SmtpDateTime.cs

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using System.Collections.Generic;
using System.Globalization;
 
namespace System.Net.Mime;
 
internal sealed class SmtpDateTime
{
    internal static readonly string[] s_validDateTimeFormats = new string[4] { "ddd, dd MMM yyyy HH:mm:ss", "dd MMM yyyy HH:mm:ss", "ddd, dd MMM yyyy HH:mm", "dd MMM yyyy HH:mm" };
 
    internal static readonly char[] s_allowedWhiteSpaceChars = new char[2] { ' ', '\t' };
 
    internal static readonly Dictionary<string, TimeSpan> s_timeZoneOffsetLookup = InitializeShortHandLookups();
 
    private readonly DateTime _date;
 
    private readonly TimeSpan _timeZone;
 
    private readonly bool _unknownTimeZone;
 
    internal DateTime Date
    {
        get
        {
            if (_unknownTimeZone)
            {
                return DateTime.SpecifyKind(_date, DateTimeKind.Unspecified);
            }
            return new DateTimeOffset(_date, _timeZone).LocalDateTime;
        }
    }
 
    internal static Dictionary<string, TimeSpan> InitializeShortHandLookups()
    {
        Dictionary<string, TimeSpan> dictionary = new Dictionary<string, TimeSpan>();
        dictionary.Add("UT", TimeSpan.Zero);
        dictionary.Add("GMT", TimeSpan.Zero);
        dictionary.Add("EDT", new TimeSpan(-4, 0, 0));
        dictionary.Add("EST", new TimeSpan(-5, 0, 0));
        dictionary.Add("CDT", new TimeSpan(-5, 0, 0));
        dictionary.Add("CST", new TimeSpan(-6, 0, 0));
        dictionary.Add("MDT", new TimeSpan(-6, 0, 0));
        dictionary.Add("MST", new TimeSpan(-7, 0, 0));
        dictionary.Add("PDT", new TimeSpan(-7, 0, 0));
        dictionary.Add("PST", new TimeSpan(-8, 0, 0));
        return dictionary;
    }
 
    internal SmtpDateTime(DateTime value)
    {
        _date = value;
        switch (value.Kind)
        {
        case DateTimeKind.Local:
        {
            TimeSpan utcOffset = TimeZoneInfo.Local.GetUtcOffset(value);
            _timeZone = ValidateAndGetSanitizedTimeSpan(utcOffset);
            break;
        }
        case DateTimeKind.Unspecified:
            _unknownTimeZone = true;
            break;
        case DateTimeKind.Utc:
            _timeZone = TimeSpan.Zero;
            break;
        }
    }
 
    internal SmtpDateTime(string value)
    {
        _date = ParseValue(value, out var timeZone);
        if (!TryParseTimeZoneString(timeZone, out _timeZone))
        {
            _unknownTimeZone = true;
        }
    }
 
    public override string ToString()
    {
        return FormatDate(_date) + " " + (_unknownTimeZone ? "-0000" : TimeSpanToOffset(_timeZone));
    }
 
    internal void ValidateAndGetTimeZoneOffsetValues(string offset, out bool positive, out int hours, out int minutes)
    {
        if (offset.Length != 5)
        {
            throw new FormatException(System.SR.MailDateInvalidFormat);
        }
        positive = offset.StartsWith('+');
        if (!int.TryParse(offset.AsSpan(1, 2), NumberStyles.None, CultureInfo.InvariantCulture, out hours))
        {
            throw new FormatException(System.SR.MailDateInvalidFormat);
        }
        if (!int.TryParse(offset.AsSpan(3, 2), NumberStyles.None, CultureInfo.InvariantCulture, out minutes))
        {
            throw new FormatException(System.SR.MailDateInvalidFormat);
        }
        if (minutes > 59)
        {
            throw new FormatException(System.SR.MailDateInvalidFormat);
        }
    }
 
    internal void ValidateTimeZoneShortHandValue(string value)
    {
        for (int i = 0; i < value.Length; i++)
        {
            if (!char.IsLetter(value, i))
            {
                throw new FormatException(System.SR.Format(System.SR.MailHeaderFieldInvalidCharacter, value));
            }
        }
    }
 
    internal string FormatDate(DateTime value)
    {
        return value.ToString("ddd, dd MMM yyyy HH:mm:ss", CultureInfo.InvariantCulture);
    }
 
    internal DateTime ParseValue(string data, out string timeZone)
    {
        if (string.IsNullOrEmpty(data))
        {
            throw new FormatException(System.SR.MailDateInvalidFormat);
        }
        int num = data.IndexOf(':');
        if (num == -1)
        {
            throw new FormatException(System.SR.Format(System.SR.MailHeaderFieldInvalidCharacter, data));
        }
        int num2 = data.IndexOfAny(s_allowedWhiteSpaceChars, num);
        if (num2 == -1)
        {
            throw new FormatException(System.SR.Format(System.SR.MailHeaderFieldInvalidCharacter, data));
        }
        string s = data.AsSpan(0, num2).Trim().ToString();
        if (!DateTime.TryParseExact(s, s_validDateTimeFormats, CultureInfo.InvariantCulture, DateTimeStyles.AllowWhiteSpaces, out var result))
        {
            throw new FormatException(System.SR.MailDateInvalidFormat);
        }
        string text = data.AsSpan(num2).Trim().ToString();
        int num3 = text.IndexOfAny(s_allowedWhiteSpaceChars);
        if (num3 != -1)
        {
            text = text.Substring(0, num3);
        }
        if (string.IsNullOrEmpty(text))
        {
            throw new FormatException(System.SR.MailDateInvalidFormat);
        }
        timeZone = text;
        return result;
    }
 
    internal bool TryParseTimeZoneString(string timeZoneString, out TimeSpan timeZone)
    {
        if (timeZoneString == "-0000")
        {
            timeZone = TimeSpan.Zero;
            return false;
        }
        if (timeZoneString[0] == '+' || timeZoneString[0] == '-')
        {
            ValidateAndGetTimeZoneOffsetValues(timeZoneString, out var positive, out var hours, out var minutes);
            if (!positive)
            {
                if (hours != 0)
                {
                    hours *= -1;
                }
                else if (minutes != 0)
                {
                    minutes *= -1;
                }
            }
            timeZone = new TimeSpan(hours, minutes, 0);
            return true;
        }
        ValidateTimeZoneShortHandValue(timeZoneString);
        return s_timeZoneOffsetLookup.TryGetValue(timeZoneString, out timeZone);
    }
 
    internal TimeSpan ValidateAndGetSanitizedTimeSpan(TimeSpan span)
    {
        TimeSpan result = new TimeSpan(span.Days, span.Hours, span.Minutes, 0, 0);
        if (Math.Abs(result.Ticks) > 3599400000000L)
        {
            throw new FormatException(System.SR.MailDateInvalidFormat);
        }
        return result;
    }
 
    internal string TimeSpanToOffset(TimeSpan span)
    {
        if (span.Ticks == 0L)
        {
            return "+0000";
        }
        uint num = (uint)Math.Abs(Math.Floor(span.TotalHours));
        uint num2 = (uint)Math.Abs(span.Minutes);
        string text = ((span.Ticks > 0) ? "+" : "-");
        if (num < 10)
        {
            text += "0";
        }
        text += num;
        if (num2 < 10)
        {
            text += "0";
        }
        return text + num2;
    }
}