public static class DatePattern
{
private class RegexFunc
{
public Regex Pattern;
public Func<string, DateTime> Converter;
}
private static class RegexFuncParsers
{
private static CultureInfo enCulture = new CultureInfo("en-US");
private static DateTime nowTime { get { return DateTime.Now; } }
public static RegexFunc[] DateParsers =
{
new RegexFunc //now
{
Pattern = new Regex("(?i)(now)"),
Converter = (string match) => nowTime
},
new RegexFunc // (?i)\d+ min ago [5 mins]
{
Pattern = new Regex(@"(?i)^\d+.*?(?=min)"),
Converter = (string match) =>
{
string minutes = Regex.Match(match, @"(?i)^\d+.*?(?=min)").Value.Trim();
return nowTime.AddMinutes(0-int.Parse(minutes));
}
},
new RegexFunc //(?i)\d+ hours ago [1 hour, 2hours, 1 hr, 2hrs]
{
Pattern = new Regex(@"(?i)^(\d+).*?(?=h(?:ou)?r)"),
Converter = (string match) =>
{
string hours = Regex.Match(match, @"(?i)^(\d+).*?(?=h(?:ou)?r)").Value.Trim();
return nowTime.AddHours(0-int.Parse(hours));
}
},
new RegexFunc //(?i)today H/h:mm(?:\s?tt) [Today at 8:20 AM, Today at 8:20am, Today at 8:20]
{
Pattern = new Regex(@"(?i)^today.*?(\d+:\d+(?:\s?[apm]{2})?)$"),
Converter = (string match) =>
{
string tt = Regex.IsMatch(match, @"(?i)\d+:\d+(?:\s?[apm]{2})") ? "tt" : "";
string h = tt.Any<char>() ? "h" : "H";
match = Regex.Replace(match, @"(?i)^today.+?(?=\d+:)", "");
match = Regex.Replace(match, @"(?i)(?<=:\d.+)\s(?=[apm]{2})", ""); //delete space
match = DateTime.Today.ToString("yyyy MM dd ") + match;
string format = "yyyy MM dd " + h + ":mm" + tt;
return DateTime.ParseExact(match, format, enCulture);
}
},
new RegexFunc //(?i)yesterday H/h:mm(?:\s?tt) [Yesterday at 8:20 AM, Yesterday at 8:20am, Yesterday at 8:20]
{
Pattern = new Regex(@"(?i)^yesterday.*?(\d+:\d+(?:\s?[apm]{2})?)$"),
Converter = (string match) =>
{
string tt = Regex.IsMatch(match, @"(?i)\d+:\d+(?:\s?[apm]{2})") ? "tt" : "";
string h = tt.Any<char>() ? "h" : "H";
match = Regex.Replace(match, @"(?i)^yesterday.+?(?=\d+:)", "");
match = Regex.Replace(match, @"(?i)(?<=:\d.+)\s(?=[apm]{2})", ""); //delete space
match = DateTime.Today.AddDays(-1.0).ToString("yyyy MM dd ") + match;
string format = "yyyy MM dd " + h + ":mm" + tt;
return DateTime.ParseExact(match, format, enCulture);
}
}
};
}
public static DateTime Convert(string date_pattern)
{
date_pattern = date_pattern.Trim();
var dateParsers = RegexFuncParsers.DateParsers;
for (int i = 0; i < dateParsers.Length; i++)
{
var match = dateParsers[i].Pattern.Match(date_pattern);
if (!match.Success)
continue;
return dateParsers[i].Converter(date_pattern);
}
throw new Exception("no pattern in dateParsers for " + date_pattern);
}
}
