }
            xmlDoc.Add(timezonesEl);

            xmlDoc.Save(fileName);
        }

        /// <summary>
        /// Loads the timezones list with the information from the Windows Registry.
        /// </summary>
        private void SetTimeZoneInfo()
        {
            timezones = new List<TimeZoneInformationStruct>();

            using (RegistryKey key = Registry.LocalMachine.OpenSubKey(
                       @"SOFTWARE\Microsoft\Windows NT\CurrentVersion\Time Zones"))
            {
                string[] zoneNames = key.GetSubKeyNames();

                foreach (string zoneName in zoneNames)
                {
                    using (RegistryKey subKey = key.OpenSubKey(zoneName))
                    {
                        TimeZoneInformationStruct timezone = new TimeZoneInformationStruct();
                        timezone.Display = (string)subKey.GetValue("Display");
                        timezone.Std = (string)subKey.GetValue("Std");
                        timezone.Dlt = (string)subKey.GetValue("Dlt");
                        timezone.Tzi = (byte[])subKey.GetValue("Tzi");
                        timezones.Add(timezone);
                    }
                }
            }
        }
    }

    /// <summary>
    /// A struct with all the needed info contained in the registry.
    /// </summary>
    struct TimeZoneInformationStruct
    {
        public string Display
        { get; set; }
        public string Std
        { get; set; }
        public string Dlt
        { get; set; }
        public byte[] Tzi
        { get; set; }
    }
}