using System;
using System.Globalization;
using System.Text.RegularExpressions;

namespace CookComputing.XmlRpc
{
  public static class DateTime8601
  {
    static Regex _dateTime8601Regex = new Regex(
        @"(((?<year>\d{4})-(?<month>\d{2})-(?<day>\d{2}))|((?<year>\d{4})(?<month>\d{2})(?<day>\d{2})))"
      + @"T"
      + @"(((?<hour>\d{2}):(?<minute>\d{2}):(?<second>\d{2}))|((?<hour>\d{2})(?<minute>\d{2})(?<second>\d{2})))"
      + @"(?<tz>$|Z|([+-]\d{2}:?(\d{2})?))");


    static public bool TryParseDateTime8601(string date, out DateTime result)
    {
      result = DateTime.MinValue;
      var m = _dateTime8601Regex.Match(date);
      if (m == null)
        return false;
      string normalized = m.Groups["year"].Value + m.Groups["month"].Value + m.Groups["day"].Value
        + "T"
        + m.Groups["hour"].Value + m.Groups["minute"].Value + m.Groups["second"].Value
        + m.Groups["tz"].Value;
      var formats = new string[]
      {
        "yyyyMMdd'T'HHmmss", 
        "yyyyMMdd'T'HHmmss'Z'", 
        "yyyyMMdd'T'HHmmsszzz", 
        "yyyyMMdd'T'HHmmsszz", 
      };
      // Compact Framework doesn't support TryParseExact()
      try
      {
        result = DateTime.ParseExact(normalized, formats, CultureInfo.InvariantCulture,
                System.Globalization.DateTimeStyles.AdjustToUniversal);
        return true;
      }
      catch (Exception)
      {
        return false;
      }
    }
  }
}