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Fixed header date time formatting by using a regular expression #18

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Fixed header date time formatting by using a regular expression #18

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92a20f4
Fixed header date time formatting by using a regular expression.
JohnTasler Nov 17, 2021
ab146bf
Better formatting of RegEx string
JohnTasler Jun 24, 2022
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97 changes: 30 additions & 67 deletions Usenet/Nntp/Parsers/HeaderDateParser.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -6,6 +6,18 @@ namespace Usenet.Nntp.Parsers
{
internal static class HeaderDateParser
{
private const string _dateTimeRegexString =
@"(?:\s*"
+ @"(?<dayName>Sun|Mon|Tue|Wed|Thu|Fri|Sat),)?\s*"
+ @"(?<day>\d{1,2})\s+"
+ @"(?<month>Jan|Feb|Mar|Apr|May|Jun|Jul|Aug|Sep|Oct|Nov|Dec)\s+"
+ @"(?<year>\d{2,4})\s+"
+ @"(?<hour>\d{1,2}):(?<min>\d{1,2})(?::(?<sec>\d{1,2}))?\s*"
+ @"(?<tz>[+-]\d+|(?:UT|UTC|GMT|Z|EDT|EST|CDT|CST|MDT|MST|PDT|PST|A|N|M|Y|[A-Z]+)"
+ @")?";

private static readonly Regex _dateTimeRegex = new Regex(_dateTimeRegexString, RegexOptions.IgnoreCase | RegexOptions.Compiled);

/// <summary>
/// Parses header date/time strings as described in the
/// <a href="https://tools.ietf.org/html/rfc5322#section-3.3">Date and Time Specification</a>.
Expand All @@ -18,59 +30,31 @@ internal static class HeaderDateParser
{
return null;
}
string[] valueParts = value.Split(new []{','}, StringSplitOptions.RemoveEmptyEntries);
if (valueParts.Length > 2)
{
throw new FormatException(Resources.Nntp.BadHeaderDateFormat);
}

// skip day-of-week for now
//string dayOfWeek = valueParts.Length == 2 ? valueParts[0] : null;

string dateTime = valueParts.Length == 2 ? valueParts[1] : valueParts[0];

// remove obsolete whitespace from time part
dateTime = Regex.Replace(dateTime, @"\s+:\s+", ":");

string[] dateTimeParts = dateTime.Split(new[] {' ', '\n', '\r', '\t'}, StringSplitOptions.RemoveEmptyEntries);
if (dateTimeParts.Length != 5 && (dateTimeParts.Length != 6 || dateTimeParts[5] != "(UTC)"))
var matches = _dateTimeRegex.Match(value);
if (!matches.Success)
{
throw new FormatException(Resources.Nntp.BadHeaderDateFormat);
}

ParseDate(dateTimeParts, out int year, out int month, out int day);
ParseTime(dateTimeParts[3], out int hour, out int minute, out int second);
TimeSpan zone = ParseZone(dateTimeParts[4]);
var day = int.Parse(matches.Groups["day"].Value);
var month = matches.Groups["month"].Value;
var year = int.Parse(matches.Groups["year"].Value);
var hour = int.Parse(matches.Groups["hour"].Value);
var minute = int.Parse(matches.Groups["min"].Value);
int.TryParse(matches.Groups["sec"].Value, out var second);
var tz = matches.Groups["tz"].Value;
var zone = ParseZone(tz);

return new DateTimeOffset(year, month, day, hour, minute, second, 0, zone);
}
int monthIndex = 1 + Array.FindIndex(DateTimeFormatInfo.InvariantInfo.AbbreviatedMonthNames,
m => string.Equals(m, month, StringComparison.OrdinalIgnoreCase));

private static void ParseDate(string[] dateTimeParts, out int year, out int month, out int day)
{
if (dateTimeParts.Length < 3)
if (matches.Groups["year"].Value.Length < 4)
{
throw new FormatException(Resources.Nntp.BadHeaderDateFormat);
}
if (!int.TryParse(dateTimeParts[0], out day))
{
throw new FormatException(Resources.Nntp.BadHeaderDateFormat);
}
string monthString = dateTimeParts[1];
int monthIndex = Array.FindIndex(DateTimeFormatInfo.InvariantInfo.AbbreviatedMonthNames,
m => string.Equals(m, monthString, StringComparison.OrdinalIgnoreCase));
if (monthIndex < 0)
{
throw new FormatException(Resources.Nntp.BadHeaderDateFormat);
}
month = monthIndex + 1;
if (!int.TryParse(dateTimeParts[2], out year))
{
throw new FormatException(Resources.Nntp.BadHeaderDateFormat);
}
if (dateTimeParts[2].Length <= 2)
{
year += 100 * GetCentury(year, month, day);
year += GetCentury(year, monthIndex, day) * 100;
}

return new DateTimeOffset(year, monthIndex, day, hour, minute, second, 0, zone);
}

private static int GetCentury(int year, int month, int day)
Expand All @@ -82,28 +66,6 @@ private static int GetCentury(int year, int month, int day)
: currentCentury;
}

private static void ParseTime(string value, out int hour, out int minute, out int second)
{
string[] timeParts = value.Split(new[] { ':' }, StringSplitOptions.RemoveEmptyEntries);
if (timeParts.Length < 2 || timeParts.Length > 3)
{
throw new FormatException(Resources.Nntp.BadHeaderDateFormat);
}
if (!int.TryParse(timeParts[0], out hour))
{
throw new FormatException(Resources.Nntp.BadHeaderDateFormat);
}
if (!int.TryParse(timeParts[1], out minute))
{
throw new FormatException(Resources.Nntp.BadHeaderDateFormat);
}
second = 0;
if (timeParts.Length > 2 && !int.TryParse(timeParts[2], out second))
{
throw new FormatException(Resources.Nntp.BadHeaderDateFormat);
}
}

private static TimeSpan ParseZone(string value)
{
// The time zone must be as specified in RFC822, https://tools.ietf.org/html/rfc822#section-5
Expand All @@ -112,11 +74,12 @@ private static TimeSpan ParseZone(string value)
{
switch (value)
{
// UTC is not specified in RFC822, but allowing it since it is commonly used
// UTC and empty are not specified in RFC822, but allowing them since they are commonly used
case "UTC":
case "UT":
case "GMT":
case "Z":
case "":
break;

case "EDT":
Expand Down
9 changes: 8 additions & 1 deletion UsenetTests/Nntp/Parsers/HeaderDateParserTests.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -10,6 +10,10 @@ public class HeaderDateParserTests
{
public static readonly IEnumerable<object[]> ParseData = new[]
{
new object[] {"Mon, 1 May 2017 1:55", new DateTimeOffset(2017, 5, 1, 1, 55, 0, TimeSpan.Zero)},
new object[] {"1 May 2017 1:55:33", new DateTimeOffset(2017, 5, 1, 1, 55, 33, TimeSpan.Zero)},
new object[] {"01 May 2017 13:55", new DateTimeOffset(2017, 5, 1, 13, 55, 0, TimeSpan.Zero)},
new object[] {"01 May 2017 13:55:33", new DateTimeOffset(2017, 5, 1, 13, 55, 33, TimeSpan.Zero)},
new object[] {"01 May 2017 13:55:33 +0000", new DateTimeOffset(2017, 5, 1, 13, 55, 33, TimeSpan.Zero)},
new object[] {"01 May 2017 13:55:33 -0000", new DateTimeOffset(2017, 5, 1, 13, 55, 33, TimeSpan.Zero)},
new object[] {"01 May 2017 13:55:33 +0000 (UTC)", new DateTimeOffset(2017, 5, 1, 13, 55, 33, TimeSpan.Zero)},
Expand All @@ -20,6 +24,9 @@ public class HeaderDateParserTests
new object[] {"01 May 2017 13:55 +1030", new DateTimeOffset(2017, 5, 1, 13, 55, 0, TimeSpan.FromMinutes(10 * 60 + 30))},
new object[] {"01 May 2017 13:55 -1030", new DateTimeOffset(2017, 5, 1, 13, 55, 0, -TimeSpan.FromMinutes(10 * 60 + 30))},

new object[] {"01 May 2017 13:55+1030", new DateTimeOffset(2017, 5, 1, 13, 55, 0, TimeSpan.FromMinutes(10 * 60 + 30))},
new object[] {"01 May 2017 13:55-1030", new DateTimeOffset(2017, 5, 1, 13, 55, 0, -TimeSpan.FromMinutes(10 * 60 + 30))},

new object[] {"1 Jan 2017 00:00:00 +0000", new DateTimeOffset(2017, 1, 1, 0, 0, 0, TimeSpan.Zero)},
new object[] {"1 Feb 2017 00:00:00 +0000", new DateTimeOffset(2017, 2, 1, 0, 0, 0, TimeSpan.Zero)},
new object[] {"1 Mar 2017 00:00:00 +0000", new DateTimeOffset(2017, 3, 1, 0, 0, 0, TimeSpan.Zero)},
Expand Down Expand Up @@ -75,7 +82,7 @@ public void HeaderDateShouldBeParsedCorrectly(string headerDate, DateTimeOffset

[Theory]
[MemberData(nameof(TimezoneParseFailureData))]
public void HeaderDateShouldBeNotBeParsedCorrectly(string headerDate, Type exceptionType)
public void HeaderDateShouldNotBeParsedCorrectly(string headerDate, Type exceptionType)
{
Assert.Throws(exceptionType, () => HeaderDateParser.Parse(headerDate));
}
Expand Down